Method of operating heat cycle system, heat cycle system and method of modifying heat cycle system

Abstract

A method of operating a thermal cycle system is disclosed wherein the thermal cycle system comprises a working fluid circulating through a circuit comprising a compressor (10), a condenser (11), an expander unit (130) and an evaporator (140), and wherein the expander unit (130) is configured to generate a rotary mechanical motion, the method includes operating the evaporator at an evaporator working fluid evaporation capacity that is at least about 110% of a nominal evaporator working fluid evaporation capacity. A thermal cycle system and a method of modifying a thermal cycle system are also disclosed.

Description

Technical Field

[0001] The present disclosure relates to a thermal cycle system applied in a heat pump or a cooling system and a method of operating the thermal cycle system. Background Art

[0002] Thermal cycle systems operating according to a cyclic thermal process, such as the Carnot process, are used in many applications.

[0003] In some applications, such as in a heat pump system for heating a space by taking heat from the ground, bedrock, water or air and supplying the heat to a heating system for the space, the goal is to provide heat.

[0004] In other applications, the goal is to remove heat (ie, to cool something), such as in air conditioning systems or in cooling / refrigeration systems, the goal is to remove heat from a space or from an object.

[0005] In the Carnot process, energy is input in the form of heat Q taken by the evaporator and in the form of mechanical energy W supplied by the compressor. The mechanical energy can be provided by converting electrical energy by an electric motor. In addition, energy is input in the form of heat Q supplied by the condenser. H The heating performance coefficient (COP H ) is limited to Q H / W, and the cooling performance coefficient (COP C ) is limited to O C / W.

[0006] Figure 1 A conventional thermal cycle system in which a working fluid circulates is schematically illustrated.

[0007] The system includes a compressor 10 having a compressor input end and a compressor output end, at which the working fluid is in a first state having a first pressure P1, a first temperature T1 and a first enthalpy H1, and at which the working fluid is in a second state having a second pressure P2, a second temperature T2 and a second enthalpy H2.

[0008] The compressor 10 is configured to increase the pressure of the working fluid such that P2 > P1 .

[0009] The compressor may be electric.

[0010] The system further comprises a condenser 11 having a condenser input connected to the compressor output to receive the working fluid in the second state and a condenser output at which the working fluid is in a third state P3, T3, H3.

[0011] The condenser 11 can be configured to exchange heat with a heat delivery circuit 12, where heat is delivered from the condenser 11, whereby the temperature of the working fluid can be reduced such that T3 < T2, and the enthalpy of the working fluid is reduced such that H3 < H2. At least a portion of the working fluid changes from a vapor state to a liquid state.

[0012] As an alternative, the condenser 11 can be configured to deliver heat to an air stream or merely dissipate heat to the surrounding air (as can be the case in a refrigeration system).

[0013] The heat delivery circuit 12 can be, for example, a heating circuit for providing heating to a space (such as one or more residences or the interior of a vehicle). In other applications, the heat can be used in a drying process, etc.

[0014] The system further includes an expansion valve 13 connected to the condenser output.

[0015] The expansion valve 13 is configured for isenthalpic expansion to allow the working fluid to expand to a fourth state P4, T4, H4 such that the working fluid at the expansion valve output has a lower pressure than the third state such that P4 < P3.

[0016] The system further includes an evaporator 14 that can be configured to exchange heat with a heat supply circuit 15 such that the working fluid undergoes evaporation, where heat is received by the evaporator 14, whereby the enthalpy of the working fluid will increase such that H1 > H4. Also, the temperature can increase such that T1 > T4.

[0017] The heat supply circuit 15 can be a cooling circuit in a cooling device or an air conditioning device. Alternatively, the heat supply circuit 15 can also be configured to obtain heat from, for example, air, the ground, bedrock, or water in a heat pump system.

[0018] The evaporator input is connected to receive the working fluid in the fourth state from the expansion valve 13. The evaporator output is connected to the input of the compressor 10.

[0019] It is generally desirable to improve the performance of the heat cycle system and thus improve the coefficient of performance.

[0020] As is known, for example, from WO 2013141805 A1, the heat cycle system includes an energy converter for converting the energy of a pressurized fluid into mechanical energy, which can then be used to generate electrical energy.

[0021] In Dimitriou, P.: Experimental evaluation of work recovery potential in commercial heat pumps using a pistol expander prototype(Experimental Evaluation of Work Recovery Potential in Commercial Heat Pumps Using a Piston Expander Prototype), National Technical University of Athens, 2017, discloses a thermal cycle in which the expansion valve is replaced by a piston expander that is mechanically coupled to the compressor, thereby providing driving power to the compressor.

[0022] There remains a general need to improve thermal cycle systems, particularly with respect to efficiency and / or production of electrical energy. Summary of the invention

[0023] An object of the present disclosure is to provide a thermal cycle system capable of generating electrical energy and preferably also having improved efficiency.

[0024] Specific objects include providing a thermal cycle system suitable for use as a cooling system for cooling a space or a body of material.

[0025] The invention is defined by the attached independent claim, wherein embodiments are set forth in the dependent claims, the following description and the drawings.

[0026] According to a first aspect, a method for operating a thermal cycle system is provided, wherein the thermal cycle system includes a working fluid that circulates through a circuit including a compressor, a condenser, an expander unit, and an evaporator, wherein the expander unit is configured to generate a rotational mechanical motion. The method includes: operating the compressor to receive a working fluid in a first state having a first pressure, a first temperature, and a first enthalpy, and compressing the working fluid to a second state having a second pressure, a second temperature, and a second enthalpy; operating the condenser to receive a working fluid in the second state, and condensing the working fluid to a third state having a third pressure, a third temperature, and a third enthalpy; operating the expander unit to receive a working fluid in the third state, and expanding the working fluid to a modified fourth state having a modified fourth pressure, a modified fourth temperature, and a modified fourth enthalpy; operating the evaporator to receive a working fluid in a modified fourth state, and evaporating the working fluid to the first state, wherein the nominal evaporator working fluid evaporation capacity is defined as the enthalpy reduction provided by the condenser minus the enthalpy increase provided by the compressor. The method further includes operating the evaporator at an evaporator working fluid evaporation capacity of at least about 110% of a nominal evaporator working fluid evaporation capacity.

[0027] The compression portion of the process may be substantially isentropic, ie, isentropic except for the losses.

[0028] The condensation portion of the process may be substantially isobaric and / or isothermal, ie, substantially isobaric / isothermal except for losses.

[0029] The expansion part of the process may be substantially isentropic, ie isentropic except for the losses. In particular, the expansion part of the process is not isenthalpic, as is the case with an expansion valve.

[0030] The evaporation portion of the process may be substantially isobaric and / or isothermal, ie, substantially isobaric / isothermal except for losses.

[0031] In particular, the working fluid evaporation capacity of the evaporator can be about 110%-120%, about 120%-130%, about 130%-140%, about 140%-150%, about 150%-160%, about 160%-170%, about 170%-180%, about 180%-190%, or about 190%-200% of the nominal evaporator working fluid evaporation capacity.

[0032] The inventors have surprisingly found that by operating the system as described above, electrical power can be generated without any loss in at least the coefficient of performance of the system.

[0033] The rotational movement provided by the expander unit may be used to at least partially power a compressor and / or another mechanically operated device, in particular a generator for producing electrical power.

[0034] It has also been noted that the coefficient of performance COP can be additionally increased according to the above operation.

[0035] Thus, operation according to the above provides a system having a COP at least as high as a corresponding system without an expander unit and still producing useful amounts of electrical energy.

[0036] In this method, the energy supplied to the working fluid by the evaporator exceeds the energy required to raise the enthalpy of the working fluid substantially isobarically from the enthalpy level at the condenser outlet to the enthalpy level corresponding to the humid or superheated vapor.

[0037] The evaporator power (energy) delivered to the working fluid may correspond to the sum of the thermal power (thermal energy) removed from the working fluid by the condenser and the power (mechanical energy) generated by the working fluid at the rotatable expander minus the power provided to the working fluid by the compressor.

[0038] The expander unit may be operated with the working fluid partially or fully saturated.

[0039] The working fluid pressure drop across the evaporator may be less than about 5 bar, preferably about 0.50 bar-0.75 bar; about 0.75 bar-1.00 bar; about 1.00 bar-1.25 bar; about 1.25 bar-1.50 bar; about 1.50 bar-1.75 bar; about 1.75 bar-2.00 bar; about 2.00 bar-2.25 bar; about 2.25 bar-2.50 bar; about 2.50 bar-2.75 bar; about 2.75 bar-3.00 bar; about 3.00 bar-3.25 bar; about 3.25 bar-3.50 bar; about 3.50 bar-3.75 bar; about 3.75 bar-4.00 bar; about 4.00 bar-4.25 bar; about 4.25 bar-4.50 bar; about 4.50 bar-4.75 bar; or about 4.75 bar-5.00 bar.

[0040] This represents a significant reduction in pressure drop compared to current commercially available systems which typically operate at a pressure drop of 6-8 bar across the evaporator.

[0041] The expander unit may be selected from the group consisting of a rotary expander, a swing expander, a scroll expander, a GE rotor expander, a reciprocating expander, a screw expander and a radial turbine expander.

[0042] Such an expander may be provided by reversing the rotation of the corresponding compressor, typically associated with the removal of any non-return valve originally provided in the compressor.

[0043] The method may further include operating the expander unit to at least partially power at least one device.

[0044] In the method, a generator may be mechanically connected to the expander unit for generating electricity, and when the rotatable expander is caused to rotate during expansion of the working fluid, the generator may be operated to generate electrical energy.

[0045] The method may further include subcooling the working fluid downstream of the condenser and upstream of the expander unit.

[0046] Therefore, heat can be efficiently transferred from the working fluid immediately downstream of the condenser to the working fluid immediately upstream of the compressor.

[0047] A working fluid downstream of the condenser and upstream of the expander unit may be caused to exchange heat with a working fluid upstream of the compressor and downstream of the evaporator.

[0048] The method may further comprise causing at least some of the working fluid downstream of the expander unit and upstream of the evaporator to undergo further expansion in an expansion valve.

[0049] The working fluid exiting from the expander unit may be selectively distributed between the expansion valve and a bypass connection which bypasses the expansion valve.

[0050] The expansion valve may be operated based on conditions downstream of the evaporator, preferably immediately downstream of the evaporator.

[0051] The evaporator may be caused to exchange heat with an evaporator circuit comprising a second working fluid, thereby providing, for example, a heat pump.

[0052] The second working fluid may be a liquid, such as brine.

[0053] Alternatively, the second working fluid may be a gas, such as air.

[0054] The condenser may be caused to exchange heat with a condenser circuit including a third working fluid.

[0055] The third working fluid may be a liquid.

[0056] The third working fluid may be a gas, such as air.

[0057] The evaporator may be oversized relative to the same system including a compressor, a condenser, and an expansion valve configured for isenthalpic expansion of the working fluid (rather than an expander unit).

[0058] The condenser may be caused to exchange heat with a first external working fluid in gaseous form.

[0059] The evaporator may be caused to exchange heat with a second external working fluid in gaseous form.

[0060] Thus, the method may provide an air-to-air cooling system. The thermal cycle system may operate as an irreversible cooling system for cooling a space or a body of material. Thus, the thermal cycle system is configured to only cool a space or a body of material and cannot reversibly heat the space or the body of material.]

[0061] According to a second aspect, a thermal cycle system is provided, the thermal cycle system comprising a working fluid that circulates through a circuit comprising a compressor, a condenser, an expander unit, and an evaporator, wherein the expander unit is configured to produce a rotational mechanical motion. In the thermal cycle system, a nominal evaporator working fluid evaporation capacity is defined as an enthalpy reduction provided by the condenser minus an enthalpy increase provided by the compressor. The evaporator is sized and adapted to provide an evaporator working fluid evaporation capacity that is at least 110% of the nominal evaporator working fluid evaporation capacity.

[0062] In particular, the working fluid evaporation capacity of the evaporator can be about 110%-120%, about 120%-130%, about 130%-140%, about 140%-150%, about 150%-160%, about 160%-170%, about 170%-180%, about 180%-190%, or about 190%-200% of the nominal evaporator working fluid evaporation capacity.

[0063] The evaporator may be oversized relative to the same system including a compressor, a condenser, and an expansion valve configured to expand the working fluid (rather than an expander unit).

[0064] The evaporator may be configured to evaporate the working fluid received from the expander unit to at least saturation such that the working fluid is in a saturated vapor phase at an evaporator output.

[0065] The expander unit may include a rotatable expander, wherein a working fluid flowing through the expander causes the rotatable expander to rotate, wherein the generator may be mechanically connected to the rotatable expander to generate electricity when the rotatable expander is caused to rotate,

[0066] The expander unit may be selected from the group consisting of a rotary expander, a swing expander, a scroll expander, a GE rotor expander, a reciprocating expander, a screw expander and a radial turbine expander.

[0067] Such an expander may be provided by reversing the rotation of the corresponding compressor, typically associated with the removal of any non-return valve originally provided in the compressor.

[0068] The working fluid pressure drop across the evaporator may be less than about 5 bar, preferably about 0.50 bar-0.75 bar; about 0.75 bar-1.00 bar; about 1.00 bar-1.25 bar; about 1.25 bar-1.50 bar; about 1.50 bar-1.75 bar; about 1.75 bar-2.00 bar; about 2.00 bar-2.25 bar; about 2.25 bar-2.50 bar; about 2.50 bar-2.75 bar; about 2.75 bar-3.00 bar; about 3.00 bar-3.25 bar; about 3.25 bar-3.50 bar; about 3.50 bar-3.75 bar; about 3.75 bar-4.00 bar; about 4.00 bar-4.25 bar; about 4.25 bar-4.50 bar; about 4.50 bar-4.75 bar; or about 4.75 bar-5.00 bar.

[0069] The passage connecting the expander outlet to the evaporator assembly inlet may be less than about 0.5 m, preferably less than about 0.2 m, less than about 0.1 m, or less than about 0.05 m. In particular, the expander outlet may be integrated with the evaporator inlet, for example by being formed in one piece.

[0070] The channel may be straight.

[0071] The thermal cycle system may further include a subcooler connected downstream of the condenser and upstream of the expander unit.

[0072] The thermal cycle system may further include an expansion valve connected downstream of the expander unit and upstream of the evaporator.

[0073] The thermal cycle system may further include at least one control valve for selectively distributing the working fluid exiting from the expander unit between the expansion valve and a bypass connection that bypasses the expansion valve.

[0074] The expansion valve may be operated based on conditions downstream of the evaporator, preferably immediately downstream of the evaporator.

[0075] In other embodiments, the channel may be curved at about 70-110 degrees, preferably about 80-100 degrees, about 85-95 degrees, or about 90 degrees.

[0076] Depending on the type of heat exchanger used for the evaporator, it may be advantageous to use a curved channel, which will create some turbulence in the channel, which may improve the distribution of the working fluid inside the evaporator.

[0077] The evaporator may be configured to exchange heat with an evaporator circuit including a second working fluid.

[0078] The second working fluid may be a liquid, such as brine.

[0079] The second working fluid may be a gas, such as air.

[0080] The condenser may be configured to exchange heat with a condenser circuit including a third working fluid.

[0081] The third working fluid may be a liquid.

[0082] The third working fluid may be a gas, such as air.

[0083] In particular, the condenser may be configured to exchange heat with a first external working fluid in gaseous form.

[0084] The first external fluid may include, consist of, or consist essentially of air.

[0085] The evaporator may be configured to exchange heat with a second external working fluid in gas form.

[0086] Therefore, the heat circulation system can be configured as an air-to-air heat circulation system.

[0087] The thermal cycle system may be configured to operate as an irreversible cooling system for cooling a space or a body of material.

[0088] The space may be the interior of a building, the interior of a vehicle, etc. The material body may be an ice rink, etc. Therefore, the thermal cycle system is configured to only cool the space or material body, but not to reversibly heat the space or material body.

[0089] According to a third aspect, there is provided a method for modifying a thermal cycle system, wherein the thermal cycle system comprises:

[0090] A working fluid is circulated through a circuit including a compressor, a condenser, an expansion valve, and a first evaporator. The method includes replacing the expansion valve with an expander unit configured to generate a rotary mechanical motion; and replacing the first evaporator with a second evaporator having a greater working fluid evaporation capacity than the first evaporator.

[0091] The modified thermal cycle system may be a heating system for collecting heat from a fluid in the form of air or a liquid such as brine and used to heat a building or a vehicle.

[0092] Alternatively, the heat cycle system may be a cooling system for collecting heat from a space, such as a building space or an air flow or a space in a vehicle, and for rejecting the heat to the outside.

[0093] The thermal cycle can also be a reversible system, which can be used to cool or heat buildings or vehicles.

[0094] The second evaporator can have a working fluid evaporation capacity of about 110%-120%, about 120%-130%, about 130%-140%, about 140%-150%, about 150%-160%, about 160%-170%, about 170%-180%, about 180%-190%, or about 190%-200% of the working fluid evaporation capacity of the first evaporator.

[0095] The second evaporator may exhibit a lower working fluid pressure drop than the first evaporator.

[0096] The second evaporator may exhibit a working fluid pressure drop that is less than 50%, preferably less than 40%, or less than 30% of the working fluid pressure drop of the first evaporator.

[0097] The expander unit may include a rotatable expander, wherein the working fluid flowing through the expander causes the expander to rotate, wherein the method further includes mechanically connecting the generator to the rotatable expander to generate electricity when the rotatable expander is caused to rotate.

[0098] The method may further include increasing a flow area of ​​a working fluid connection between the expander unit and the evaporator.

[0099] The method may further include increasing the flow area of ​​the expander inlet.

[0100] The method may further include shortening a working fluid connection between the expander unit and the evaporator.

[0101] For example, a shorter passage for the connection may be provided, or the expander outlet may be connected directly to the evaporator inlet. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] Figure 1 is a schematic diagram of a conventional thermal cycle system.

[0103] Figure 2 is a schematic diagram of a thermal cycle system according to a first embodiment.

[0104] Figure 3 It is a graphic Figure 1 and Figure 2 Schematic pressure-enthalpy diagram for comparison between thermal cycle systems.

[0105] Figure 4 Yes, you can Figure 2 Schematic diagram of a rotatable expander 130 used in a thermal cycle system.

[0106] Figure 5 is a schematic diagram of the evaporator 140 .

[0107] Figure 6 is based on Figure 2 Schematic diagram of a modified version of the thermal cycling system. DETAILED DESCRIPTION

[0108] Will refer to Figure 2 Disclose the inventive concept, the figure illustrates the corresponding Figure 1 The thermal cycle system of the illustrated system, wherein like components have like reference numerals.

[0109] Figure 2 The system shown is Figure 1 The system shown differs in that the expansion valve 13 has been replaced by a rotatable expander 130 and the evaporator 14 has been replaced by one with greater capacity. Furthermore, it may be advantageous to reduce the pressure drop in the evaporator 140 and to make the connection 141 between the output of the rotatable expander 130 and the evaporator 140 as short and straight as possible.

[0110] Therefore, in Figure 2 , a thermal cycle system is illustrated in which a working fluid circulates as indicated by arrows.

[0111] In some embodiments, the thermal cycle system may be formed as a refrigeration circuit for use in an air conditioning system in a stationary structure, in a ship, or in a vehicle.

[0112] In other embodiments, the thermal cycle system may be formed as a heat pump system for use in a stationary structure such as a building, in a ship, or in a vehicle.

[0113] The system includes a compressor 10 having a compressor input end and a compressor output end, at which the working fluid is in a first state having a first pressure P1, a first temperature T1 and a first enthalpy H1, and at which the working fluid is in a second state having a second pressure P2, a second temperature T2 and a second enthalpy H2.

[0114] The compressor 10 is configured to increase the pressure of the working fluid such that P2 > P1 .

[0115] The compressor may be electric.

[0116] The system further comprises a condenser 11 having a condenser input connected to the compressor output to receive the working fluid in the second state and a condenser output at which the working fluid is in a third state P3, T3, H3.

[0117] The condenser 11 may be configured to exchange heat with the heat transfer loop 12, wherein heat is transferred from the condenser 11, whereby the enthalpy of the working fluid may be reduced, such that H3 <H2。

[0118] Alternatively, the condenser 11 may be configured to deliver heat to the air flow, or simply dissipate heat to the surrounding environment (as may be the case in a refrigeration system).

[0119] The system further includes a rotatable expander 130 that replaces the expansion valve 13 ( Figure 1 ) and may have the form of, for example, a turbine, a scroll expander or a GE rotor expander. Thus, the rotatable expander 130 replaces the expansion valve 13 (which would otherwise be provided at this stage in the thermal cycle process Figure 1 ).

[0120] The expander input is connected to receive the working fluid in a third P3 , T3 , H3 state from the condenser 11 .

[0121] The rotatable expander 130 is configured to allow the working fluid to expand to a modified fourth state P40, T40 such that the working fluid at the expander output has a lower pressure and enthalpy than the third state, such that P40 < P3 and H40 < H3.

[0122] The rotatable expander 130 may be characterized as operating near isentropically, which causes not only a pressure loss but also an enthalpy loss such that at the fifth state, the modified fourth state P40, T40, the enthalpy H40 is less than the enthalpy (H3) of the third state.

[0123] The system further includes an evaporator 140, which may be configured to exchange heat with the heat supply circuit 15, where the heat is received by the evaporator 140, whereby the enthalpy of the working fluid increases and the working fluid is evaporated, such that H40 < H1.

[0124] The heat supply circuit 15 may be a cooling circuit in a cooling device or an air conditioning device. Alternatively, the heat supply circuit 15 may also be configured to obtain heat from, for example, air, the ground, bedrock, or water in a heat pump system.

[0125] The evaporator input is connected to receive the working fluid in the modified fourth state from the rotatable expander 130. The evaporator output is connected to the input of the compressor 10.

[0126] Figure 3 is a schematic pressure - enthalpy diagram Figure 1 and Figure 2 of the heat cycle in

[0127] In Figure 3 the working fluid states P1, T1, H1, P2, T2, H2 and P3, T3, H3 are indicated as the same in a conventional cycle according to Figure 1 and a modified cycle according to Figure 2 Thus, comparing the prior art system of Figure 1 with the system according to the inventive concept of Figure 2 the compressor 10 and the condenser 11 are the same, the choice of the working fluid, the mass flow rate mf, and the heat exchange conditions at the condenser and the compressor may be the same or designed for a higher inlet pressure. The described modifications allow for a higher inlet pressure to the compressor under the same conditions in the condenser.

[0128] In Figure 3 the enthalpies at the corresponding working fluid states are also indicated. Thus, at the first state P1, T1, the enthalpy is H1; at the second state P2, T2, the enthalpy is H2, and at the third state, the enthalpy is H3.

[0129] In Figure 1In the system using the expansion valve 13, the expansion of the working fluid from the third state P3, T3 to the fourth state will be isenthalpic. Therefore, the enthalpy of the fourth state P4, T4 is H3, ie, the same as the third state P3, T3.

[0130] However, in Figure 2 In the system, the rotatable expander 130 operates nearly isentropically, which causes not only pressure loss but also enthalpy loss, so that in the modified fourth state P40, T40, H40, the enthalpy H40 is less than the enthalpy (H3) of the third state.

[0131] The rotatable expander 130 may be operated completely below the saturation curve of the working fluid, so that the working fluid is in a two-phase state throughout the expansion process. Alternatively, the rotatable expander may be operated on or outside the saturation curve.

[0132] exist Figure 1 In the evaporator 14 used in the system shown, the working fluid will be evaporated and possibly superheated by adding enthalpy corresponding to the difference between the enthalpies in the first state and the third state, ie, adding enthalpies H1 - H3 in the evaporator 14 .

[0133] and Figure 1 Compared to the system, the evaporator 140 will need to Figure 2 The working fluid in the system adds more enthalpy.

[0134] Therefore, the evaporator 140 will have to evaporate the working fluid by adding enthalpy corresponding to the difference between the enthalpy in the first state and the enthalpy in the modified fourth state, ie, adding enthalpy H1 - H40 in the evaporator 140 .

[0135] therefore, Figure 2 The capacity of the evaporator 140 needs to be greater than Figure 1 The capacity of the evaporator 14.

[0136] In addition, it may be advantageous to minimize the pressure drop in the evaporator 140. Ideally, the heating of the working fluid in the evaporator 140 will occur at a constant pressure, but in practice there will be some pressure loss, depending on the design of the evaporator, such that P4>P1. In particular, the pressure drop in the evaporator 140 may be less than about 3 bar, preferably less than about 2 bar, or less than about 1.5 bar.

[0137] The reduced pressure drop may be achieved by increasing the number of flow paths through the evaporator 140 and / or by increasing the flow area of ​​the evaporator 140 .

[0138] It may also be advantageous to shorten the connection between the rotatable expander 130 and the evaporator 140 .

[0139] like Figure 3 As illustrated, the dashed line from point P40 , H40 to point P1 , T1 indicates a smaller pressure drop than the dashed line from P4 , T4 , H4 to P1 , T1 ; H1 .

[0140] See also Figure 3 The rotatable expander 130 may be provided in the form of a scroll expander or a GE rotor expander.

[0141] However, other types of rotatable expanders may also be used.

[0142] The rotatable expander 130 is mechanically connected to a generator 131 for producing electrical power.

[0143] The rotatable expander 130 receives from the output of the condenser 12 a flow rate mf of the working fluid in a third state P3 , T3 having an enthalpy H3 .

[0144] In the rotatable expander 130, the working fluid is isentropically expanded, wherein the working fluid is below the saturated liquid line, such that the working fluid is in a two-phase form.

[0145] The rotatable expander 130 outputs the working fluid at a lower pressure P40 and temperature T40 (referred to as a modified fourth state, also having a lower enthalpy H40).

[0146] The rotation of the rotatable expander 130 drives a generator 131 which outputs electric power corresponding to P (expansion) excluding losses.

[0147] See also Figure 5 , a schematic illustration of the evaporator 140 is provided.

[0148] The evaporator 140 is connected to the output of the rotatable expander 130 such that it receives a flow rate mf of the working fluid in a modified fourth state P40, T40, H40.

[0149] The connection 141 between the output of the rotatable expander 130 and the evaporator 140 may be made as short and straight as possible.

[0150] The connection 141 is connected to a distributor 142 which divides the working fluid flow into a plurality of evaporator channels 143a, 143b, 143c, each evaporator channel providing one evaporator sub-flow.

[0151] These substreams are combined by a collector 144 into an evaporator output 145 connected to the compressor 10 .

[0152] Each of the evaporator channels 143a, 143b, 143c may be formed as a corresponding flow path (such as a pipe, a tube, or a hose), which may be connected to a cooling flange (not shown) for increasing heat exchange efficiency with a gaseous fluid.

[0153] Alternatively, the evaporator channels 143a, 143b, 143c may be formed by channels in a heat exchanger for exchanging heat with a liquid.

[0154] The number of flow paths, and optionally the surface area of ​​each flow path, may be selected to provide a desired pressure drop of less than 3 bar across the heat exchanger, taking into account the type of working fluid used in the relevant application.

[0155] From the perspective of power balance, Figure 2 The system with mass flow mf in can be explained as follows:

[0156] Power Input:

[0157] Compressor – P (compression): mf×(H2-H1)

[0158] Evaporator – P (evaporation): mf×(H1-H40)

[0159] Power Output:

[0160] Condenser – P (condensation): mf×(H2-H3)

[0161] Expander – P (expansion): mf×(H3-H40)

[0162] Therefore, the evaporator will be sized so that P(evaporation) = P(condensation) + P(expansion) - P(compression).

[0163] Experimental data

[0164] To verify Figure 2 The principles of the system disclosed in , using two commercially available heat pump systems in the form of Panasonic S-250PE3E5B as a starting point. These systems will be labeled "original system" and "modified system" accordingly.

[0165] The "Modified System" is modified as follows:

[0166] The expansion valve was replaced by a scroll expander of type DENSO SCSA06C 447220-6572HFC134a. The scroll expander was modified by removing its one-way check valve and by increasing the flow area at the expander input to a diameter of about 14 mm.

[0167] The expander is connected to a brake of the type Delta AC Servo ModellECMA-J11330R4 kW 3,0 / 3000 rpm from Delta Electronics (Sweden) AB, which is used to simulate a generator connected to the output shaft of the rotatable expander 130 .

[0168] The evaporator is replaced with one with higher capacity and lower pressure drop.

[0169] The evaporator was constructed from two open gable evaporator blocks of type AIR0332 600 x 600-4R available from Aircoil AB (SE). The evaporator blocks were connected in parallel and mounted in a V-shaped construction block at a 90 degree angle.

[0170] The evaporator 140 includes a total of 16 channels having an inner diameter of 6.4 mm and an average length of about 1400 mm.

[0171] The output of the rotatable expander 130 is connected to the distributor of the evaporator using a 500 mm long pipe.

[0172] These systems are further equipped with pressure and temperature sensors as follows.

[0173] The modified system is equipped with pressure sensors GP01 and GP02 immediately upstream and downstream of the compressor 10; temperature sensors GT03 and GT01 are installed immediately upstream and downstream of the compressor 10; pressure sensors GP03 and GP04 are installed immediately upstream and downstream of the rotatable expander 130; temperature sensors GT02 and GT504 are installed immediately upstream and downstream of the rotatable expander 130; and a temperature sensor GT503 is installed at the inlet of the rotatable expander, downstream of the temperature sensor GT02.

[0174] The modified system is also equipped with temperature sensors GT501 and GT502 in the air stream immediately upstream and downstream of the evaporator 140 .

[0175] All pressure sensors were Carel 0-10 bar / 0-10 V / SPKT0011 CO 45 / 20 available from Carel Industries SpA (IT).

[0176] All temperature sensors were of the PT1000 type available from Regin Controls Sverige AB (SE).

[0177] Pressure and temperature data were recorded using an EXOcompact Ardo available from Regin Controls Sverige AB (SE).

[0178] The systems were installed in a climate chamber with an ambient temperature of 33°C-34°C and a relative humidity of 25%-30%.

[0179] The systems are installed in parallel and in the same environment so that their operating conditions will be the same.

[0180] The resulting data for the original system and the modified system are disclosed in the table below.

[0181] The condenser is caused to exchange heat with the ambient air in the climate chamber.

[0182] The evaporator of the modified system was caused to exchange heat with an air flow moving at a rate of 9550m3 / h in another climate chamber with a temperature of 25-35 degrees Celsius and a relative humidity of 35%-46%, driven by the fan provided in the original system.

[0183] The values ​​of GP01-GP04 and GT01-GT03 for the original system are residual values ​​from the installation operation of the system. These values ​​are not used to calculate the COP of the original system C .

[0184] During the 15-minute operating cycle of the original system, the temperature sensors GT501, GT502, GT503 and GT504 ( Figure 1 ) collected the following data:

[0185] serial number GP01 GP02 GP03 GP04 GT01 GT02 GT03 GT501 GT502 GT503 GT504 1 14.31 14.33 10.11 10.10 22.31 22.38 22.27 23.56 9.33 23.48 23.27 2 14.32 14.34 10.11 10.10 22.33 22.41 22.36 23.65 9.26 23.48 23.29 3 14.33 14.35 10.12 10.11 22.37 22.48 22.33 23.54 9.26 23.48 23.38 4 14.34 14.36 10.11 10.10 22.35 22.49 22.32 23.73 9.26 23.48 23.39 5 14.35 14.37 10.11 10.10 22.40 22.51 22.42 23.78 9.22 23.51 23.44 6 14.36 14.38 10.12 10.11 22.43 22.55 22.42 23.64 9.30 23.55 23.48 7 14.37 14.39 10.12 10.11 22.46 22.54 22.46 23.89 9.24 23.59 23.60 8 14.37 14.39 10.12 10.10 22.45 22.61 22.50 24.04 9.27 23.59 23.68 9 14.38 14.39 10.12 10.11 22.50 22.68 22.53 24.24 9.34 23.66 23.70 10 14.39 14.40 10.12 10.12 22.55 22.67 22.54 24.54 9.27 23.70 23.80 11 14.39 14.41 10.12 10.12 22.54 22.68 22.59 24.38 9.35 23.71 23.87 12 14.40 14.42 10.13 10.12 22.59 22.71 22.58 24.01 9.34 23.81 23.92 13 14.41 14.42 10.13 10.12 22.60 22.75 22.61 23.75 9.26 23.81 23.94 14 14.42 14.43 10.13 10.13 22.66 22.76 22.66 24.12 9.59 23.86 24.00

[0186] In addition to Pc, the following values ​​are calculated for the original system:

[0187]

[0188]

[0189] The pressure difference is calculated as follows: dPex = GP04 - GP03; dP23 = GP02 - GP03; dP41 = GP04 - GP01.

[0190] Qev is calculated as 5040*0.34*(GT501-GT502), where the value 5040 from the equipment supplier is the air volume per fan of the original system in m3 / h, and the value 0.34 is the well-known conversion factor from m3 / h to kg / s for air at 285K and 1 bar.

[0191] Pc is the standard power input value of the original system.

[0192] COP is calculated as Qev / Pc.

[0193] Therefore, the average COP of the original system is 2.72.

[0194] During a 45 minute operating cycle of the modified system, the following data was collected by the pressure sensors GP01, GP02, GP03, GP04 and the temperature sensors GT01, GT02, GT03, GT04, GT501, GT502, GT503 and GT504:

[0195] serial number GP01 GP02 GP03 GP04 GT01 GT02 GT03 GT501 GT502 GT503 GT504 1 9.1 18.9 18.7 10.3 75.3 33.0 11.6 22.9 12.9 28.2 15.1 2 9.3 19.1 18.6 10.4 76.3 33.7 11.8 22.9 13.2 28.6 16.1 3 9.4 19.7 19.2 10.6 77.8 34.8 12.0 23.7 13.7 29.9 16.7 4 9.4 19.6 19.4 10.8 78.0 34.8 12.2 23.8 13.9 30.0 16.8 5 9.4 21.1 21.0 10.6 81.2 36.6 12.9 24.1 14.0 32.2 16.6 6 9.3 21.7 21.5 10.7 84.1 37.5 13.8 23.9 14.0 33.0 16.6 7 9.5 21.4 21.1 10.8 83.8 37.4 13.6 25.2 14.6 32.9 17.2

[0196] In the same manner as for the original system, the pressure difference values ​​Qev, Pc and COP are calculated based on the measured values ​​for the modified system as follows:

[0197] serial number dPex dP23 dP41 Bf rpm Pex[W] Qev[kW] Pc COP* 1 8.60 0.27 1.3 40 520 206.9 33.5 7.46 4.63 2 8.65 0.52 1.2 40 640 254.7 32.5 7.68 4.38 3 9.08 0.48 1.2 45 590 264.1 33.4 7.90 4.38 4 8.78 0.21 1.4 45 600 268.6 33.1 7.94 4.32 5 10.55 0.14 1.2 58 435 251.0 33.8 7.94 4.40 6 11.01 0.15 1.3 58 395 227.9 33.1 7.95 4.29 7 10.60 0.35 1.3 52 425 219.9 35.5 8.04 4.53

[0198] The torque ratio Bf and rpm measurements are provided by the brake. Bf is measured as a percentage of the brake's maximum torque.

[0199] Pex is calculated as (2×π×n) / 60×Mn×Bf, where n is rpm, Mn is the maximum torque, and Bf is the torque ratio.

[0200] With an average value of Qev of 33.6 and an average value of Pc of 7.84, it can be deduced that the average value of COP is 4.42.

[0201] As can be deduced from the table above, the COP of the modified heat pump system is improved in all respects compared to the original system, and the modified system is also able to produce an additional 0.2 kW of electrical power, which corresponds to about 1700 kWh for 365 days of continuous operation. By comparison, the average electrical power consumption of an average single-family house in Sweden will be in the range of 5000 kWh-20000 kWh per year, depending on which heating method is used (the lower part of the range will be for houses with district heating).

[0202] The results achieved with the modified system are considered conservative, since the measured values ​​of electrical power have been as high as 0.3kW-0.35kW in a system where, for example, the connecting pipes are longer than in a properly packaged and optimized system. It is estimated that at least 0.4KW-0.5KW should be achievable.

[0203] Figure 6 Schematically illustrates the reference Figure 2Further development of the illustrated thermal cycle system. This further development aims to further increase the efficiency of the thermal cycle system.

[0204] In the following, only the Figure 2 The difference in thermal cycles.

[0205] Figure 6 The illustrated thermal cycle system includes a subcooler 110 connected in series with the condenser 11 and downstream of the condenser so that the working fluid leaving the condenser 11 is introduced into the subcooler 110 .

[0206] Providing a subcooler 110 may increase the amount of liquid working fluid available at the inlet of the expander unit 130 , which may in turn reduce leakage in the expander and thus increase expander efficiency.

[0207] The subcooler 110 may be caused to exchange heat with the working medium at a point upstream of the compressor 10 , such as immediately upstream of the compressor, so that heat is efficiently transferred from the working medium downstream of the condenser 11 to the working medium upstream of the compressor 10 .

[0208] Tests were carried out with a modified version of the above system. Specifically, a heat exchanger in the form of an Aircoil 600×200 3R Air 0331 was connected downstream of the condenser by means of a 3 / 8 inch connector.

[0209] A second modification may be made in the portion between the expander unit 130 and the evaporator 140, as the expansion valve 162 may be connected in series with the expander unit 130 upstream of the evaporator 140. The expansion valve 162 may operate in response to conditions downstream of the evaporator 140, particularly immediately downstream of the evaporator 140.

[0210] The expansion valve 162 may form part of an expansion arrangement 160 which may include a bypass connection 161 which enables the outlet of the expander unit 130 to be directly connected to the evaporator 140, thereby bypassing the expansion valve 162. One or more control valves 163, 164, 165 may be provided for switching and / or regulating the flow between the expansion valve 162 and the bypass passage 161. For example, the expansion arrangement 160 may be controlled based on a measurement of the pressure and / or temperature downstream of the evaporator 140. The control valves 163, 164, 165 may be adjusted between certain profiles, such as 50-50, 70-30, etc.

[0211] Providing the expansion arrangement 160 allows fine-tuning of the amount of liquid working medium input to the evaporator 140 , which in turn increases the efficiency of the evaporator 140 .

[0212] The system may further include one or more maintenance valves 151 , 152 , which may be binary valves or may be continuously or step-wise adjustable valves.

[0213] The arrangement of the subcooler and expansion arrangement 160 has been shown to be effective in increasing the COP of the system from about 2.8 to about 3.8, which is significant.

[0214] To verify the reference Figure 6 The functionality of the described modification (hereinafter referred to as the "second modified system") was additionally tested. In particular, with reference to Figure 1 The original system described and the reference Figure 2 The modified system described (hereinafter referred to as "first modified system") is used for comparison.

[0215] In additional tests, the expansion valve 162 was implemented as a Carel EV235 from CAREL INDUSTRIES SpA of Padova, Italy.

[0216] The subcooler 110 was implemented as an Aircoil 600×200 3R, Air 0331 with 3 / 8 inch connections from Aircoil AB, Orjen, Sweden.

[0217] Additional testing was conducted with the original system and the first modified system tested as described above, but with a lower air flow rate over the evaporator.

[0218] system Qev(kW) Pc(kW) COP* original 22.5 8.00 2.81 original 21.3 8.02 2.66 original 22.9 8.30 2.76 First modified 22.7 8.43 2.84 First modified 22.0 7.79 2.98 First modified 18.1 7.66 2.47 The second modified 27.9 7.65 3.86 The second modified 24.7 7.65 3.43 The second modified 28.0 7.76 3.82 The second modified 28.8 7.88 3.83 The second modified 29.5 7.70 3.98

[0219] From these tests, it is noted that for the original system, the average COP* is 2.74, and for the first modified system, the average COP* is 2.77. However, for the second modified system, the average COP* is 3.78. It can be inferred that the second modified system provides a significant efficiency improvement.

Claims

1. A method of operating a thermal cycle system, in, The thermal cycle system includes a working fluid that circulates through a circuit that includes a compressor (10), a condenser (11), an expander unit (130), and an evaporator (140). wherein the expander unit (130) is configured to generate a rotational mechanical motion, Among them, the method includes: The compressor (10) is operated to receive a working fluid in a first state having a first pressure (P1), a first temperature (T1) and a first enthalpy (H1), and compress the working fluid to a second state having a second pressure (P2), a second temperature (T2) and a second enthalpy (H2), The condenser (11) is operated to receive the working fluid in the second state and condense the working fluid to a third state having a third pressure (P3), a third temperature (T3) and a third enthalpy (H3), operating the expander unit (130) to receive the working fluid in the third state and to expand the working fluid to a modified fourth state having a modified fourth pressure (P40), a modified fourth temperature (T40), and a modified fourth enthalpy (H40), operating the evaporator (140) to receive the working fluid in the modified fourth state and evaporate the working fluid to the first state, wherein the nominal evaporator working fluid evaporation capacity is defined as the enthalpy reduction provided by the condenser (H2-H3) minus the enthalpy increase provided by the compressor (H2-H1), It is characterized in that The evaporator is operated at an evaporator working fluid evaporation capacity of at least about 110% of the nominal evaporator working fluid evaporation capacity.

2. The method of claim 1, wherein: The power (mf×(H1-H40)) supplied by the evaporator to the working fluid is greater than the power required to raise the entropy of the working fluid substantially isobarically from the entropy level (H3) at the condenser outlet to the entropy level (H1) corresponding to saturation (H1).

3. The method according to claim 1 or 2, wherein: The evaporator power delivered to the working fluid corresponds to the sum of the thermal power removed from the working fluid by the condenser (mf×(H2-H3)) and the power generated by the working fluid at the rotatable expander (mf×(H3-H40)) minus the power provided to the working fluid by the compressor (mf×(H2-H1)).

4. A method as claimed in any one of the preceding claims, wherein: The working fluid pressure drop across the evaporator is less than about 5 bar, preferably about 0.50 bar-0.75 bar; about 0.75 bar-1.00 bar; about 1.00 bar-1.25 bar; about 1.25 bar-1.50 bar; about 1.50 bar-1.75 bar; about 1.75 bar-2.00 bar; about 2.00 bar-2.25 bar; about 2.25 bar-2.50 bar; about 2.50 bar-2.75 bar; about 2.75 bar-3.00 bar; about 3.00 bar-3.25 bar; about 3.25 bar-3.50 bar; about 3.50 bar-3.75 bar; about 3.75 bar-4.00 bar; about 4.00 bar-4.25 bar; about 4.25 bar-4.50 bar; about 4.50 bar-4.75 bar; or about 4.75 bar-5.00 bar.

5. A thermal cycle system as claimed in any one of the preceding claims, wherein: The expander unit (130) is selected from the group consisting of a rotary expander, a swing expander, a scroll expander, a GE rotor expander, a reciprocating expander, a screw expander and a radial turbine expander.

6. A method as claimed in any one of the preceding claims, in, a generator (131) mechanically connected to the expander unit (130) for generating electricity, and Wherein, when the rotatable expander (130) is caused to rotate during the expansion of the working fluid, the generator (131) operates to generate electrical power.

7. The method according to any of the preceding claims, further comprising subcooling the working fluid downstream of the condenser (11) and upstream of the expander unit (130).

8. The method of claim 7, wherein: The working fluid downstream of the condenser (11) and upstream of the expander unit (130) is caused to exchange heat with the working fluid upstream of the compressor (10) and downstream of the evaporator (140).

9. The method of any of the preceding claims, further comprising causing at least some of the working fluid downstream of the expander unit (130) and upstream of the evaporator (140) to undergo further expansion in an expansion valve (162).

10. The method of claim 9, wherein: The working fluid exiting from the expander unit (130) is selectively distributed between the expansion valve (162) and a bypass connection (161) which bypasses the expansion valve (162).

11. The method according to claim 9 or 10, wherein: The expansion valve (162) is operable based on conditions downstream of the evaporator (140), preferably immediately downstream of the evaporator (140).

12. A method as claimed in any one of the preceding claims, wherein: The condenser (11) is caused to exchange heat with a first external working fluid in gaseous form.

13. A method as claimed in any one of the preceding claims, wherein: The evaporator (140) is caused to exchange heat with a second external working fluid in gaseous form.

14. A thermal cycle system comprising: a working fluid that circulates through a circuit that includes a compressor (10), a condenser (11), an expander unit, and an evaporator (140), wherein the expander unit is configured to generate a rotational mechanical motion, wherein the nominal evaporator working fluid evaporation capacity is defined as the enthalpy reduction provided by the condenser (H2-H3) minus the enthalpy increase provided by the compressor (H2-H1), It is characterized in that The evaporator is sized and adapted to provide an evaporator working fluid evaporation capacity that is at least 110% of the nominal evaporator working fluid evaporation capacity.

15. The thermal cycle system of claim 14, wherein: The expander unit comprises a rotatable expander (130), wherein a working fluid flowing through the expander causes the rotatable expander to rotate, Wherein, a generator (131) is mechanically connected to the rotatable expander to generate electricity when the rotatable expander is caused to rotate.

16. The thermal cycle system according to claim 14 or 15, wherein: The expander unit is selected from the group consisting of a rotary expander, a swing expander, a scroll expander, a GE rotor expander, a reciprocating expander, a screw expander and a radial turbine expander.

17. The thermal cycle system according to any one of claims 14 to 16, wherein: The working fluid pressure drop across the evaporator is less than about 5 bar, preferably about 0.50 bar-0.75 bar; about 0.75 bar-1.00 bar; about 1.00 bar-1.25 bar; about 1.25 bar-1.50 bar; about 1.50 bar-1.75 bar; about 1.75 bar-2.00 bar; about 2.00 bar-2.25 bar; about 2.25 bar-2.50 bar; about 2.50 bar-2.75 bar; about 2.75 bar-3.00 bar; about 3.00 bar-3.25 bar; about 3.25 bar-3.50 bar; about 3.50 bar-3.75 bar; about 3.75 bar-4.00 bar; about 4.00 bar-4.25 bar; about 4.25 bar-4.50 bar; about 4.50 bar-4.75 bar; or about 4.75 bar-5.00 bar.

18. The thermal cycle system according to any one of claims 14 to 17, wherein: The passage connecting the expander outlet to the evaporator assembly inlet is less than about 0.5 m, preferably less than about 0.2 m, less than about 0.1 m, or less than about 0.05 m.

19. The thermal cycle system according to any one of claims 14 to 17, further comprising a subcooler (110) connected downstream of the condenser (11) and upstream of the expander unit (130).

20. The thermal cycle system according to any one of claims 14 to 19, further comprising an expansion valve (162) connected downstream of the expander unit (130) and upstream of the evaporator (140).

21. The method of claim 20, further comprising at least one control valve (163, 164), which is used to selectively distribute the working fluid leaving the expander unit (130) between the expansion valve (162) and a bypass connection (161), which bypasses the expansion valve (162).

22. The method of claim 20 or 21, wherein: The expansion valve (162) is operable based on conditions downstream of the evaporator (140), preferably immediately downstream of the evaporator (140).

23. The thermal cycle system according to any one of claims 14 to 22, wherein: The condenser (11) is configured to exchange heat with a first external working fluid in gaseous form.

24. The thermal cycle system according to any one of claims 14 to 23, wherein: The evaporator (140) is configured to exchange heat with a second external working fluid in gas form.

25. The thermal cycle system according to any one of claims 14 to 24, wherein: The thermal cycle system is configured to operate as an irreversible cooling system for cooling a space or a body of material.

26. A method of modifying a thermal cycle system, in, The thermal cycle system includes: a working fluid which circulates through a circuit comprising a compressor (10), a condenser (11), an expansion valve (13) and a first evaporator (14), Among them, the method includes: replacing the expansion valve (13) with an expander unit configured to generate a rotary mechanical motion, and The first evaporator (14) is replaced with a second evaporator (140) having a greater working fluid evaporation capacity than the first evaporator (14).

27. The method of claim 26, wherein: The second evaporator (140) exhibits a lower working fluid pressure drop than the first evaporator (14).

28. The method of claim 26 or 27, further comprising increasing the flow area of ​​a working fluid connection (141) between the expander unit (130) and the evaporator (140).

29. The method of any one of claims 26-28, further comprising shortening a working fluid connection (141) between the expander unit (130) and the evaporator (140).

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