Split-expansion heat pump cycle

Abstract

The present disclosure provides a heat pump cycle that allows for improved matching of the T(Q) slope of the heat pump cycle. More specifically, the high-temperature heat exchange is separated into two stages. Furthermore, a portion of the working fluid cooled in the first stage is further cooled by expansion before being mixed with the heated working fluid for input to the heat exchanger.

Description

Technical Field

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[0001] (Cross - Reference to Related Applications) This application claims priority to and is a continuation of U.S. Patent Application No. 16867447, filed on May 5, 20, the contents of which are incorporated herein by reference.

Background Art

[0002] This section introduces information from the relevant technical field that may be related to, or provide background for, some aspects of the technology described and / or claimed herein. This information is background information to facilitate a better understanding of what is disclosed herein. This is a discussion of "related" technologies. Such technologies are by no means meant to imply that they are also "prior art". Related technologies may or may not be prior art. This discussion should be read from this perspective and should not be read as an admission of prior art.

[0003] Referring to FIG. 1, in a conventional heat pump cycle, the working fluid is compressed from a relatively low - temperature and low - pressure state (state 2) to one of higher temperatures and pressures (state 3). Then, this heat can be transferred to a heat transfer object HTR that receives and uses or stores this heat. In FIG. 1, the heat transfer object HTR starts under the conditions of HTRc and is stored at HTRh. During the process of heating the material containing HTR from HTRc to HTRh, the working fluid is cooled to state 4.

[0004] The process of transferring heat from the working fluid to the HTR is carried out in a counter - flow heat exchanger. This heat transfer process uses supercritical carbon dioxide ("sCO2") at a pressure of 30 MPa as the working fluid and silica sand as the HTR medium, as shown in a "TQ" (temperature - heat flow) graph as shown in FIG. 2 or in the figure.

Summary of the Invention

Means for Solving the Problems

[0005] In some embodiments, the heat pump includes a heat transfer source, an object to which heat is transferred, and a closed fluid loop for circulating a working fluid. The closed fluid loop further includes a compressor, a counterflow heat exchanger, a low-temperature expansion device, a low-temperature heat exchanger, a high-temperature expansion device, and a reheat exchanger. Each of these elements of the closed fluid loop acts on the working fluid within the closed fluid loop.

[0006] More specifically, during operation, the compressor receives the working fluid in a first state and increases the temperature and pressure of the working fluid through mechanical work, bringing it to a second state. The counterflow heat exchanger includes a first stage and a second stage. The first stage is in thermal communication with the heat transfer object, receives the working fluid from the compressor in a second state, and transfers heat from the received working fluid to the heat transfer object, cooling the working fluid to a third state. The second stage is in thermal communication with the heat transfer object, receives a first portion of the working fluid in the third state from the first stage, and transfers heat from the received first portion of the working fluid in the third state to the heat transfer object, cooling the working fluid to a fourth state.

[0007] The low-temperature expansion device, while operating, receives working fluid in state 5 and expands it to state 6. The low-temperature heat exchanger is in thermal communication with a heat transfer source, receives working fluid in state 6, and transfers heat from the heat transfer source to the working fluid in state 6, heating it to state 7. The high-temperature expansion device receives the second portion of working fluid in state 3 from the first stage of the counterflow heat exchanger and expands the received second portion of working fluid to state 8. The reheating heat exchanger transfers heat from the working fluid in state 4, received from the second stage of the counterflow heat exchanger, to a mixture of working fluid in state 7 received from the high-temperature expansion device and working fluid in state 8, received from the low-temperature heat exchanger, thereby heating the mixed working fluid to state 1 and cooling the working fluid in state 4 to state 5.

[0008] In another example, a heat pump includes an object to be heated, a heat transfer source, and a closed fluid loop for circulating a working fluid. The closed fluid loop includes a compressor, means for performing split expansion of the working fluid, a low-temperature heat exchanger, and a reheat exchanger. The compressor receives the working fluid in a first state and heats and pressurizes the received working fluid to a second state. The means for performing split expansion of the working fluid in the second state further cools the second portion of the working fluid in the third state to a fourth state, which is cooled twice, and then further cools it to a fifth state, after which it expands the first portion of the working fluid in the third state to a eighth state and the second portion of the working fluid in the third state to a sixth state. The low-temperature heat exchanger is in thermal communication with the heat transfer source and receives the working fluid in the sixth state and transfers heat from the heat transfer source to the working fluid in the sixth state, heating the working fluid to a seventh state. The regenerating heat exchanger transfers heat from the working fluid in the fourth state, received from the second stage of the counterflow heat exchanger, to a mixture of the working fluid in the seventh state, received from the high-temperature expansion device, and the working fluid in the eighth state, received from the low-temperature heat exchanger. This heats the mixed working fluid to the first state and cools the working fluid in the fourth state to the fifth state.

[0009] Further embodiments describe a method for operating a heat pump in a closed fluid loop, comprising compressing a working fluid in a first state to raise its temperature and pressure to a second state, and cooling the working fluid in the second state within a counterflow heat exchanger. The cooling in the counterflow heat exchanger includes cooling the working fluid in the second state in a first stage to a third state, and cooling a first portion of the working fluid in the third state in a second stage to a fourth state. This method further includes expanding the working fluid in a fifth state to a sixth state, heating the working fluid in the sixth state to a seventh state, expanding a second portion of the working fluid in the third state to an eighth state, mixing the working fluid in the seventh state with the working fluid in the eighth state, and heating the mixture of the working fluids in the seventh and eighth states to a first state while cooling the working fluid in the fourth state to a fifth state within a reheat exchanger.

[0010] The above provides a simplified overview to offer a basic understanding of some aspects of the present invention. This overview is not intended to provide an overview of the entirety of the present invention, nor is it intended to identify any major or important elements of the present invention or to describe the scope of the invention in detail. Its sole purpose is to briefly illustrate some of the concepts prior to the detailed description that follows.

[0011] The subject matter disclosed below can be understood by referring to the following description in conjunction with the accompanying drawings, in which similar reference numbers identify similar elements. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic diagram of a conventional heat pump employing a conventional heat pump cycle. [Figure 2] Figure 2 is a T(Q) plot of the counterflow heat exchanger in the heat pump cycle shown in Figure 1. [Figure 3] Figure 3 is a plot of heat capacity versus temperature for a heat pump cycle 1, showing the change in heat capacity as the temperature of the working fluid and heat transfer medium changes. [Figure 4] Figure 4 is a second T(Q) plot for the counterflow heat exchanger of the heat pump cycle in Figure 1, showing how the rate of change of the working fluid temperature increases as the working fluid flow rate increases relative to the heat transfer medium flow rate until a point is reached where further increases in the working fluid flow rate can no longer lower the working fluid outlet temperature. [Figure 5] Figure 5 is a schematic diagram of a split-expansion heat pump using a split-expansion heat pump cycle according to one or more embodiments of the subject claimed below. [Figure 6] Figure 6 is a pressure-enthalpy diagram of the working fluid at a specific point in the heat pump cycle of Figure 5 in one specific embodiment. [Figure 7] Figure 7 is the T(Q) plot of the counterflow heat exchanger in the heat pump cycle shown in Figure 5. [Figure 8]Figure 8 is a graph of the coefficient of performance ("COP") of the heat pump cycle as a function of the flow portion extracted between the first and second stages of the counterflow heat exchanger in the heat pump cycle shown in Figure 5. [Figure 9] Figure 9 is a schematic diagram of a second specific embodiment of the split-expansion heat pump cycle shown in Figure 5. [Modes for carrying out the invention]

[0013] While the disclosed technology is subject to various modifications and alternative forms, the drawings illustrate specific embodiments described herein in detail as examples. However, it should be understood that the descriptions of specific embodiments herein are not intended to limit the claims to the specific embodiments disclosed, but rather to encompass all modifications, equivalents, and alternatives that fall within the spirit and scope of the appended claims.

[0014] Herein, exemplary embodiments of the subject matter described below are disclosed. For clarity, not all features of actual implementations are described herein. It will be understood that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific objectives, such as compliance with system-related and business-related constraints. Furthermore, it will be understood that such development efforts, even if complex and time-consuming, are routine work for those skilled in the art who are interested in this disclosure.

[0015] Referring again to the conventional heat pump cycle described above in Figures 1 and 2, the slopes of the Twf and Thtr curves in the TQ plot are determined by the fluid flow rate and heat capacity ("cp"). Both of these fluids show a significant change in heat capacity as their respective temperatures change across the heat exchanger, as shown in Figure 3. This change can be seen as curvature in the T(Q) plot in Figure 3. Because the heat capacity curves are mismatched, the amount of heat that can be transferred from the working fluid to the HTR medium is limited.

[0016] As the working fluid flow rate decreases relative to the HTR medium flow rate, the slope of the Twf curve decreases until the T(Q) plot intersects at point 400, as shown in Figure 4. At this intersection, further decreases in the working fluid flow rate cannot reduce the working fluid outlet temperature because the heat transfer process cannot proceed faster due to the near-zero temperature difference between the fluids at the point where the curves intersect. This phenomenon is often called a "pinch" and occurs in the middle of the heat exchanger in this case.

[0017] Since heat pump performance is affected by this pinch phenomenon, it would be beneficial to match the gradients of the working fluid and the HTR medium T(Q) plot. Because heat capacity is a thermodynamic property of the two materials and therefore cannot be changed, the T(Q) gradient can only be changed by changing the flow rate of one or both materials. Furthermore, controlling the flow rate of the HTR medium is difficult for two or more heat transfer objects as shown in Figure 1, and storage becomes complex and very costly.

[0018] The technology of this disclosure enables improved matching of the T(Q) gradient and provides a heat pump cycle that improves the performance of the heat pump cycle. More specifically, the high-temperature heat exchange (e.g., occurring in the counterflow heat exchanger HTX in Figure 1) is instead separated into two stages. Furthermore, a portion of the working fluid cooled in the first stage is further cooled by expansion and then mixed with the heated working fluid for input to the heat exchanger. Further embodiments show yet another variation.

[0019] FIG. 5 is a schematic diagram of a heat pump 500 using a split expansion heat pump cycle according to one or more embodiments. The heat pump 500 includes a heat transfer source 502, a heat transfer target 504, and a closed fluid loop 506. The closed fluid loop 506 circulates a working fluid used for heat transfer in a manner further described below during operation. The working fluid can be, for example, carbon dioxide. Depending on the point within the closed fluid loop 506 under discussion, the working fluid can be referred to as a "heated working fluid", a "compressed working fluid", a "cooled working fluid", etc. during the discussion of the operation of the closed fluid loop 506.

[0020] The heat transfer source 502 includes a heat transfer medium not otherwise shown. The heat transfer medium may have a variable heat capacity, but not all embodiments are so limited and it may be a fluid or a solid. In the case of a fluid, the heat transfer medium can be, for example, a synthetic oil heat transfer fluid, water, or sand. Depending on the embodiment, the heat transfer source 502 can be, for example, a fluid circulating in a conduit. If the heat transfer medium is a solid, the solid can be, for example, a solid mass or flowing sand contained in a reservoir.

[0021] The heat transfer target 504 includes a heat transfer medium not otherwise shown, although not all embodiments are so limited and it can be a variable heat capacity material(s). The heat transfer medium can be a fluid or a solid. In the case of a fluid, the heat transfer medium can be, for example, a synthetic oil heat transfer fluid, water, or sand. The fluid can be circulated, for example, within a conduit. Thus, the heat transfer target 504 can be a fluid circulating in a conduit. If the heat transfer medium is a solid, the solid can be, for example, a solid mass or sand.

[0022] The closed fluid loop 506 of FIG. 5 circulates a working fluid and includes a reheater 508, a compressor 510, a counterflow heat exchanger 512, a cryogenic expansion device 514, a cryogenic heat exchanger 516, and a high-temperature expansion device 518. During operation, the compressor 510 receives the working fluid in a first state from the reheater 508. The compressor 510 raises the temperature and pressure of the working fluid in the first state to a second state by mechanical work. The compressor 510 provides motive power for circulating the working fluid through the closed fluid loop 506 during operation.

[0023] The counterflow heat exchanger 512 includes a first stage 538 and a second stage 540, both of which are in thermal communication with the heat transfer object 504. The counterflow heat exchanger 512 can be implemented in various ways depending on the embodiment. For example, in some embodiments, the counterflow heat exchanger 512 may be implemented by two single-stage heat exchangers, and each individual single-stage heat exchanger implements one of the first stage 538 or the second stage 540. In other embodiments, the counterflow heat exchanger 512 may be a single heat exchanger having an intermediate manifold. Those skilled in the art who enjoy the benefits of the present disclosure can understand further other variations in the implementation of the counterflow heat exchanger 512.

[0024] During operation, the first stage 538 of the counterflow heat exchanger 512 receives the working fluid in the second state, transfers heat from it to the heat transfer object 504, and cools the working fluid to a third state. The second stage 540 receives a first portion 544 of the working fluid in the third state, transfers heat from it to the heat transfer object 504, and cools the working fluid from the third state to a fourth state.

[0025] Note that in the third state, which maximizes the coefficient of performance ("COP") of the heat pump 500, there is an optimal flow split between the first portion 544 and the second portion 550 of the working fluid. This can be inferred from Figure 8 for the heat pump cycle in Figure 5, where "optimal" refers to the maximum achievable heat pump performance defined by the net work required to transfer a given amount of heat to the heat transfer object 504. The optimal flow split is a function of the thermodynamic properties (specifically, heat capacity) of the working fluid and heat transfer medium of the heat transfer object 504.

[0026] When operating, the cryogenic expansion device 514 receives working fluid in a fifth state from the regenerating heat exchanger 508. The cryogenic expansion device 514 reduces the pressure of the working fluid in a first state, lowers its temperature, and cools it to a sixth state. The cryogenic expansion device 514 may be implemented, for example, in an expansion valve or a turbine.

[0027] The low-temperature heat exchanger 516 is in thermal communication with the heat transfer source 502. During operation, the low-temperature heat exchanger 516 receives working fluid in the sixth state from the low-temperature expansion device 514 and heats the working fluid to the seventh state.

[0028] The counterflow heat exchanger 512, the low-temperature expansion device 514, and the high-temperature expansion device 518, as examples and illustrative, in some embodiments, form means for performing a split expansion of a working fluid in a second state, which includes expanding a partially cooled first portion of a working fluid in a third state to a fourth state, further cooled to a fifth state, and then expanding a partially cooled first portion of a working fluid in a third state to a sixth state. Other embodiments may include modifications of the configuration disclosed in Figure 5. It should be understood that such means may be implemented in structural equivalents that perform the enumerated functions.

[0029] The high-temperature expansion device 518 receives the second portion 550 of the working fluid in the third state. The high-temperature expansion device 518 expands the second portion 550 of the working fluid in the third state, reducing its pressure and temperature to the eighth state. The high-temperature expansion device 518 may be implemented, for example, in an expansion valve or a turbine.

[0030] Referring further to Figure 5, the heat pump 500 transfers heat from the working fluid in the fourth state to the combination or mixture 526 of the working fluid in the seventh state and the working fluid in the eighth state. As a result, the working fluid in the fourth state returns to the fifth state, and the mixture 526 returns to the first state. Then, the working fluid in the first state is compressed to increase its temperature and pressure as described above.

[0031] More specifically, when the regenerating heat exchanger 508 is in operation, it receives a working fluid that has been cooled twice to a fourth state from the counterflow heat exchanger 512, and a mixture 526 of a working fluid in a seventh state from the low-temperature heat exchanger 516 and a working fluid in an eighth state from the high-temperature expansion device 518. Heat transfer in the regenerating heat exchanger 508 returns the working fluid in the fourth state to the fifth state and brings the mixture 526 to the first state.

[0032] The heat pump 500 performs split expansion of the working fluid. As used herein, “split expansion” refers to the characteristic where a portion of the working fluid expands after being partially cooled in the first-stage heat exchange, and the remainder of the working fluid expands after being cooled in both the first-stage and second-stage heat exchanges. Thus, in Figure 5, both the first portion 544 and the second portion 550 are expanded in such split expansion. The first portion 544 is heat-exchanged in both the first stage 538 and the second stage 540, and then expanded by the low-temperature expansion device 514. The second portion 550 is cooled only in the first stage 538 of heat transfer before being expanded by the high-temperature expansion device 518. Thus, the working fluid in the heat pump 500 undergoes “split expansion”.

[0033] For further understanding of the subject matter described below, one particular embodiment is disclosed herein. Figure 6 is a pressure-enthalpy diagram of the working fluid at a certain point in the heat pump cycle of the heat pump 500 of Figure 5 in one particular embodiment. In this particular embodiment, the working fluid is carbon dioxide (CO2). The heat transfer medium of the heat transfer object 512 is sand.

[0034] The heat pump cycle 500, similar to the heat pump 500 in Figure 5, divides the high-temperature heat exchange into two stages 538 and 540. In this particular embodiment, the two stages 538 and 540 are implemented as two stages of similar size. "Similar size" refers to the thermal conductivity of the heating stages. Thermal conductivity, generally called "UA," is the product of the average heat transfer coefficient ("U") and the heat transfer area ("A"). In other embodiments, the relative sizes of the two stages 538 and 540 may differ, with one being larger than the other. The specific sizes of the stages 538 and 540 can be selected during the design process depending on the relative thermodynamic properties of the working fluid (e.g., heat capacity) and the heat transfer medium of the heat transfer object 504.

[0035] The working fluid in the second state flows out of the compressor 510 and into the first stage 538. In the first stage 538, the temperature of the working fluid in the second state decreases as the first stage 538 completes heating the heat transfer medium within the heat transfer object 504. The first portion 544 of the working fluid 542, once cooled, then proceeds to the second stage 540 in the third state.

[0036] The first portion 544 of the working fluid in the third state, once cooled, is further cooled in the second stage 540 by the heat transfer medium of the heat transfer object 504 while the heat transfer medium is being heated. This first portion 544 of the working fluid in the third state is then cooled to the fourth state, becoming the twice-cooled working fluid 524 in the fourth state. The twice-cooled working fluid in the fourth state can still contain heat at a useful temperature that can be returned to the working fluid before the inlet 511 of the compressor 510 in another heater. This other heater is the reheat exchanger 508.

[0037] The recovered working fluid 532 is still under high pressure (i.e., state 5 in Figure 6). Next, the working fluid in state 5 is expanded through a cryogenic expansion device 514, which may be either a valve or a cryogenic turbine ("LT turbine"). This process significantly reduces the temperature of the working fluid in state 5, thereby generating the working fluid in state 6.

[0038] The temperature drop in the low-temperature expansion device 514 allows the working fluid in the second state to receive heat from the heat transfer source 502. The heat transfer medium of the heat transfer source 502 is a synthetic oil heat transfer fluid, water, or sand. In this case, the working fluid in the sixth state (CO2) is either a liquid or a liquid / vapor. Heat is transferred to the working fluid in the low-temperature heat exchanger 516. This heat transfer causes the working fluid to evaporate, generating the working fluid in the seventh state. The working fluid in the seventh state is then mixed with the working fluid in the eighth state. Next, the mixture 526 of the working fluid in the seventh state and the working fluid in the eighth state is further heated to the first state in the reheat exchanger 508 before being compressed again.

[0039] Once cooled, the second portion 550 of the working fluid in the third state is extracted between the first stage 538 and the second stage 540 and expanded through a high-temperature expansion device 518, which in this embodiment is a high-temperature turbine. In the high-temperature expansion device 518, shaft work is generated that can offset the work required by the working fluid to operate the charge compressor 510. The working fluid obtained in the eighth state is then mixed and returned to the primary fluid flow downstream of the low-temperature heat exchanger 516 and upstream of the regenerative heat exchanger 508, as shown in Figure 5.

[0040] Figure 7 shows the T(Q) plot of the counterflow heat exchanger 512 in the heat pump cycle 500, where the change in gradient at approximately 70% Q / Qtot is point 700, where approximately 34% of the working fluid is extracted between the first stage 538 and the second stage 540. The coefficient of performance ("COP") of the heat pump cycle for heat pump 500 is shown in Figure 8 as the function of the portion of the flow extracted between the first stage 538 and the second stage 540, and for this set of conditions and assumptions, the improvement in COP is approximately 10%.

[0041] As described above with respect to the embodiment in Figure 5, there is an "optimal" split in the proportion of expanding working fluid. This ratio is set so that the slope of the working fluid temperature curve and the heat transfer medium temperature curve are approximately the same, as shown in Figure 7. Recalling that the slopes of these curves are inversely proportional to the product of the fluid's mass flow rate and its heat capacity (i.e., the slope is ~1 / (m cp)), it is possible to calculate the approximate flow rate of the working fluid at each stage of the counterflow heat exchanger that brings about this slope agreement.

[0042] Figure 9 is a schematic diagram of a heat pump 900 showing several modifications that may be found in several embodiments. Some parts of the heat pump 900 are common with the heat pump 500 in Figure 5, and similar parts have similar numbering. In one modification, the counterflow heat exchanger 912 is implemented in a single heat exchanger having an intermediate manifold 939 defining a first stage 938 and a second stage 940. The second portion 550 of the cooled working fluid 542 is released from the intermediate manifold 939. In a second modification, the heating side 922 includes an auxiliary heat exchanger 950 positioned between the regenerating heat exchanger 508 and the low-pressure expansion device 514. The auxiliary heat exchanger 950 removes heat from the second portion 546 of the recovered working fluid 532 to the ambient environment before the second portion 546 is received by the low-pressure expansion device 514. Those skilled in the art who benefit from the present disclosure will be able to understand yet another variant.

[0043] The heat pump cycle disclosed below is applicable to any heat pump application in which the heated fluid (e.g., heat transfer medium) has a heat capacity-to-temperature curve substantially different from that of the working fluid (e.g., CO2) that encompasses the most practical fluids. For example, the heat capacity of commercially available heat transfer fluids such as DURATHERM HF® or DOWTHERM® follows a temperature dependence similar to that of sand (increasing cp with temperature).

[0044] The above is a detailed description. The specific embodiments disclosed above are illustrative only, and the claimed subject matter can be modified and implemented in ways that are clearly different but equivalent to those of a person skilled in the art who are interested in the teachings of this specification. Furthermore, the details of the configuration or design described herein are not limited beyond the scope of the appended claims. Accordingly, it is clear that the specific embodiments disclosed above may be modified or altered, and all such variations will be considered to be within the scope of the claims and spirit. Accordingly, the subject matter for which protection is claimed herein is as described in the appended claims. The following are some embodiments (configurations) of the present invention. [Aspect 1] It is a heat pump, Heat transfer source and Heat transfer object and It comprises a closed fluid loop for circulating the working fluid, The closed fluid loop is A compressor that receives a working fluid in a first state, increases the temperature and pressure of the working fluid through mechanical work, and brings the working fluid to a second state. A counterflow heat exchanger, A first stage that is thermally in communication with the heat transfer target, the first stage receives the working fluid in the second state, transfers heat from the received working fluid to the heat transfer target, and cools the working fluid to the third state. A counterflow heat exchanger including a second stage which is thermally in communication with the heat transfer target, the second stage receiving a first portion of the working fluid in the third state, and transferring heat from the first portion of the working fluid in the third state received to the heat transfer target, thereby cooling the working fluid to a fourth state, A low-temperature expansion device that receives the working fluid in the fifth state and expands the working fluid to the sixth state, A low-temperature heat exchanger that is in thermal communication with the heat transfer source, the low-temperature heat exchanger receives the working fluid in the sixth state, and transfers heat from the heat transfer source to the working fluid in the sixth state to heat the working fluid up to the seventh state, A high-temperature expansion device that receives a second portion of the working fluid in the third state and expands the received second portion of the working fluid in the third state to the eighth state, A reheat exchanger that transfers heat from a working fluid in the fourth state received from the second stage of the counterflow heat exchanger to a mixture of the working fluid in the seventh state received from the high-temperature expansion device and the working fluid in the eighth state received from the low-temperature heat exchanger, thereby heating the mixed working fluid to the first state and cooling the working fluid in the fourth state to the fifth state, A heat pump equipped with [a specific feature]. [Aspect 2] The heat pump according to embodiment 1, wherein at least one of the high-temperature expansion device and the low-temperature expansion device comprises a turbine or a valve. [Aspect 3] The heat pump according to embodiment 1, wherein at least one of the heat transfer source and the heat transfer object has a heat transfer medium comprising at least one of a fluid and a solid. [Aspect 4] The heat pump according to embodiment 3, wherein the fluid flows through a conduit. [Aspect 5] The heat pump according to embodiment 3, wherein the solid is a solid mass or sand. [Aspect 6] The heat pump according to embodiment 3, wherein the fluid is water, a water / propylene glycol mixture, or air. [Aspect 7] The heat pump according to embodiment 1, wherein the heat transfer medium is a synthetic oil heat transfer fluid, water, or sand. [Aspect 8] The heat pump according to embodiment 1, wherein the counterflow heat exchanger has two single-stage heat exchangers or a single heat exchanger having an intermediate manifold. [Aspect 9] The heat pump according to embodiment 8, wherein the two single-stage heat exchangers are of the same size. [Aspect 10] The heat pump according to embodiment 1, further comprising an auxiliary heat exchanger positioned between the reheating heat exchanger and a low-pressure expansion device, wherein the auxiliary heat exchanger discharges heat from the reheating heat exchanger to the ambient environment from the second portion of the reheated working fluid before the second portion of the reheated working fluid is received by the low-pressure expansion device. [Aspect 11] The heat pump according to embodiment 1, wherein the working fluid is carbon dioxide. [Aspect 12] It is a heat pump, Heat transfer source and The object to which heat is transferred, It comprises a closed fluid loop for circulating the working fluid, The closed fluid loop is A compressor that receives working fluid in a first state and heats and compresses the received working fluid to a second state, Means for performing a split expansion of the working fluid in the second state, wherein the split expansion includes expanding a first portion of the working fluid in a partially cooled third state to an eighth state, and expanding the second portion of the working fluid in the third state, after the second portion has been cooled to a fourth state and further cooled to a fifth state, to a sixth state. A low-temperature heat exchanger that is in thermal communication with the heat transfer source, which receives the working fluid in the sixth state and transfers heat from the heat transfer source to the working fluid in the sixth state to heat the working fluid up to the seventh state, A reheat exchanger that transfers heat from the working fluid in the fourth state, received from the second stage of the counterflow heat exchanger, to a mixture of the working fluid in the seventh state, received from the high-temperature expansion device, and the working fluid in the eighth state, received from the low-temperature heat exchanger, thereby heating the mixed working fluid to the first state and cooling the working fluid in the fourth state to the fifth state, A heat pump equipped with [a specific feature]. [Aspect 13] The means for carrying out the aforementioned split expansion is, A counterflow heat exchanger, A first stage that is thermally in communication with the heat transfer target, the first stage receiving the working fluid in the second state from the compressor, transferring heat from the received working fluid in the second state to the heat transfer target, and cooling the received working fluid in the second state to a partially cooled third state, A counterflow heat exchanger comprising: a second stage that is thermally in communication with the heat transfer object, the second stage receiving a first portion of the working fluid in the second state which has been partially cooled from the first stage, transferring heat from the partially cooled working fluid in the second state to the heat transfer object, and cooling the working fluid to a fourth state which has been cooled twice; A low-temperature expansion device that expands the working fluid in the fifth state received from the regenerating heat exchanger to the sixth state, A high-temperature expansion device that receives a second portion of the working fluid in the third state from the first stage of the counterflow heat exchanger and expands the received second portion of the working fluid to the eighth state, A heat pump according to embodiment 12, comprising: [Aspect 14] The heat pump according to embodiment 13, wherein the cooling loop removes the heat of the working fluid in the fifth state from the regenerating heat exchanger to the surrounding environment. [Aspect 15] The heat pump according to embodiment 12, wherein the counterflow heat exchanger includes two single-stage heat exchangers or a single heat exchanger having an intermediate manifold. [Aspect 16] A heat pump cycle in a closed fluid loop, To raise the temperature and pressure to the second state, the working fluid in the first state is compressed, Cooling the working fluid in a second state within a counterflow heat exchanger, In the first stage, the working fluid in the second state is cooled down to the third state, Cooling the working fluid, which includes cooling the first portion of the working fluid in the third state to the fourth state in the second stage, Expanding the working fluid from the fifth state to the sixth state, Heating the working fluid in the sixth state to the seventh state, Expanding the second portion of the working fluid in the third state to the eighth state, Mixing the working fluid in the seventh state and the working fluid in the eighth state, The mixture of the working fluids in the seventh and eighth states is heated to the first state, while the working fluid in the fourth state is cooled to the fifth state in the reheat exchanger. A heat pump cycle equipped with this feature. [Aspect 17] The heat pump cycle according to embodiment 16, wherein the first stage is a first heat exchanger and the second stage is a second heat exchanger. [Aspect 18] The heat pump cycle according to embodiment 16, wherein the first and second stages comprise a single heat exchanger section having an intermediate manifold. [Aspect 19] The heat pump cycle according to embodiment 16, further comprising cooling the working fluid in the fifth state by discharging heat to the surrounding environment before expanding the working fluid in the fifth state to the sixth state.

Claims

1. It is a heat pump, Heat transfer source and Heat transfer object and It comprises a closed fluid loop for circulating the working fluid, The closed fluid loop is A compressor that receives a working fluid in a first state, increases the temperature and pressure of the working fluid through mechanical work, and brings the working fluid to a second state. A counterflow heat exchanger, A first stage that is thermally in communication with the heat transfer target, the first stage receives the working fluid in the second state, transfers heat from the received working fluid to the heat transfer target, and cools the working fluid to the third state. A counterflow heat exchanger including a second stage which is thermally in communication with the heat transfer target, the second stage receiving a first portion of the working fluid in the third state, and transferring heat from the first portion of the working fluid in the third state received to the heat transfer target, thereby cooling the working fluid to a fourth state, A low-temperature expansion device that receives the working fluid in the fifth state and expands the working fluid to the sixth state, A low-temperature heat exchanger that is in thermal communication with the heat transfer source, the low-temperature heat exchanger receives the working fluid in the sixth state, and transfers heat from the heat transfer source to the working fluid in the sixth state, thereby heating the working fluid to the seventh state, A high-temperature expansion device that receives the second portion of the working fluid in the third state and expands the received second portion of the working fluid in the third state to the eighth state, A reheat exchanger that transfers heat from the working fluid in the fourth state received from the second stage of the counterflow heat exchanger to a mixture of the working fluid in the eighth state received from the high-temperature expansion device and the working fluid in the seventh state received from the low-temperature heat exchanger, thereby heating the mixed working fluid to the first state and cooling the working fluid in the fourth state to the fifth state, A heat pump equipped with [a specific feature].

2. The heat pump according to claim 1, wherein at least one of the high-temperature expansion device and the low-temperature expansion device comprises a turbine or a valve.

3. The heat pump according to claim 1, wherein at least one of the heat transfer source and the heat transfer object has a heat transfer medium comprising at least one of a fluid and a solid.

4. The heat pump according to claim 3, wherein the fluid flows through a conduit.

5. The heat pump according to claim 3, wherein the solid is a solid mass or sand.

6. The heat pump according to claim 3, wherein the fluid is water, a water / propylene glycol mixture, or air.

7. The heat pump according to claim 1, wherein the heat transfer target is a synthetic oil heat transfer fluid, water, or sand.

8. The heat pump according to claim 1, wherein the counterflow heat exchanger has two single-stage heat exchangers or a single heat exchanger having an intermediate manifold.

9. The heat pump according to claim 8, wherein the two single-stage heat exchangers are of the same size.

10. The heat pump according to claim 1, further comprising an auxiliary heat exchanger disposed between the reheating heat exchanger and a low-temperature expansion device, wherein the auxiliary heat exchanger discharges heat from the first portion of the reheated working fluid to the ambient environment before the first portion of the reheated working fluid is received by the low-temperature expansion device.

11. The heat pump according to claim 1, wherein the working fluid is carbon dioxide.

12. It is a heat pump, Heat transfer source and The object to which heat is transferred, It comprises a closed fluid loop for circulating the working fluid, The closed fluid loop is A compressor that receives working fluid in a first state and heats and compresses the received working fluid to a second state, Means for performing a split expansion of the working fluid in the second state, wherein the split expansion includes expanding a second portion of the working fluid in a partially cooled third state to an eighth state, and expanding the first portion of the working fluid in the third state, after it has been cooled to a fourth state and further cooled to a fifth state, to a sixth state. A low-temperature heat exchanger that is in thermal communication with the heat transfer source, which receives the working fluid in the sixth state and transfers heat from the heat transfer source to the working fluid in the sixth state to heat the working fluid up to the seventh state, A reheat exchanger that transfers heat from the working fluid in the fourth state, received from the second stage of the counterflow heat exchanger, to a mixture of the working fluid in the eighth state, received from the high-temperature expansion device, and the working fluid in the seventh state, received from the low-temperature heat exchanger, thereby heating the mixed working fluid to the first state and cooling the working fluid in the fourth state to the fifth state, A heat pump equipped with [a specific feature].

13. The means for carrying out the aforementioned split expansion is, A counterflow heat exchanger, A first stage that is thermally in communication with the heat transfer target, the first stage receiving the working fluid in the second state from the compressor, transferring heat from the received working fluid in the second state to the heat transfer target, and cooling the received working fluid in the second state to a partially cooled third state, A counterflow heat exchanger comprising: a second stage that is thermally in communication with the heat transfer object, the second stage receiving a first portion of the working fluid in the third state which has been partially cooled from the first stage, transferring heat from the partially cooled working fluid in the third state to the heat transfer object, and cooling the working fluid to a fourth state which has been cooled twice; A low-temperature expansion device that expands the working fluid in the fifth state received from the regenerating heat exchanger to the sixth state, A high-temperature expansion device that receives a second portion of the working fluid in the third state from the first stage of the counterflow heat exchanger and expands the received second portion of the working fluid to the eighth state, The heat pump according to claim 12, comprising:

14. The heat pump according to claim 13, wherein the closed fluid loop removes heat from the working fluid in the fifth state from the auxiliary heat exchanger to the ambient environment.

15. The heat pump according to claim 12, wherein the counterflow heat exchanger includes two single-stage heat exchangers or a single heat exchanger having an intermediate manifold.

16. A heat pump cycle in a closed fluid loop, To raise the temperature and pressure to the second state, the working fluid in the first state is compressed, The process involves cooling the working fluid in a second state within a counterflow heat exchanger, In the first stage, the working fluid in the second state is cooled down to the third state, Cooling the working fluid, which includes cooling the first portion of the working fluid in the third state to the fourth state in the second stage, Expanding the working fluid from the fifth state to the sixth state, Heating the working fluid in the sixth state to the seventh state, Expanding the second portion of the working fluid in the third state to the eighth state, Mixing the working fluid in the seventh state and the working fluid in the eighth state, In the reheat exchanger, heat is exchanged between the mixture of the working fluid in the seventh state and the working fluid in the eighth state and the working fluid in the fourth state, thereby heating the mixture of the working fluids in the seventh and eighth states to the first state, while cooling the working fluid in the fourth state to the fifth state within the reheat exchanger. A heat pump cycle equipped with this feature.

17. The heat pump cycle according to claim 16, wherein the first stage is a first heat exchanger and the second stage is a second heat exchanger.

18. The heat pump cycle according to claim 16, wherein the first and second stages comprise a single heat exchanger having an intermediate manifold.

19. The heat pump cycle according to claim 16, further comprising cooling the working fluid in the fifth state by releasing heat into the surrounding environment before expanding the working fluid in the fifth state to the sixth state.

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