Method for operating a thermal circulation system, thermal circulation system, and method for improving a thermal circulation system

Abstract

A method of operating a heat circulation system, the heat circulation system including a working fluid circulated through a circuit including a compressor (10), a condenser (11), an expander unit (130), and an evaporator (140). The expander unit (130) is configured to generate a rotary mechanical motion. In the method, the evaporator operates at an evaporator working fluid evaporation capacity that is at least about 110% of a nominal evaporator working fluid evaporation capacity. Also disclosed are a heat circulation system and an improved method of the heat circulation system.

Description

Technical Field

[0001] The present disclosure relates to a heat circulation system (heat cycle system) for use in a heat pump or a cooling system, and a method of operating the heat circulation system.

Background Art

[0002] Heat circulation systems operating according to periodic heat processes such as the Carnot cycle are used in many applications.

[0003] The purpose of the application is to supply heat. For example, a heat pump system that heats a space by pumping heat from the ground, rock, water, or air and supplying the heat to the heating system of the space is applicable.

[0004] Another application is to remove heat, that is, to cool something. That is, it is intended to remove heat from a space or an object, such as an air conditioning system or a cooling / refrigeration system.

[0005] In the Carnot cycle, energy is input in the form of heat Q absorbed by an evaporator and mechanical energy W supplied by a compressor. The mechanical energy may be supplied by conversion of electrical energy by an electric motor. Further, energy is output in the form of heat Q supplied by a condenser. The heating coefficient of performance (COP) is defined as Q / W. The cooling coefficient of performance (COP) is defined as O / W. H of H which H is C defined C as

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

[0007] The system includes a compressor 10 (compressor 10). The compressor 10 has a compressor input and a compressor output. At the compressor input, the working fluid is in a first state having a first pressure P1, a first temperature T1, and a first enthalpy H1. At the compressor output, 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. As a result, P2 > P1.

[0009] The compressor may be powered electrically.

[0010] The system further includes a condenser 11 (capacitor 11). The condenser 11 has a condenser input and a condenser output. The condenser input is connected to the compressor output to receive the working fluid in the second state. At the condenser output, the working fluid becomes the third state P3, T3, H3.

[0011] The condenser 11 may be configured to exchange heat with a heat transfer circuit 12. Heat is transferred from the condenser 11. Thereby, the temperature of the working fluid decreases, and T3 < T2. The enthalpy of the working fluid decreases, and H3 < H2. At least a part of the working fluid changes from the vapor state to the liquid state.

[0012] Alternatively, the condenser 11 may be configured to supply heat to an air flow or simply dissipate heat to the surrounding air, as in the case of a cooling system.

[0013] The heat transfer circuit 12 may be, for example, a heating circuit. The heating circuit supplies heating to a space such as one or more residences or the interior of an automobile. In other applications, the heat may be used in a drying process or the like.

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

[0015] The expansion valve 13 is configured for isentropic expansion. The expansion valve 13 enables the working fluid to expand to a fourth state P4, T4, H4. Thereby, the working fluid has a lower pressure at the expansion valve output than the third state, i.e., P4 < P3.

[0016] The system further includes an evaporator 14. The evaporator 14 may be configured to exchange heat with a heat supply circuit 15. Thereby, the working fluid evaporates. Heat is received by the evaporator 14. Thereby, the enthalpy of the working fluid increases, H1 > H4. Also, the temperature rises, T1 > T4.

[0017] The heat supply circuit 15 may be a cooling circuit of a cooling device or an air conditioning device. Alternatively, the heat supply circuit 15 may be configured to extract heat from, for example, air, the ground, rock, 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] Generally, there is a desire to improve the performance of the heat circulation system and thereby improve the coefficient of performance.

[0020] For example, in International Publication No. 2013 / 141805, it is known that a heat circulation system includes an energy converter for converting the energy of a pressurized fluid into mechanical energy, and the mechanical energy can be used for generating electrical energy.

[0021] Dimitriou, P., “Experimental evaluation of work recovery potential in commercial heat pumps using a piston expander prototype”, National Technical University of Athens, 2017 discloses a heat cycle in which an expansion valve is replaced by a piston expander which is mechanically coupled to a compressor and supplies the compressor with a driving force.

[0022] There is still a need to improve the heat cycle system, particularly from the perspective of efficiency and / or the production of electrical energy. SUMMARY OF THE INVENTION

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

[0024] A particular object includes providing a heat cycle system suitable for use as a cooling system for cooling a space or a body of matter.

[0025] The invention is defined by the appended independent claims, and its embodiments are described in the dependent claims, the following description and the drawings.

[0026] According to a first aspect, a method of operating a thermal circulation system is provided. The thermal circulation system comprises a working fluid circulated through a circuit including a compressor, a condenser, an expander unit (expansion device), and an evaporator. The expander unit is configured to generate a rotary mechanical motion. In the method, the compressor operates to receive the working fluid in a first state having a first pressure, a first temperature, and a first enthalpy and compress the working fluid to a second state having a second pressure, a second temperature, and a second enthalpy. In the method, the condenser operates to receive the working fluid in the second state and condense the working fluid to a third state having a third pressure, a third temperature, and a third enthalpy. In the method, the expander unit operates to receive the working fluid in the third state and expand the working fluid to a modified fourth state having a modified fourth pressure, a modified fourth temperature, and a modified fourth enthalpy. In the method, the evaporator operates to receive the working fluid in the modified fourth state and evaporate the working fluid to the first state. The nominal evaporator working fluid evaporation capacity is defined as the amount obtained by subtracting the enthalpy increase provided by the compressor from the enthalpy decrease provided by the condenser. In the method, the evaporator operates with an evaporator working fluid evaporation capacity that is at least about 110% of the nominal evaporator working fluid evaporation capacity.

[0027] The compression part of the process may be substantially isentropic, i.e., isentropic except for losses.

[0028] The condensation part of the process may be substantially isobaric and / or isothermal, i.e., essentially isobaric / isothermal except for losses.

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

[0030] The evaporation part of the process may be substantially isobaric and / or isothermal. That is, except for losses, it is substantially isobaric / isothermal.

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

[0032] The inventors have surprisingly discovered that by operating the system as described above, it is possible to produce at least electricity without causing a loss in the coefficient of performance of the system.

[0033] The rotational motion provided by the expander unit (expander unit) (expansion device) can be used, at least in part, to power the compressor and / or another mechanically operating device, particularly a generator for generating electricity.

[0034] It is also pointed out that the coefficient of performance (COP) may be further improved by the operation as described above.

[0035] Therefore, a system is provided that has at least the same coefficient of performance (COP) as a corresponding system without an expander unit with the above-described drive and that generates a useful amount of electrical energy.

[0036] In this method, the energy supplied to the working fluid by the evaporator exceeds the energy required to substantially isobarically increase the enthalpy of the working fluid. The substantial isobaric increase in the enthalpy of the working fluid is the increase from the enthalpy level at the condenser outlet to the enthalpy level corresponding to wet vapor or superheated vapor.

[0037] The evaporator power (energy) transferred to the working fluid from the evaporator is equivalent to the total of the heat power (thermal energy) removed from the working fluid by the condenser and the power (mechanical energy) generated by the working fluid in the rotary expander, minus the power supplied to the working fluid by the compressor.

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

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

[0040] This means that the pressure loss is significantly reduced compared to currently commercially available systems. Generally, in currently commercially available systems, a pressure loss of 6 - 8 bar occurs in the evaporator.

[0041] The expander unit can be selected from a rotary expander, a swing expander, a scroll expander, a GE rotor expander, a reciprocating expander, a screw expander, a radial turbo expander.

[0042] Such an expander can be obtained by reversing the corresponding compressor. It is usually provided in combination with the removal of the check valve originally provided in the compressor.

[0043] The method may further include operating an expander unit to at least partially supply energy to at least one device.

[0044] In the method, a generator may be mechanically connected to the expander unit to generate electric power. The generator may be operated to generate electrical energy by rotating a rotatable expander during expansion of the working fluid.

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

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

[0047] The working fluid downstream of the condenser and the working fluid upstream of the expander unit may be arranged to perform heat exchange between the working fluid upstream of the compressor and the working fluid downstream of the evaporator.

[0048] The method may further include further expanding at least a portion of the working fluid downstream of the expander unit and upstream of the evaporator within an expansion valve.

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

[0050] The expansion valve is operable based on the condition downstream of the evaporator, preferably immediately downstream of the evaporator.

[0051] The evaporator may be arranged to exchange heat with an evaporator circuit. The evaporator circuit includes a second working fluid, for example to provide 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 exchange heat with a condenser circuit composed of 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 enlarged for the same system. In the same system, a compressor, a condenser, and an expansion valve are included. The expansion valve is provided for the isenthalpic expansion of the working fluid instead of an expander unit.

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

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

[0060] Therefore, the method can provide an air-to-air cooling system. The heat circulation system can operate as an irreversible cooling system for cooling a space or a body of a substance. Therefore, the heat circulation system is configured to cool a space or a body of a substance instead of heating it, but it is not reversible.

[0061] According to a second aspect, a thermal circulation system including a working fluid is provided. The system circulates through a circuit including a compressor, a condenser, an expander unit, and an evaporator. The expander unit is configured to generate a rotary mechanical motion. In the thermal circulation system, the nominal evaporation capacity of the evaporator working fluid is defined as the amount obtained by subtracting the enthalpy increase provided by the compressor from the enthalpy decrease provided by the condenser. The evaporator is sized and adapted to provide an evaporation capacity of the evaporator working fluid that is at least 110% of the nominal evaporation capacity of the evaporator working fluid.

[0062] In particular, the evaporation capacity of the working fluid of the evaporator is 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%.

[0063] The evaporator may be oversized with respect to the same system. In the same system, a compressor, a condenser, and an expansion valve are included. The expansion valve is provided for the expansion of the working fluid instead of the expander unit.

[0064] The evaporator may be configured to evaporate the working fluid received from the expander unit to at least saturation. Thereby, the working fluid can be brought into a saturated vapor phase at the output of the evaporator.

[0065] The expander unit may include a rotatable expander. In the expander, the working fluid flowing through the expander rotates the rotatable expander. A generator may be mechanically connected to the rotatable expander so as to generate electric power when the rotatable expander is rotated.

[0066] The expander unit may be selected from a rotary expander, a swing expander, a scroll expander, a GE rotor expander, a reciprocating expander, a screw expander, and a radial turbo expander.

[0067] Such an expander can be obtained by reversing the corresponding compressor. It is usually provided in combination with the removal of the check valve originally provided in the compressor.

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

[0069] The flow path (channel) connecting the expander outlet and 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 integrally formed.

[0070] The flow path may be linear.

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

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

[0073] The heat circulation system may further include at least one control valve. The control valve selectively distributes the working fluid exiting the expander unit between the expansion valve and a bypass connection that bypasses the expansion valve.

[0074] The expansion valve is operable based on the state downstream of the evaporator, preferably immediately downstream of the evaporator.

[0075] In other embodiments, the flow path is bent 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 in the evaporator, it is preferable to use a curved flow path that generates some turbulent flow in the flow path. This can improve the distribution of the working fluid in the evaporator.

[0077] The evaporator may exchange heat with an evaporator circuit. The evaporator circuit contains 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 exchange heat with a condenser circuit consisting of 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 exchange heat with a first external working fluid in gaseous form.

[0084] The first external fluid may contain air, consist of air, or be essentially composed of air.

[0085] The evaporator may exchange heat with a second external working fluid in gaseous form.

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

[0087] The thermal circulation system can operate as an irreversible cooling system for cooling the interior of a space or a substance.

[0088] The space can be the interior of a building, the interior of a vehicle, etc. The body of the substance can be an ice rink, etc. Therefore, the thermal circulation system cools the interior of a space or the body of a substance instead of heating it, and it is not reversible.

[0089] According to a third aspect, a method for improving (modifying) a thermal circulation system, the thermal circulation system comprising: namely, the thermal circulation system includes a circuit through which a working fluid circulates, the circuit including a compressor, a condenser, an expansion valve, and a first evaporator. In this method, the expansion valve is replaced with an expander unit. The expander unit is configured to generate a rotary mechanical motion. In this method, the first evaporator is replaced with a second evaporator having a working fluid evaporation capacity larger than that of the first evaporator.

[0090] The improved thermal circulation system may be a heating system that collects heat from a fluid. The fluid is in the form of air or a liquid, and the liquid is, for example, salt water. The heating system may be for heating a building or a vehicle.

[0091] Alternatively, the thermal circulation system may be a cooling system that collects heat from a space and discharges the heat to the outside. The space may be an air flow or a space within a building space or a vehicle.

[0092] The thermal circulation may be a reversible system, in which case it can be used for either cooling or heating a building or a vehicle.

[0093] The working fluid evaporation capacity of the second evaporator is 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.

[0094] The second evaporator may have a lower pressure drop of the working fluid than the first evaporator.

[0095] The second evaporator may exhibit a pressure drop of the working fluid that is less than 50%, preferably less than 40%, or less than 30% of that of the first evaporator.

[0096] The expander unit may include a rotatable expander. In the expander unit, the working fluid flowing through the expander causes the rotation of the expander. The method may further include mechanically connecting a generator to the rotatable expander. When the expander is rotated, the generator generates electricity.

[0097] The method may further include increasing the flow passage area of the connection of the working fluid between the expander unit and the evaporator.

[0098] The method may further include increasing the flow passage area at the expander inlet.

[0099] The method may further include shortening the connection of the working fluid between the expander unit and the evaporator.

[0100] For example, a shorter flow path for connection may be provided. Alternatively, the expander outlet may be directly connected to the evaporator inlet.

Brief Description of the Drawings

[0101]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0102] With reference to FIG. 2, the concepts according to the present invention are disclosed. FIG. 2 shows a heat circulation system corresponding to the system shown in FIG. 1, and the same reference numerals are given to the same components.

[0103] The system shown in FIG. 2 is different from the system shown in FIG. 1 in that the expansion valve 13 is replaced by a rotary expander 130 (rotary expander 130), and the evaporator 14 is replaced by one with a larger capacity. Further, it is preferable to reduce the pressure drop in the evaporator 140 and make the connection part 141 between the output of the rotary expander 130 and the evaporator 140 as short and straight as possible.

[0104] As shown by the arrows in FIG. 2, a heat circulation system in which the working fluid circulates is shown.

[0105] In some embodiments, the heat circulation system may be formed as a cooling circuit for use in an air conditioning system in a stationary structure, a ship, or a vehicle.

[0106] In other embodiments, the heat circulation system may be formed as a heat pump system (heat pump system) for use in a stationary structure such as a building, a ship, or a vehicle.

[0107] The system includes a compressor 10 having a compressor input and a compressor output. At the compressor input, the working fluid is in a first state having a first pressure P1, a first temperature T1, and a first enthalpy H1. At the compressor output, the working fluid is in a second state having a second pressure P2, a second temperature T2, and a second enthalpy H2.

[0108] The compressor 10 is configured to increase the pressure of the working fluid. As a result, P2 > P1.

[0109] The compressor may be powered electrically.

[0110] The system further comprises a condenser 11 having a condenser input and a condenser output. The condenser input is connected to the compressor output and receives the working fluid in the second state. At the condenser output, the working fluid is in the third state P3, T3, H3.

[0111] The condenser 11 may be configured to exchange heat with a heat transfer circuit 12. Heat is transferred from the condenser 11. Thereby, the enthalpy of the working fluid may be reduced such that H3 < H2.

[0112] Alternatively, the condenser 11 may be configured to transfer heat to an air stream or simply dissipate heat to the ambient environment, as in the case of a cooling system.

[0113] The system further includes a rotary expander 130 in place of the expansion valve 13 (FIG. 1). The expander may be in the form of, for example, a turbine, a scroll expander, or a GE rotor expander. The rotary expander 130 is a replacement for the expansion valve 13 (FIG. 1) that would otherwise be provided at this stage of the heat circulation process.

[0114] The expander input is connected to receive the working fluid in the third state P3, T3, H3 from the condenser 11.

[0115] The rotary expander 130 is configured such that the working fluid can expand to an improved fourth state P40, T40. The pressure and enthalpy of the working fluid at the expander output are lower than in the third state, such that P40 < P3 and H40 < H3.

[0116] The rotary expander 130 may be characterized by operating in a state close to isentropy. This causes not only pressure loss but also enthalpy loss. In the fifth state where the fourth state P40, T40 is modified, the enthalpy H40 is smaller than that in the third state (H3).

[0117] The system further includes an evaporator 140. The evaporator 140 exchanges heat with the heat supply circuit 15. The evaporator 140 receives heat. Thereby, the enthalpy of the working fluid increases, the working fluid evaporates, and H40 < H1.

[0118] The heat supply circuit 15 may be a cooling circuit of a cooling device or an air conditioning device. Alternatively, the heat supply circuit 15 may be configured to draw heat from, for example, air, the ground, rock, or water in a heat pump system.

[0119] The evaporator input is connected to receive the working fluid in the improved fourth state from the rotary expander 130. The evaporator output is connected to the input of the compressor 10.

[0120] Figure 3 is a schematic pressure - enthalpy diagram showing the heat cycle of Figures 1 and 2.

[0121] In Figure 3, it is shown that the states P1, T1, H1, P2, T2, H2, P3, T3, H3 of the working fluid are the same for the conventional cycle based on Figure 1 and the improved cycle based on Figure 2. Therefore, when comparing the prior - art system of Figure 1 and the system according to the inventive concept of Figure 2, the compressor 10 and the condenser 11 are the same, and the selection of the working fluid is also the same. The mass flow rate mf (mass flow mf) and the heat exchange conditions in the condenser and the compressor are also the same. Or they are designed for a higher inlet pressure. With the improvements described here, the inlet pressure to the compressor can be increased while keeping the condenser conditions the same.

[0122] In FIG. 3, the enthalpy in the state of each working fluid is also shown. Therefore, in the first state P1, T1, the enthalpy is H1, in the second state P2, T2, the enthalpy is H2, and in the third state, the enthalpy is H3.

[0123] In the system of FIG. 1, an expansion valve 13 is used, and the expansion of the working fluid from the third state P3, T3 to the fourth state is isentropic. Therefore, the enthalpy of the fourth state P4, T4 is H3, that is, the same as that of the third state P3, T3.

[0124] However, in the system of FIG. 2, since the rotary expander 130 operates approaching isentropy, not only a pressure loss but also an enthalpy loss occurs. Therefore, in the improved (modified) fourth state P40, T40, H40, the enthalpy H40 is smaller than the enthalpy H3 of the third state.

[0125] The rotary expander 130 may operate completely below the saturation curve of the working fluid so that the working fluid remains in a two-phase state throughout the expansion. Alternatively, the rotary expander may operate on or outside the saturation curve.

[0126] In the evaporator 14 used in the system shown in FIG. 1, by adding an enthalpy corresponding to the difference in enthalpy between the first state and the third state, the working fluid evaporates and may be superheated in some cases. That is, the enthalpy H1 - H3 is added to the evaporator 14.

[0127] The evaporator 140 needs to add more enthalpy to the working fluid in the system of FIG. 2 compared to the system of FIG. 1.

[0128] Therefore, the evaporator 140 needs to evaporate the working fluid by adding an enthalpy corresponding to the difference in enthalpy between the first state and the improved fourth state. That is, the enthalpy H1 - H40 is added to the evaporator 140.

[0129] Therefore, the capacity of the evaporator 140 in FIG. 2 needs to be larger than the capacity of the evaporator 14 in FIG. 1.

[0130] Furthermore, it is preferable to minimize the pressure drop in the evaporator 140. Ideally, the heating of the working fluid in the evaporator 140 is performed under a constant pressure, but actually, a certain amount of pressure loss occurs depending on the design of the evaporator. As a result, 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.

[0131] The reduction of the pressure drop can be achieved by increasing the number of flow paths through the evaporator 140 and / or increasing the flow path area of the evaporator 140.

[0132] Also, it is preferable to shorten the connection portion between the rotary expander 130 and the evaporator 140.

[0133] As shown in FIG. 3, the broken line from the points P40, H40 to the points P1, T1 indicates that the pressure drop is less than that of the broken line from the points P4, T4, H4 to the points P1, T1, H1.

[0134] Referring to FIG. 3, the rotary expander 130 may be provided in the form of a scroll type expander or a GE rotor type expander.

[0135] However, other types of rotary expanders may also be used.

[0136] The rotary expander 130 is mechanically connected to the generator 131 to generate electricity.

[0137] The rotary expander 130 receives the flow rate mf of the working fluid in the third state P3, T3 having the enthalpy H3 from the output of the condenser 12.

[0138] In the rotary expander 130, the working fluid expands isentropically, the working fluid is below the saturated liquid line, and the working fluid becomes a two-phase state.

[0139] The rotary expander 130 outputs the working fluid at a lower pressure P40, temperature T40, and also lower enthalpy H40, which is called the improved fourth state (deformed fourth state).

[0140] The rotation of the rotary expander 130 drives the generator 131 to output electric power corresponding to P(exp) excluding losses.

[0141] FIG. 5 shows a schematic diagram of the evaporator 140.

[0142] The evaporator 140 is connected to the output of the rotary expander 130. Thereby, it receives the flow rate mf of the working fluid in the improved fourth state P40, T40, H40.

[0143] The connection part 141 between the output of the rotary expander 130 and the evaporator 140 may be as short and straight as possible.

[0144] The connection part 141 is connected to a distributor 142 that divides the flow of the working fluid into a plurality of evaporator flow paths 143a, 143b, 143c. Each of the flow paths provides an evaporator sub-flow.

[0145] The sub-flow is merged into the evaporator output 145 by a collector 144. The evaporator output 145 is connected to the compressor 10.

[0146] Each of the evaporator flow paths 143a, 143b, 143c is formed as a respective flow path, for example, a pipe, a tube, a hose. Each of the evaporator flow paths 143a, 143b, 143c may be connected to a cooling flange (not shown) for enhancing the heat exchange efficiency with the gaseous fluid.

[0147] Alternatively, the evaporator flow paths 143a, 143b, 143c may be formed by the flow paths in a heat exchanger for performing heat exchange with a liquid.

[0148] The number of flow paths and, optionally, the surface area of each flow path can be selected such that a desired pressure drop of less than 3 bar is obtained across the entire heat exchanger. At this time, the selection is made after fully considering the type of working fluid used in the relevant application.

[0149] From the perspective of power balance, the system of Figure 2 with a mass flow rate mf can be explained as follows.

[0150] Input power: Compressor - P(comp): mf × (H2 - H1) Evaporator - P(evap): mf × (H1 - H40) Output power: Condenser - P(cond): mf × (H2 - H3) Expander - P(exp): mf × (H3 - H40)

[0151] Therefore, the evaporator is sized such that P(evap) = P(cond) + P(exp) - P(comp).

[0152] <Experimental data> To verify the principle of the system disclosed in Figure 2, two commercially available heat pump systems in the form of Panasonic S - 250PE3E5B were used as a starting point. These systems were respectively labeled as the "original system" and the "improved system (modified system)".

[0153] The "improved system (modified system)" was improved (modified) as follows.

[0154] The expansion valve was replaced with a scroll expander of the DENSO SCSA06C 447220 - 6572 HFC134a type. The scroll expander was modified by removing the check valve for preventing reverse flow and increasing the flow passage area at the inlet of the expander to a diameter of approximately 14 mm.

[0155] The expander was connected to a brake. This was in the form of a Delta AC servo model ECMA-J11330R4 kW 3.0 / 3000 rpm manufactured by Delta Electronics (Sweden). This was used to emulate a generator connected to the output shaft of the rotary expander 130.

[0156] The evaporator was replaced with an evaporator having a higher capacity and lower pressure loss.

[0157] The evaporator consists of two open-gable evaporator blocks of the AIR0332 600×600 - 4R type manufactured by Aircoil (SE). The evaporator blocks were connected in parallel and the blocks were mounted in a V-shape at a 90-degree angle.

[0158] In total, the evaporator 140 has 16 flow channels with an inner diameter of 6.4 mm and an average length of approximately 1400 mm.

[0159] A 500-mm long pipe was used to connect the output of the rotary expander 130 to the distributor of the evaporator.

[0160] The following pressure and temperature sensors were further installed in the system.

[0161] In the improved system, pressure sensors GP01 and GP02 were installed immediately upstream and downstream of the compressor 10, temperature sensors GT03 and GT01 were installed immediately upstream and downstream of the compressor 10, pressure sensors GP03 and GP04 were installed immediately upstream and downstream of the rotary expander 130, pressure sensors GP03 and GP04 were installed immediately upstream and downstream of the rotary expander 130, temperature sensors GT02 and GT504 were installed immediately upstream and downstream of the rotary expander 130, and a temperature sensor GT503 was installed downstream of the temperature sensor GT02 at the inlet of the rotary expander.

[0162] In the improved system, temperature sensors GT501 and GT502 were also installed in the air flow immediately upstream and downstream of the evaporator 140.

[0163] All pressure sensors are Carel 0-10 bar / 0-10V / SPKT0011CO 45 / 20 available from Carel Industries S.p.A (IT).

[0164] All temperature sensors are of the PT1000 type available from Regin Controls Sverige AB (SE).

[0165] Pressure and temperature data were recorded using EXOCompact Ardo available from Regin Controls Sverige AB (SE).

[0166] The system was installed in an environmental chamber with an environmental temperature of 33 - 34°C and a relative humidity of 25 - 30%.

[0167] The systems were installed in parallel and placed in the same environment, so the operating conditions were the same.

[0168] The measurement results of the original system and the improved system are shown in the following table.

[0169] The condenser was made to exchange heat with the environmental air in the environmental chamber.

[0170] The evaporator of the improved system exchanges heat with an air flow of 9550 m3 / h in another environmental chamber. The said another environmental chamber has a temperature of 25 - 35°C and a relative humidity of 35 - 46%. The said another environmental chamber is driven by a fan provided in the original system.

[0171] The values of GP01 - GP04 and GT01 - GT03 of the original system are the residual values during the installation and operation of the system. These values are not used in the calculation of the COP of the original system C of the original system.

[0172] During the 15 - minute operation cycle of the original system, the following data was collected by the temperature sensors GT501, GT502, GT503, GT504 (Figure 1).

[0173]

Table 1

[0174] Except for Pc, the following values are those calculated in the original system.

[0175]

Table 2

[0176] The pressure differences were calculated by the following equations. That is, dPex = GP04 - GP03, dP23 = GP02 - GP03, dP41 = GP04 - GP01.

[0177] Qev was calculated as 5040 * 0.34 * (GT501 - GT502). The value 5040 is the value provided by the equipment supplier. This is the air volume per fan (m3 / h) in the original system. The value 0.34 is the well - known conversion coefficient for converting from (m3 / h) to (kg / s) for air at 285K and 1 bar.

[0178] Pc is the standard input value of the original system.

[0179] COP was calculated as Qev / PC.

[0180] Therefore, the average COP of the original system is 2.72.

[0181] During the 45 - minute operation cycle of the improved 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, GT504.

[0182]

Table 3

[0183] Similar to the original system, based on the measured values of the improved system, the values of the pressure difference, Qev, Pc, and COP were calculated as follows.

[0184]

Table 4

[0185] The measured data of the torque ratio Bf and rpm were obtained from the brake. Bf was measured as a percentage of the maximum torque of the brake.

[0186] Pex is calculated as (2×π×n) / 60×Mn×Bf when n is rpm, Mn is the maximum torque, and Bf is the torque ratio.

[0187] Since the average value of Qev is 33.6 and the average value of PC is 7.84, it can be concluded that the average value of COP is 4.42.

[0188] As can be concluded from the above table, the COP of the improved heat pump system is improved compared to the original system. The improved system can further generate 0.2 kW of electricity. This corresponds to approximately 1700 kWh for continuous operation for 365 days. In comparison, the average electricity consumption of a typical single-family house in Sweden varies depending on the heating method used, but is between 5000 and 20000 kWh per year (the lower limit of this range is for houses using district heating).

[0189] The results obtained with the improved system seem conservative because the measured electricity values are as high as 0.3 - 0.35 kW. For example, in a system where the connection pipes are longer than those in a system where the connection pipes are properly packaged and optimized, at least 0.4 - 0.5 kW should be achievable.

[0190] Figure 6 schematically shows a further development of the thermal circulation system described in Figure 2. This further development aims to further improve the efficiency of the thermal circulation system.

[0191] In the following, only the differences from the thermal circulation in Figure 2 will be described.

[0192] The thermal circulation system shown in Figure 6 includes a subcooler 110. The subcooler 110 is connected in series downstream of the condenser 11. As a result, the working fluid exiting the condenser 11 is introduced into the subcooler 110.

[0193] By providing the subcooler 110, the amount of liquid working fluid available at the inlet of the expander unit 130 increases. As a result, the leakage of the expander decreases and the expander efficiency improves.

[0194] The subcooler 110 may exchange heat with the working medium upstream of the compressor 10, for example, immediately upstream of the compressor. Thereby, heat is effectively transferred from the working medium downstream of the condenser 11 to upstream of the compressor 10.

[0195] Tests were conducted on an improved version (modified version) of the above system. In particular, a heat exchanger in the form of AirCoil 600×200 3R Air 0331 was connected downstream of the condenser using a 3 / 8-inch connector.

[0196] The second improvement can be made in the section between the expander unit 130 and the evaporator 140. Specifically, an expansion valve 162 can be connected in series to the expander unit 130 upstream of the evaporator 140. The expansion valve 162 is operable in response to the conditions downstream of the evaporator 140, particularly the conditions immediately downstream of the evaporator 140.

[0197] The expansion valve 162 can form part of the expansion device 160. This includes a bypass connection 161. The bypass connection 161 enables the outlet of the expander unit 130 to be directly connected to the evaporator 140. Thereby, the expansion valve 162 can be bypassed. One or more control valves 163, 164, 165 may be provided to change and / or adjust the flow between the expansion valve 162 and the bypass flow path 161. For example, the expansion device 160 may be controlled based on measurements of the pressure and / or temperature downstream of the evaporator 140. The control valves 163, 164, 165 may be adjustable between specific distributions such as 50-50, 70-30, etc.

[0198] By providing the expansion device 160, it becomes possible to finely adjust the amount of the liquid working medium input to the evaporator 140. As a result, the efficiency of the evaporator 140 is improved.

[0199] The system may further include one or more service valves 151, 152. These may be binary valves or valves that can be adjusted continuously or stepwise.

[0200] It has been proven effective to increase the COP of the system from about 2.8 to about 3.8 by arranging the subcooler and the expansion device 160, which is important.

[0201] To verify the function of the modification (improvement) described in FIG. 6, an additional test hereinafter referred to as the "Second Modified System (Second Improved System)" was conducted. In particular, the original system described in FIG. 1 and the modified system (improved system) described with reference to FIG. 2 (hereinafter referred to as the "First Modified System (First Improved System)") were used as comparison targets.

[0202] In the additional test, the expansion valve 162 was embodied by a Carel EV235 of CAREL INDUSTRIES S.p.A. in Padua, Italy.

[0203] The subcooler 110 was embodied as an Aircoil 600x200 3R, Air 0331 with 3 / 8-inch connections from Aircoil in Örnsköldsvik, Sweden.

[0204] Additional tests were conducted on the original system and the first modified system in the same manner as the above-described tests, but the air flow rate of the evaporator was set lower.

[0205]

Table 5

[0206] As a result of the tests, it was found that the average COP* was 2.74 for the original system and 2.77 for the first modified system. However, the average COP* was 3.78 for the second modified system. It was found that the efficiency was significantly improved in the second modified system.

Claims

Claim 1 A method of operating a heat circulation system, wherein the heat circulation system comprises a working fluid circulated through a circuit including a compressor (10), a condenser (11), an expander unit (130), and an evaporator (140); the expander unit (130) is configured to generate a rotary mechanical motion; the method comprises: operating the compressor (10) to receive the 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); operating the condenser (11) 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 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; a nominal evaporator working fluid evaporation capacity is defined as an amount obtained by subtracting an enthalpy increase amount (H2 - H1) provided by the compressor from an enthalpy decrease amount (H2 - H3) provided by the condenser; The method of operating the evaporator with an evaporator working fluid evaporation capacity that is at least about 110% of the nominal evaporator working fluid evaporation capacity. Claim 2 The method according to claim 1, wherein the power (mf×(H1 - H40)) supplied to the working fluid by the evaporator is greater than the power required to substantially isobarically increase the entropy of the working fluid from the entropy level (H3) at the condenser outlet to the entropy level (H1) corresponding to saturation (H1). Claim 3 The evaporator power transferred to the working fluid is the sum obtained by subtracting the power supplied to the working fluid by the compressor (mf×(H2 - H1)) from the heat power removed from the working fluid by the condenser (mf×(H2 - H3)) and the power generated by the working fluid in the rotary expander (mf×(H3 - H40)), according to the method of claim 1 or 2.

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

5. The expander unit (130) is selected from a rotary expander, a swing expander, a scroll expander, a GE rotor expander, a reciprocating expander, a screw expander, and a radial turbo expander, according to the heat circulation system of any one of the preceding claims.

6. The generator (131) is mechanically connected to the expander unit (130) to generate electricity, During the expansion of the working fluid, as the rotary expander (130) rotates, the generator (131) is driven for power generation, according to the method of any one of the preceding claims.

7. The method of any one of the preceding claims further includes subcooling the working fluid downstream of the condenser (11) and upstream of the expander unit (130).

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

9. The method according to any one of the preceding claims, further comprising, in the expansion valve (162), further expanding at least a part of the working fluid on the downstream side of the expander unit (130) and on the upstream side of the evaporator (140).

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

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

12. The method according to any one of the preceding claims, wherein the condenser (11) exchanges heat with a first external working fluid in gaseous form.

13. The method according to any one of the preceding claims, wherein the evaporator (140) exchanges heat with a second external working fluid in gaseous form.

14. A heat circulation system comprising a working fluid circulating in a circuit including a compressor (10), a condenser (11), an expander unit, and an evaporator (140), wherein the expander unit is configured to generate a rotary mechanical motion, the nominal evaporator working fluid evaporation capacity is defined as the amount obtained by subtracting the enthalpy increase amount (H2 - H1) provided by the compressor from the enthalpy decrease amount (H2 - H3) provided by the condenser, and the evaporator is sized and adapted to provide an evaporator working fluid evaporation capacity that is at least about 110% of the nominal evaporator working fluid evaporation capacity.

15. The expander unit includes a rotatable expander (130), the working fluid passing through the expander rotates the rotary expander, a generator (131) is mechanically connected to the rotary expander, and the generator (131) generates electricity as the rotatable expander rotates. The heat circulation system according to claim 14.

16. The heat circulation system according to claim 14 or 15, wherein the expander unit is selected from a rotary expander, a swing expander, a scroll expander, a GE rotor expander, a reciprocating expander, a screw expander, and a radial turbo expander.

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

18. The flow path connecting the expander outlet and 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. The heat circulation system according to any one of claims 14 to 17.

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

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

21. Further comprising at least one control valve (163, 164), The at least one control valve (163, 164) selectively distributes the working fluid coming out of the expander unit (130) between the expansion valve (162) and the bypass connection (161), The bypass connection (161) bypasses the expansion valve (162). The method according to claim 20.

22. The expansion valve (162) is operable based on the state on the downstream side of the evaporator (140), preferably the state immediately downstream of the evaporator (140). The method according to claim 20 or 21.

23. The condenser (11) exchanges heat with a first external working fluid in gaseous form. The heat circulation system according to any one of claims 14 to 22.

24. The evaporator (140) exchanges heat with a second external working fluid in gaseous form. The heat circulation system according to any one of claims 14 to 23.

25. The heat circulation system according to any one of claims 14 to 24, which operates as an irreversible cooling system for cooling the main body of a space or a substance.

26. A method for improving a heat circulation system, comprising: The heat circulation system includes: a working fluid circulating through a circuit including a compressor (10), a condenser (11), an expansion valve (13), and a first evaporator (140); The method includes: replacing the expansion valve (13) with an expander unit configured to generate a rotary mechanical motion; replacing the first evaporator (14) with a second evaporator (140) having a higher evaporation capacity of the working fluid than the first evaporator (14).

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

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

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

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