REFRIGERANT CIRCUIT

Description

[0001] The invention relates to a refrigerant circuit comprising at least one refrigerant compressor which compresses refrigerant supplied to a suction connection to high pressure so that a compressor mass flow of the refrigerant compressed to high pressure exits at a pressure connection, at least one high-pressure side heat-emitting heat exchanger with an inlet to which the refrigerant circuit supplies the compressor mass flow and with an outlet from which a cooled total mass flow of refrigerant exits, at least one expansion unit comprising an activatable or deactivatable expansion compression unit having an expander and a compressor stage, which expands an expansion mass flow of the total mass flow, guided from the refrigerant circuit in the direction of the suction connection of the refrigerant compressor, from high pressure to an expansion pressure,and at least one cooling stage with at least one heat-absorbing heat exchanger, to which the refrigerant circuit supplies a main mass flow comprised of the expansion pressure mass flow expanded by the expansion unit and supplies this main mass flow to the suction connection of the refrigerant compressor after leaving the cooling stage.

[0002] Such refrigerant circuits are known from EP 2 244 037 A1.

[0003] The problem with these is always how to operate them as optimally as possible.

[0004] This object is achieved by a refrigerant circuit according to claim 1 and an expansion unit according to claim 12.

[0005] This allows the operation of the expansion unit to be further stabilized, especially in the event of a thermal or mass flow imbalance occurring in the subcooling unit.

[0006] Such a mass flow recirculation has the advantage that it can be used to influence the mass flow through the subcooling unit by recirculating a mass flow of refrigerant that is conveyed by the compressor and thus supplementing the mass flow passed through the subcooling unit and thereby reducing the mass flow passed through the subcooling unit.

[0007] It is particularly advantageous if the mass flow return comprises a compressor bypass line and a control valve associated therewith, which is thus capable of regulating or controlling the magnitude of the mass flow flowing through the compressor bypass line. In particular, the control valve is controlled by a controller that detects temperature differences between a temperature present on the boiling pressure side of the subcooling unit and a temperature present downstream of the expansion device and / or a superheat difference on the input side of the compressor stage and / or a degree of opening of the expansion device.

[0008] In order to stabilize the operation of the expansion unit, an advantageous solution provides that the expansion unit has a control which, in order to stabilize the operation of the same, determines a temperature of the refrigerant present on the high-pressure side before entering the subcooling unit and a temperature of the refrigerant exiting the subcooling unit and present at the inlet pressure of the compressor stage, that the control determines a temperature difference between these two temperatures and checks whether this is greater or smaller than a maximum difference, and in the event that this is greater than the maximum difference, activates and / or increases the mass flow through the mass flow return.

[0009] Preferably, the maximum difference is in the range of 2 to 5 Kelvin.

[0010] A further advantageous solution provides that the expansion unit has a control which, in order to stabilize the operation of the same, determines a temperature of the refrigerant present on the high-pressure side after leaving the subcooling unit and a temperature of the refrigerant present before entering the subcooling unit, expanded to subcooling pressure, that the control determines a temperature difference between these two temperatures and checks whether this is smaller or larger than a minimum difference, and in the event that this is smaller than a minimum difference, activates and / or increases the mass flow through the mass flow return.

[0011] Preferably, the minimum difference is in the range of 2 to 4 Kelvin.

[0012] A further advantageous solution provides that the expansion unit has a control which, in order to stabilize the operation of the same, determines a pressure of the refrigerant present at the inlet pressure of the compressor stage, determines the evaporation temperature of the same therefrom, and also determines the temperature of the refrigerant rotating out of the subcooling unit and present at the inlet pressure of the compressor stage, and determines a superheat difference from these temperatures and, in the event that this superheat difference is smaller than a minimum superheat value, activates and / or increases the mass flow recirculation.

[0013] In particular, the minimum superheat value is in the range of 3 to 7 Kelvin.

[0014] In addition to the solutions described above, the expansion unit can also be stabilized with regard to its operation in that the expansion unit has a control system which, in order to stabilize its operation, determines a temperature of the refrigerant present on the high-pressure side before entering the subcooling unit and a temperature of the refrigerant exiting the subcooling unit and present at the inlet pressure of the compressor stage, that the control system determines a temperature difference between these two temperatures and checks whether this is greater or smaller than a maximum difference and, in the event that this is greater than the maximum difference, generates and / or increases a bypass mass flow by activating the bypass line.

[0015] A further advantageous solution provides that the expansion unit has a control which, in order to stabilize the operation of the same, determines a temperature of the refrigerant present on the high-pressure side after leaving the subcooling unit and a temperature of the refrigerant present at subcooling pressure before entering the subcooling unit, that the control determines a temperature difference between these two temperatures and checks whether this is smaller or larger than a minimum difference, and in the event that this is smaller than a minimum difference, generates and / or increases a bypass mass flow by activating the bypass line.

[0016] In addition to one of the solutions described above, a further solution provides that the expansion unit has a control system which, in order to stabilize its operation, determines a pressure of the refrigerant present at the inlet pressure of the compressor stage, determines the evaporation temperature of the same from these temperatures, and also determines the temperature of the refrigerant emerging from the subcooling unit and present at the inlet pressure of the compressor stage and determines a superheat difference therefrom and, in the event that this superheat difference is smaller than a minimum value, generates and / or increases a bypass mass flow by activating the bypass line.

[0017] In addition, a further solution provides that the expansion unit has a control system which determines a degree of opening of the expansion element controlling the subcooling mass flow and controls the expansion element functionally assigned to the bypass line in accordance with the degree of opening.

[0018] A further advantageous solution provides that the expansion unit has an electrically operating control which detects at least one of the following variables such as a temperature influenced by or corresponding to the ambient temperature, a temperature (T amb ) of the mass flow of the refrigerant supplied to the expansion unit and / or the expander stage, a high pressure of the total mass flow or the expansion mass flow upstream of the expander stage and activates the bypass line and generates the bypass mass flow in accordance with this temperature and / or optionally this high pressure of the total mass flow or the expansion mass flow.

[0019] It is particularly advantageous with this solution if the control system controls the bypass mass flow by controlling the expansion element functionally assigned to the bypass line.

[0020] To control the high pressure of the total mass flow, it is particularly advantageous if an electrically operating control is provided which detects at least one of the following variables such as: an ambient temperature, a temperature of the mass flow of the refrigerant supplied to the expansion unit and / or the expander stage and an inlet pressure of the compressor stage, and according to this temperature and / or optionally this inlet pressure of the compressor stage, sets an inlet pressure of the expansion unit or the expander stage - and thus indirectly the high pressure of the total mass flow - and / or optionally an inlet pressure of the compressor stage by controlling the subcooling mass flow by means of the expansion element electrically controlled by the control.

[0021] The advantage of this solution is that the expansion unit operates with high energy efficiency, since no throttling device is provided in the mass flow supplied to the expander stage to adjust the mass flow flowing to the expander stage.

[0022] Rather, the mass flow flowing to the expander stage and relevant for the inlet pressure of the expansion unit or the expansion compression unit is adjusted exclusively by controlling the subcooling mass flow by means of the expansion device controlled by the controller, so that during the expansion of the mass flow in the expander stage, maximum energy recovery takes place, which can be used to compress the subcooling mass flow in the compressor stage, so that at the same time optimal subcooling of the expanded mass flow takes place before its expansion.

[0023] In particular, the expansion element comprises an electrically driven servo motor.

[0024] With regard to measuring the temperature of the refrigerant mass flow, a wide variety of solutions are conceivable.

[0025] One solution provides that the control system detects the ambient temperature and / or the temperature of the mass flow of the refrigerant before an inlet of the subcooling unit and / or before the latter enters the expander by means of a sensor.

[0026] Another solution that comprehensively records the temperature of the refrigerant mass flow involves measuring the temperature of the refrigerant mass flow with a sensor before it enters the subcooling unit and before it enters the expander.

[0027] Another solution provides that the control system detects the ambient temperature by means of a sensor and takes this into account alone or, if necessary, in combination with the temperature of the mass flow of the refrigerant before it enters the subcooling unit and / or before it enters the expander for the control of the expansion device.

[0028] It is particularly advantageous if the control is an electronic control comprising a processor which electrically controls the expansion element by means of a control program, since with a processor the diverse correlations between the measured temperature and the subcooling mass flow to be controlled by the expansion element can be realized in a simple manner.

[0029] In particular, with this design of the control system, it is possible to always control the expansion device in such a way that the subcooling mass flow exits the subcooling unit in the superheated state, thus preventing partially liquid refrigerant in the subcooling mass flow from exiting the subcooling unit and being fed to the expansion stage.

[0030] In order to monitor the temperature of the subcooling mass flow leaving the subcooling unit, a sensor connected to the controller is provided in a connecting line between the subcooling unit and the compressor stage in order to detect an inlet pressure of the compressor stage, for example when it is to be controlled.

[0031] In the described solution, the control program is designed in particular in such a way that it comprises either an algorithm for determining the control of the expansion element or a stored correlation table which correlates the setting of the expansion element with the measured temperature of the supplied mass flow.

[0032] With regard to the position of the branch for branching off the subcooling mass flow from the total mass flow, various possibilities are conceivable.

[0033] One possibility is that the branch is arranged in front of a high-pressure side inlet of the subcooling unit.

[0034] With this solution, the subcooling unit is only flowed through by the expansion mass flow and cooled by the subcooling mass flow.

[0035] A favorable solution provides that the branch is arranged between the subcooling unit and the expansion-compression unit and branches off the subcooling mass flow from the total mass flow after the subcooling unit.

[0036] This solution is energetically advantageous because the diverted subcooling mass flow has also already been pre-cooled in the subcooling mass unit.

[0037] This solution is particularly advantageous for subcritical heat dissipation and allows for greater subcooling.

[0038] Furthermore, this solution has the advantage that pulsations emanating from the expansion compression unit are dampened by the supply line leading away from the branch with the expansion device.

[0039] No further details have been provided so far regarding the design of the subcooling unit.

[0040] The subcooling unit can be designed in different ways.

[0041] One solution provides that the subcooling unit is designed as a heat exchanger unit and cools the mass flow of the refrigerant flowing to the expander stage by the subcooling mass flow passing through it in countercurrent.

[0042] Another advantageous solution provides that the subcooling unit is designed as a collecting tank in which a bath of liquid refrigerant of the subcooling mass flow is formed, which cools an element leading the mass flow of the refrigerant flowing to the expander stage through the bath, wherein a gas volume is formed above the bath, from which the gaseous subcooling mass flow is discharged.

[0043] This solution has the advantage that, on the one hand, the mass flow passing through the element is optimally subcooled and, on the other hand, by removing the subcooling mass flow from the gas volume, it can be ensured that no liquid refrigerant is supplied to the compressor stage for compression.

[0044] No further details have been provided so far regarding the connection between the expander and the compressor stage.

[0045] In principle, the expander and the compressor stage could be coupled, for example, by a generator motor unit.

[0046] However, a particularly advantageous solution provides that the expander and the compressor stage of the expansion compression unit are mechanically functionally coupled.

[0047] Such a mechanical functional coupling means that the energy generated in the expander is transferred directly to the compressor stage via a mechanical connection.

[0048] On the other hand, this solution also has the advantage that the solution according to the invention, namely the control of the mass flow expanded by the expander, can be controlled in a simple manner via the subcooling mass flow compressed by the compressor stage.

[0049] In principle, the expander stage and the compressor stage can be formed by suitable types of rotating driven machines.

[0050] A particularly advantageous solution provides that the expander stage and the compressor stage are formed by a free piston machine in which at least one free piston is freely movable in a piston chamber.

[0051] Preferably, the expansion compression unit is designed such that it has two piston chambers, in each of which a free piston is movable.

[0052] Furthermore, the free pistons are preferably movable in a coupled manner.

[0053] In the free-piston engine according to the invention, it is preferably provided that a first free piston in the respective piston chamber separates a first expansion chamber and a first compression chamber from one another.

[0054] Furthermore, it is advantageously provided that a second free piston in the respective piston chamber separates a second expansion chamber from a second compression chamber.

[0055] In order to operate the two free pistons in an advantageous manner, it is preferably provided that the two free pistons are arranged coaxially to one another in the piston chambers and are movable.

[0056] Advantageously, the first piston chamber is separated from the second piston chamber by a separating body.

[0057] Advantageous operation of the expansion compression unit can be achieved if the two expansion chambers are arranged adjacent to the separating body in the piston chambers.

[0058] Furthermore, it is preferably provided that the two compression chambers are arranged on the sides of the respective free pistons opposite the expansion chambers.

[0059] In principle, the free pistons can work independently of each other.

[0060] However, an advantageous solution provides that a coupling element coupling the free pistons extends through the separating body and is movable relative to it, in particular in a sealed manner.

[0061] In the simplest case, the coupling element is designed in such a way that it extends through the expansion chambers to the respective free piston.

[0062] With regard to the flow of refrigerant to the expansion chambers, it is preferably provided that these can be controlled by a slide system.

[0063] Such a slide system is designed, for example, as a change-over slide, so that in one slide position the refrigerant flows into one expansion chamber and flows out of the other expansion chamber and in the other slide position the refrigerant flows into the other expansion chamber and flows out of the other expansion chamber.

[0064] To control the slide system, it is preferably provided that the slide system can be controlled by a slide drive with which the two slide positions can be adjusted.

[0065] Such a slide drive can be carried out by an electrical control which detects at least one position of the free pistons by means of at least one position sensor assigned to them.

[0066] Alternatively, an advantageous solution provides that the slide drive can be controlled by a pressure difference between an expander inlet and an expander outlet.

[0067] Preferably, the slide drive is designed as a double-acting actuating cylinder, the piston of which is acted upon on the one hand by the pressure at the expander inlet and on the other hand by the pressure at the expander outlet.

[0068] To control such a drive unit, it is expediently provided that the slide drive can be controlled by a control slide, which controls the application of pressure to the piston at the expander inlet on the one hand and at the expander outlet on the other hand.

[0069] The control slide is preferably designed to detect the positions of the free pistons and move accordingly.

[0070] In particular, it is provided that the control slide is movable by the free pistons.

[0071] In order to be able to supply the expansion unit according to the invention preferably as a single, fully assembled unit and to install it in a refrigerant circuit, it is preferably provided that the expansion unit has a device base on which the subcooling unit and the expansion compression unit are arranged.

[0072] Furthermore, it is advantageous if the control unit is also arranged on the device base.

[0073] In addition, it is advantageous for installation if a high pressure inlet connection and an expansion pressure outlet connection are arranged on the device base.

[0074] Furthermore, in an advantageous solution, a high-pressure outlet connection is arranged on the device base, via which the compressed subcooling mass flow flows out when the expansion unit is installed.

[0075] A further advantageous solution provides for heat exchanger connection units to be provided on the device base, with which several high-pressure side heat exchangers can be connected.

[0076] In particular, each of the heat exchanger connection units is designed in such a way that it has a three-way valve and a bypass for the respective heat exchanger, so that the three-way valve makes it possible to control the flow through the respective heat exchanger.

[0077] In particular, it is provided that at least one of the heat exchanger connection units is connected to a high-pressure side heat exchanger that releases heat to the ambient air.

[0078] In principle, within the framework of the solution described so far, it is conceivable to operate the cooling stage without its own expansion device and to work in the cooling stage with the mass flow expanded by the expansion unit.

[0079] In this case, it is advantageous if a phase separator is arranged following the cooling stage, the gas phase of which is fed to the refrigerant compressor from a suction pressure line.

[0080] Such a phase separator has the advantage that it prevents liquid refrigerant from being fed to the refrigerant compressor for compression.

[0081] Another advantageous solution provides that the cooling stage has at least one expansion element, so that it is possible to set the desired pressure in the cooling stage.

[0082] A further advantageous embodiment provides that an operating adjustment unit is assigned to the refrigerant circuit, which comprises an activatable and deactivatable bypass line that bypasses the expansion compression unit, and that in the event of a suboptimal operating state of the expansion unit, the operating adjustment unit transfers the bypass line from an inactive state to an active state in which it generates a bypass mass flow for the cooling stage by diverting the high-pressure refrigerant and supplies it to the refrigerant circuit for further transmission to the cooling stage.

[0083] The advantage of the solution according to the invention is that the operating adjustment unit according to the invention solves the problem that in the event of unstable operation of the expansion unit, in particular of the expansion-compression unit, the refrigerant circuit is no longer functional or only functional to a very limited extent, so that it cannot provide sufficient cooling capacity to the cooling unit and thus the cooling capacity provided by the refrigerant circuit during normal operation is reduced, which would lead to considerable damage, for example, in refrigerant circuits for cooling systems, in particular for temperature-sensitive goods.

[0084] Such a problem can be avoided by the operation adjustment unit according to the invention, since it is able to continue to provide cooling capacity due to the generated bypass mass flow.

[0085] Furthermore, the invention provides the possibility of either deactivating the operation adjustment unit and activating the expansion compression unit, or deactivating the expansion compression unit and activating the operation adjustment unit, or operating both the expansion compression unit and the operation adjustment unit activated in parallel.

[0086] With regard to the routing of the bypass line, a wide variety of solutions are conceivable.

[0087] An advantageous solution provides that the bypass line of the operating adjustment unit supplies the bypass mass flow directly or indirectly to an expansion line of the refrigerant circuit which receives it.

[0088] This means that the bypass line does not necessarily have to flow directly into the expansion line, but can also flow into the refrigerant circuit upstream of the expansion line, for example, provided that it is ensured that the bypass mass flow is indirectly fed to the expansion line.

[0089] Alternatively or additionally, it is preferably provided that the bypass line supplies the bypass mass flow to a line of the refrigerant circuit which, during normal operation of the refrigerant circuit, carries the expansion pressure mass flow present at expansion pressure.

[0090] This ensures that the refrigerant circuit can essentially continue to operate with the bypass mass flow, since the line carrying the expansion pressure mass flow during normal operation is supplied with the bypass mass flow.

[0091] No further details have been provided so far regarding the control and function of the operational adjustment unit.

[0092] A particularly advantageous solution provides that the operating adjustment unit is controlled in such a way that the operating adjustment unit detects a temperature at the high-pressure side, heat-emitting heat exchanger that is influenced by an ambient temperature in order to activate or deactivate the bypass line.

[0093] By detecting the temperature influenced by the ambient temperature, it is possible to detect conditions in the refrigerant circuit in which the expansion unit enters an unstable operating state.

[0094] A further advantageous solution provides that the operation adjustment unit is controlled in such a way that the operation adjustment unit deactivates the bypass line at a detected temperature which is above a temperature threshold required for a stable operating state of the expansion unit, since stable operation of the expansion unit is possible at such temperatures above the temperature threshold.

[0095] Furthermore, it is preferably provided that the operating adjustment unit is controlled in such a way that the operating adjustment unit activates the bypass line at a detected temperature which is below a temperature threshold necessary for a stable operating state of the expansion unit.

[0096] This makes it possible to avoid, and in particular to prevent, unstable operation of the expansion unit.

[0097] In particular, in the simplest case, it is provided that the operating adjustment unit is controlled in such a way that the operating adjustment unit deactivates the expansion unit after activating the bypass line in order to prevent unstable operating conditions of the expansion unit.

[0098] A further advantageous solution provides that the operation adjustment unit is controlled in such a way that the operation adjustment unit switches off the expansion unit with a delay after the bypass line has been activated, so that there is no abrupt transition of the refrigerant circuit from operation with the expansion unit to operation with the bypass line of the operation adjustment unit activated, but rather the delayed deactivation of the expansion unit results in a period of parallel operation of the expansion unit and the operation adjustment unit, which also prevents unstable operating conditions.

[0099] A further advantageous solution provides that the operation adjustment unit is controlled in such a way that the operation adjustment unit activates or deactivates the bypass line according to a pulse width modulation when the detected temperature is below a lower temperature threshold which is lower than the temperature threshold for activating the bypass line.

[0100] This solution has the advantage that at very low ambient temperatures a very strong reduction in the high pressure occurs, which can be counteracted by operating the bypass line of the operating adjustment unit in a pulse width modulated manner in order to prevent a reduction in the high pressure.

[0101] An advantageous solution provides that a control of the operating adjustment unit is detected based on an expansion fault of the expansion unit.

[0102] Such an expansion disturbance can be detected by various pressure and temperature sensors.

[0103] For example, it is provided that a control of the operating adjustment unit detects the high pressure of the total mass flow or the expansion mass flow before it enters the expander.

[0104] In addition, an advantageous solution provides that the operation adjustment unit is controlled based on a pressure difference between the high pressure of the total mass flow and / or the expansion mass flow before it enters the expander and a line section of the refrigerant circuit at expansion pressure.

[0105] In this case, a differential pressure is recorded to control the operating adjustment unit.

[0106] Another possibility is that the operation adjustment unit is controlled based on the high pressure of the total mass flow or the expansion mass flow before it enters the expander in terms of its absolute value.

[0107] For this purpose, for example, a pressure sensor is provided.

[0108] In order to be able to detect unstable operation of the expansion unit, in particular an expansion fault of the expansion unit, it is further expediently provided that the operation adjustment unit is controlled based on a comparison of the high pressure of the total mass flow or the expansion mass flow before it enters the expander with a reference high pressure.

[0109] A transition of the operational adjustment unit from the inactive state to the active state can be realized particularly advantageously if the operational adjustment unit is assigned a controller which activates and / or deactivates the operational adjustment unit.

[0110] Such a control system compares, for example, the detected high pressure of the total mass flow or the expansion mass flow before it enters the expander with a stored reference pressure, for example.

[0111] There are a variety of options for activating the bypass line.

[0112] A simple solution provides that the bypass line can be activated and deactivated by means of a switching valve, whereby such a switching valve only changes between two states, namely the open and the closed state, so that no control of the size of the mass flow through the bypass line is possible.

[0113] However, this solution allows the switching valve to be designed in such a way that, when activated, it allows the bypass mass flow to pass through without pressure loss, so that an optimally large mass flow flows through the bypass line and any pressure drop can be avoided.

[0114] Alternatively, an advantageous solution provides that at least one expansion element is functionally assigned to the bypass line, which is effective in the activated state of the bypass line and allows control or regulation of the mass flow, i.e. the size of the mass flow.

[0115] Such an expansion element works like a conventional expansion device and is able to completely replace the expansion unit with the expansion compression unit in terms of its function, i.e. the mass flow flowing through the bypass line is in the same order of magnitude as the expansion mass flow that would flow through the expansion unit.

[0116] Such an operating adjustment unit thus opens up the possibility of operating the operating adjustment unit in parallel with the expansion unit, for example, in all cases where the total mass flow in the refrigerant circuit is greater than the mass flow through the expansion unit, so that an increase in high pressure cannot be prevented. In this case, the operating adjustment unit with the expansion element opens up the possibility of counteracting such an increase in high pressure in a controlled manner and thus regulating the high pressure to a desired high pressure level.

[0117] In order to ensure that a defined operation of the refrigerant circuit is possible in the active state of the operating adjustment unit, it is preferably provided that the operating adjustment unit comprises at least one shutdown element for switching off the expansion compression unit.

[0118] This ensures that, for example, a leak in the expansion compression unit does not further disrupt the function of the refrigerant circuit and that faulty operation of the expander and compressor stage does not cause a disruption of the refrigerant circuit that could counteract or even disrupt the function of the operating adjustment unit.

[0119] With regard to the arrangement of the shutdown element, a wide variety of solutions are conceivable.

[0120] An advantageous solution provides that the shutdown element of the operating adjustment unit is arranged either before an expander inlet or after an expander outlet, so that it is primarily possible to switch off the expander of the expansion compression unit.

[0121] In addition, an advantageous solution provides that a switching element is arranged in the bypass line of the operating adjustment unit, which creates a direct or indirect connection between an expansion element for generating the subcooling mass flow of the expansion unit and an expansion pressure output connection of the expansion unit.

[0122] This solution has the advantage that an expansion device already present in the expansion unit for generating a subcooling mass flow can be used by the operating adjustment unit to generate the bypass mass flow instead of the subcooling mass flow, so that no additional expansion device is required in the operating adjustment unit.

[0123] For example, it is provided that the switching element can be controlled with the control of the operating adjustment unit.

[0124] It is particularly advantageous if the switching element is a switching valve.

[0125] Another advantageous solution provides that the switching element is a 3 / 2-way valve, which connects either the bypass line or an expander outlet with the expansion pressure outlet connection.

[0126] Preferably, a 3 / 2-way valve also serves to close the expander outlet when the bypass line is connected to the expansion pressure outlet connection or to close the bypass line when the expander outlet is connected to the expansion pressure outlet connection.

[0127] Alternatively or in addition to the embodiments described so far, a further solution to the problem according to the invention provides that a pulsation damper unit is arranged in the refrigerant circuit.

[0128] Such a pulsation damper unit has the great advantage of being able to dampen pulsations, in particular pulsations generated by the expansion-compression unit, in order to prevent damage and / or noise in the refrigerant circuit caused by such pulsations.

[0129] A variant of such a pulsation damper unit provides that it has a damper housing enclosing a damper chamber in which at least one gas bubble of refrigerant is formed and that the gas bubble absorbs pulsations via a pulsation transmission line leading to a line of the refrigerant circuit and is able to dampen them.

[0130] In the case of operation of the refrigerant circuit in the transcritical range, this usually leads to the refrigerant being in the transcritical range and thus transmitting the pulsations in this state.

[0131] However, pulsations are more serious when the refrigerant is in the subcritical range in the refrigerant circuit, as the pulsations then spread through the refrigerant in the liquid state.

[0132] For this reason, particularly in the case of operation of the refrigerant circuit in the subcritical range, it is provided that the gas bubble is located above a refrigerant bath and, in particular in this case, there is liquid refrigerant in the pulsation transmission line, which transfers the pulsations into the refrigerant bath of liquid refrigerant.

[0133] In order to ensure that a gas bubble is always present in the pulsation damper unit, it is preferably provided that the pulsation damper unit is provided with a heater to maintain the gas bubble of refrigerant, so that even during subcritical operation of the refrigerant circuit it can be ensured that the gas bubble damping the pulsations is always present in the pulsation damper unit in sufficient size.

[0134] For example, the pulsation damper unit, in particular its damper housing, is heated by coupling the heating with a heat transport circuit, which extracts heat in the refrigerant circuit to a pressure in the range of high-pressure compressed refrigerant.

[0135] Another variant of a pulsation damper unit according to the invention provides that the pulsation damper unit has a damper housing with a piston movable therein and two chambers adjacent to the piston on opposite sides and separated from each other by the piston, and that a gas bubble of refrigerant is formed in at least one of the chambers.

[0136] In this case, the piston also serves to exert a damping effect through the gas bubble that forms in at least one of the chambers.

[0137] It is particularly advantageous if the piston itself in the damper housing is additionally loaded by elastic elements, for example springs, which hold the piston in an initial position, from which the piston can then move against the force effect of the elastic elements to dampen pulsations.

[0138] In order to achieve optimal pulsation damping in this case, it is preferably provided that each of the chambers is connected by means of a pulsation transmission line to different flows of refrigerant-carrying lines of the refrigerant circuit.

[0139] Thus, such a pulsation damper unit serves in particular to dampen pulsations by using a connection between different flows of refrigerant-carrying lines, which may for example also be at different pressure levels, to dampen pulsations in one of the two lines or in both of these lines, whereby these lines remain decoupled by the piston, but a pulsation in one of the lines can be transmitted to the other of the lines in a dampened manner and thus, in addition to the piston itself, a damping effect occurs through the coupling of the different flows of refrigerant-carrying lines.

[0140] For example, in such a case, it is provided that one pulsation transmission line is directly or indirectly connected to an inlet of the heat-dissipating heat exchanger and the other pulsation transmission line is directly or indirectly connected to an outlet of the heat-dissipating heat exchanger.

[0141] Furthermore, the damping effect of such a pulsation damper unit can be further improved if at least one pulsation transmission line is coupled to the refrigerant circuit via a throttle.

[0142] Alternatively or in addition to the solutions described so far, the problem mentioned above is also solved by arranging an intermediate pressure collector between the expansion unit and the cooling stage, in whose bath a liquid phase of the refrigerant collects and in whose gas volume above the bath a gas phase of the refrigerant collects.

[0143] In this solution, the liquid phase is preferably fed to the cooling stage for expansion in the expansion device thereof.

[0144] In this case, the intermediate pressure receiver has the advantage that additional subcooling can be achieved by the refrigerant kept at intermediate pressure in the intermediate pressure receiver.

[0145] In the case of an intermediate pressure collector, it is preferably provided that an additional mass flow is discharged from the gas volume of the intermediate pressure collector.

[0146] Such an additional mass flow can be supplied in particular via an expansion device of the suction pressure line.

[0147] In addition, there is the possibility that the additional mass flow expanded by the expansion device additionally subcools a main mass flow led to the cooling stage in a heat exchanger, so that the main mass flow can be cooled even further.

[0148] Furthermore, it is preferably also possible within the scope of this solution for a deep-freeze stage in the form of a booster to be added to the cooling stage.

[0149] The provision of an intermediate pressure collector and an expansion device for controlling the additional mass flow discharged from the intermediate pressure collector also creates the possibility of regulating an intermediate pressure in the intermediate pressure collector to a specific pressure value by means of an intermediate pressure control that controls the expansion device.

[0150] In the solutions known from the prior art, regulation to a fixed pressure value of the intermediate pressure is usually carried out, which is in particular independent of the regulation or control of the high pressure in the total mass flow, which is carried out via the control assigned to the expansion unit.

[0151] However, in order to improve the COP (coefficient of performance), i.e. the ratio of cooling capacity to mechanical power used, especially in summer operation, or to expand a functional range of the expansion compression unit, especially in continued operation, several alternatives are conceivable.

[0152] One solution is that the intermediate pressure control controlling the expansion device detects the pressure and / or the temperature of the total mass flow in the high-pressure discharge line as well as the value of the inlet pressure of the compressor stage and controls the intermediate pressure in such a way that a predetermined value of the inlet pressure is set that is suitable for these detected values.

[0153] Another favorable solution provides that the pressure value to which the intermediate pressure in the intermediate pressure receiver is regulated by the intermediate pressure control is determined from a base value, for example a value in the range of 30 bar to 45 bar in the case of CO2 as refrigerant, and additional values ​​with amounts, for example in the range of 0.5 bar to 7 bar in the case of CO2 as refrigerant.

[0154] This solution has the advantage that additional efficiency increases are possible by adjusting the intermediate pressure and, for example, also due to the feedback on the expansion unit, in particular on the inlet pressure of the compressor stage.

[0155] For example, this is achieved by having the surcharge values ​​have positive values ​​for summer operation and negative values ​​for winter operation, with the amounts of the surcharge values ​​being in the range mentioned above.

[0156] Furthermore, it is advantageous if the size of the additional values ​​depends on the high pressure values ​​that occur when the high pressure is regulated.

[0157] This means that depending on the values ​​set by the control of the high pressure by means of the expansion unit mentioned above, the size of the additional values ​​also varies.

[0158] For example, in summer operation, the additional values ​​are planned to be higher at high high pressure values ​​than at low high pressure values.

[0159] Furthermore, it is advantageously provided that in winter operation the additional values ​​are smaller at high high pressure values ​​than at low high pressure values.

[0160] The amounts of the surcharge values ​​are in the above-mentioned range of 0.5 bar to 7 bar.

[0161] No further details were given regarding the expansion unit itself, except that it comprises an expansion-compression unit with an expander and a compressor stage.

[0162] Furthermore, the invention relates to an expansion unit, in particular for a refrigerant circuit according to one or more of the preceding features, comprising an activatable and deactivatable expansion compression unit having an expander stage and a compressor stage, which expands an expansion mass flow supplied at a high pressure inlet connection from high pressure to an expansion pressure.

[0163] Such expansion units are also known from the state of the art, although these expansion units also have the problem of operating them as optimally as possible.

[0164] In order to avoid instabilities during operation of the expansion unit according to the invention, it is provided in an expansion unit, in particular with the features known from the prior art mentioned at the outset, that the expansion unit has a mass flow return for the compressor stage, with which a mass flow can be controlled from a line leading away from the compressor outlet to a line leading to the compressor inlet.

[0165] Such mass flow feedback also makes it possible to suppress or prevent instabilities in the expansion unit by controlling the mass flow through the compressor.

[0166] In order to stabilize the operation of the expansion unit, the solution according to the invention provides that the expansion unit has a control which, in order to stabilize the operation of the same, determines a temperature of the refrigerant present on the high-pressure side before entering the subcooling unit and a temperature of the refrigerant exiting the subcooling unit and present at the inlet pressure of the compressor stage, that the control determines a temperature difference between these two temperatures and checks whether this is greater or smaller than a maximum difference, and in the event that this is greater than the maximum difference, activates and / or increases the mass flow through the mass flow return.

[0167] Preferably, the maximum difference is in the range of 2 to 5 Kelvin.

[0168] It is preferably provided that the mass flow return has a compressor bypass line and a control valve associated therewith, for example an expansion device, in order to be able to control or regulate the mass flow through the mass flow return.

[0169] In addition to this, a further advantageous solution provides that the expansion unit has a control which, in order to stabilize the operation of the same, determines a temperature of the refrigerant present on the high-pressure side after leaving the subcooling unit and a temperature of the refrigerant present before entering the subcooling unit, expanded to subcooling pressure, that the control determines a temperature difference between these two temperatures and checks whether this is smaller or larger than a minimum difference, and in the event that this is smaller than a minimum difference, activates and / or increases the mass flow through the mass flow return.

[0170] Preferably, the minimum difference is in the range of 2 to 4 Kelvin.

[0171] A further advantageous solution provides that the expansion unit has a control which, in order to stabilize the operation of the expansion unit, determines a pressure of the refrigerant present at the inlet pressure of the compressor stage, determines the evaporation temperature of the same therefrom, and also determines the temperature of the refrigerant rotating out of the subcooling unit and present at the inlet pressure of the compressor stage, and determines a superheat difference from these temperatures and, in the event that this superheat difference is smaller than a minimum superheat value, activates and / or increases the mass flow recirculation.

[0172] In particular, the minimum superheat value is in the range of 3 to 7 Kelvin.

[0173] In addition, a further solution provides that the expansion unit has a control which determines an opening degree of the expansion element controlling the subcooling mass flow and controls the control valve of the mass flow return according to the opening degree.

[0174] As an alternative or in addition to the solutions described above, the expansion unit can also be stabilized with regard to its operation in that the expansion unit has a control system which, in order to stabilize its operation, determines a temperature of the refrigerant present on the high-pressure side before entering the subcooling unit and a temperature of the refrigerant exiting the subcooling unit and present at the inlet pressure of the compressor stage, that the control system determines a temperature difference between these two temperatures and checks whether this is greater or smaller than a maximum difference and, in the event that this is greater than the maximum difference, generates and / or increases a bypass mass flow by activating the bypass line.

[0175] In addition or alternatively, a further advantageous solution provides that the expansion unit has a control which, in order to stabilize the operation of the same, determines a temperature of the refrigerant present on the high-pressure side after exiting the subcooling unit and a temperature of the refrigerant present at subcooling pressure before entering the subcooling unit, that the control determines a temperature difference between these two temperatures and checks whether this is smaller or larger than a minimum difference, and in the event that this is smaller than a minimum difference, generates and / or increases a bypass mass flow by activating the bypass line.

[0176] Alternatively or in addition to the solutions described above, a further solution provides that the expansion unit has a control which, in order to stabilize the operation of the expansion unit, determines a pressure of the refrigerant present at the inlet pressure of the compressor stage, determines the evaporation temperature of the same from this, and also determines the temperature of the refrigerant emerging from the subcooling unit and present at the inlet pressure of the compressor stage and determines a superheat difference from these temperatures and, in the event that this superheat difference is smaller than a minimum value, generates and / or increases a bypass mass flow by activating the bypass line.

[0177] In addition or alternatively, a further solution provides that the expansion unit has a control which determines a degree of opening of the expansion element controlling the subcooling mass flow and controls the expansion element functionally assigned to the bypass line in accordance with the degree of opening.

[0178] A further advantageous solution provides that the expansion unit has an electrically operating control which detects at least one of the following variables such as a temperature influenced by or corresponding to an ambient temperature, a temperature of the mass flow of the refrigerant supplied to the expansion unit and / or the expander stage, a high pressure of the total mass flow or the expansion mass flow upstream of the expander stage and activates the bypass line and generates the bypass mass flow in accordance with this temperature and / or optionally this high pressure of the total mass flow or the expansion mass flow.

[0179] It is particularly advantageous with this solution if the control system controls the bypass mass flow by controlling the expansion element functionally assigned to the bypass line.

[0180] The object mentioned at the outset is also achieved according to the invention by an expansion unit, in particular comprising the features known from the prior art, in that the expansion unit has an electrically operating control which detects at least one of the following variables such as: a temperature (T amb ) influenced by or corresponding to an ambient temperature, a temperature of the mass flow of the refrigerant supplied to the expansion unit and / or the expander stage, an inlet pressure of the compressor stage, and according to this temperature and / or optionally this inlet pressure of the compressor stage, sets an inlet pressure of the expansion unit or the expander stage and / or optionally a particularly predeterminable inlet pressure of the compressor stage by controlling the subcooling mass flow by means of the expansion element electrically controlled by the control.

[0181] Furthermore, it is preferably provided that the control detects the ambient temperature and / or the temperature of the mass flow of the refrigerant upstream of an inlet of the subcooling unit and / or upstream of an expander inlet by means of a sensor.

[0182] In all the controls described above, it is preferably provided that the control is an electronic control comprising a processor which electrically controls the respective components by means of a control program.

[0183] With regard to the design of the subcooling unit, no further details were given in connection with the exemplary embodiments described above.

[0184] An advantageous solution provides that the subcooling unit is designed as a heat exchanger and cools the mass flow of the refrigerant flowing to the expander stage by the subcooling mass flow guided through it in countercurrent.

[0185] Furthermore, it is expediently provided that the branch is arranged in front of a high-pressure side inlet of the subcooling unit.

[0186] Alternatively, it is provided that the branch is arranged between the subcooling unit and the expansion-compression unit and branches off the subcooling mass flow from the total mass flow after the subcooling unit.

[0187] A further advantageous solution provides that the expander stage and / or the compressor stage of the expansion compression unit are mechanically functionally coupled, in particular rigidly coupled to one another.

[0188] With regard to the design of the expansion-compression unit, it is particularly advantageous if the expander stage and the compressor stage are formed by a free-piston machine in which at least one free piston is freely movable in a piston chamber.

[0189] For example, it is advantageously provided that the expansion compression unit has two piston chambers, in each of which a free piston is movable.

[0190] Furthermore, the free pistons are preferably movable in a coupled manner.

[0191] In the free-piston engine according to the invention, it is preferably provided that a first free piston in the respective piston chamber separates a first expansion chamber and a first compression chamber from one another.

[0192] Furthermore, it is advantageously provided that a second free piston in the respective piston chamber separates a second expansion chamber from a second compression chamber.

[0193] In order to operate the two free pistons in an advantageous manner, it is preferably provided that the two free pistons are arranged coaxially to one another in the piston chambers and are movable.

[0194] Advantageously, the first piston chamber is separated from the second piston chamber by a separating body.

[0195] Advantageous operation of the expansion compression unit can be achieved if the two expansion chambers are arranged adjacent to the separating body in the piston chambers.

[0196] Furthermore, it is preferably provided that the two compression chambers are arranged on the sides of the respective free pistons opposite the expansion chambers.

[0197] In principle, the free pistons can work independently of each other.

[0198] However, an advantageous solution provides that a coupling element coupling the free pistons extends through the separating body and is movable relative to it, in particular in a sealed manner.

[0199] In the simplest case, the coupling element is designed in such a way that it extends through the expansion chambers to the respective free piston.

[0200] With regard to the flow of refrigerant to the expansion chambers, it is preferably provided that these can be controlled by a slide system.

[0201] Such a slide system is designed, for example, as a change-over slide, so that in one slide position the refrigerant flows into one expansion chamber and flows out of the other expansion chamber and in the other slide position the refrigerant flows into the other expansion chamber and flows out of the other expansion chamber.

[0202] To control the slide system, it is preferably provided that the slide system can be controlled by a slide drive with which the two slide positions can be adjusted.

[0203] Such a slide drive can be carried out by an electrical control which detects at least one position of the free pistons by means of at least one position sensor assigned to them.

[0204] Alternatively, an advantageous solution provides that the slide drive can be controlled by a pressure difference between an expander inlet and an expander outlet.

[0205] Preferably, the slide drive is designed as a double-acting actuating cylinder, the piston of which is acted upon on the one hand by the pressure at the expander inlet and on the other hand by the pressure at the expander outlet.

[0206] To control such a drive unit, it is expediently provided that the slide drive can be controlled by a control slide, which controls the application of pressure to the piston at the expander inlet on the one hand and at the expander outlet on the other hand.

[0207] The control slide is preferably designed to detect the positions of the free pistons and move accordingly.

[0208] In particular, it is provided that the control slide is movable by the free pistons.

[0209] In order to be able to supply the expansion unit according to the invention preferably as a single, fully assembled unit and to install it in a refrigerant circuit, it is preferably provided that the expansion unit has a device base on which the subcooling unit and the expansion compression unit are arranged.

[0210] Furthermore, it is advantageous if the control unit is also arranged on the device base.

[0211] In addition, it is advantageous for installation if a high pressure inlet connection and an expansion pressure outlet connection are arranged on the device base.

[0212] Furthermore, in an advantageous solution, a high-pressure outlet connection is arranged on the device base, via which the compressed subcooling mass flow flows out when the expansion unit is installed.

[0213] A further advantageous solution provides for heat exchanger connection units to be provided on the device base, with which several high-pressure side heat exchangers can be connected.

[0214] In particular, it is provided that at least one of the heat exchanger connection units is connected to a high-pressure side heat exchanger that releases heat to the ambient air.

[0215] In addition, in an expansion unit of the type mentioned above, it is provided that the expansion compression unit is assigned an operating adjustment unit which comprises an activatable and deactivatable bypass line bypassing the expansion compression unit, and that the operating adjustment unit, in the event of a suboptimal operating state of the expansion unit, transfers the bypass line from an inactive to an active state in which it generates a bypass mass flow by diverting the high-pressure refrigerant and feeds it to an expansion pressure output connection.

[0216] The advantage of the solution according to the invention can also be seen in the fact that the operating adjustment unit according to the invention solves the problem that, in the event of unstable operation of the expansion unit, in particular of the expansion-compression unit, its function is limited with regard to the expansion to be achieved, so that sufficient cooling capacity can no longer be provided in a refrigerant circuit. The operating adjustment unit according to the invention solves this problem by being able to generate a bypass mass flow and supply it to the expansion pressure output connection of the expansion unit.

[0217] In addition to the solution according to the invention described above, it is provided that in an expansion unit, in particular with the features known from the prior art, the expansion unit has a subcooling unit for subcooling at least the expansion mass flow of the refrigerant supplied to the expansion unit, that the expansion unit has the expansion-compression unit comprising the expander stage and the compressor stage, a branch which branches off a subcooling mass flow from the total mass flow supplied to the expansion unit and which is connected to a supply line which leads the subcooling mass flow to an inlet of the subcooling unit, that the expansion unit has an expansion element provided in the supply line which expands the subcooling mass flow to a subcooling pressure, and that the expansion unit has a connecting line,which feeds the subcooling mass flow emerging from the subcooling unit to the compressor stage, which in turn compresses the subcooling mass flow to a return high pressure, which in particular corresponds to at least one high pressure of a compressor mass flow to which the subcooling mass flow is fed.

[0218] Such a design of the expansion unit allows it to be operated with high energy efficiency.

[0219] The expansion unit according to the invention thus provides the possibility of deactivating the operational adjustment unit and activating the expansion compression unit or of deactivating the expansion compression unit and activating the operational adjustment unit or of operating both the expansion compression unit and the operational adjustment unit activated in parallel.

[0220] No further details have been provided so far regarding the activation and deactivation of the operational adjustment unit and the expansion compression unit.

[0221] An advantageous solution provides that the operating adjustment unit is controlled in such a way that the operating adjustment unit is activated and the expansion compression unit is activated.

[0222] In this case, it is particularly possible to use the operating adjustment unit to compensate for the mass flow through the expansion compression unit in order to be able to adapt the overall flow of the various mass flows in the expansion unit.

[0223] Another possibility is to control the operating adjustment unit in such a way that after the bypass line is activated, the expansion compression unit is deactivated.

[0224] This is particularly intended if the expansion is to be carried out by the operating adjustment unit alone, since the expansion unit runs so unstably that it makes the most sense to deactivate the expansion compression unit.

[0225] Alternatively, another solution provides that the operation adjustment unit is controlled in such a way that after the bypass line is activated, the expansion compression unit is deactivated with a delay, so that parallel operation of the operation adjustment unit and the expansion compression unit is provided for a certain period of time, during which the operation of the expansion unit can be stabilized, but that if instabilities continue to occur during the operation of the expansion unit, the expansion compression unit is deactivated.

[0226] No further details have been provided so far regarding the type of parameters intended to control the operational adjustment unit.

[0227] An advantageous solution provides that the operating adjustment unit is controlled in such a way that the operating adjustment unit detects a temperature influenced by an ambient temperature in order to activate or deactivate the bypass line.

[0228] This can either be the ambient temperature directly or a temperature influenced by the ambient temperature, in particular a temperature proportional to it or changed by a certain offset.

[0229] A particularly simple solution provides for the control of the operating adjustment unit in such a way that the operating adjustment unit deactivates the bypass line when the detected temperature is above a temperature threshold required for a stable operating state of the expansion unit, i.e. in this case the operating adjustment unit is inactive and the expansion compression unit is active.

[0230] Another advantageous solution provides that the operating adjustment unit is controlled in such a way that the operating adjustment unit activates the bypass line when the detected temperature is below a temperature threshold necessary for a stable operating state of the expansion unit, i.e. in this case the operating adjustment unit is active, wherein in this case the operating adjustment unit can be operated in parallel to the active expansion compression unit or, if further major instabilities occur in the area of ​​the expansion unit, the expansion compression unit can be deactivated.

[0231] In addition, a further advantageous solution provides that the operation adjustment unit is controlled in such a way that, at a detected temperature which is below a lower temperature threshold which is lower than the temperature threshold for activating the bypass line, the operation adjustment unit either activates or deactivates the bypass line at intervals or controls a mass flow through the bypass line by means of an expansion device.

[0232] The advantage of this solution is that it makes it possible to control the mass flow through the bypass line at very low temperatures either by activating and deactivating it at intervals or by means of an expansion device.

[0233] No further details have been provided so far regarding the control of the expansion unit.

[0234] An advantageous solution provides that the operating adjustment unit is controlled based on an expansion disturbance of the expansion unit.

[0235] Such expansion control of the expansion unit can be detected either by strong pressure fluctuations, for example of the high pressure, or by temperature fluctuations, for example of the temperatures at the subcooling unit.

[0236] A further advantageous solution provides that a control of the operating adjustment unit detects the high pressure of the total mass flow entering at the high pressure inlet connection or of the expansion mass flow before it enters the expander stage.

[0237] A further advantageous solution provides that the operation adjustment unit is controlled based on a pressure difference between the high pressure of the total mass flow or the expansion mass flow before it enters the expander and the expansion pressure output connection.

[0238] Another possibility for controlling the operational adjustment unit is that it is based on the high pressure of the total mass flow or the expansion mass flow before it enters the expander stage with regard to an absolute value.

[0239] Another solution provides for the control of the operation adjustment unit based on a comparison of the high pressure of the total mass flow or the expansion mass flow before it enters the expander stage with a predetermined reference high pressure.

[0240] With regard to the design of the control of the operational adaptation unit, a wide variety of options are conceivable.

[0241] An advantageous solution provides that the operational adjustment unit is assigned a control which activates and / or deactivates the operational adjustment unit.

[0242] With regard to the activation or deactivation of the bypass line, a wide variety of designs are conceivable.

[0243] A particularly simple embodiment provides that the bypass line can be activated and deactivated by means of a switching valve.

[0244] This means that with such a simply constructed switching valve, it is not possible to continuously control the mass flow through the bypass line, but only to activate and deactivate it.

[0245] The only way to control the mass flow is then to activate or deactivate the switching valve at intervals.

[0246] Such a switching valve can preferably be designed so that, in the activated state, it allows the bypass mass flow to pass without pressure loss.

[0247] Another advantageous solution provides that at least one expansion element is functionally assigned to the bypass line, which is effective in the activated state of the bypass line and which opens up the possibility of controlling the bypass mass flow.

[0248] In order to deactivate the expansion compression unit in a simple manner, it is preferably provided that the expansion unit has at least one shutdown element for deactivating the expansion compression unit.

[0249] The shutdown element is preferably arranged either before an expander input or after an expander output.

[0250] A further solution provides that a switching element is provided in the bypass line of the operating adjustment unit, which establishes a direct or indirect connection between the expansion element for generating the subcooling mass flow of the expansion unit and an expansion pressure output connection of the expansion unit.

[0251] In this case, no separate expansion device is required in the bypass line, but the bypass line is arranged in such a way that the expansion device can be used to generate the subcooling mass flow to activate the bypass mass flow, whereby in this case preferably no subcooling mass flow occurs, since in this case the expansion compression unit is expediently deactivated.

[0252] The switching element can either be controlled by a control of the expansion unit.

[0253] However, it is also conceivable to control the switching element with a control of the operating adjustment unit.

[0254] In the simplest case, the switching element is designed as a switching valve.

[0255] Another solution provides for the switching element to be a three-way / two-way valve, which connects either the bypass line or an expander outlet to the expansion pressure outlet connection. Further features and advantages of the invention are the subject of the following description and the drawings of some exemplary embodiments.

[0256] The drawing shows: Fig. 1 is a schematic representation of a first embodiment of a refrigerant circuit according to the invention with a first embodiment of an expansion unit according to the invention with a first embodiment of an operational adjustment unit; Fig. 2 is an enlarged schematic representation of the first embodiment of an expansion unit according to the invention with the first embodiment of an operational adjustment unit; Fig. 3 is a schematic representation of a first embodiment of an expansion unit according to the invention; Fig. 4 is a schematic representation similar Fig. 3 a second embodiment of an expansion unit according to the invention; Fig. 5 a schematic representation of a second embodiment of the refrigerant circuit according to the invention with a second embodiment of an operational adjustment unit; Fig. 6 a schematic representation of the first embodiment of the expansion unit with a third embodiment of an operational adjustment unit; Fig. 7 a schematic representation of the first embodiment of the expansion unit with a fourth embodiment of an operational adjustment unit; Fig. 8 a schematic representation of the first embodiment of the expansion unit with a fifth embodiment of an operational adjustment unit; Fig. 9 a schematic representation of a second embodiment of an expansion unit according to the invention with a sixth embodiment of an operational adjustment unit; Fig.10 shows a schematic representation of a third embodiment of an expansion-compression unit according to the invention with the sixth embodiment of the operational adjustment unit; Fig. 11 shows a schematic representation of the first embodiment of the expansion unit with a seventh embodiment of an operational adjustment unit in a first position of a 3 / 2-way valve; Fig. 12 shows a schematic representation of the first embodiment of an expansion unit with the seventh embodiment of an operational adjustment unit in a second position of the 3 / 2-way valve; Fig. 13 shows a schematic representation of a third embodiment of an expansion unit; Fig. 14 shows a schematic representation of a third embodiment of the expansion unit with a modified compressor bypass; Fig.15 a schematic representation of the third embodiment of the expansion unit with a second embodiment of the operational adjustment unit integrated into the expansion system; Fig. 16 a schematic representation of a third embodiment of a refrigerant circuit according to the invention; Fig. 17 a schematic representation of a fourth embodiment of a refrigerant circuit according to the invention; Fig. 18 a schematic representation of a fifth embodiment of a refrigerant circuit according to the invention; Fig. 19 a flow chart relating to the activation or deactivation of the expansion units with the expansion compression units and the operational adjustment units in the embodiments according to. Fig. 1 bis 18 ; Fig. 20 a diagram illustrating the activation and / or deactivation of the expansion units with the expansion compression units and the operation adjustment units in the embodiments according to Fig. 1 bis 18 graphically; Fig. 21 a schematic representation of the third embodiment of the refrigerant circuit according to the invention corresponding Fig. 16 with an operational adjustment unit in which a bypass mass flow is not adjustable or controllable but only activated or deactivated; Fig. 22 a schematic representation of a fourth embodiment of a refrigerant circuit according to the invention corresponding Fig. 17 with an operational adjustment unit in which the bypass mass flow is not controllable or regulatable but only activatable or deactivatable; Fig. 23 a schematic representation of the fifth embodiment of a refrigerant circuit according to the invention with an operational adjustment unit in which the mass flow is not controllable or regulatable but only activatable or deactivatable and Fig. 24 a flow chart for the activation or deactivation of the expansion units with the expansion compression units in the embodiments according to the Fig. 21 and 23 and Fig. 25 a diagram schematically showing the activation and / or deactivation of the expansion units with the expansion compression units and the operation adjustment units in the embodiments according to the Fig. 21 bis 23 represents.

[0257] A first embodiment of a refrigeration system according to the invention, shown in Fig. 1 , comprises a first embodiment of a refrigerant circuit according to the invention, designated as a whole by 10, in which a refrigerant compressor unit, designated as a whole by 12, is arranged, which comprises, for example, at least one refrigerant compressor.

[0258] The refrigerant compressor unit 12 has a suction connection 14 and a pressure connection 16, wherein refrigerant compressed to high pressure PH1 is usually present at the pressure connection 16.

[0259] The term "high-pressure compressed refrigerant" means that the refrigerant has the highest pressure present in the refrigerant circuit.

[0260] From the pressure connection 16, a high-pressure line 18 carries a compressor mass flow V compressed by the refrigerant compressor unit 12 to high pressure PH1 to an inlet 24 of a high-pressure side heat-emitting heat exchanger, designated as a whole by 22, which releases heat in particular to the ambient air and thus cools the refrigerant, so that at an outlet 26 of the high-pressure side heat exchanger 22 there is a total mass flow G of refrigerant cooled by the high-pressure side heat exchanger 22, which is fed from a high-pressure discharge line 28 carrying refrigerant at a high pressure PH2, which is slightly lower than the high pressure PH1 due to the heat exchanger 22, to a high-pressure regulating expansion unit 32, designated as a whole by 32, which has a high-pressure inlet connection 34 connected to the high-pressure discharge line 28, an expansion pressure outlet connection 36 and a high-pressure outlet connection 38.

[0261] The expansion pressure outlet connection 36, which is at an expansion pressure PE, is connected to an expansion line 42, which in the case of Fig. 1 illustrated simplest embodiment leads to a cooling stage 62 which, in the simplest case, has a heat exchanger 64 which absorbs heat from an external medium for cooling this medium.

[0262] In this simplified embodiment, the heat-absorbing heat exchanger 64 is at the expansion pressure PE, so that no separate expansion valve is connected upstream of this heat exchanger 64.

[0263] To protect the refrigerant compressor unit 12, a phase separator 72 is connected downstream of the heat-absorbing heat exchanger 64, which is arranged in a suction pressure line 74 that leads from the cooling stage 62 to the suction connection 14 of the refrigerant compressor unit 12 and prevents liquid refrigerant from being sucked in by the refrigerant compressor unit 12 at the suction connection 14.

[0264] From the expansion pressure outlet connection 36, an expansion pressure mass flow EPM at expansion pressure PE thus flows through the expansion line 42 to the cooling stage 62 and from the cooling stage 62 in turn via the suction pressure line 74 to the refrigerant compressor unit 12.

[0265] In this case, the expansion pressure mass flow EPM does not correspond to the total mass flow, but in the expansion unit 32 the total mass flow G is divided into an expansion mass flow EM and a subcooling mass flow UM, which is discharged from the expansion unit 32 at the high pressure outlet connection 38 at a return pressure PR as a subcooling return mass flow URM of a return line 78 and is fed from there to the compressor mass flow V before it enters the heat-emitting high-pressure side heat exchanger 22.

[0266] The refrigerant circuits 10 according to the invention, which are described below, are all preferably designed for carbon dioxide, that is to say CO2, or ammonia, so that under common ambient conditions a transcritical cycle usually occurs, in which only before the expansion of the refrigerant is carried out by the expansion unit 32, for example by means of the heat exchanger 22, the refrigerant is cooled to a temperature which corresponds to the isotherm running above the dew and boiling line or saturation curve, so that there is no liquefaction of the refrigerant.

[0267] Only in the case of very low temperatures for cooling the high-pressure side heat-emitting heat exchanger is it possible to carry out a subcritical cycle, so that in this case condensation of the refrigerant takes place at a temperature which corresponds to an isotherm passing through the dew and boiling line or saturation curve of the refrigerant.

[0268] The first embodiment of the expansion unit 32 designed according to the invention used in the first embodiment of the refrigerant circuit comprises, as shown in Fig. 2 Shown enlarged, an expansion system 30 having a device base designated as a whole by 82, on which the high-pressure inlet connection 34, the expansion pressure outlet connection 36, and the high-pressure outlet connection 38 are arranged. Furthermore, in the expansion system 30, an expansion-compression unit 84 is connected to the device base 82. The expansion-compression unit 84 comprises an expander stage 86 and a compressor stage 88, which are integrated in the expansion-compression unit 84 and rigidly coupled to one another.

[0269] The expansion compression unit 84 includes an expander inlet 92 and an expander outlet 94 connected to the expansion pressure output port 36, as well as a compressor inlet 96 and a compressor outlet 98, which in turn is connected to the high pressure output port 38.

[0270] Furthermore, in the expansion system 30, a subcooling unit 102 is arranged on the device base 82, which in the first embodiment is designed as a counterflow heat exchanger and has an inlet 104 and an outlet 106 for the mass flow to be cooled, in particular in this case the total mass flow G, as well as an inlet 112 and an outlet 114 for the subcooling mass flow UM guided as a counterflow through the heat exchanger.

[0271] The subcooling mass flow UM is branched off in the expansion system 30 at a branch 116 from the subcooled total mass flow G exiting at the outlet 106 of the subcooling unit 102, so that an expansion mass flow EM is guided from the branch 116 through a feed line to the expander inlet 92 and the subcooling mass flow UM is guided through a shut-off device 124 and an expansion device 122 driven by an actuator 123 in the feed line 126, in which the subcooling mass flow UM is expanded to a pressure PU, and then fed to the inlet 112 of the subcooling unit 102, wherein the subcooling mass flow UM in the subcooling unit 102 subcools the total mass flow G flowing from the inlet 104 to the outlet 106 in countercurrent and from the outlet 114 via a connecting line 128 to the compressor inlet 96 is supplied.

[0272] The mechanical energy released in the expander stage 86 by expansion of the expansion mass flow EM is fed directly to the compressor stage 88 in the expansion compression unit 84 by a mechanical functional coupling and leads therein to a compression of the subcooling mass flow UM from an inlet pressure EP of the compressor stage 88 present at the outlet 114 of the subcooling unit 102 to a return high pressure PR which corresponds to or is higher than the pressure level PH1 in the high pressure line 18, so that the subcooling return mass flow URM can be fed from the high pressure outlet connection 38 via a high pressure return line 78 to the compressor mass flow V.

[0273] Furthermore, a controller 132 is provided in the expansion system 30, which on the one hand, for example with a sensor 134, which is in particular a pressure and / or temperature sensor, detects the temperature of the mass flow of the refrigerant before its expansion in the expansion stage 86 and, for example, controls the expansion element 122 according to this temperature by means of the actuator 123.

[0274] For this purpose, the sensor 134 is arranged, for example, between the branch 116 and the expander stage 86 as sensor 134 1.

[0275] Furthermore, a pressure and / or temperature sensor 135 is assigned to the control, with which it is able to detect the inlet pressure EP of the compressor stage 88.

[0276] Alternatively or additionally, the sensor 134 can also be used as sensor 134 2 between the high-pressure inlet connection 34 and the subcooling unit 102.

[0277] Alternatively or additionally, it is provided in particular that the sensor 134 as sensor 134s measures the ambient temperature, which significantly influences the temperature of the total mass flow G of the refrigerant at the outlet 26 of the heat exchanger 22, in particular due to the ambient air flowing through the heat exchanger 22.

[0278] The controller 132 can, for example, operate autonomously, so that the controller 132 is part of the expansion system 30 installed as an independent unit in the refrigerant circuit.

[0279] However, it is also provided that the control 132 is coupled to an external controller 138, which - as in Fig. 1 shown - alternatively or in addition to the sensors 134, the temperature of the total mass flow G in the high-pressure compartment 28 and / or the temperature or pressure in the refrigerant compressor 12 is detected in order to control the actuator 123 directly or indirectly or by means of the controller 132.

[0280] The expansion element 122 serves to control the subcooling mass flow UM and thereby to regulate the high pressure PH2 at the high pressure inlet connection 34 and thus also the high pressure PH2 in the high pressure discharge line 28 according to a relationship specified by the controller 132 and / or the external regulator 138, in particular a relationship stored therein as a file or algorithm, as a function of the respectively measured temperature of the refrigerant and thus as a function of the possibilities for cooling the refrigerant located on the high pressure PH2, for example as a function of the ambient temperature present for cooling in the heat exchanger 22.

[0281] The controller 132 and / or the external regulator 138 comprise, for example, a processor and a memory in which an algorithm or a correlation table is stored, by means of which a correlation between the settings of the expansion element 122 and the measured temperatures or pressures is stored, so that the settings of the expansion element 122, made by the actuator 123 controlled by the controller 132, result in the high pressure PH2 corresponding to the temperature being set at the high pressure inlet connection 34 and / or at the inlet 104 of the subcooling unit 102 and / or at the expander inlet 92.

[0282] The control of the high pressure PH2 by controlling the subcooling mass flow UM is possible because, due to the mechanical functional coupling of the expander 86 with the compressor stage 88, the expansion mass flow EM is directly correlated with the subcooling mass flow UM according to a fixed volume ratio, so that the expansion mass flow EM can be specified by specifying the subcooling mass flow UM. Typically, the subcooling mass flow UM comprises approximately 15% to 35% of the total mass flow G, so that the expansion mass flow EM comprises approximately 85% to 65% of the total mass flow G.

[0283] In particular, the high pressure PH2 is controlled such that in the subcooling unit 102 the temperature of the total mass flow G on the hot side, i.e. at the inlet 104, is only a few Kelvin, for example less than 4 Kelvin, even better less than 3 Kelvin, in particular one to two Kelvin, above the temperature of the subcooling mass flow UM at the outlet 114 of the subcooling unit 102 in order to essentially completely evaporate the refrigerant in the subcooling mass flow U.

[0284] In order to be able to reliably monitor the temperature and / or pressure of the subcooling mass flow UM at the outlet 114, a sensor 135 connected to the controller 132 is provided in particular in the connecting line 128.

[0285] However, it is also possible to use the controller 132 and / or 138 to detect the inlet pressure EP by means of the sensor 135 and to regulate it to a suitable value corresponding to the variables such as pressure and / or temperature of the total mass flow G and the size of the inlet pressure EP, wherein the suitable values ​​for the said variables are stored, for example, in the controller 132 and / or 138.

[0286] Due to the arrangement of the control unit 132, the expansion element 122, the subcooling unit 102 and the expansion-compression unit 84 on the device base 82, this unit forms a unit that can be mounted independently in the cooling circuit 10 and that regulates the operating states of the refrigerant circuit 10 by regulating the high pressure PH2 that is present on the output side of the heat-emitting heat exchanger 22.

[0287] As in Fig. 3 As shown, the expansion compression unit, designated as a whole by 84, is designed as a free piston machine having a cylinder housing 142 in which two separate piston chambers 144 and 146 are arranged, wherein a movable free piston 152, 154 is arranged in each piston chamber.

[0288] The free pistons 152 and 154 divide the respective piston chambers 144 and 146 into expansion chambers 162 and 164 and compression chambers 166 and 168.

[0289] Furthermore, the free pistons 152 and 154 are preferably mechanically coupled to one another in such a way that, when the first expansion chamber 162 has a maximum volume, the first piston 152 is positioned such that the first compression chamber 166 has a minimum volume and, at the same time, the second free piston 154 is positioned such that its expansion chamber 164 has a minimum volume while the compression chamber 168 has the maximum volume, or vice versa.

[0290] Thus, for example, an increase in the volume of the first expansion chamber 162 when it is subjected to the high pressure at the expander inlet 92 leads to a compression of refrigerant of the subcooling mass flow U in the first compression chamber 166, simultaneously to a displacement of the refrigerant in the second compression chamber 168 in the direction of the expander outlet 94 and to a suction of refrigerant in the second compression chamber 168 via the compressor inlet 96.

[0291] Conversely, pressurization of the second expansion chamber 164 by high-pressure refrigerant supplied via the expander inlet 92 results in compression of the refrigerant in the second compression chamber 168 and thus in displacement of the same to the compressor outlet 98, while at the same time displacement of the refrigerant in the first expansion chamber 162 takes place in the direction of the expander outlet 94 and suction of refrigerant in the first compression chamber 166 takes place via the compressor inlet 96.

[0292] Preferably, the first free piston 152 and the second free piston 154 are arranged coaxially to one another and move in piston chambers 144 and 146, which are also arranged coaxially to one another and are separated from one another by a separating body 148, wherein the separating body 148 is sealed by a coupling element 172 which couples the movement of the two free pistons 152 and 154.

[0293] In the simplest case, the coupling element 172 can be designed as a coupling rod which passes through the separating body 158 and moves with the free pistons 152, 154, which rod rests freely on the free pistons 152 and 154, i.e. is not firmly connected to them.

[0294] Due to the fact that when refrigerant flows in via the expander inlet 92, the pressure in this expansion chamber 162 or 164 acts on the respective free piston 152 or 154 and at the same time a pressure acts in the respective compression chamber 168 or 166 of the other free piston 154 or 152 which is higher than the pressure at the expander outlet 94, which is present in the respective expansion chamber 164 or 162, a pressure can be generated in the compression chamber 166 or 168 acted upon by the free piston 152 or 154 which is higher than the high pressure present at the expander inlet 92, so that the subcooling mass flow U can be compressed to a pressure present at the compressor outlet 98 which corresponds at least to the high pressure PH1 at the inlet 24 of the heat-emitting heat exchanger or the pressure in the high pressure line 18, although the high pressure PH2,the expander inlet is available due to pressure losses in the heat exchanger 22 is slightly smaller than the high pressure PH1.,

[0295] To connect the compression chambers 166 and 168 to the compressor inlet 96, supply lines 182 are provided from the compressor inlet 96, which lead to the inlet valves 184 and 186 assigned to the compression chambers 166 and 168, and the compressor outlet 98 is also connected to a pressure line 192, which leads from the outlet valves 194 and 196 assigned to the compression chambers 166 and 168, respectively, to the compressor outlet 98.

[0296] An alternating connection between the expander inlet 92 and the expander outlet 94 with the expansion chambers 162 and 164 is made via a slide system 202 which is piston position controlled.

[0297] For example, the slide system 202 comprises a controller 203 which detects the positions of the free pistons 152 and 154, respectively, by means of position sensors 204 and 206 and controls, by means of an electric drive 207, a changeover slide valve designated as a whole by 208, which has two slide positions and, in one slide position, connects the expander inlet 92 to the expansion chamber 162 and the expander outlet 94 to the expansion chamber 164, and in the other slide position, connects the expander inlet to the expansion chamber 164 and the expander outlet 94 to the expansion chamber 162.

[0298] Alternatively, as in Fig. 4 represents, in a slide system 202' a pressure control of the changeover slide 208 is provided, wherein the drive 207' has a pressure-driven cylinder with a piston 205, which is controlled by an auxiliary slide 209 alternately acted upon on the one hand by the pressure at the expander inlet 92 and on the other hand by the pressure at the expander outlet 94 or vice versa, wherein the auxiliary slide 209 is also designed as a changeover slide and whose slide positions are determined by mechanical detection of the positions of the free pistons 152 and 154 in their end positions facing the separating body 148.

[0299] Since, for example, when the expansion compression unit 84 is designed as a free piston machine, malfunctions, for example suboptimal, in particular unstable operating states, can occur, so that no expansion pressure mass flow EPM or no sufficiently large expansion pressure mass flow EPM would be available for the cooling unit 62, no cooling capacity would be available at the cooling unit 62, so that the refrigerant circuit 10 would no longer be functional.

[0300] In addition, the high pressure PH1 and PH2 would rise to a level that would cause damage to the heat exchanger 22 and / or the refrigerant compressor 12.

[0301] For this reason, the refrigerant circuit 10 is provided with an operation adjustment unit 230 which prevents this case.

[0302] A first embodiment of an operational adjustment unit 230 provided in the expansion system 30 comprises, for example, an additional expansion element 232, which is arranged in a bypass line 234, which in turn is connected in parallel with the expander stage 86, in particular between its expander inlet 92 and expander outlet 94, and is designed as a controllable expansion element that can be controlled by the controller 132 or 138, which, for example, detects the high pressure PH2 and then opens in a controlled manner when a predeterminable high pressure level is exceeded and acts as an expansion element in the bypass line 234, so that a bypass mass flow ULM is supplied to the expansion line 42 through the expansion element 232 in the bypass line 234, which can then absorb heat in the cooling unit 62, so that the refrigerant circuit 10 can continue to run stably ( Fig. 1 and Fig. 2 ).

[0303] The bypass mass flow ULM is controlled in such a way that the intended maximum of the high pressure PH1 and PH2 is not exceeded.

[0304] With activation of the bypass line 234 or independently thereof, the expansion compression unit 84 can be deactivated by means of a switching valve 236, wherein the switching valve is controlled by the controls 132 and 138 or by a separate control to deactivate the expansion compression unit 84 if, for example, one or more of the sensors 134 1 , 134 2 and 135 detects an unstable operating state of the expansion unit 32, in particular one that cannot be stabilized by further measures.

[0305] In order to keep the operation of the expansion unit 32 stable over the widest possible ranges, a mass flow return 240 is provided which is assigned to the compressor 88 and which comprises a compressor bypass line 242 which connects the line 128 leading to the compressor inlet 96 with a line leading away from the compressor outlet 98 and in which a controlled control valve 244 is provided with which a returned mass flow flowing through the compressor bypass line 242 from the compressor outlet 98 to the compressor inlet 96 can be controlled in order to reduce the subcooling mass flow UM.

[0306] The control valve 244 can be controlled in a variety of ways.

[0307] In a first variant, it is provided that the controller 132, 138, in order to stabilize the operation of the expansion unit 32, determines a temperature of the refrigerant present on the high-pressure side before entering the subcooling unit 102 and a temperature of the refrigerant exiting the subcooling unit and present at the inlet pressure of the compressor stage, that the controller 132, 138 determines a temperature difference between these temperatures and checks whether this is greater or smaller than a maximum difference, and in the event that this is greater than the maximum difference, activates and / or increases the mass flow through the mass flow return.

[0308] Preferably, the maximum difference is in the range of two to five Kelvin.

[0309] A variant of the control of the control valve 244 provides that the controller 132, 138, in order to stabilize the operation of the expansion unit 32, determines a temperature of the refrigerant present on the high-pressure side after exiting the subcooling unit and a temperature of the refrigerant present before entering the subcooling unit 102, expanded to subcooling pressure PU, that the controller 132, 138 determines a temperature difference between these two temperatures and checks whether this is smaller or larger than a minimum difference, and in the event that this is smaller than the minimum difference, activates and / or increases the mass flow through the mass flow return.

[0310] A further variant concerning the control of the control valve provides that the controller 132, 138 determines a pressure of the refrigerant present at the inlet pressure EP of the compressor stage 88 in order to stabilize the operation of the expansion unit, determines the evaporation temperature of the same and also determines the temperature of the refrigerant emerging from the subcooling unit 102 and present at the inlet pressure EP of the compressor stage 88 and determines a superheat difference from these temperatures and, in the event that this superheat difference is smaller than a maximum superheat value, activates and / or increases the mass flow recirculation.

[0311] Preferably, the maximum superheat value is in the range of 3 to 7 Kelvin.

[0312] Another possibility for controlling the control valve 244 provides that the controller 132, 138 determines an opening degree of the expansion element 122 for the subcooling mass flow and controls the control valve 244 according to the opening degree of the expansion element.

[0313] In addition, there are further options for stabilizing the expansion unit.

[0314] Thus, a further advantageous solution provides that, in order to stabilize the operation of the expansion unit 32, the controller 132, 138 determines a temperature of the refrigerant present on the high-pressure side before entering the subcooling unit 102 and a temperature of the refrigerant exiting the subcooling unit 102 and present at the inlet pressure EP of the compressor stage 88, that the controller determines a temperature difference between these two temperatures and checks whether this is greater or smaller than a maximum difference, and in the event that this is greater than the maximum difference, generates and / or increases a bypass mass flow ULM by activating the bypass line 234.

[0315] The bypass mass flow ULM is preferably controlled by the expansion element 232 functionally assigned to the bypass line 234.

[0316] A further advantageous solution provides that, in order to stabilize the operation of the expansion unit 32, the controller 132, 138 determines a temperature of the refrigerant present on the high-pressure side after exiting the subcooling unit 102 and a temperature of the refrigerant present at subcooling pressure PU before entering the subcooling unit 102, that the controller 132, 138 determines a temperature difference between these two temperatures and checks whether this is smaller or larger than a minimum difference, and in the event that this is smaller than the minimum difference, generates and / or increases a bypass mass flow ULM by activating the bypass line 234.

[0317] In this case, too, the expansion element functionally assigned to the bypass line is preferably controlled.

[0318] A further advantageous solution provides that the controller 132, 138, in order to stabilize the operation of the expansion unit 32, determines a pressure of the refrigerant present at the inlet pressure EP of the compressor stage 88, determines the evaporation temperature of the same therefrom, and also determines the temperature of the refrigerant emerging from the subcooling unit 102 and present at the inlet pressure EP of the compressor stage 88 and determines a superheat difference from these temperatures and, in the event that this superheat difference is smaller than a minimum value, generates and / or increases a bypass mass flow ULM by activating the bypass line 234.

[0319] In this case, too, the expansion element 232 functionally associated with the bypass line 234 is preferably controlled.

[0320] A further advantageous solution for stabilizing the operation of the expansion unit provides that the controller 132, 138 determines a degree of opening of the expansion element 122 generating the subcooling mass flow UM and, in accordance with the degree of opening of this expansion element 122, activates the bypass line 234 and generates and / or increases a bypass mass flow ULM, wherein preferably the expansion element 232 functionally assigned to the bypass line 234 is controlled in accordance with the degree of opening of the expansion element 122.

[0321] Particularly when using the free-piston machine as an expansion-compression unit 84, there is the problem of pulsations in the refrigerant circuit 10.

[0322] For this reason, in the first embodiment of the refrigerant circuit 10, a pulsation damper 260 is preferably connected to parts of the refrigerant circuit 10 adjacent to the expander stage 86, for example to the expansion line 42, which comprises a damper housing 262 enclosing a damper chamber 264, in which, at least in a subcritical operating state, a bubble 266 of gaseous refrigerant forms above a refrigerant bath 268 of liquid refrigerant, the refrigerant bath 268 being connected, for example, to the expansion line 42 via a pulsation transmission line 272.

[0323] The bubble 264 of gaseous refrigerant thus makes it possible to dampen pulsations in the expansion pressure mass flow EPM, which also affect the bath 268 of the refrigerant.

[0324] In order to ensure that the bubble 266 of gaseous refrigerant always forms in the damper housing 262 above the refrigerant bath 268 of liquid refrigerant, the damper housing 262 is preferably provided with a heater 274 in the area surrounding the bubble 266, which heater supplies heat from the return line 78 to the damper housing 262 via a heat transport circuit 276 to maintain the bubble 266 of vaporous refrigerant.

[0325] In a second embodiment of a refrigerant circuit 10' according to the invention, shown in Fig. 5 A second embodiment of the operational adjustment unit 230' is not part of the expansion system 30, as described in connection with the first embodiment of the refrigerant circuit 10 according to the invention, but a unit independent of the expansion system 30, wherein the expansion element 232 is arranged in the bypass line 234', which in this case connects the high-pressure line 28 to the expansion line 42 and is thus connected in parallel to the entire expansion unit 32 ( Fig. 5 ).

[0326] The control of the expansion element 232 is carried out, for example, by the controller 138 according to the high pressure PH2 as in the first embodiment.

[0327] Furthermore, in the second embodiment, those elements which are identical to the first embodiment are provided with the same reference numerals, so that in this regard, reference can be made in full to the explanations relating to the first embodiment.

[0328] In the first embodiment of a refrigerant circuit according to the invention, a third embodiment of an operational adjustment unit 230" is assigned to the first embodiment of the expansion unit 30, which is designed such that the controllable expansion element 232 is arranged in a bypass line 234" ( Fig. 6 ), which is connected in parallel to the expander stage 86 and a shut-off element 236 arranged upstream of the expander inlet 92, so that when the expansion element 232 is activated, it is possible either to operate the operation adjustment unit 230" simultaneously with the expansion compression unit or to deactivate the expander stage 86 and thus the entire expansion compression unit 84 via the shut-off valve 236, so that only the bypass mass flow ULM flows from the high pressure inlet connection 34 to the expansion pressure outlet connection 36.

[0329] Because the expander stage 86 is deactivated by the shut-off element 236, the compressor stage 88 is also deactivated, so that no subcooling return mass flow URM flows to the high-pressure line 18 via the high-pressure outlet connection 38 and the return line 78.

[0330] In this embodiment, it is necessary to actively control the expansion element 232 and the shut-off element 236, for example by an operation adjustment control 238, which uses a sensor 246 to detect the high pressure PH2 present in the refrigerant circuit 10 upstream of the expander stage 86, for example the high pressure between the outlet 106 of the subcooling unit 102 and the expander inlet 92 ( Fig. 6 ).

[0331] Furthermore, to stabilize the operation of the expansion unit 32, a modified mass flow return 240' is provided, the compressor bypass line 242' of which connects the compressor outlet 98 to the inlet 112 of the subcooling unit 102, which is at a pressure present after the expansion element 122.

[0332] In this case, the controllable valve 244' is controlled by the controller 132, which detects the pressure difference in the same way as in the first embodiment.

[0333] Furthermore, all elements of the third embodiment which are identical to those of the first embodiment are provided with the same reference numerals, so that reference can be made in full to the explanations relating to the first embodiment.

[0334] In a fourth embodiment of an operation adjustment unit 230''', shown in Fig. 7 , the shut-off element 236 is not arranged in front of the expander inlet 92, but immediately after the expander outlet 94 and the bypass line 234‴ is thus connected in parallel with the expander stage 86 with the shut-off element 236, which is arranged following the expander outlet 94.

[0335] In this case too, the operating adjustment control 238 is provided on the one hand to control the expansion element 232 and the shut-off element 236.

[0336] Furthermore, those elements of the fourth embodiment which are identical to those of the preceding embodiments are provided with the same reference numerals, so that reference is made in full to the explanations thereon.

[0337] In a fifth embodiment of an operation adjustment unit 230"", shown in Fig. 8 the operation adjustment unit 230ʺʺ comprises the shut-off element 237 and the shut-off element 236.

[0338] In this embodiment, in the same way as in the third embodiment, the shut-off element 236 is arranged in front of the expander inlet 92 in order to deactivate the expander stage 86 by interrupting the expansion mass flow EM flowing into the expander stage 86, while the bypass line 234ʺʺ connects the supply line 126, into which the subcooling mass flow UM enters after flowing through the expansion element 122, and the expansion pressure output connection 36.

[0339] In this case, the further shut-off element 237 is also provided in the bypass line 234ʺʺ, while the expansion element 122 provided for the expansion of the subcooling mass flow UM also serves as an expansion element for the operation adjustment unit 230ʺʺ and therefore determines the bypass line mass flow ULM, which is guided to the expansion pressure output connection 36 bypassing the expander 86, in particular when the expansion compression unit is deactivated by the shut-off element 236.

[0340] In this case, too, the operational adjustment control 238 is provided, which controls the shut-off elements 236 and 237 when the sensor 242 detects an undesirable increase in the high pressure PH2.

[0341] In a sixth embodiment of an operational adjustment unit 230ʺʺ associated with a second embodiment of an expansion unit 32', shown in Fig. 9 , the operation adjustment unit 230ʺʺ is also formed by the bypass line 234ʺ‴ with the shut-off element 237, while the shut-off element 236 is arranged directly following the expander outlet 94, so that the bypass line 234‴ʺ is led from the supply line 126 to the expansion pressure outlet connection 36 and opens into a line 233 between the shut-off element 236 and the expansion pressure outlet connection 36.

[0342] In this second embodiment of the expansion unit 32', the pulsation transmission line 272 also opens into this line 233 and is led to a pulsation damper 260 which is designed in the same way as described in connection with the first embodiment, wherein in this case the heat transport circuit 276 is also part of the expansion system 30 and extracts heat from a bypass line between the compressor outlet 98 and the high-pressure outlet connection 38 and supplies it to the heater 274.

[0343] In a third embodiment of an expansion unit 32" according to the invention, shown in Fig. 10 , the expansion system 30" is provided with the operation adjustment unit 230' according to the sixth embodiment, so that in this regard, reference can be made in full to the explanations of the sixth embodiment.

[0344] In contrast to the first and second embodiments of the expansion unit 32 and 32', however, a pulsation damper unit 280 is provided between the high-pressure inlet connection 34 and the high-pressure outlet connection 38, which has a damper housing 282 in which a piston 284 is arranged, which separates a first chamber 286 arranged in the damper housing 282 from a second chamber 288, wherein, for example, the first chamber 282 is connected to the high-pressure inlet connection 34 via a first pulsation transmission line 292 and the second chamber 288 is connected to the high-pressure outlet connection 38 via a second pulsation transmission line 294.

[0345] The pulsation damper unit 280 is thus able to dampen pulsations propagating to the high-pressure inlet port 34 or to the high-pressure outlet port 38 by transmitting the pulsation through the piston, wherein the piston 284 is preferably mounted between two spring-elastic damping elements 296 and 298 which are arranged in the chambers 286 and 288, respectively.

[0346] A seventh embodiment of an operation adjustment unit 230""" is shown in Fig. 11 and Fig. 12 , is based in principle on the fourth embodiment of the operational adjustment unit 230‴‴, wherein in this case the operational adjustment unit 230‴‴ has a bypass line 234‴‴ which leads from the supply line 126 to a 3 / 2-way valve 235 which is able to either connect the expander outlet 94 to the expansion pressure output connection 36 and close the bypass line 234‴‴ or to connect the bypass line 234‴‴ to the expansion pressure output connection 36 and close the expander outlet 94, wherein the 3 / 2-way valve 235 is also controlled by the operational adjustment control 238 which, for example, detects the high pressure of the expansion mass flow EM before it enters the expander.

[0347] Thus, in this embodiment too, the expansion element 122, which is actually intended for the expansion of the subcooling mass flow UM, serves as an expansion element for this operating adjustment unit 230‴‴ in the case of the activated operating adjustment unit 230ʺʺ emergency operation.

[0348] In a third embodiment of an expansion unit 32" shown in Fig. 13 , the expansion unit 32" is modified in such a way that the branch 116‴ is arranged between the high-pressure inlet connection 34 and the inlet 104 of the subcooling unit 102 and thus the subcooling mass flow UM is branched off from the total mass flow G before flowing through the subcooling unit 102, wherein in the same way as in the preceding embodiments the shut-off element 124 and the expansion element 122 are provided, which are arranged between the branch 116' and the inlet 112 for the counterflow flowing through the subcooling unit 102.

[0349] This embodiment of the expansion unit 32" is also controlled by the controller 132 in the same way as in the first embodiment.

[0350] This third embodiment of the expansion unit can also be provided with various operational adjustment units, for example with an operational adjustment unit 230' according to the second embodiment, and the expansion element 232.

[0351] However, the expansion unit 32" can also be provided with operational adjustment units 230", 230"', 230"", 230‴ʺ, and / or with pulsation damper units 260, 280, as described in connection with the preceding embodiments of the refrigerant circuit 10, so that reference is made in this regard to the preceding explanations regarding these operational adjustment units.

[0352] Furthermore, in the third embodiment, the mass flow return 240 is provided for stabilizing the expander unit 32", which has already been described in connection with the first embodiment.

[0353] As an alternative to the compressor bypass 240, in the solution according to the third embodiment, as shown in Fig. 14 shown, but also a compressor bypass 240' is realized, which has already been described in connection with the third embodiment of the operation adjustment unit 230" in connection with Fig. 6 was explained.

[0354] In the third embodiment according to Fig. 13 but it is also, as in Fig. 15 As shown, it is conceivable to provide the expansion unit 32" with an operating adjustment unit 230' arranged directly on the expansion system 30" and integrated therein, the bypass line 234' of which runs between the high pressure inlet connection 34 and the expansion pressure outlet connection 36.

[0355] Furthermore, the shut-off valve 231 is still integrated into the expansion system 30", which can be controlled to deactivate the expansion compression unit 84.

[0356] The control of the expansion element 232 is carried out in the solution according to Fig. 15 by means of the controller 132 in the context of the Fig. 1 and 2 described first embodiment of the operation adjustment unit 230.

[0357] In a third embodiment of a refrigerant circuit 10" according to the invention, shown in Fig. 16 , those elements which are identical to those of the first embodiment are provided with the same reference numerals, so that with regard to the description, reference can be made in full to the explanations relating to these in connection with the first embodiment.

[0358] However, the third embodiment is provided with the first embodiment of the operation adjustment unit 230, with regard to which reference is made to the above explanations regarding this first embodiment.

[0359] Alternatively, all other embodiments of the operational adaptation unit described above could also be used.

[0360] In contrast to the first embodiment, in the third embodiment of the refrigerant circuit 10", the expansion line 42 does not lead directly to the cooling stage 62, but rather to an intermediate pressure collector 44, in which a bath 46 of liquid refrigerant forms at expansion pressure PE, from which liquid refrigerant is supplied via a liquid line 48 to the cooling stage 62", which in this case comprises not only the heat-absorbing heat exchanger 64, but also a shut-off element 68 and an expansion element 66.

[0361] Furthermore, a gas volume 52 of refrigerant is formed in the intermediate pressure collector 44 above the bath 46, from which an additional mass flow Z is fed to the suction line 74 via an expansion element 54.

[0362] The intermediate pressure collector 44 makes it possible to divide the expansion mass flow E at expansion pressure PE into a main mass flow H, which is fed via the liquid line to the cooling stage 62", and a gaseous additional mass flow Z, which is fed via the expansion element 54 to the suction pressure line 74, so that the temperature of the main mass flow H reaching the cooling stage 62" can be adjusted by means of the expansion element 54.

[0363] In the third embodiment of the refrigerant circuit 10", the high-pressure discharge line 28 is also assigned a pulsation damper 260 which corresponds to the pulsation damper 260 shown in the first embodiment of the refrigerant circuit 10 according to Fig. 1 , which is assigned to the expansion line 42, so that with regard to its function, reference can be made in full to the above explanations.

[0364] Alternatively, the pulsation damper 260 can also be arranged in the area of ​​the expansion unit 32 or even integrated into the expansion system 30.

[0365] In a fourth embodiment of a refrigerant circuit 10‴ according to the invention, shown in Fig. 17 the elements which are identical to those of the first and third embodiments of the refrigerant circuit are provided with the same reference numerals, so that with regard to the description thereof, reference can be made in full to the explanations of the first and second embodiments.

[0366] Furthermore, the fourth embodiment of the refrigerant circuit 10‴ is also provided with the first embodiment of the operation adjustment unit 230, although all other embodiments could also be used.

[0367] In addition to the features of the third embodiment, the fourth embodiment is provided with a pulsation damper unit 280 instead of the pulsation damper 260, which in this embodiment is connected in parallel to the heat exchanger 22 and thus dampens pulsations between the high-pressure line 18 and the high-pressure discharge line 28.

[0368] The pulsation damper unit 280 is designed identically to the pulsation damper unit 280 integrated in the third embodiment of the expansion unit 32" ( Fig. 10 ), so that reference can be made in full to the above statements in this regard.

[0369] In addition, however, a throttle 302 is provided between the second pulsation transmission line 294 and the high pressure line 18 in order to obtain an improved damping effect.

[0370] In a fifth embodiment of a refrigerant circuit 10" according to the invention, shown in Fig. 18 , those elements which are identical to those of the first to fourth embodiments of the refrigerant circuits are provided with the same reference numerals, so that with regard to the description thereof, reference can be made in full to the explanations relating to the first to fourth embodiments.

[0371] In contrast to the third and fourth embodiments of the refrigerant circuits, the additional mass flow Z from the gas volume 52 is not fed directly to the suction pressure line 74 via the expansion element 54, but is again passed through a subcooler 58 provided in the liquid line 48, which subcools the main mass flow H flowing in the liquid line 48 again.

[0372] Furthermore, the cooling stage 62‴ is designed, for example, as a normal cooling stage and, in addition, a deep-freeze stage 212 is provided, which has a heat-absorbing heat exchanger 214 as well as a shutdown device 218 and an expansion device 216.

[0373] The refrigerant expanded in the deep-freeze stage 212 is fed via a suction pressure line 224 to a deep-freeze compressor unit 222, which compresses the refrigerant again to such an extent that it can be fed to the suction pressure line 74 for the refrigerant compressor unit 12 for compression to high pressure.

[0374] In addition, a subcooler 226 is preferably provided in the suction pressure line 224 of the deep-freeze compressor unit 222, which subcooler further subcools the refrigerant supplied to the deep-freeze stage 212 via the liquid line 48 before it enters the deep-freeze stage 212, namely by means of the expanded refrigerant emerging from the deep-freeze stage 212 and guided in the suction pressure line 224.

[0375] In connection with the third, fourth and fifth embodiments according to the Fig. 14 , 15 and 16The solution according to the invention describes the presence of the intermediate pressure collector 44 and also the supply of the additional mass flow Z via the expansion element 54 to the suction pressure line 74 as well as the control of the temperature of the main mass flow H.

[0376] This control of the temperature of the main mass flow H comprises the control of an intermediate pressure PM in the intermediate pressure collector 44 by means of the expansion element 54, which in this case can be controlled via an intermediate pressure control 55.

[0377] In principle, in the third, fourth and fifth embodiments, according to the Fig. 14 , 15 and 16It is possible, on the one hand, to control the high pressure PH2 in the high pressure discharge line by means of the controls 132 and / or 138 in accordance with an optimal operation of the expansion unit 32 at the respective temperature of the refrigerant in the high pressure discharge line 28 and, for example, the respective outside temperature and, with the intermediate pressure control 55, to only set a constant intermediate pressure PM in the intermediate pressure collector 44.

[0378] The efficiency of the refrigerant circuit can be increased by the above-mentioned detection of the inlet pressure EP of the compressor stage 88 by means of the controls 132, 138.

[0379] However, the refrigerant circuit 10 according to the invention can also be optimized with regard to the achievable COP, i.e. the ratio of cooling capacity to the mechanical power used, in particular in summer operation, and with regard to the extension of the functional operation of the expansion compression unit, in particular in winter operation, by additional operating state-dependent control of the intermediate pressure PM, which affects the inlet pressure EP of the compressor stage 88 due to the volume ratios of the expansion compression unit 84.

[0380] In this operating condition-dependent control of the intermediate pressure PM, for example, the intermediate pressure PM is controlled by means of the intermediate pressure control 55 and the expansion device 54 to a pressure value which results on the one hand from a basic value which is generally set once and from additional values ​​to this basic value which vary depending on the operating condition.

[0381] For example, the base value for CO2 as a refrigerant is in the range from 30 bar to 45 bar, so that a value from this range, for example 35 bar, is set as the base value, and the additional values ​​for CO2 as a refrigerant have amounts in the range from 0.5 bar to 7 bar.

[0382] In principle, the surcharge values ​​could be fixed values ​​from the range of surcharge values ​​provided for them, but it is particularly advantageous if the surcharge values ​​vary within this range depending on the operating condition.

[0383] In addition, a differentiation is preferably made between summer operation and winter operation, with the additional values ​​having positive values ​​for summer operation and negative values ​​for winter operation, so that, for example, with CO2 as a refrigerant, the values ​​are in the range of 0.5 bar to 7 bar for summer operation and in the range of -0.5 bar to -7 bar for winter operation.

[0384] It is particularly advantageous if the size of the additional values ​​depends on the values ​​within the control range of the high pressure PH2 and therefore varies depending on the values ​​of the high pressure PH2.

[0385] In particular, it is intended that the surcharge values ​​are higher at high high pressure values ​​than at low high pressure values.

[0386] For example, in the case of CO2 as a refrigerant in summer operation, additional values ​​in the range of +0.5 bar to +3 bar result if the high pressure PH2 has values ​​in the range of 75 bar to 80 bar, and additional values ​​in the range of +3 bar to +7 bar if the high pressure PH2 has values ​​in the range greater than 80 bar, preferably values ​​greater than 80 bar to 120 bar.

[0387] For example, in summer operation, with a high pressure PH2 in the range of 80 bar, an additional value in the range of 3 bar is used, while with a high pressure PH2 in the range of 90 bar, an additional value in the range of 5 bar is used.

[0388] In the same way, the additional values ​​for winter operation are, for example, in the range of -0.5 bar to -3 bar, provided that the high pressure PH2 is in the range of 55 bar to 65 bar and the additional values ​​are in the range of -3 bar to -5 bar, provided that the high pressure PH2 is in the range of less than 50 bar to 40 bar.

[0389] In particular, in winter operation, for example, at a high pressure PH2 in the range of 60 bar, an additional value in the range of -3 bar is used and at a high pressure in the range of 50 bar, an additional value in the range of -5 bar is used.

[0390] In the above examples of summer and winter operation, the base value is preferably always the same.

[0391] The above control of the intermediate pressure PM thus has the following consequences in summary: By changing the intermediate pressure PM, the inlet pressure EP at the compressor stage 88 changes and thus a subcooler output of the subcooling unit 102.

[0392] If the intermediate pressure PM is increased, the inlet pressure EP at the compressor stage 88 increases and thus the subcooling mass flow UM and thus the subcooler capacity of the subcooling unit 102 is increased, so that the COP also increases.

[0393] If the intermediate pressure PM is reduced, the inlet pressure EP at the compressor stage 88 also decreases. However, the pressure difference at the expander stage 86 is increased and thus the functional range of the expansion compression unit 84 is also increased.

[0394] In the case of an alternative solution according to Fig. 18 It is provided that the intermediate pressure control 55 detects the variables, in particular the temperature and / or the pressure of the total mass flow G in the high-pressure discharge line 28 and the value of the inlet pressure EP of the compressor stage 88 and, depending thereon, controls the intermediate pressure PM in order to regulate to a predetermined value of the inlet pressure EP that is suitable for the detected variables and, for example, stored in the intermediate pressure control 55.

[0395] All compressor units can be any compressor or combination of compressors (parallel, in series, multi-stage).

[0396] Likewise, one or more of the compressors can be provided with a power control, which can be achieved by switching off compressors, by mechanical power control (for example switching off, in particular cyclical switching off of parts (cylinder banks) of a compressor) or by speed control of the compressor.

[0397] In all embodiments and embodiments according to the Fig. 1 bis 18 It was not discussed in detail to what extent the operational adjustment unit 230 and the expansion unit 32 comprising the expansion compression unit 84 are activated or deactivated.

[0398] In the above embodiments, it is always provided that a controllable or adjustable expansion element 232 or 122 is assigned to the operation adjustment unit 230, so that the mass flow flowing through the bypass line 234 is controllable or adjustable.

[0399] In these cases, the Fig. 19 The flow chart shown is provided for the respective controller 132, 138, which on the one hand detects a temperature T amb corresponding to the ambient temperature in the region of the high-pressure side heat exchanger, for example by means of the sensor 134 3 , and checks whether this is higher or lower than a temperature threshold value TS, above which the expansion unit 32 having the expansion compression unit 84 can be operated stably and below which instabilities occur during operation of the expansion unit 32 having the expansion compression unit 84.

[0400] If the temperature T amb is lower than the temperature threshold TS, the expansion compression unit 84 is switched off and the refrigerant circuit 10 operates with the operation adjustment unit 230, which variably adjusts the mass flow ULM through the respective bypass line 234.

[0401] The temperature threshold TS is preferably in the range of 15°C to 20°C when CO2 is used as a refrigerant.

[0402] In addition, the controller 132, 138 checks according to the flowchart in Fig. 19 whether the total mass flow G, which occurs at high pressure, is greater than the sum of the subcooling mass flow UM and the expansion mass flow EPM in the expansion unit 32.

[0403] If this is the case, the expansion compression unit 84 is no longer able to prevent an increase in pressure of the high pressure PH2.

[0404] In this case, the operation adjustment unit 230 is also activated in such a way that it adjusts the mass flow ULM flowing through the bypass line 234 so that the high pressure PH2 can be kept at a constant level.

[0405] In all other cases, the expansion unit 32 comprising the expansion compression unit 84 is operated exclusively with the operation adjustment unit 230 deactivated.

[0406] These ratios are also shown in the diagram according to Fig. 20 shown schematically so that it can be seen in which cases the operation adjustment unit 230 and the expansion compression unit 84 are activated or deactivated.

[0407] In the Fig. 21 bis 23 are the Fig. 16 bis 18 corresponding refrigerant circuits 10 and expansion units 32 are shown, which are identical in terms of their overall structure, the embodiment according to Fig. 21 the the Fig. 16 , the embodiment according to Fig. 22 the the Fig. 17 and the embodiment according to Fig. 23 the the Fig. 18 corresponds.

[0408] In terms of their basic structure, the operational adaptation units 230 and 230' are also identical to the operational adaptation units of the Fig. 16 bis 18 identical, but with the difference that in the bypass lines 234 and 234', respectively, no controllable expansion elements 232 and 232' are provided for activating or deactivating them, but only switching valves 231 and 231', respectively, which can either be opened or closed, wherein in particular the sound valves 231 and 231' are designed such that in the open, i.e. activated, state thereof, no pressure loss occurs, so that ultimately, when the operating adjustment unit 230 and 230' is activated, high pressure PH2 is present at the expansion pressure output connection 36 of the respective expansion unit 32.

[0409] Such a switching valve 231 or 231' is of simpler construction and thus more cost-effective and also more cost-effective to operate than an expansion element 232, since no control is required, but rather only a signal for opening or closing has to be generated by the respective control 132, 138.

[0410] In this case, the control flow chart is designed as shown in Fig. 24 is shown.

[0411] The temperatures T amb recorded in the area of ​​the high-pressure side heat exchanger 22 are compared with the temperature threshold value TS and a further lower temperature threshold value TUS, which is lower than the temperature threshold value TS.

[0412] The temperature threshold TS is preferably in the range of 15°C to 20°C when CO2 is used as refrigerant and the lower temperature threshold TUS is preferably in the range of 8°C to 12°C.

[0413] If the temperatures T amb are still below the lower temperature threshold TUS, it is necessary to no longer keep the switching valve 231 permanently activated, but to close it temporarily so that the operation adjustment unit 230 is activated and deactivated at time intervals, for example pulse width modulated, in order to keep the high pressure PH2 at an appropriate level.

[0414] If the temperatures T amb are below the temperature threshold TS, the expansion compression unit 84 is deactivated, i.e. switched off, and the operation adjustment unit 230 is permanently activated, combined with a particularly permanent opening of the valve 231 in the corresponding bypass line 234.

[0415] At temperatures T amb that are greater than the temperature threshold TS, only the respective expansion unit 32 is operated with the expansion compression unit 84.

[0416] These ratios are also shown in the diagram according to Fig. 25 shown, where Fig. 25 additionally, an overlap is provided for the deactivation of the expansion compression unit 84 and the activation of the operational adjustment unit 230, as well as an overlap is provided for the deactivation of the permanent activity of the operational adjustment unit 230 and the transition to the pulse width-controlled activation and deactivation of the operational adjustment unit 230.

Claims

1. A refrigerant circuit (10), comprising at least one refrigerant compressor (12), which compresses refrigerant fed at a suction connection (14) to high pressure (PH1) such that a compressor mass flow (V) of the refrigerant compressed to high pressure (PH1) exits at a pressure connection, at least one heat-emitting heat exchanger (22) on the high-pressure side, having an inlet (24) to which the refrigerant circuit (10) feeds the compressor mass flow (V) and having an outlet (26) from which a cooled total mass flow (G) of refrigerant exits, at least one expansion unit (32), comprising an expansion compression unit (84), which has an expander stage (86) and a compressor stage (88) and which expands an expansion mass flow (EM) of the total mass flow (G), conducted by the refrigerant circuit (10) in the direction of the suction connection (14) of the refrigerant compressor (12), starting from high pressure (PH2) to an expansion pressure (PE), and at least one cooling stage (62) having at least one heat-absorbing heat exchanger (64) to which the refrigerant circuit (10) feeds a main mass flow (H) comprised by the expansion mass flow (EM) expanded by the expansion unit (32), and feeds this main mass flow (H), after leaving the cooling stage (62), to the suction connection (14) of the refrigerant compressor (12), characterised in that the expansion unit (32) has a supercooling unit (102) for supercooling at least the expansion mass flow (EM) of the refrigerant fed to the expansion unit (32), in that the expansion unit has the expansion compression unit (84) comprising the expander stage (86) and the compressor stage (88), and a branch (116), which branches off a supercooling mass flow (UM) from the total mass flow (G) fed to the expansion unit (32) and is connected to a feed conduit (126), which conducts the supercooling mass flow (UM) to an inlet (112) of the supercooling unit (102), in that the expansion unit (32) has an expansion member (122, 124) which is provided in the feed conduit (126) and which expands the supercooling mass flow (UM) to a supercooling pressure (PU), and in that the expansion unit (32) has a connection conduit (128), which feeds the supercooling mass flow (UM) exiting from the supercooling unit (102) to the compressor stage (88), which in turn compresses the supercooling mass flow (UM) to a return high pressure (PR), which corresponds to least one high pressure (PH1) of the compressor mass flow (V), to which the supercooling mass flow (UM) is fed, and in that the expansion unit (32) has a mass flow return (240, 240') for the compressor stage (88), with which there is controllable a mass flow from a conduit leading away from the compressor outlet (98) to a conduit (126, 102, 128) leading to the compressor inlet (96).

2. A refrigerant circuit in accordance with claim 1, characterised in that the mass flow return (240, 240') has a compressor bypass conduit (242) and a control valve (244, 244') associated therewith.

3. A refrigerant circuit in accordance with claim 1 or 2, characterised in that the refrigerant circuit (10) has an electrically operating controller (132, 138), which detects at least one of the following variables, such as: an ambient temperature, a temperature (Tamb) of the mass flow of the refrigerant fed to the expansion unit (32) and / or the expander stage (86), and an inlet pressure (EP) of the compressor stage (88), and, in accordance with this temperature (Tamb) and / or as applicable this inlet pressure (EP) of the compressor stage (88), establishes an inlet pressure of the expansion unit (32) or of the expander stage (86) and / or as applicable an inlet pressure (EP) of the compressor stage (88) by controlling the supercooling mass flow (UM) by means of the expansion member (122) electrically actuated by the controller (132, 138).

4. A refrigerant circuit in accordance with claim 2, characterised in that this has an electrically operating controller (132, 138), in that the control valve (244, 244') is controlled by the controller (132, 138), in that the controller (132, 138) detects temperature differences between a pressure applied on the high-pressure side to the supercooling unit (102) and a temperature present downstream of the expansion member (122) and / or detects a superheating difference on the input side of the compressor stage and / or a degree of opening of the expansion member (122), and in that in particular the controller (132, 138) compares the pressure difference with a reference value.

5. A refrigerant circuit in accordance with claim 4, characterised in that the expansion member (122) has an electrically actuated expansion member, and in that the electrically operating controller (132, 138) detects at least one of the following variables, such as: an ambient temperature, a temperature (Tamb) of the mass flow of the refrigerant fed to the expansion unit (32) and / or the expander stage (86), an inlet pressure (EP) of the compressor stage (88), and, in accordance with this temperature (Tamb) and / or as applicable this inlet pressure (EP) of the compressor stage (88), establishes an inlet pressure of the expansion unit (32) or of the expander stage (86) and / or as applicable an inlet pressure (EP) of the compressor stage (88) by controlling the supercooling mass flow (UM) by means of the expansion member (122) electrically actuated by the electrically operating controller (132, 138).

6. A refrigerant circuit in accordance with preceding claims 3 to 5, characterised in that the electrically operating controller (132, 138) detects the ambient temperature and / or the temperature of the mass flow of the refrigerant upstream of an inlet (104) of the supercooling unit (102) and / or upstream of an expander inlet (92) by means of a sensor (134).

7. A refrigerant circuit in accordance with preceding claims 5 to 6, characterised in that the electrically operating controller (132, 138) is an electronic controller (132, 138) comprising a processor, which controller electrically actuates the electrically operating expansion member (122) by means of a control program.

8. A refrigerant circuit in accordance with claims 1 to 7, characterised in that the supercooling unit (102) is configured as a heat exchanger and cools the mass flow of the refrigerant flowing to the expander stage (86) by the supercooling mass flow U conducted in counter current through said heat exchanger.

9. A refrigerant circuit in accordance with claims 1 to 8, characterised in that the branch (116) is arranged upstream of a high-pressure-side inlet of the supercooling unit (102).

10. A refrigerant circuit in accordance with claims 1 to 9, characterised in that the branch (116) is arranged between the supercooling unit (102) and the expansion compression unit (84) and branches off the supercooling mass flow (UM) from the total mass flow (G) downstream of the supercooling unit (102).

11. A refrigerant circuit in accordance with the preceding claims, characterised in that the expander stage (86) and the compressor stage (88) of the expansion compression unit (84) are mechanically functionally coupled, in that in particular the expander stage (86) and the compressor stage (88) are formed by a free-piston machine, in which at least one free piston (152, 154) is freely movable in a piston chamber (144, 146), in that in particular the expansion compression unit (84) has two piston chambers (144, 146), in each of which a free piston (152, 154) is movable.

12. An expansion unit (32), in particular for a refrigerant circuit in accordance with the preceding claims, comprising an activatable and deactivatable expansion compression unit (84) which has an expander stage (86) and a compressor stage (88) and which expands an expansion mass flow (EM), fed at a high-pressure inlet connection (34), starting from high pressure (PH2) to an expansion pressure (PE), characterised in that the expansion unit (32) has a mass flow return (240, 240') for the compressor stage (88), with which a mass flow from a conduit leading away from the compressor outlet (98) to a conduit (126, 102, 128) leading to the compressor inlet (96) is controllable, in that the expansion unit (32) has a controller (132, 138), which, to stabilise the operation of the expansion unit, determines a temperature of the refrigerant present on the high-pressure side prior to entry into the supercooling unit (102) and a temperature of the refrigerant exiting from the supercooling unit (102) and present at inlet pressure (EP) of the compressor stage (88), in that the controller (132, 138) determines a temperature difference between these two temperatures and checks whether this is greater or smaller than a maximum difference, and, in the event that it is greater than the maximum difference, activates and / or increases the mass flow through the mass flow return (240).

13. An expansion unit in accordance with claim 12, characterised in that the controller (132, 138) of the expansion unit (32), to stabilise operation thereof, determines a temperature of the refrigerant present on the high-pressure side after exit from the supercooling unit (102) and a temperature of the refrigerant expanded prior to entry into the supercooling unit (102) and expanded to supercooling pressure (PU), in that the controller (132, 138) determines a temperature difference between these two temperatures and checks whether this is smaller or greater than a minimum difference, and, in the event that it is smaller than the minimum difference, activates and / or increases the mass flow through the mass flow return (240, 240').

14. An expansion unit in accordance with claim 12 or 13, characterised in that the controller (132, 138) of the expansion unit (32), to stabilise operation thereof, determines a pressure of the refrigerant present at inlet pressure (EP) of the compressor stage (88), determines the evaporation point of the refrigerant, and additionally determines therefrom the temperature of the refrigerant exiting from the supercooling unit (102) and present at inlet pressure (EP) of the compressor stage (88), and from these temperatures determines a superheating difference and, in the event that this superheating difference is smaller than a superheating minimum value, activates and / or increases the mass flow return (240, 240').

15. An expansion unit in accordance with one of claims 12 to 14, characterised in that the controller (132, 138) of the expansion unit (32) determines a degree of opening of the expansion member (122) controlling the supercooling mass flow (UM) and controls the control valve (244, 244') of the mass flow return (240) in accordance with the degree of opening.

16. An expansion unit in accordance with one of claims 12 to 13, characterised in that the controller (132, 138) of the expansion unit (32), to stabilise operation thereof, determines a temperature of the refrigerant present on the high-pressure side prior to entry into the supercooling unit (102) and a temperature of the refrigerant exiting from the supercooling unit (102) and present at inlet pressure (EP) of the compressor stage (88), in that the controller (132, 138) determines a temperature difference between these two temperatures and checks whether this is greater or smaller than a maximum difference, and, in the event that it is greater than the maximum difference, generates and / or increases a bypass mass flow (ULM) by activating the bypass conduit (234).

17. An expansion unit in accordance with claims 12 to 16, characterised in that the controller (132, 138) of the expansion unit (32), to stabilise operation thereof, determines a temperature of the refrigerant present on the high-pressure side after exit from the supercooling unit (102) and a temperature of the refrigerant present prior to entry into the supercooling unit (102) and present at supercooling pressure (PU), in that the controller determines a temperature difference between these two temperatures and checks whether this is smaller or greater than a minimum difference, and, in the event that it is smaller than a minimum difference, generates and / or increases a bypass mass flow (ULM) by activating the bypass conduit (234).

18. An expansion unit in accordance with claims 12 to 17, characterised in that the controller (132, 138) of the expansion unit (32), to stabilise operation thereof, determines a pressure of the refrigerant present at inlet pressure (EP) of the compressor stage (88), determines therefrom the evaporation point of the refrigerant, and additionally determines the temperature of the refrigerant exiting from the supercooling unit (102) and present at inlet pressure (EP) of the compressor stage (88), and from these temperatures determines a superheating difference and, in the event that this superheating difference is smaller than a minimum value, generates and / or increases a bypass mass flow (ULM) by activating the bypass conduit (234).

19. An expansion unit in accordance with claims 12 to 18, characterised in that the controller (132, 138) of the expansion unit (32) determines a degree of opening of the expansion member (122) controlling the supercooling mass flow (UM) and controls the expansion element (232) functionally associated with the bypass line (234) in accordance with the degree of opening.

20. An expansion unit in accordance with one of claims 12 to 19, characterised in that the controller (132) of the expansion unit (32) has an electrically operating controller, which detects at least one of the following variables, such as: a temperature (Tamb) corresponding to an ambient temperature, a temperature of the mass flow of the refrigerant fed to the expansion unit (32) and / or the expander stage (86), a high pressure (PHZ) of the total mass flow (G) or of the expansion mass flow (EM) upstream of the expander stage (86), and, in accordance with this temperature and / or as applicable this high pressure (PHZ) of the total mass flow (G) or of the expansion mass flow (EM), activates the bypass conduit (234) and generates the bypass mass flow (ULM), in that in particular the electrically operating controller controls the bypass mass flow (ULM) by actuating the expansion element (232, 122) functionally associated with the bypass conduit (234).