Refrigeration machine and method for implementing a refrigeration cycle by means of such a machine

Abstract

A refrigeration machine (1, 100) configured to carry out a vapour compression refrigeration cycle by means of a refrigerant fluid, comprising a first and a second heat exchanger (2, 3), an expansion device (4) and compression means (5), wherein said compression means (5) comprise a first and a second compression stages (51, 52), and wherein said refrigeration machine (1) further comprises an intercooler (6), interposed between the first and second compression stages (51, 52), and a heat recovery exchanger (7), configured to allow a heat exchange between the refrigerant fluid exiting from the first heat exchanger (2) and the refrigerant fluid exiting from the second heat exchanger (3).

Description

[0001] REFRIGERATION MACHINE AND METHOD FOR IMPLEMENTING A REFRIGERATION CYCLE BY MEANS OF SUCH A MACHINE.

[0002] DESCRIPTION

[0003] The invention relates to a refrigeration machine, e.g. a chiller or heat pump, configured to carry out a vapour compression refrigeration cycle by means of a refrigerant fluid.

[0004] In particular, the invention relates to a heat pump for heating domestic or industrial indoor environments.

[0005] The invention further relates to a chiller for cooling domestic or industrial indoor environments.

[0006] Furthermore, the invention relates to a method for implementing a refrigeration cycle by means of the aforesaid refrigeration machine.

[0007] Typically, such a refrigeration machine of known type comprises two heat exchangers, an expansion device and refrigerant fluid compression means connected together so as carry out a vapour compression refrigeration cycle. Such a refrigeration machine, although well known and appreciated, has some important limitations related to the overall efficiency of the refrigeration machine itself.

[0008] In particular, these refrigeration machines, although widely used, suffer from a relatively limited overall efficiency.

[0009] Refrigeration machines are known which use an internal recovery exchanger to increase the overall efficiency of such refrigeration machines.

[0010] However, the heat exchange between the fluid exiting from the condenser and the fluid exiting from the evaporator is limited by a further constraint of the known refrigeration machines related to the end compression temperature.

[0011] In particular, the end compression temperature typically has an upper limit related to the physical structure of the compressor and the properties of the oil circulating in such a compressor.

[0012] Therefore, disadvantageously, the suction temperature of the compressor cannot be too high.

[0013] Consequently, in refrigeration machines it is not possible to exploit all the available heat of the fluid exiting from the condenser in favour of the fluid exiting from the evaporator.

[0014] Therefore, disadvantageously, also in this case the refrigeration machine will not be particularly efficient.The task of the present invention is to develop a refrigeration machine capable of obviating the aforementioned drawbacks and limitations of the prior art.

[0015] In particular, it is the aim of the present invention to make a refrigeration machine which is overall more efficient with respect to the known refrigeration machines. The above-mentioned task and aim are achieved by a refrigeration machine according to claim 1.

[0016] Further characteristics of the refrigeration machine according to claim 1 are described in the dependent claims.

[0017] The task and the aforesaid aim, together with the advantages that will be mentioned below, are highlighted by the description of some embodiments of the invention, which are given, by way of indication but not limitation, with reference to the attached drawing tables, where:

[0018] - Figure 1 depicts a schematic view of a first embodiment of the circuit of a refrigeration machine according to the invention;

[0019] - Figure 2 depicts a schematic view of a second embodiment of the circuit of a refrigeration machine according to the invention;

[0020] - Figure 3 depicts a schematic entropic diagram of the refrigeration cycle of the refrigeration machine of the invention.

[0021] With reference to the above-mentioned figures, a first embodiment of a refrigeration machine according to the invention is indicated as a whole with the number 1.

[0022] Such a refrigeration machine 1 is configured to carry out a vapour compression refrigeration cycle by means of a refrigerant fluid.

[0023] Preferably, the refrigeration machine 1 of the invention is a heat pump for heating domestic or industrial indoor environments.

[0024] However, the refrigeration machine 1 of the invention could be a chiller for cooling domestic or industrial indoor environments.

[0025] Such a refrigeration machine 1 comprises:

[0026] - a first heat exchanger 2 configured to allow a heat exchange between the refrigerant fluid and a first secondary fluid by means of an at least partial condensation of the aforesaid refrigerant fluid;

[0027] - a second heat exchanger 3 also configured to allow a heat exchange between the refrigerant fluid and a second secondary fluid by means of an at least partial evaporation of such refrigerant fluid;

[0028] - an expansion device 4;- compression means 5 configured to compress said refrigerant fluid.

[0029] According to the invention, the compression means 5 comprise a first compression stage 51 and a subsequent second compression stage 52.

[0030] Furthermore, the refrigeration machine 1 also comprises:

[0031] - an intercooler 6 interposed between the aforesaid first and second compression stages 51, 52;

[0032] - a heat recovery exchanger 7 configured to allow a heat exchange between the refrigerant fluid exiting from the first heat exchanger 2 and the refrigerant fluid exiting from the second heat exchanger 3.

[0033] The configuration described allows to obtain a refrigeration machine which is overall more efficient than the known refrigeration machines.

[0034] In particular, the refrigeration machine of the invention allows exploiting substantially all the available heat of the fluid exiting from the condenser in favour of the fluid exiting from the evaporator.

[0035] In fact, the heat recovery exchanger 7 is configured to be able to exchange the maximum amount of heat between the refrigerant fluid exiting from the first heat exchanger 2 and the refrigerant fluid exiting from the second heat exchanger 3. Furthermore, the presence of the first and of the second compression stages 2, 3 and of the intercooler 6 allows the refrigeration machine 1 to maintain a high temperature of the refrigerant fluid input to the first compression stage 2, as the described configuration allows the end compression temperature to be limited. It is not excluded that compression means 5 comprise further compression stages with further intercoolers interposed between such further stages.

[0036] According to the invention, the refrigeration machine 1 comprises bypass means 8 configured to allow the refrigerant fluid to bypass the second compression stage 52.

[0037] Preferably, but not necessarily, the refrigeration machine 1 comprises further bypass means 81 configured to allow the refrigerant fluid to bypass the first compression stage 51.

[0038] The first and the second compression stages 51, 52 can be actuated separately and independently according to predefined logic.

[0039] The aforesaid first and second compression stages 51, 52 can have different constructive and / or performance characteristics, such as different compression volumes, compression ratios, operating pressures and / or power consumption. Such a configuration allows the first and the second compression stages 51, 52to be operated individually and enables the efficiency of the thermodynamic cycle to be adjusted to the power required by the refrigeration machine.

[0040] Furthermore, the possibility of switching off one of the two compression stages while keeping the other in operation allows the oil quantity between the compressors to be rebalanced.

[0041] In fact, preferably, the first and the second compression stages 51, 52 respectively comprise a first and a second oil sump connected to each other by means of a duct 12 comprising a flow regulator 13.

[0042] Such a flow regulator 13, in a possible version of the invention, is an active device, for example an actuated valve.

[0043] In a further possible version of the invention, the flow regulator 13 is a passive device, for example a capillary tube.

[0044] Of course, in each case, the flow regulator 13 allows the oil flow to be regulated between the first and the second compression stages 51, 52.

[0045] Again, in a further possible version of the invention, the first and the second compression stages 51, 52 are of the oil-free type.

[0046] It should be noted that, preferably, each of said first and second compression stages 51, 52 can be configured to maintain a geometric compression ratiovfinalless than , or a compression ratiopfmalless than , where Vinitial

[0047]

[0048] Pmin P initial Pmin Pmax is the maximum condensation pressure and pmin is the minimum operating evaporation pressure declared by the refrigeration machine.

[0049] A further aspect of refrigeration machine 1 lies in the fact that it comprises a secondary circuit 9 for the aforesaid first secondary fluid.

[0050] Such a secondary circuit 9 is configured so as to allow the first secondary fluid to pass through the first heat exchanger 2 and the intercooler 6.

[0051] Preferably, the secondary circuit 9 is configured so that the entire flow of the first secondary fluid passes through both the first heat exchanger 2 and the intercooler 6.

[0052] A compact and efficient intercooler 6 is thereby obtained.

[0053] According to the invention, the refrigeration machine 1 comprises a liquid receiver 11 interposed between the first heat exchanger 2 and the heat recovery exchanger 7 and configured to receive the refrigerant fluid coming from the first heat exchanger 2.

[0054] Such a liquid receiver 11 is configured to store the liquid refrigerant downstream of the first heat exchanger 2, ensuring a constant flow of refrigerant fluid.Furthermore, the aforesaid liquid receiver 11 allows the separation of liquid and gas by outputting only liquid refrigerant.

[0055] According to the preferred embodiment of the invention, the heat recovery exchanger 7 is of the separate circuit type.

[0056] It is emphasised that in the heat recovery exchanger 7 no mixing occurs between the refrigerant fluid coming from the first heat exchanger and the refrigerant fluid coming from the second heat exchanger.

[0057] Such a configuration allows to optimise the heat exchange in the heat recovery exchanger 7.

[0058] In a second possible embodiment of the invention, which can be seen in Figure 2, the refrigeration machine of the invention is denoted by the number 100 and has all the characteristics of the first embodiment described above. Furthermore, the refrigeration machine 100 also comprises a four-way valve 10 configured to allow the reversal of the refrigeration cycle.

[0059] Such a configuration allows to obtain a reversible refrigeration machine.

[0060] For example, if the refrigeration machine 100 is a heat pump, the four-way valve 10 allows the refrigeration cycle to be reversed and to switch to chiller mode. If the refrigeration machine 100 is instead a chiller, the four-way valve 10 allows the refrigeration cycle to be reversed and to switch to heat pump mode.

[0061] It should be noted that, according to the invention, the secondary circuit 9 comprises a three-way valve 91 configured to allow such a first secondary fluid to bypass the intercooler 6.

[0062] In such a case, the flow of the first secondary fluid passing through the first heat exchanger 2 remains unaffected.

[0063] Such a configuration is particularly useful in the aforesaid second embodiment of the invention in which the refrigeration machine 100 comprises the four-way valve 10.

[0064] In fact, if, for example, the refrigeration machine 100 is a heat pump, in operation in chiller mode the heat exchanger 1 will carry out an evaporation of the refrigerant fluid while the heat exchanger 2 will carry out a condensation of the refrigerant fluid.

[0065] In this case, the fact that the first secondary fluid can bypass the intercooler 6 will be particularly useful, otherwise the latter would pour heat into such first secondary fluid, reducing the useful effect.

[0066] As mentioned at the beginning of the present description, a method forimplementing a refrigeration cycle by means of the refrigeration machine 1, 100 is also part of the invention.

[0067] In particular, such a method of implementing a refrigeration cycle by means of a refrigeration machine 1, 100 provides that inside the heat recovery exchanger 7 there is a maximum heat exchange between the refrigerant fluid exiting from the first heat exchanger 2 and the refrigerant fluid exiting from the second heat exchanger 3, such that the exiting temperature of the refrigerant fluid evaporated by the heat recovery exchanger 7 is close to or equal to the entering temperature of the refrigerant fluid condensed in the heat recovery exchanger 7.

[0068] A “close temperature” means that the exiting temperature of the evaporated refrigerant fluid from the heat recovery exchanger 7 is lower with respect to the entering temperature of the refrigerant fluid by a limited range.

[0069] For example, such a range can be 10°C.

[0070] Preferably, such a range is 1°C.

[0071] Preferably, the method provides a step of opening or closing the expansion device 4 so as to maximise the heat exchanged between the refrigerant fluid exiting from the first heat exchanger 2 and the refrigerant fluid exiting from the second heat exchanger 3.

[0072] It is thereby advantageously possible to maximise the COP (coefficient of performance) of the refrigeration machine 1, 100.

[0073] In particular, such a method provides for maintaining the enthalpy of the refrigerant fluid entering the compression means 5 substantially stable and opening or closing the expansion device 4 in such a way as to increase or decrease the enthalpy of the refrigerant fluid exiting the heat exchanger 3 so as to maximise the heat exchanged between the refrigerant fluid exiting from the first heat exchanger 2 and the refrigerant fluid exiting from the second heat exchanger 3.

[0074] Furthermore, the opening or closing step of the expansion device 4 is implemented so as to reduce the temperature difference between the second secondary fluid and the refrigerant fluid inside the second heat exchanger 3. Such a method, for example, provides for opening the expansion device 4 so as to increase the evaporation temperature of the refrigerant fluid in the second heat exchanger 3. This will thereby decrease the enthalpy of the refrigerant fluid exiting from the heat exchanger 3. Such a decrease in enthalpy will be compensated for by an increased heat exchange in the heat recoveryexchanger 7.

[0075] Or, for example, the method provides for closing the expansion device 4 so as to decrease the evaporation temperature of the refrigerant fluid in the second heat exchanger 3. This will thereby increase the enthalpy of the refrigerant fluid exiting from the heat exchanger 3.

[0076] Obviously, the refrigeration machine 1, 100 of the invention comprises a logic unit. The opening and closing of the expansion device 4 are controlled by such a logic unit based on the required heat output regime.

[0077] The aforesaid logic unit is configured to maximise the COP of the refrigeration machine 1, 100 by means of the method described above.

[0078] According to the preferred embodiment of the invention, the refrigeration machine 1 , 100 comprises a logic unit configured to control an opening or closing of the expansion device 4 so as to vary the enthalpy of the refrigerant fluid exiting from the second heat exchanger 3 while maintaining the enthalpy of the refrigerant fluid entering the compression means 5 substantially stable, so as to maximise the heat exchange in the heat recovery exchanger 7 so that the exiting temperature of the refrigerant fluid evaporated by the heat recovery exchanger 7 is close to or equal to the entering temperature of the refrigerant fluid condensed in the heat recovery exchanger 7.

[0079] The refrigeration machine 1, 100 also comprises a plurality of sensors X1, X2, X3, X4, X5, X6, X7 of temperature and / or pressure of the refrigerant fluid arranged so as to allow monitoring the fluid along the entire circuit.

[0080] In particular:

[0081] - a first sensor X1 is arranged between the first compression stage 51 and the intercooler 6;

[0082] - a second sensor X2 is arranged between the intercooler 6 and the second compression stage 52;

[0083] - a third sensor X3 is arranged downstream of the second compression stage 52;

[0084] - a fourth sensor X4 arranged after the first heat exchanger 2, preferably between the liquid receiver 11 and the heat recovery exchanger 7;

[0085] - a fifth sensor X5 arranged between the heat recovery exchanger 7 and the expansion device 4;

[0086] - a sixth sensor X6 arranged between the expansion device 4 and the second heat exchanger 3;- a seventh sensor X7 arranged downstream of the second heat exchanger 3. Each sensor of such a plurality of sensors X1, X2, X3, X4, X5, X6, X7 is connected to the logic unit and is configured to communicate to such a logic unit the acquired temperature and / or pressure measurement so that such a logic unit processes such measurements and controls the opening or closing of the expansion device 4.

[0087] In particular, the logic unit is configured to process such measurements and determine the enthalpy of the refrigerant fluid and dynamically control the expansion device 4 to vary the enthalpy of the refrigerant fluid exiting from the second heat exchanger 3.

[0088] According to the preferred embodiment of the invention, the method for implementing the refrigeration cycle by means of the refrigeration machine 1, 100 comprises the following steps:

[0089] - acquiring, by means of the aforesaid plurality of sensors X1, X2, X3, X4, X5, X6, X7, temperature and / or pressure measurements of the refrigerant fluid along the circuit;

[0090] - processing such measurements by means of said logic unit to determine the enthalpy of the refrigerant fluid;

[0091] - dynamically controlling the expansion device 4 by means of said logic unit to vary the enthalpy of the refrigerant fluid exiting from the second heat exchanger 3;

[0092] - keeping the enthalpy of the refrigerant fluid entering the compression means 5 substantially stable by means of said dynamic control;

[0093] - maximising the heat exchange in the heat recovery exchanger 7 so that the exiting temperature of the refrigerant fluid evaporated by said recovery exchanger 7 is kept close to or equal with respect to the entering temperature of the refrigerant fluid condensed in such a heat recovery exchanger 7.

[0094] It has in practice been established that the invention achieves the intended task and aim.

[0095] In particular, with the invention, a refrigeration machine was developed that is more efficient with respect to the known refrigeration machines.

Claims

CLAIMS1) A refrigeration machine (1, 100) configured to carry out a vapour compression refrigeration cycle by means of a refrigerant fluid, comprising: - a first heat exchanger (2) configured to allow a heat exchange between said refrigerant fluid and a first secondary fluid by means of an at least partial condensation of said refrigerant fluid;- a second heat exchanger (3) configured to allow a heat exchange between said refrigerant fluid and a second secondary fluid by means of an at least partial evaporation of said refrigerant fluid;- an expansion device (4);- compression means (5) configured to compress said refrigerant fluid; said compression means (5) comprising:- a first compression stage (51 );- a second compression stage (52) subsequent to said first compression stage (51);said refrigeration machine (1) also comprising:- an intercooler (6) interposed between said first and second compression stages (51 , 52);- a heat recovery exchanger (7) configured to allow a heat exchange between the refrigerant fluid exiting from said first heat exchanger (2) and the refrigerant fluid exiting from said second heat exchanger (3), characterised by comprising a logic unit configured to control an opening or a closing of said expansion device (4) so as to vary the enthalpy of the refrigerant fluid exiting from said second heat exchanger (3) while maintaining the enthalpy of the refrigerant fluid entering said compression means (5) substantially stable, so as to maximise the heat exchange in said heat recovery exchanger (7) so that the exiting temperature of the refrigerant fluid evaporated by said heat recovery exchanger (7) is close to or equal to the entering temperature of the refrigerant fluid condensed in said heat recovery exchanger (7).2) A refrigeration machine (1 , 100) according to claim 1 , characterised by comprising bypass means (8) configured to allow said refrigerant fluid to bypass said second compression stage (52).3) A refrigeration machine (1, 100) according to claim 1 or 2, characterised by comprising a secondary circuit (9) for said first secondary fluid configured so as to allow said first secondary fluid to pass through said first heatexchanger (2) and said intercooler (6).4) A refrigeration machine (1 , 100) according to claim 3, characterised in that said secondary circuit (9) comprises a three-way valve (91) configured to allow said first secondary fluid to bypass said intercooler (6).5) A refrigeration machine (1, 100) according to any one of the preceding claims in combination with claim 2, characterised by comprising further bypass means (81) configured to allow the refrigerant fluid to bypass said first compression stage (51), said first and second compression stages (51, 52) being separately and independently operable according to pre-defined logic.6) A refrigeration machine (1, 100) according to any one of the preceding claims, characterised in that said heat recovery exchanger (7) is of the separate circuit type.7) A refrigeration machine (100) according to any one of the preceding claims, characterised by comprising a four-way valve (10) configured to allow the reversal of the refrigeration cycle.8) A refrigeration machine (1, 100) according to any one of the preceding claims, characterised in that said first and second compression stages (51 , 52) respectively comprise a first and a second oil sump connected to each other by means of a duct (12) comprising a flow regulator (13).9) A refrigeration machine (1, 100) according to any one of the preceding claims, characterised by being a heat pump.10) A refrigeration machine (1, 100) according to any of claims 1 to 8, characterised by being a chiller.11 ) A refrigeration machine (1, 100) according to any one of the preceding claims, characterised by comprising a plurality of temperature and / or pressure sensors (X1 , X2, X3, X4, X5, X6, X7) connected to said logic unit and adapted to send temperature and / or pressure measurements of the refrigerant fluid to said logic unit, said logic unit being configured to process said measurements and determine the enthalpy of the refrigerant fluid.12) A method for implementing a refrigeration cycle by means of a refrigeration machine (1, 100) according to any one of the preceding claims, characterised by providing that within said heat recovery exchanger (7) there is substantially a maximum heat exchange between the refrigerant fluid exiting from said first heat exchanger (2) and the refrigerant fluid exiting from said second heat exchanger (3) such that the exiting temperature of the refrigerantfluid evaporated by said heat recovery exchanger (7) is close to or equal to the entering temperature of the refrigerant fluid condensed in said heat recovery exchanger (7).13) A method for implementing a refrigeration cycle according to claim 12, characterised in that the maximum heat exchange between the refrigerant fluid exiting from said first heat exchanger (2) and the refrigerant fluid exiting from said second heat exchanger (3) is obtained by means of a dynamic control phase of the expansion device (4) by said logic unit to vary the enthalpy of the refrigerant fluid exiting from the second heat exchanger (3) and a substantially stable maintenance phase of the enthalpy of the refrigerant fluid entering the compression means (5) by means of said dynamic control.14) A method according to claim 13 implemented by means of a refrigeration machine (1, 100) according to claim 11, characterised in that prior to said dynamic control phase there is a phase of acquiring, by means of said plurality of sensors (X1, X2, X3, X4, X5, X6, X7), temperature and / or pressure measurements of the refrigerant fluid along the circuit and a phase of processing said measurements by means of said logic unit to determine the enthalpy of the refrigerant fluid.

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