Thermodynamic cycle

Abstract

To provide a method of operating a thermodynamic apparatus configured as a heat engine or heat pump.SOLUTION: A thermodynamic apparatus comprises, in flow series, a first heat exchanger, an expansion sub-chamber and a second heat exchanger. A method includes transferring a fluid from the first heat exchanger to the second heat exchanger via the expansion sub-chamber by: sending a fluid flow from the first heat exchanger to the expansion sub-chamber at an intake pressure by increasing the volume of the expansion sub-chamber: fluidly separating the fluid in the expansion sub-chamber from the first heat exchanger; expanding the fluid in the expansion sub-chamber by further increasing the volume of the expansion sub-chamber to lower the pressure of the fluid from the intake pressure; fluidly coupling the expansion sub-chamber to the second heat exchanger; and taking out the fluid from the expansion sub-chamber and transferring the same to the second heat exchanger be reducing the volume of the expansion sub-chamber.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] The present disclosure relates to a method of operating a thermodynamic device configured as a heat engine or a heat pump, and to a thermodynamic device configured as a heat engine or a heat pump.

Background Art

[0002] Thermodynamic cycles were first developed and classified as such in the early 19th century as devices that convert heat into power, and were then further developed as devices that use power to transfer heat from a lower temperature to a higher temperature in refrigeration and heat pump systems.

[0003] A thermodynamic cycle typically consists of a series of processes for compressing and expanding a fluid and for transferring heat to and from the surrounding environment.

[0004] The original theoretical cycle, named the Carnot cycle, defines the maximum amount of work that can be extracted from a heat source when heat is transferred to a heat sink. The ideal Carnot cycle includes an expansion process at a constant temperature, a subsequent expansion process at a constant entropy, a subsequent compression process at a constant temperature, and a subsequent compression process at a constant entropy. This is shown in FIG. 1.

[0005] Other theoretical and ideal cycles, such as the Stirling cycle, are also described. The Stirling cycle includes an expansion process at a constant temperature, a subsequent expansion process at a constant volume, a subsequent compression process at a constant temperature, and a subsequent compression process at a constant volume. The Brayton cycle includes an expansion process at a constant pressure, a subsequent expansion process at a constant entropy, a subsequent compression process at a constant pressure, and a subsequent compression process at a constant entropy.

[0006] As a further improvement of these processes, there is the timing of the selection of the working fluid that undergoes a phase change during the heat transfer process. The most common example is the Rankine cycle, which is a modified form of the Brayton cycle. The Rankine cycle incorporates condensing the working fluid during the heat rejection process and evaporating the working fluid during the heat absorption process. These compression and expansion processes are nominally constant-pressure processes, but due to the phase change, these processes also become constant-temperature processes. The Rankine cycle forms the basis of most power generation systems that use water as the working fluid in thermal power plants and also serves as the basis for organic Rankine cycle systems for generating electricity from heat.

[0007] However, in reality, an ideal thermodynamic cycle cannot be achieved due to losses within the system. Therefore, a real thermodynamic cycle aims to come as close as possible to the ideal cycle.

[0008] Making practical machines for converting heat into power or for utilizing power input to transfer heat requires a certain degree of compromise. These practical machines typically contain a fluid that circulates within a closed cycle and undergoes compression and / or expansion.

[0009] Friction within the machine cannot be eliminated, which means that the compression and expansion processes are not lossless and thus not reversible.

[0010] When a two-phase working fluid is used, certain compression and expansion techniques need to be protected from the adverse effects of liquid ingress or liquid formation during the process. For example, certain types of turbines need to have a dry gas inlet. Certain types of compressors need to have a completely liquid-free inlet and further need to ensure that no liquid is formed during the compression process. Other types of compressors can withstand the liquid droplets of the mist at the inlet but cannot handle larger chunks of liquid at high frequencies. All of these preventive measures may limit the application range of the machine, or may increase its complexity or reduce its thermodynamic efficiency. In some cases, the droplets can cause serious physical damage to the compressor or expander.

Summary of the Invention

Problems to be Solved by the Invention

[0011] An object of the present invention is to overcome at least some of the drawbacks mentioned above.

Means for Solving the Problems

[0012] According to the present disclosure, there is provided a thermodynamic device as described in the claims, and a method of operating a thermodynamic device configured as a heat engine or a heat pump. Other features of the present invention will become apparent from the dependent claims and the following description.

[0013] According to a first aspect, a method of operating a thermodynamic device configured as a heat engine or a heat pump is provided. The thermodynamic device comprises a first heat exchanger, an expansion sub-chamber, and a second heat exchanger in a series of flows. The method includes feeding a fluid flow at an intake pressure from the first heat exchanger into the expansion sub-chamber by increasing the volume of the expansion sub-chamber, fluidly isolating the fluid within the expansion sub-chamber from the first heat exchanger, expanding the fluid within the expansion sub-chamber by further increasing the volume of the expansion sub-chamber to reduce the pressure of the fluid from the intake pressure, fluidly connecting the expansion sub-chamber to the second heat exchanger, and transferring the fluid out of the expansion sub-chamber and to the second heat exchanger by decreasing the volume of the expansion sub-chamber, thereby including transferring the fluid from the first heat exchanger to the second heat exchanger via the expansion sub-chamber.

[0014] By providing the method described above, an efficient technique for transporting an expanding fluid between a first heat exchanger and a second heat exchanger becomes possible. The method enables a high work output or high energy transfer as required and is applicable across a wide range of applications.

[0015] The thermodynamic device can comprise a compression sub-chamber, and the method includes transferring the fluid out of the second heat exchanger at a transfer pressure and to the compression sub-chamber by increasing the volume of the compression sub-chamber.

[0016] The method can include fluidly isolating the compression sub-chamber from the second heat exchanger and compressing the fluid within the compression sub-chamber by decreasing the volume of the compression sub-chamber to increase the pressure of the fluid. In other words, the method can include fluidly isolating the compression sub-chamber from the second heat exchanger and increasing the pressure of the fluid within the compression sub-chamber by decreasing the volume of the compression sub-chamber.

[0017] This method can include fluidly connecting a compression sub-chamber to a first heat exchanger and transferring fluid out of the compression sub-chamber and to the first heat chamber by reducing the volume of the compression sub-chamber.

[0018] In one embodiment, the temperature of the fluid exiting the expansion sub-chamber is approximately equal to the temperature of the fluid exiting the compression sub-chamber.

[0019] The process of feeding a fluid flow into the expansion sub-chamber from the first heat exchanger at an intake pressure can be substantially isobaric.

[0020] The process of expanding the fluid in the expansion sub-chamber by further increasing the volume of the expansion sub-chamber can be approximately adiabatic.

[0021] The process of transferring the fluid flow out of the second heat exchanger and to the compression sub-chamber can be substantially isobaric.

[0022] The process of increasing the pressure of the fluid in the compression sub-chamber by reducing the volume of the compression sub-chamber can be approximately adiabatic.

[0023] The apparatus can include an expansion chamber and can include a first piston, and the expansion sub-chamber can be an aspect of a variable volume defined by the expansion chamber and the first piston.

[0024] In one embodiment, the step of increasing the volume of the expansion sub-chamber to feed a fluid flow into the expansion sub-chamber from the first heat exchanger is performed during an intake phase of an intake stroke in which there is relative movement in a first direction between the first piston and the expansion chamber.

[0025] The step of further increasing the volume of the expansion sub-chamber until the fluid reaches a predetermined volume at which the fluid reaches the first threshold pressure can be performed during the expansion phase of the intake stroke in which there is a continuous relative movement in the first direction between the first piston and the expansion sub-chamber.

[0026] The step of discharging the fluid flow from the expansion sub-chamber by reducing the volume of the expansion sub-chamber and transferring it to the second heat exchanger is performed during the exhaust stroke in which there is a relative movement of the first piston and the expansion chamber in a second direction that is opposite to the direction of the relative movement in the intake stroke.

[0027] The apparatus can include a compression chamber and can include a second piston, where the compression sub-chamber is a variable volume aspect defined by the compression chamber and the second piston, and here, the step of discharging the fluid flow from the second heat exchanger to the compression sub-chamber at the transfer pressure by increasing the volume of the compression sub-chamber is performed during the intake stroke in which there is a relative movement of the second piston and the compression chamber.

[0028] The step of increasing the pressure of the fluid in the compression sub-chamber by reducing the volume of the compression sub-chamber can be performed during the compression phase of the exhaust stroke in which there is a relative movement of the second piston in a direction opposite to the direction of the relative movement in the intake stroke of the compression sub-chamber.

[0029] The first piston and the second piston may be integral with each other.

[0030] The expansion sub-chamber and the compression sub-chamber can be located on either side of the first piston within the reciprocating machine, where the movement of the first piston changes the volumes of the expansion sub-chamber and the compression sub-chamber.

[0031] The expansion sub-chamber and the compression sub-chamber can be located in different reciprocating machines.

[0032] The thermodynamic device can comprise a second expansion sub-chamber and a second compression sub-chamber, and the method includes transferring the fluid flow from the second expansion sub-chamber at the transfer pressure to the second heat exchanger by reducing the volume of the second expansion sub-chamber, where the fluid flow is fed and expanded within the first expansion sub-chamber.

[0033] The method can include transferring the fluid flow from the second heat exchanger into the second compression sub-chamber by increasing the volume of the second compression sub-chamber, where the fluid flow is transferred such that it exits the second expansion sub-chamber, isolating the second compression sub-chamber fluidly from the second heat exchanger, and compressing the fluid within the second compression sub-chamber by reducing the volume of the second compression sub-chamber to increase the pressure of the fluid. In other words, the method includes the step of fluidly isolating the second compression sub-chamber from the second heat exchanger and the step of increasing the pressure of the fluid within the second compression sub-chamber by reducing the volume of the second compression sub-chamber.

[0034] The method can include fluidly connecting the second compression sub-chamber to the first heat exchanger and continuing to reduce the volume of the second compression sub-chamber to transfer the fluid flow from the second compression sub-chamber to the first heat exchanger, where these steps are performed when the fluid flow is transferred from the first expansion sub-chamber to the second heat exchanger.

[0035] The device may be configured to operate as a heat engine, where heat is removed from the fluid as it passes through the second heat exchanger.

[0036] The device may be configured to operate as a heat pump, where heat is added as the fluid passes through the second heat exchanger.

[0037] According to a second embodiment, a thermodynamic device configured as a heat engine or a heat pump is provided, where the device comprises an expansion sub-chamber, and by increasing the volume of the expansion sub-chamber, a fluid flow is fed into the expansion sub-chamber at the suction pressure, the fluid in the expansion sub-chamber is fluidically isolated, and by further increasing the volume of the expansion sub-chamber to reduce the pressure of the fluid from the suction pressure, the fluid in the expansion sub-chamber is expanded, the expansion sub-chamber is fluidically connected to a heat exchanger, and by reducing the volume of the expansion sub-chamber, the fluid charge is discharged from the expansion sub-chamber and transferred to the heat exchanger as described above.

[0038] The device can include a first heat exchanger and a second heat exchanger, where the fluid is fed from the first heat exchanger into the expansion sub-chamber and transferred from the expansion sub-chamber to the second heat exchanger.

[0039] The thermodynamic device comprises a compression sub-chamber, and the device is configured to transfer a fluid flow from the second heat exchanger to the compression sub-chamber at a transfer pressure by increasing the volume of the compression sub-chamber.

[0040] The device can be configured to fluidically isolate the compression sub-chamber from the second heat exchanger and compress the fluid in the compression sub-chamber by reducing the volume of the compression sub-chamber to increase the pressure of the fluid. In other words, the device can be configured to fluidically isolate the compression sub-chamber from the second heat exchanger and increase the pressure of the fluid in the compression sub-chamber by reducing the volume of the compression sub-chamber.

[0041] The device can be configured to fluidically connect the compression sub-chamber to the first heat exchanger and transfer a fluid flow from the compression sub-chamber to the first heat chamber by reducing the volume of the compression sub-chamber.

[0042] The device can comprise an expansion chamber and can comprise a first piston, and the expansion sub-chamber is an aspect of a variable volume defined by the expansion chamber and the first piston.

[0043] The volume of the expansion sub-chamber may be configured to be increased to feed a fluid flow from the first heat exchanger into the expansion sub-chamber during an intake phase of an intake stroke in which there is relative movement in a first direction.

[0044] The device is configured to further increase the volume of the expansion sub-chamber during an expansion phase of an intake stroke in which relative movement of the first piston and the expansion chamber continues to move in a first direction.

[0045] The first piston may be configured to move in a second direction, opposite to the first direction, relative to the expansion chamber during an exhaust stroke to decrease the volume of the expansion sub-chamber and transfer a fluid flow out of the expansion sub-chamber to the second heat exchanger.

[0046] The device comprises a compression chamber and a second piston, and the compression sub-chamber is an aspect of a variable volume defined by the compression chamber and the second piston, where the volume of the compression sub-chamber is configured to be increased during an intake stroke in which there is relative movement of the second piston and the compression chamber.

[0047] According to a third aspect, a method of operating a thermodynamic device configured as a heat engine or a heat pump may be provided, the method comprising inducing a fluid flow from a first heat exchanger into a compression sub-chamber at an intake pressure by increasing the volume of the compression sub-chamber, fluidly isolating the fluid within the compression sub-chamber from the first heat exchanger, increasing the pressure of the fluid within the compression sub-chamber by decreasing the volume of the compression sub-chamber, fluidly connecting the compression sub-chamber to a second heat exchanger, and inducing a fluid flow out of the compression sub-chamber to the second heat exchanger by further decreasing the volume of the expansion sub-chamber.

[0048] According to another aspect, a method of changing a fluid volume may be provided, the method including inducing fluid from a first heat exchanger to an expansion sub-chamber, isolating the fluid in the expansion sub-chamber from the first heat exchanger, and expanding the fluid in the expansion sub-chamber until the fluid reaches a first threshold pressure.

[0049] In one embodiment, an apparatus for a heat engine or a heat pump is provided, the apparatus including a first expansion sub-chamber configured to cycle through a first expansion sub-chamber intake stroke and a first expansion chamber exhaust stroke, and a first compression sub-chamber configured to cycle through a first compression sub-chamber intake stroke and a first compression sub-chamber exhaust stroke, wherein the apparatus is equipped with an expansion sub-chamber inlet port for admitting fluid into the expansion sub-chamber during the expansion sub-chamber intake stroke, an expansion sub-chamber outlet port for discharging fluid from the expansion sub-chamber during the expansion sub-chamber exhaust stroke, a compression sub-chamber inlet port for admitting fluid into the compression sub-chamber during the compression sub-chamber intake stroke, and a compression sub-chamber outlet port for discharging fluid from the compression sub-chamber during the compression sub-chamber exhaust stroke, and wherein the apparatus is configured to open the expansion chamber inlet port during a first part of the first expansion sub-chamber intake stroke and to close the expansion chamber inlet port during a second part of the first expansion sub-chamber intake stroke, and wherein the apparatus is configured to close the compression sub-chamber outlet port during a first part of the first compression sub-chamber exhaust stroke and to open the compression sub-chamber outlet port during a second part of the first compression sub-chamber exhaust stroke.

[0050] The first expansion sub-chamber and the first compression sub-chamber may be configured to operate in antiphase.

[0051] In one embodiment, there is a second expansion sub-chamber configured to cycle through a second expansion sub-chamber intake stroke and a second expansion sub-chamber exhaust stroke, wherein the first and second expansion sub-chambers are configured to operate in antiphase, a second compression sub-chamber configured to cycle through a second compression sub-chamber intake stroke and a second compression sub-chamber exhaust stroke, wherein the first and second compression sub-chambers are configured to operate in antiphase. Here, an expansion chamber inlet port is provided for introducing fluid into each expansion sub-chamber during each intake stroke, and an expansion sub-chamber outlet port is provided for discharging fluid from each expansion sub-chamber during each exhaust stroke. A compression sub-chamber inlet port is provided for introducing working fluid into each compression sub-chamber during each intake stroke, and a compression sub-chamber outlet port is provided for discharging fluid from each compression sub-chamber during each exhaust stroke. Here, the apparatus is configured to open the expansion chamber inlet port to each expansion sub-chamber during a first part of each expansion sub-chamber intake stroke and to close the expansion chamber inlet port to each expansion sub-chamber during a second part of each expansion sub-chamber intake stroke, and the apparatus is configured to close the compression sub-chamber outlet port to each compression sub-chamber during a first part of each expansion sub-chamber exhaust stroke and to open the compression sub-chamber outlet port to each compression sub-chamber during a second part of each compression sub-chamber exhaust stroke.

[0052] In one embodiment, the apparatus is configured such that the compression sub-chamber outlet port is closed when the expansion chamber inlet port is opened and the expansion chamber inlet port is closed when the compression sub-chamber outlet port is opened.

[0053] According to another aspect, a fluid pump may be provided for transferring a saturated fluid from the second heat exchanger to the first heat exchanger. The fluid pump may be added to and used in the compression subchamber or may replace the compression subchamber.

[0054] The present disclosure relates to a thermodynamic cycle for use with expansion equipment that is typically classified or referred to as "positive displacement" with respect to nature and operation.

[0055] The features mentioned above are combined together in various combinations.

[0056] Next, embodiments of the present disclosure will be described with reference to the accompanying drawings.

Brief Description of the Drawings

[0057]

Figure 1

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 3E

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Figure 5A

Figure 5B

Figure 5C

Figure 5D

Figure 5E

Figure 5F

Figure 6A

Figure 6B

Figure 6C

Figure 6D

Figure 6E

Figure 7

Figure 8

Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0058] FIG. 1 shows a pressure / volume graph of an ideal Carnot cycle when functioning as a heat engine. In this cycle, the working fluid is configured to pass through four thermodynamic processes.

[0059] Between points 1 and 2 of the graph shown in FIG. 1, heat is isothermally transferred from the fluid at a constant temperature T2 to a low-temperature reservoir. The fluid in the engine is in thermal contact with the cold reservoir at temperature T2. For example, by driving a piston to reduce the volume of the chamber containing the fluid, the surrounding environment does work on the fluid, whereby an amount of heat energy Q out leaves the system and moves to the low-temperature reservoir, and the entropy of the system decreases.

[0060] Between points 2 and 3 of the graph shown in FIG. 1, the fluid undergoes adiabatic compression (isentropic compression). Again, the fluid in the engine is thermally insulated from the high-temperature and low-temperature reservoirs, and the engine is assumed to be frictionless and, by extension, reversible. During this step, for example, by further driving the piston to further reduce the volume of the chamber containing the fluid, the surrounding environment continues to do work on the fluid. This has the effect of increasing the internal energy of the fluid and raising its temperature back to T1 by the work done on the system, while maintaining a state where the entropy does not change.

[0061] At point 3 of the diagram, the fluid is in a relatively high-pressure state in a relatively small volume. Between points 3 and 4 of the graph, heat is reversibly transferred from a high-temperature reservoir at a constant temperature (i.e., isothermal heating).

[0062] During this step, the fluid expands and does work on the surrounding environment, for example by pushing a piston. The pressure decreases from point 3 to point 4, but the temperature of the fluid does not change during this process. The reason is that the fluid is in thermal contact with the high-temperature reservoir at T1, causing the expansion to be isothermal. Heat energy Q in is absorbed from the high-temperature reservoir, thereby increasing the entropy of the fluid.

[0063] Between points 4 and 1 of the graph shown in Figure 1, the fluid is thermally insulated from both the high-temperature reservoir and the low-temperature reservoir and undergoes an isentropic expansion (or reversible adiabatic expansion). The fluid continues to expand due to the pressure drop and does work on the surrounding environment, for example by continuously moving the piston to increase the volume of the chamber that contains the fluid. The fluid will lose an amount of internal energy equal to the work done. The gas expansion without heat input will cool it to a temperature T2 that is "lower". The entropy remains in an unchanged state.

[0064] At this point, the fluid returns to the same state as at the start of step 1.

[0065] Each of these four processes of the Carnot cycle follows the polytropic relationship PV n = C, where n is the polytropic index.

[0066] When the polytropic index n is equal to 0, the process is isobaric. When the index n is equal to 1, the process is isothermal. In both of these processes, both heat and work can be transferred during the process. When the index is equal to the specific heat ratio of the fluid used (also known as the isentropic index) γ, the process is isentropic. As the index n increases and exceeds γ, the process tends towards isochoric (n tends towards infinity). This is another special case where heat is transferred but no work is done by or on the surroundings.

[0067] In the above example of the Carnot cycle, the index n varies as follows. Steps 1 - 2: - (Isothermal compression): n = 1 Steps 2 - 3: - (Adiabatic compression): n = γ Steps 3 - 4: - (Isothermal expansion): n = 1 Steps 4 - 1: - (Adiabatic expansion): n = γ

[0068] Figure 2A shows a very schematic example of an apparatus 100 configured as a heat engine or a heat pump. The apparatus 100 is configured to vary the volume of a fluid. The apparatus 100 includes an expansion sub - chamber 102 for receiving the fluid. As will be described in more detail later, the apparatus 100 can be configured to receive and transfer the fluid between a first heat exchanger 106 and a second heat exchanger 108. In one embodiment, the apparatus 100 includes the first heat exchanger 106, the expansion sub - chamber 102, and the second heat exchanger 108 in a series of flows. The apparatus 100 can further include a compression sub - chamber 104 located after the second heat exchanger 108 in a series of flows. The expansion sub - chamber 102 and the compression sub - chamber 104 can be regarded as an integral fluid displacement device 101.

[0069] The expansion sub - chamber 102 can be regarded as a temporary but variable - sized aspect of the expansion chamber 103. That is, the volume of the expansion sub - chamber 102 can change throughout the operation of the apparatus 100.

[0070] The expansion chamber 103 may be a chamber of fixed size, where displacement means such as the first piston 112 can move relative to the expansion chamber 103, thereby changing the volume of the expansion sub-chamber 102. The first piston 112 is configured to move relative to the expansion chamber 103, thereby changing the volume of the expansion sub-chamber 102. The first piston 112 can be used to compress and / or expand the fluid within the expansion sub-chamber 102 in response to operation. That is, in certain instances, the expansion chamber 103 may be fixed and the first piston 112 may be movable through the expansion chamber 103 to change the volume of the expansion sub-chamber 102. In other embodiments, both the first piston 112 and the expansion chamber 103 move to change the volume of the expansion sub-chamber 102 (e.g., the first piston 112 may simply be rotatable). In other embodiments, the first piston 112 may be fixed and the expansion chamber 103 may be movable to change the volume of the expansion sub-chamber 102. In these embodiments, the first piston 112 is configured to move relative to the expansion chamber 103, thereby changing the volume of the expansion sub-chamber 102.

[0071] Similarly, the compression sub-chamber 104 can be regarded as a temporary but variable-size aspect of the compression chamber 105. That is, the volume of the compression sub-chamber 104 can change through the operation of the device 100. The compression chamber 105 may be a chamber of fixed size, where volumetric means such as the second piston 114 can move relative to the compression sub-chamber 104, thereby being able to change the volume of the compression sub-chamber 104.

[0072] The second piston 114 within the compression chamber 105 may be configured to sweep the compression chamber 105 to vary the volume of the compression sub-chamber 104. The second piston 114 may be used to compress and / or expand the fluid within the compression sub-chamber 104 in response to operation. That is, in certain instances, the compression chamber 105 may be considered fixed and the second piston 114 may be movable through the compression chamber 105 to vary the volume of the compression sub-chamber 104. In other embodiments, both the second piston 114 and the compression chamber 105 move to vary the volume of the compression sub-chamber 104 (e.g., the second piston 114 may simply rotate). In other embodiments, the second piston 114 may be fixed and the compression chamber 105 may be movable to vary the volume of the compression sub-chamber 104.

[0073] The piston is used herein to describe volumetric means, but any alternative volumetric means may also be used. Such alternatives include, but are not limited to, diaphragms.

[0074] In one embodiment, the first piston 112 and the second piston 114 are integral with each other. For example, the first piston 112 and the second piston 114 are provided on top of one another as shown, for example, in FIG. 8.

[0075] The first heat exchanger 106 may serve as the first reservoir. In certain embodiments, the first heat exchanger 106 provides a source of thermal energy that may be added to the fluid within the device 100.

[0076] The second heat exchanger 108 may serve as the second reservoir. The second heat exchanger 108 may be a heat sink, and thermal energy may be removed from the fluid passing through the second heat exchanger 108.

[0077] In one embodiment, the volumes of the first heat exchanger 106 and the second heat exchanger 108 can be orders of magnitude larger than the expansion sub-chamber 102 and the compression sub-chamber 104. In one embodiment, the first heat exchanger 106 and the second heat exchanger 108 are between 5 and 15 times larger than the volumes of the expansion sub-chamber 102 and the compression sub-chamber 104, and preferably at least 10 times (or more) larger than the volumes of the expansion sub-chamber 102 and the compression sub-chamber 104. By providing a larger heat exchanger compared to the expansion chamber, the expansion process and the compression process can proceed relatively quickly to reduce the potential in chamber heat transfer. However, heat transfer within the heat exchanger can proceed at a relatively low speed. That is, this difference in volume enables a heat exchange process that is relatively slow compared to the compression process or the expansion process described later. A "fast flowing small volume heat exchanger" is not practical or attractive in a real heat engine or heat exchange application. In contrast, the present disclosure seeks to maximize the volume, surface area, and heat transfer during the heat exchange process. Further, considering that a large volume of the heat exchanger reduces the pressure fluctuations resulting from the expansion sub-chamber 102 and the compression sub-chamber 104, and any change in pressure would only be wasted energy, it is actively pursued to eliminate changes in pressure during the fluid transfer process that is substantially isobaric as much as possible.

[0078] In some embodiments, the volumes of the first heat exchanger 106 and the second heat exchanger 108 are not the same.

[0079] In an embodiment, there may be pipes 110 or ducts for connecting the expansion sub-chamber 102 to the first heat exchanger 106 and the second heat exchanger 108. The apparatus 100 can further include pipes 110 or ducts for connecting the compression sub-chamber 104 to the first heat exchanger 106 and the second heat exchanger 108.

[0080] In one embodiment, device 100 includes a plurality of valves 113 that can be disposed between various elements of device 100. For example, one or more valves may be present between the first heat exchanger 106 and the expansion subchamber 102. When the valve between the first heat exchanger 106 and the expansion subchamber 102 is not closed, fluid can flow between the first heat exchanger 106 and the expansion subchamber 102 (or vice versa depending on the intended operation). When the valve is opened between two elements and fluid can flow between those two elements, these elements are considered to be fluidly connected together. When the valve is closed, fluid flow between the first heat exchanger 106 and the expansion subchamber 102 is prevented (or vice versa depending on the intended operation). When the valve is closed, these elements are considered to be fluidly isolated from each other.

[0081] Being fluidly connected means that fluid can flow between various elements. Being fluidly connected is similar to being fluidly connected.

[0082] In one embodiment, the expansion chamber 103 can include an inlet port 140 through which fluid can flow into the expansion sub-chamber 102. The expansion chamber 103 can further include an outlet port 142 through which fluid can flow out of the expansion sub-chamber 102. For example, when operating as a heat engine, the expansion sub-chamber 102 is fluidly connected to a first heat exchanger 106 to feed fluid into the expansion sub-chamber 102, and the inlet port 140 is considered open. When the expansion sub-chamber 102 is fluidly connected to a second heat exchanger 108 to transfer fluid to the second heat exchanger 108, the outlet port 104 is open. When the expansion sub-chamber 102 is fluidly isolated, the inlet port 140 and the outlet port 142 are closed. The compression chamber 103 can include an inlet port 144 through which fluid can flow into the compression sub-chamber 104. The compression chamber 103 can further include an outlet port 146 through which fluid can flow out of the compression sub-chamber 104. In an embodiment of a heat engine, the fluid is configured to flow through the inlet port 144 from the second heat exchanger 108 and to flow from the outlet port 146 to the first heat exchanger 106.

[0083] In one embodiment, the ports 140, 142, 144, 146 can be disposed within a housing around the expansion sub-chamber 102 and the compression sub-chamber 104.

[0084] The valve between the first heat exchanger 106 and the expansion sub-chamber 102 can be disposed at the inlet port 140 of the expansion chamber 103, at the port of the first heat exchanger 106, or within the pipe 110 between the first heat exchanger 106 and the expansion sub-chamber 102. Similar valves can exist between the expansion sub-chamber 102 and the second heat exchanger 108, between the second heat exchanger 108 and the compression sub-chamber 104, and between the compression sub-chamber 104 and the first heat exchanger 106. In other embodiments, the apparatus 100 does not include valves, but the arrangement of the apparatus is set such that various elements are fluidly isolated / fluidly integrally connected as required (e.g., by opening / closing ports 140, 142, 144, 146 according to the relative positions of the expansion sub-chamber 102 and the compression sub-chamber 104 through the operation of the apparatus).

[0085] In one embodiment, the expansion sub-chamber 102 and the compression sub-chamber 104 can be located on either side of a single piston within a single chamber. That is, the expansion sub-chamber 102 may be a region of a single chamber on the first side of the piston, and the compression sub-chamber 104 can be regarded as a region of a single chamber on the second side of the piston. In this embodiment, a single piston can be used to compress / expand the fluid within the expansion sub-chamber 102 and the compression sub-chamber 104.

[0086] In one embodiment, the expansion sub-chamber 102 and the compression sub-chamber 104 are separate chambers (i.e., the expansion sub-chamber 102 and the compression sub-chamber 104 do not share a common wall or boundary, or a drive train), and the movement of the pistons 112, 114 is not linked. In other embodiments, the pistons within the expansion chamber 103 and the compression chamber 105 are linked. For example, a connecting rod can connect the piston 112 within the expansion chamber 103 and the piston 114 within the compression chamber 105 to a movement mechanism such as a flywheel 116.

[0087] In an embodiment of the apparatus 100 operating as a heat engine, work may be extracted from the apparatus 100 by a fluid that does work on one or more pistons 112, 114, whereby, in some embodiments, a crank, flywheel, or drive shaft is moved. This work may be used to drive a power train or to generate electricity.

[0088] In an embodiment of the apparatus 100 operating as a heat pump, work may be input to the apparatus 100, for example, by the movement of a piston. A motor may be used to drive a crank-driven drive shaft to drive the pistons 112, 114. The heat engine may be used to transfer heat from one location to another.

[0089] In some embodiments, the volume of the expansion sub-chamber 102 and the volume of the compression sub-chamber 104 are substantially equal. In other embodiments, the volume of the expansion sub-chamber 102 is greater than the volume of the compression sub-chamber. In some embodiments, the presence of a connecting rod or piston rod within the compression sub-chamber 104 is a major factor in the desired difference in volume between the expansion sub-chamber 102 and the compression sub-chamber 104.

[0090] Figure 2B shows an example chart of the pressure of a fluid during a thermodynamic cycle proceeding on the apparatus when configured as a heat engine in conjunction with a compressible fluid. In other embodiments, the fluid may be partially or fully saturated and may not be compressible and may need to be pumped between a first threshold pressure and a second threshold pressure.

[0091] The angle on the x-axis represents the relative position of the apparatus through one cycle (0 degrees is the start of the cycle and 360 degrees represents the apparatus returning to the same position as the start of the cycle).

[0092] Refer to Figure 2B when considering the various steps of the apparatus 100 shown in Figures 3A - 3E.

[0093] FIG. 3A shows a schematic view of an initial arrangement configuration of an example of apparatus 100 according to an embodiment in which the apparatus 100 is configured to operate as a heat engine. In one example, the expansion sub-chamber 102 may be referred to as the first sub-chamber, and the compression sub-chamber 104 may be referred to as the second sub-chamber. In this example of the apparatus 100 operating as a heat engine, the volume of the expansion chamber 103 may be larger than the volume of the compression chamber 105. This difference in volume is a partial major factor in the volume reduction when heat entering the second heat exchanger is blocked and heat is added to the fluid passing through the first heat exchanger 106.

[0094] In this schematic example, the piping 110 is shown as either existing or not existing to indicate whether fluid can flow between various elements of the apparatus (or to indicate whether ports are open or closed). For example, the presence of the piping 110 can indicate that a valve is open between elements, and the absence of the piping can indicate that a valve is closed between elements. Alternatively, the presence of the piping 110 can indicate that the arrangement of the apparatus 100 has been moved to a position such that the elements connected to allow fluid flow are open relative to each other.

[0095] Focusing on the operation of the expansion sub-chamber 102, FIG. 3A shows an example of an initial arrangement configuration or starting point of the piston 112 within the expansion sub-chamber 102 at its minimum volume. In this initial arrangement configuration, the expansion sub-chamber 102 is fluidly connected to the first heat exchanger 106 (i.e., the inlet port is open). The initial arrangement configuration shown in FIG. 3A corresponds to point 200 on the chart of FIG. 2B.

[0096] FIG. 3B shows the next step in the process, where the intake stroke within the expansion sub-chamber 102 has been initiated. A fluid connection between the expansion sub-chamber 102 and the first heat exchanger 106 is maintained open (e.g., the inlet port is kept open). By increasing the volume of the expansion sub-chamber 102, fluid is induced or fed from the first heat exchanger 106 into the expansion sub-chamber 102. In one embodiment, the first piston 112 moves relative to the expansion chamber 103 to increase the volume of the expansion sub-chamber 102, thereby feeding fluid into the expansion chamber 102. In FIG. 3B, the piston 112 has initiated the intake stroke and is moving in the first direction. The movement of the piston 112 feeds fluid from the first heat exchanger 106 into the expansion sub-chamber 102. The fluid is fed into the expansion sub-chamber 102 at the intake pressure. The first part (or phase) of the intake stroke may be recognized as the intake phase, where fluid is fed into the expansion sub-chamber 102. This is represented at step 202 in FIG. 2B.

[0097] Figure 3C shows the next step in the process (second part of the intake stroke or expansion phase). At a predetermined point in the intake stroke of piston 112, the expansion sub-chamber 102 is fluidly isolated from the first heat exchanger 106. In other words, the fluid connection between the expansion sub-chamber 102 and the first heat exchanger 106 is closed. That is, the inlet port is closed. This is shown at point 204 in Figure 2B and in Figure 3C by the removal of the pipe 110 between the expansion sub-chamber 102 and the first heat exchanger 106. However, in practice, this can occur by closing a valve between the expansion sub-chamber 102 and the first heat exchanger 106, and / or by rotating the expansion sub-chamber 102 to a position where it is not open to or in fluid communication with the first heat exchanger 106. As mentioned above, the valve can be located at the inlet port of the expansion chamber or the first heat exchanger (or both), or within the pipe between the expansion sub-chamber 102 and the first heat exchanger 106.

[0098] After the expansion sub-chamber 102 has been fluidly isolated from the first heat exchanger 106, the piston 112 continues to move in the same direction (i.e., the first direction) as during the fluid intake phase into the expansion sub-chamber 102 so as to increase the volume of the expansion sub-chamber 102. That is, the piston 112 continues its intake stroke. This second part of the intake stroke is known as the expansion phase and is shown at step 206 in Figure 2B. The fluid fed into the expansion sub-chamber 102 expands throughout the remainder of the expansion phase.

[0099] In one embodiment, the predetermined point during the intake stroke at which the expansion sub-chamber 102 becomes fluidly isolated can be 50% of the elapsed intake stroke. That is, during the first half of the intake stroke, fluid is fed into the expansion sub-chamber 102 (i.e., the intake phase). Then, when the piston 112 passes the midpoint of the expansion chamber 103, the expansion sub-chamber 102 becomes fluidly isolated from the first heat exchanger 106, and the remaining 50% of the intake stroke is used to expand the fluid within the expansion sub-chamber 102 (i.e., the expansion phase). The ratio of the volume of the fluid within the expansion sub-chamber 102 at the end of the intake stroke when the expansion sub-chamber 102 becomes fluidly isolated (end of the intake phase) to the volume of the fluid within the expansion sub-chamber is known as the expansion ratio. In this embodiment, there is an expansion ratio of 2:1, and the volume of the fluid doubles. This predetermined point can be at least 10%, 25%, 33%, 40% of the elapsed intake stroke. The predetermined point can be up to 60%, 67%, 75%, or 90% of the elapsed intake stroke.

[0100] In one embodiment, the predetermined point is between 10% and 90% of the elapsed intake stroke, more preferably between 25% and 75% of the elapsed intake stroke.

[0101] Accordingly, the entire intake stroke associated with the increase in volume of the expansion sub-chamber 102 consists of two parts: intake and expansion. The ratio for their comparison is known as the in-chamber volumetric expansion ratio. In one embodiment, the predetermined point at which intake ends and expansion begins during the volume increase can be 50% of the elapsed intake stroke. When the intake stroke ends at 100% volume, in this case, the resulting in-chamber volumetric expansion ratio is 2:1. In other embodiments, the predetermined point can occur at 10%, 20%, 30%, 40%, 60%, 70%, 80%, 90% of the intake stroke.

[0102] When the volume of the fluid in the expansion sub-chamber is increased during the expansion phase, the pressure of the fluid will decrease and the temperature of the fluid will decrease. The amount of volume increase and the amounts of pressure and temperature decrease are determined by the expansion ratio described above. The expansion ratio of the expansion sub-chamber (and, thereby, a predetermined point when the expansion sub-chamber 102 is fluidically isolated) is set to enable the pressure of the fluid in the expansion sub-chamber to reach a first threshold pressure at the end of the expansion phase. The first threshold pressure is less than the intake pressure as shown across step 206 of FIG. 2B. That is, the pressure of the fluid in the expansion sub-chamber 102 decreases until it drops to a pressure following the first threshold pressure.

[0103] FIG. 3D shows the piston 112 in the expansion chamber 103 at the end of the intake stroke such that the expansion sub-chamber 102 is at its maximum volume. When the piston 112 completes the intake stroke, the fluid in the expansion sub-chamber 102 will reach a first predetermined threshold (or, minimum chamber pressure). Then, for example, by opening the expansion chamber outlet port, the expansion sub-chamber 102 is fluidically connected to the second heat exchanger 108. This is shown at step 208 of FIG. 2B. As described above, this fluidic connection can be achieved by opening a valve between the expansion sub-chamber 102 and the second heat exchanger 108 and / or by moving the expansion sub-chamber 102 to a position such that it will open with respect to the second heat exchanger 108. The expansion sub-chamber 102 is not connected to either the first heat exchanger 106 or the second heat exchanger 108 simultaneously.

[0104] At this stage, further, the compression sub-chamber 104 is fluidically connected to the second heat exchanger 108. That is, both the expansion sub-chamber 102 and the compression sub-chamber 104 are simultaneously connected to the second heat exchanger 108.

[0105] Figure 3E shows the next stage in the process. Due to the decrease in the volume of the expansion sub-chamber 102, the fluid is discharged from the expansion sub-chamber 102 and transferred to the second heat exchanger 108. That is, the piston 112 in the expansion chamber 102 starts the exhaust stroke to decrease the volume of the expansion sub-chamber 102, or moves in a second direction opposite to the first direction. The exhaust stroke effectively transfers the fluid through the second heat exchanger 108, which is shown by step 210 in Figure 2B.

[0106] In an embodiment where the device 100 is configured to operate as a heat engine, the second heat exchanger 108 is configured to receive heat from the fluid. In other words, when the fluid passes through the second heat exchanger 108, the enthalpy of the fluid is reduced. The second heat exchanger 108 may also be referred to as a heat sink in this embodiment. The expansion sub-chamber 102 and the second heat exchanger 108 may be fluidly connected during the entire exhaust stroke of the expansion sub-chamber 102.

[0107] During the exhaust stroke, the pressures of the fluids in the expansion sub-chamber 102, the second heat exchanger 108, and the compression sub-chamber 104 may become substantially equal (e.g., a first threshold pressure), but the pressure of the fluid may decrease as a result of the frictional force acting on the fluid when passing through the pipe 110 and the second heat exchanger 108.

[0108] At the end of the exhaust stroke, as shown in Figure 3A, the piston 112 returns to the starting position in the expansion chamber 103 (i.e., the expansion sub-chamber 102 reaches its maximum volume), and the process starts again.

[0109] Next, attention is turned to the compression sub-chamber 104. The expansion sub-chamber 102 and the compression sub-chamber 104 can operate in opposite phases. This arrangement is shown in Figure 3D. That is, when the volume of the expansion sub-chamber 104 is minimized, the volume of the expansion sub-chamber 102 can be maximized.

[0110] When the piston 112 in the expansion chamber 103 starts the exhaust stroke, the piston 114 in the expansion chamber 105 starts the intake stroke. That is, the compression sub-chamber 104 is fluidly connected to the second heat exchanger 108, and fluid is fed from the second heat exchanger 108 into the compression sub-chamber 104. In other words, the inlet port of the compression sub-chamber 104 opens. This step is shown in step 212 of FIG. 2B. The fluid is fed into the second sub-chamber 104 at a transfer pressure, which can be the same as the first threshold pressure described above. However, as a result of the frictional force acting on the fluid when passing through the pipe 110 and the second heat exchanger 108, the pressure may drop slightly. This is shown in FIG. 3E.

[0111] The compression sub-chamber 104 and the second heat exchanger 108 can be fluidly connected during the entire intake stroke of the piston 114 in the compression chamber 105. That is, when the volume of the compression sub-chamber increases from minimum to maximum, the compression sub-chamber 104 is fluidly connected to the second heat exchanger 108, and fluid is fed from the second heat exchanger 108 into the compression sub-chamber 104.

[0112] When the volume of the compression sub-chamber 104 reaches its maximum, the device returns to the state shown in FIG. 3A. Next, the fluid in the compression sub-chamber 104 will be described. When the compression sub-chamber 104 is at its maximum volume, the compression sub-chamber 104 is fluidly isolated from the second heat exchanger 108. That is, the fluid connection between the compression sub-chamber 104 and the second heat exchanger 108 is eliminated. In other words, the compression chamber inlet port is closed. This is shown at step 214 of FIG. 2B. This may be the result of a valve closing, and / or may occur by rotating the compression sub-chamber 104 to a position where it is closed with respect to the second heat exchanger 108. For completeness, at this stage the compression sub-chamber 104 is also not fluidly connected to the first heat exchanger 106.

[0113] Figure 3B shows the next step in the process. The second piston 114 within the compression sub-chamber 104 begins the exhaust stroke. The exhaust stroke consists of a compression phase and an expulsion phase. The compression phase occurs during the first part of the exhaust stroke, and the expulsion phase occurs during the second part of the exhaust stroke. During the compression phase, the volume of the compression sub-chamber 104 is decreased to compress the fluid within the compression sub-chamber 104. The fluid within the compression sub-chamber 104 can reach a second threshold pressure at the end of the compression phase. The second threshold pressure is greater than the transfer pressure mentioned above. The compression phase is shown in step 216 of Figure 2B.

[0114] Figure 3C is used to show the next step in the process. At a predetermined point, the compression sub-chamber 104 is fluidly connected to the first heat exchanger 106. In other words, the fluid connection between the compression sub-chamber 104 and the first heat exchanger 106 is opened. This is represented by adding a pipe 110 between the compression sub-chamber 104 and the first heat exchanger 106 in Figure 3C. In other words, the outlet port of the compression chamber is opened. In practice, this can be due to opening a valve between the compression sub-chamber 104 and the first heat exchanger 106 and / or rotating the expansion sub-chamber 104 to a position such that it opens to the first heat exchanger 106. As mentioned above, the valve can be disposed at the port of the compression sub-chamber 104.

[0115] After the compression chamber 104 is fluidly connected to the first heat exchanger 106, the exhaust stroke enters the expulsion phase, where the fluid is expelled from the compression sub-chamber 106 and transferred into the first heat chamber 106 by further decreasing the volume of the compression sub-chamber 104. This can be achieved by the piston 14 continuing to move in the same direction. That is, the piston 114 continues its exhaust stroke. The expulsion phase is shown at step 220 of Figure 2B. Then, the fluid compressed during the compression phase of the exhaust stroke is transferred into the first heat exchanger 106 during the expulsion phase of the exhaust stroke.

[0116] In certain embodiments, a predetermined point during the exhaust stroke can be 50% of the exhaust stroke. That is, when the piston 114 passes the midpoint of the compression subchamber 104, the compression subchamber 104 is fluidly connected to the first heat exchanger 106, and the remaining 50% of the exhaust stroke is used to transfer fluid to the first heat exchanger 106. The ratio of the volume of fluid at the start of the exhaust stroke to the volume of fluid in the compression subchamber 104 at the predetermined point at which the compression subchamber 104 is fluidly connected to the first heat exchanger 106 is known as the compression ratio. In this embodiment, a compression ratio of 2:1 will exist, reducing the volume of fluid by half. This predetermined point can be at least 10%, 25%, 33%, or 40% of the compression stroke. This predetermined point can be up to 60%, 67%, 75%, or 90% of the compression stroke. In one embodiment, this predetermined point is between 10% and 90% of the exhaust stroke, more preferably between 25% and 75% of the exhaust stroke.

[0117] As the volume of fluid in the compression subchamber 104 is reduced, the pressure of the fluid will increase and the temperature of the fluid will increase. The amount of volume reduction and the amount of pressure and temperature increase are determined by the compression ratio of the compression subchamber 104. The compression ratio of the compression subchamber 104 (and thus the predetermined point at which the compression subchamber 104 is fluidly connected to the first heat exchanger 106) can be set such that the pressure of the fluid reaches a second pressure threshold at the predetermined point. The second threshold pressure is higher when compared to the transfer pressure. That is, during the compression stroke, the pressure of the fluid in the second subchamber 104 will increase until it reaches the second threshold pressure.

[0118] Once the fluid is transferred to the first heat exchanger 106, a full cycle has occurred and the process returns to FIG. 3A.

[0119] As shown in the figure, in this embodiment, there may be two or more processes occurring simultaneously. For example, when the fluid is compressed within the compression sub-chamber 104, the fluid may be fed into the expansion sub-chamber 102. When the fluid is transferred from the compression sub-chamber 104 to the first heat exchanger 106, the fluid may be expanded within the expansion sub-chamber 102. In other words, the intake stroke within the expansion sub-chamber 102 may occur simultaneously with the exhaust stroke within the compression sub-chamber 104. Further, the exhaust stroke within the expansion sub-chamber 102 may occur simultaneously with the intake stroke within the compression sub-chamber 104.

[0120] Figure 4A shows an example of a pressure-volume diagram of the process in which the device 100 functions as a heat engine. Before the fluid is drawn into the expansion sub-chamber 102, the fluid is in a state between point 3 and point 4. Point 4 on the chart represents the point at which the expansion sub-chamber 102 is fluidically isolated from the first heat exchanger 106.

[0121] Between point 4 and point 1, the fluid undergoes approximately adiabatic expansion. The fluid expansion between point 4 and point 1 is correlated with the expansion of the fluid after the expansion sub-chamber 102 is fluidically isolated.

[0122] Between point 1 and point 2, the fluid undergoes substantial isobaric compression. Substantial isobaric compression means that the pressure does not change by more than 10%. This corresponds to the fluid being transferred through the second heat exchanger 108 to the compression sub-chamber 104. During this step, heat is extracted from the fluid.

[0123] Between point 2 and point 3, when the compression sub-chamber is fluidically isolated, the fluid is compressed within the compression sub-chamber 104. This corresponds to the compression within the compression sub-chamber 104 shown in Figure 3B. At this stage, the fluid can be considered to undergo approximately adiabatic compression.

[0124] Between point 3 and point 4, the fluid exits the compression subchamber 104 and enters the first heat exchanger 106 to receive heat input. It should be noted that the stage between 3 and 4 represents the change in the fluid state when the fluid exits the compression subchamber 104 and is held in the first heat exchanger 106 for a certain period of time and then enters the expansion subchamber 102. The fluid can be considered to undergo expansion due to heat addition. This step can be substantially isobaric. Substantially isobaric expansion means that the pressure does not change by more than 10%.

[0125] Points 1, 2, 3, and 4 are also shown during the process of Figure 2B.

[0126] The process of fluid expansion after the expansion subchamber 102 is fluidically isolated means that the "polytropic" index changes at a predetermined point through the expansion stroke. The polytropic index is defined by the relationship PV n = C (where n is the polytropic index).

[0127] In other words, during the first part (or the intake phase) of the intake stroke in which the expansion subchamber 102 is in fluid communication with the first heat exchanger 106, the fluid follows a substantially isobaric expansion (represented by the line between point 3 and point 4 in Figure 4A). During the substantially isobaric expansion, the polytropic index is approximately equal to 0 (i.e., PV 0 = C or P = C). Similarly, substantially isobaric means that the pressure does not change by more than 10%.

[0128] When the expansion subchamber 102 is fluidically isolated, the fluid can follow a substantially adiabatic expansion. During the adiabatic expansion, the polytropic index is approximately equal to the ratio of specific heats γ, and γ is approximately 1.4 for air.

[0129] In other words, the polytropic index changes at a predetermined point during the expansion stroke of the piston 112 in the expansion chamber 102.

[0130] When the compression sub-chamber 104 is fluidly isolated and then the compression chamber 104 is fluidly connected to the first heat exchanger 102, the process of compressing the fluid within the compression sub-chamber 104 means that the polytropic index changes at a predetermined point through the exhaust stroke of the piston 114.

[0131] In other words, during the first part of the exhaust stroke in which the compression chamber 104 is fluidly isolated (i.e., during the compression phase of the exhaust stroke), the fluid follows approximately adiabatic compression. During adiabatic compression, the polytropic index is approximately equal to the ratio of specific heats γ, which is about 1.4 for air.

[0132] Then, during the second part of the exhaust stroke (the discharge phase) in which the compression sub-chamber 104 is fluidly connected to the first heat exchanger 106, the fluid can follow a substantial isobaric compression (represented by the line between point 1 and point 2 in FIG. 4A). During isobaric compression, the polytropic index is approximately equal to 0 (i.e., PV 0 = C or P = C). Substantial isobaric compression means that the pressure does not change by more than 10%.

[0133] In other words, the polytropic index changes at a predetermined point during the exhaust stroke within the compression sub-chamber 104 (i.e., at the end of the compression phase and the start of the discharge phase).

[0134] By setting the fluid expansion ratio of the expansion sub-chamber 102, the compression ratio of the compression sub-chamber 104, and the relative volumes of the expansion sub-chamber 102 and the compression sub-chamber 104, the Carnot efficiency of the apparatus 100 can be adjusted.

[0135] FIG. 4B shows an overlay of the pressure / volume cycle of the present invention compared to the pressure / volume cycle of the Carnot cycle. The cycle defined by the solid line representing the Carnot cycle is equal to the cycle shown in FIG. 1. The dashed line in FIG. 4B represents the difference between the disclosed cycle being compared to the Carnot cycle. Qin * and Qout *is the thermal energy absorbed by the fluid and the thermal energy released from the fluid in the cycle of the present disclosure. The lines between 3 and 4 and between 1 and 2 of the present disclosure are substantially isobaric. The use of feeding the fluid flow substantially isobarically and its pursuit are the results of significant modeling and testing by the applicant.

[0136] Figure 4C shows a pressure - enthalpy graph during the process, and Figure 4D shows a temperature - enthalpy graph during the process.

[0137] In one embodiment, the first pressure threshold and the second pressure threshold are set to substantially match the temperature of the fluid leaving the expansion sub - chamber 102 with the temperature of the fluid leaving the compression sub - chamber 104. When the fluid temperatures leaving the expansion sub - chamber 102 and the compression sub - chamber 104 are substantially equal, an optimal balance of work and efficiency is achieved. However, there are exceptions for alternative fluids or when it is preferred to prioritize either work or efficiency over the other.

[0138] In one embodiment, the apparatus 100 includes two fluid displacement devices 101 each having an expansion sub - chamber and a compression sub - chamber. The two fluid displacement devices 101 are identical, but for the purposes of this description, the sub - chambers of the second fluid displacement device are referred to as the second expansion sub - chamber 102b and the second compression sub - chamber 104b. In other words, the apparatus includes a first fluid displacement device 101 having a first expansion sub - chamber 102a and a first compression sub - chamber 104a, and a second fluid displacement device 101 having a second expansion sub - chamber 102b and a second compression sub - chamber 104b. An example of an apparatus including two fluid displacement devices 101 is shown in FIGS. 5A - 5E.

[0139] The second expansion sub-chamber 102b operates in the same manner as the first expansion sub-chamber 102a, with the exception that the second expansion sub-chamber 102b may be "phase-shifted" 180 degrees from the first expansion sub-chamber 102a. That is, when the piston 112 in the first expansion chamber 103 starts the intake phase of the intake stroke to pump fluid into the first expansion sub-chamber 102a, the piston 124 in the second expansion chamber can start the exhaust stroke to transfer fluid from the second expansion sub-chamber 102b to the second heat exchanger 108.

[0140] Similarly, the second compression sub-chamber 104b operates in the same manner as the first compression sub-chamber 104, with the exception that the second compression sub-chamber 104b may be "phase-shifted" 180 degrees from the first compression sub-chamber 104. That is, when the piston 114 in the compression chamber 105 starts the compression phase of the exhaust stroke to compress the fluid in the compression sub-chamber 104, the piston 126 in the second compression chamber starts the intake stroke to pump fluid from the second heat exchanger 108 into the second compression sub-chamber 104b.

[0141] In one embodiment, the second fluid displacement device 101 may be phase-shifted 90 degrees from the first fluid displacement device 101.

[0142] Providing the second fluid displacement device 101 means that there is a consistent fluid flow through the heat exchanger throughout the entire cycle. The calculation of the optimal fluid displacement device 101 will be determined by a combination of commercial and efficiency goals at a very high frequency. Usually, more sub-chambers that are complementarily arranged with respect to timing function to stabilize the flow and pressure fluctuations in the heat exchanger. Tendentially, better stabilizing and matching the pressure on each side of the fluid transfer point at a higher frequency improves the efficiency.

[0143] In an alternative embodiment, the apparatus 100 may be operable as a heat pump. That is, the apparatus 100 is configured to receive work, for example, in the form of work driving pistons 112, 114, and to transfer heat from a low temperature reservoir (e.g., the second heat exchanger 108) to a high temperature reservoir (e.g., the first heat exchanger 106).

[0144] The steps of the process are shown in FIGS. 6 - 6E. The apparatus 100 used as a heat pump is substantially identical to the apparatus 100 used as a heat engine, except that the process is reversed.

[0145] In this embodiment, the expansion sub - chamber 102 can have a smaller volume compared to the compression sub - chamber 104.

[0146] In an embodiment of the apparatus 100 functioning as a heat pump, the expansion sub - chamber 102 and the compression sub - chamber 104 are effectively “switched” with respect to their arrangement in the apparatus functioning as a heat engine. In other words, here, the expansion sub - chamber 102 is shown at the bottom of the apparatus of FIG. 6A and the compression sub - chamber 104 is shown at the top of the apparatus of FIG. 6A. This is for ease of reference in describing the sub - chambers, and in reality, various relative arrangements and configurations of the expansion sub - chamber 102 and the compression sub - chamber 104 are possible.

[0147] FIGS. 6A - 6E show various steps of the operation of the apparatus 100 operating as a heat pump. These operations are the same as those of FIGS. 3A - 3E, except that the fluid flow is reversed. Further, heat is added to the fluid in the second exchanger 108 and heat is extracted from the fluid in the first heat exchanger 106.

[0148] Similar to the embodiment of the apparatus 100 operating as a heat engine, the apparatus 100 operating as a heat pump can also be a second fluid displacement device as shown in FIG. 7.

[0149] The fluid may be a refrigerant fluid or other medium such as, but not limited to, air, ethanol, R22, supersaturated CO2, ammonia (NH3), or propane (C3H8).

[0150] In one embodiment, the apparatus comprises a fluid displacement device having a rotatable shaft 150, and a first piston 112 is provided on the rotatable shaft 150. This apparatus is shown in FIG. 8. The shaft defines a first axis 152, and the piston rotates about the first axis 152. The fluid displacement device can further include a first axle defining a second axis of rotation 154, and the first shaft extends through the first axle. The first piston extends from the first axle toward the distal end of the first shaft. The fluid displacement device includes a first rotor 156 carried on the first axle, the first rotor having an expansion chamber 103, and the first piston 112 extending through the expansion chamber 103. The expansion sub-chamber 102 can be considered a temporary but variable-sized aspect of the expansion chamber 103 on the first side of the piston 112. In this embodiment, the apparatus can include two expansion sub-chambers 102 located on either side of the piston 112. These are referred to as the first expansion sub-chamber 102a and the second expansion sub-chamber 102b. In other words, both the first expansion sub-chamber 102a and the second expansion sub-chamber 102b are located within the expansion chamber 103.

[0151] The first expansion sub-chamber 102a and the second expansion sub-chamber 102b operate 180 degrees out of phase with each other. That is, when the first expansion sub-chamber 102a undergoes an intake stroke, the second expansion sub-chamber 102b located on the other side of the piston 112 undergoes an exhaust stroke. Additionally, when the first expansion sub-chamber 102a undergoes an exhaust stroke, the second expansion sub-chamber 102b located on the other side of the piston 112 undergoes an intake stroke.

[0152] Both the intake stroke and the exhaust stroke are realized from the relative movement between the first piston 112 and the expansion chamber 103. Throughout one rotation of the shaft 150, the first and second expansion sub-chambers will receive the same operation with a phase shift of exactly 180 degrees from each other. Therefore, in Figure 8, only the first 180 degrees of rotation are shown. The reason is that the operation of the first expansion sub-chamber 102a between 180 degrees and 360 degrees is equal to the operation of the second expansion sub-chamber 102b between 0 degrees and 180 degrees. The operation of the second expansion sub-chamber 102a is equal to the operation of the first expansion sub-chamber 102b at 0 degrees to 180 degrees.

[0153] The expansion chamber 103 can include a first port and a second port for realizing fluid communication with the expansion chamber 103. The first port and the second port of the expansion chamber can be recognized as the expansion chamber inlet port 140 and the outlet port 142, respectively.

[0154] The fluid displacement device can further include a compression chamber 105 and two compression sub-chambers 104 (referred to as the first compression sub-chamber 104a and the second compression sub-chamber 104b), which operate in a similar manner by the relative movement of a second piston 114 that moves relative to the compression chamber 105. That is, the first compression sub-chamber 104a and the second compression sub-chamber 104b are located within the compression chamber 105.

[0155] The compression chamber 105 can further have a first port and a second port. The first port and the second port of the compression chamber can be recognized as the second chamber inlet port 144 and the outlet port 146, respectively.

[0156] In this embodiment, the first rotor 156 and the first axle are rotatable with the first shaft 150 about the first axis of rotation 152, and the first rotor is pivotable about the axle about the second axis of rotation 154, such that when the first rotor rotates about the first axis of rotation, the first rotor 156 can pivot with respect to the first piston 112. During operation, the first axis 152 may be fixed, and the second axis 154 rotates about the first axis.

[0157] The fluid displacement device may be arranged such that through a 360-degree rotation of the shaft 150 about the first axis 152, the first expansion subchamber 102a will come into fluid contact with the first heat exchanger or the second heat exchanger 108 at selected points during rotation. That is, the first expansion subchamber 102a may be arranged with respect to the first heat exchanger 106 and the second heat exchanger 108 such that through rotation of the shaft, it will be fluidly connected to the first heat exchanger 106 or the second heat exchanger 108 at various timings and will be fluidly isolated from the first heat exchanger 106 and the second heat exchanger 108. There may be timings when the first expansion subchamber 102a is fluidly isolated from both heat exchangers, connected to only one of the heat exchangers, or fluidly connected to both heat exchangers. The first compression subchamber 104a may be arranged in a similar manner such that through various timings during rotation of the shaft, it is fluidly connected to or fluidly isolated from the first heat exchanger 106 and the second heat exchanger 108. There may be timings when the first compression subchamber 104a is fluidly isolated from both heat exchangers, connected to only one of the heat exchangers, or fluidly connected to both heat exchangers.

[0158] In one embodiment, the apparatus includes the first fluid displacement device and the second fluid displacement device described above. The second fluid displacement device can be out of phase with the first fluid displacement device by 90 degrees or 180 degrees. By providing the first fluid displacement device and the second fluid displacement device, commercial or performance advantages can be obtained, and a number of sub-chambers can be employed. These numerous sub-chambers may be connected, may be independent, or may be displaced with timing consideration to operate complementarily.

[0159] FIG. 8 shows an example of a cycle of the apparatus 100 when used in a heat engine or a heat pump. Column (i) of FIG. 8 shows the alignment of the inlet port 140 and the outlet port 142 of the expansion chamber 103 with respect to the first expansion sub-chamber 102a and the second expansion sub-chamber 102b.

[0160] Column (ii) of FIG. 8 shows a cross-section of the apparatus.

[0161] Column (iii) of FIG. 8 shows the alignment of the inlet port 144 and the outlet port 146 of the compression chamber 105 with respect to the first compression sub-chamber 104a and the second compression sub-chamber 104b.

[0162] Row (a) of FIG. 8 shows the states of the respective sub-chambers 102a, 102b, 104a, 104b when the pistons 112, 114 are at the nominal 0-degree angular position during the cycle, where the angular position is related to rotation about the first axis 152. The first expansion sub-chamber 102a and the second compression sub-chamber 104b are at minimum volume and are ready to start a charging stroke to feed fluid into them respectively. The second expansion sub-chamber 102b and the first compression sub-chamber 104a are at maximum volume and are ready to start an exhaust stroke respectively.

[0163] During the cycle, the first expansion sub-chamber 102a and the first compression sub-chamber 104a operate out of phase with each other.

[0164] That is, when one of the first expansion sub-chambers 102a and the first compression sub-chamber 104a undergoes a charging stroke, the other chamber undergoes an exhaust stroke. In addition, the first expansion sub-chamber 102a and the second expansion sub-chamber 102b operate in opposite phases to each other, and the first compression sub-chamber 104a and the second compression sub-chamber 104b operate in opposite phases to each other.

[0165] Row (b) of FIG. 8 shows the states of the respective sub-chambers 102a, 102b, 104a, 104b when the shaft 150 (and thus the pistons 112, 114) has rotated to the 45-degree position during the cycle.

[0166] At this stage, the first expansion sub-chamber 102a undergoes the intake phase of the intake stroke. In other words, the first expansion sub-chamber 102a can be fluidly connected to the first heat exchanger to feed fluid. The inlet port 140 of the expansion chamber 103 may be considered open, and fluid can flow into the first expansion sub-chamber 102a through the inlet port of the expansion chamber 140. The first expansion sub-chamber 102a can receive fluid at a substantially constant pressure. The volume of the first expansion sub-chamber 102a increases to feed fluid.

[0167] Between row (a) and row (b) of FIG. 8, the first compression sub-chamber 104a starts the compression phase of the exhaust stroke. That is, the volume of the first compression sub-chamber 104a decreases, and the fluid in the first compression sub-chamber 104a increases.

[0168] As shown in row (b(iii)) of FIG. 8, the first compression sub-chamber 104a remains fluidly isolated even during the compression phase of the exhaust stroke. In this embodiment, this may be due to the fact that the first compression sub-chamber 104a is not in fluid communication with the compression chamber outlet port 146. In other words, the compression chamber outlet port 146 is closed.

[0169] Accordingly, the fluid is compressed within the first compression sub-chamber 104a, thereby increasing the pressure of the fluid and raising the temperature of the fluid. In this compression phase, the pressure of the fluid can increase up to a second threshold pressure.

[0170] In row (b) of FIG. 8, the expansion chamber outlet port 142 is open to the second expansion sub-chamber 102b and the compression chamber inlet port 144 is open to the second compression sub-chamber 104b. The fluid exits the second expansion sub-chamber 102b and enters the second heat exchanger 108, and the fluid enters the second compression sub-chamber 104b from the second heat exchanger 108. Accordingly, as the shaft 150 rotates through the configuration shown in row (b) of FIG. 8, the volume of the second expansion sub-chamber 102b decreases and the volume of the second compression sub-chamber 104b increases.

[0171] Row (c) of FIG. 8 shows the state of each of the sub-chambers 102a, 102b, 104a, 104b rotated to the 90-degree position in the cycle. In row (c) of FIG. 8, here the first expansion sub-chamber 102a is fluidly isolated. In one embodiment, this is due to the fluid connection between the expansion chamber inlet port 140, which is here closed, and the first expansion sub-chamber 102a (i.e., the expansion chamber inlet port 140 is closed). The second expansion sub-chamber 102b remains open and remains fluidly connected to the second heat exchanger 108, such that at this stage the fluid is transferred to the second heat exchanger 108.

[0172] After progressing 90 degrees, the first compression sub-chamber 140a begins to open to the compression chamber outlet port 146. In other words, the first compression sub-chamber 104a and the first heat exchanger 106 become fluidly connected from 90 degrees. In other words, the compression chamber discharge port 146 opens from 90 degrees.

[0173] The second compression sub-chamber 104b remains open to the compression chamber inlet port 144.

[0174] Row (d) of FIG. 8 shows the states of the respective chambers 102a, 102b, 104c, 104d rotated to the 135-degree position during the cycle. At this stage, the first expansion sub-chamber 102a is fluidly isolated and undergoes the expansion phase of the intake stroke. That is, when the first expansion sub-chamber 102a is fluidly isolated, the volume of the first expansion sub-chamber 102a increases.

[0175] The second expansion sub-chamber 102b remains fluidly connected to the second heat exchanger and continues the exhaust stroke for transferring fluid to the second heat exchanger 108.

[0176] Here, the first compression sub-chamber 104a is in fluid communication with the first heat exchanger 106 and is thus in the transfer phase of the exhaust stroke. In other words, the first compression chamber 104a can be in fluid communication with the compression chamber outlet port 146.

[0177] The second compression sub-chamber 104b remains fluidly connected to the second heat exchanger 108 for receiving fluid from the second heat exchanger 108.

[0178] The above process is repeated between 180 degrees and 360 degrees, but the expansion sub-chambers 104a, 104b are reversed, and further the compression chambers 104a, 104b are reversed.

[0179] FIG. 9 shows a flowchart of a method of operating a thermodynamic device 100 configured as a heat engine or a heat pump, the thermodynamic device 100 comprising a first heat exchanger 106, an expansion sub-chamber 102, and a second heat exchanger 108 in a series of flows. Step 202 is associated with feeding a fluid flow at suction pressure from the first heat exchanger 106 into the expansion sub-chamber 102 by increasing the volume of the expansion sub-chamber 102. Step 204 is associated with fluidly isolating the fluid within the expansion sub-chamber 102 from the first heat exchanger 106. Step 206 is associated with expanding the fluid within the expansion sub-chamber 102 by further increasing the volume of the expansion sub-chamber 102 until the fluid reaches a first threshold pressure, the first threshold pressure being less than the suction pressure. Step 208 is associated with fluidly connecting the expansion sub-chamber 102 to the second heat exchanger 108. Step 210 is associated with transferring a fluid flow out of the expansion sub-chamber 102 and to the second heat exchanger 108 by decreasing the volume of the expansion sub-chamber 102.

[0180] In one embodiment, the fluid is not compressed within the compression sub-chamber 104. For example, if the fluid exiting the second heat exchanger is a liquid, the compression sub-chamber 104 can function as a pump, can be supplemented by a pump, or can be replaced by a pump to transfer the fluid. The pump can be used to transfer the liquid from the first threshold pressure to the second threshold pressure without undergoing compression.

[0181] In one embodiment, the method described above can also be operated with an alternative positive displacement machine to that described above.

Claims

1. 1. A method of operating a thermodynamic device configured as a heat engine or heat pump, comprising: The thermodynamic device includes, in series, a first heat exchanger, an expansion subchamber, and a second heat exchanger, and the method includes: forcing a fluid flow from the first heat exchanger into the expansion subchamber at a suction pressure by increasing a volume of the expansion subchamber; fluidly isolating the fluid in the expansion subchamber from the first heat exchanger; expanding the fluid in the expansion subchamber by further increasing the volume of the expansion subchamber to reduce the pressure of the fluid from the suction pressure; fluidly connecting the expansion subchamber to a second heat exchanger; transferring fluid out of the expansion subchamber to a second heat exchanger by decreasing the volume of the expansion subchamber; and transferring the fluid from the first heat exchanger to the second heat exchanger through the expansion subchamber by The method wherein the process of forcing the fluid flow from the first heat exchanger into the expansion subchamber at suction pressure is substantially isobaric.

2. The thermodynamic device includes a compression subchamber, and the method includes: transferring fluid out of the second heat exchanger at a transfer pressure to the compression subchamber by increasing the volume of the compression subchamber; The method of claim 1 , comprising:

3. fluidly isolating the compression subchamber from the second heat exchanger; decreasing a volume of the compression subchamber to thereby increase the pressure of the fluid in the compression subchamber; The method of claim 2 , comprising:

4. fluidly connecting the compression subchamber to a first heat exchanger; transferring fluid out of the compression subchamber to the first thermal chamber by decreasing the volume of the compression subchamber; The method of claim 3 , comprising:

5. 5. The method of claim 3 or 4, wherein the temperature of the fluid exiting the expansion subchamber is approximately equal to the temperature of the fluid exiting the compression subchamber.

6. A method according to any one of claims 1 to 5, wherein the process of expanding the fluid in the expansion subchamber by further increasing the volume of the expansion subchamber is substantially adiabatic.

7. A method according to any one of claims 1 to 6, wherein the process of transporting the fluid flow out of the second heat exchanger to the compression sub-chamber is substantially isobaric.

8. A method as claimed in any one of claims 4 to 7 when dependent on claim 3, wherein the process of increasing the pressure of the fluid in the compression sub-chamber by decreasing the volume of the compression sub-chamber is substantially adiabatic.

9. A method according to any one of claims 1 to 8, wherein the apparatus comprises an expansion chamber and a first piston, the expansion sub-chamber being an aspect of a variable volume defined by the expansion chamber and the first piston.

10. 10. The method of claim 9, wherein the step of increasing the volume of the expansion subchamber to force fluid flow from the first heat exchanger into the expansion subchamber occurs during an intake phase of the intake stroke when there is relative movement between the first piston and the expansion chamber in the first direction.

11. 11. The method of claim 10, wherein the step of further increasing the volume of the expansion subchamber occurs during an expansion phase of the intake stroke when there is continued relative movement in the first direction between the first piston and the expansion subchamber.

12. 12. The method of claim 10 or 11, wherein the step of transferring the fluid flow out of the expansion subchamber and to the second heat exchanger by reducing the volume of the expansion subchamber occurs during an exhaust stroke when there is relative movement of the first piston and the expansion chamber in a second direction that is opposite to the direction of relative movement during the intake stroke.

13. 13. The method of claim 11 or 12 when dependent on claim 3, wherein the apparatus comprises a compression chamber and a second piston, the compression sub-chamber being an aspect of a variable volume defined by the compression chamber and the second piston, and wherein the step of transferring the fluid flow at transfer pressure out of the second heat exchanger and to the compression sub-chamber by increasing the volume of the compression sub-chamber occurs during an intake stroke when there is relative movement of the second piston and the compression chamber.

14. 14. The method of claim 13, wherein the step of increasing the pressure of the fluid in the compression subchamber by decreasing the volume of the compression subchamber occurs during a compression phase of the exhaust stroke when there is relative movement of the second piston in a direction that is opposite to a direction of relative movement of the compression subchamber during the intake stroke.

15. 15. The method of claim 13 or 14, wherein the first piston and the second piston are integral with each other.

16. 16. A method as claimed in any one of claims 10 to 15, wherein fluid isolation of fluid in the expansion subchamber from the first heat exchanger occurs at a predetermined point between 10% and 90% during the intake stroke.

17. 13. A method according to any one of claims 9 to 12, wherein the expansion and compression subchambers are located on either side of a first piston in the reciprocating machine, and movement of the first piston changes the volumes of the expansion and compression subchambers.

18. A method according to any one of claims 9 to 12, wherein the expansion sub-chamber and the compression sub-chamber are located in different reciprocating machines.

19. The thermodynamic device includes a second expansion subchamber and a second compression subchamber, and the method includes: A method as claimed in any one of claims 2 to 5, claim 8 or claims 13 to 18, comprising the step of transferring the fluid flow out of the second expansion subchamber at a transfer pressure to a second heat exchanger by reducing the volume of the second expansion subchamber as the fluid flow is forced into and expanded in the first expansion subchamber.

20. transferring the fluid flow out of the second heat exchanger and into the second compression subchamber by increasing the volume of the second compression subchamber as the fluid flow is transferred out of the second expansion subchamber; fluidly isolating the second compression subchamber from the second heat exchanger; increasing the pressure of the fluid in the second compression subchamber by decreasing the volume of the second compression subchamber; 20. The method of claim 19, comprising:

21. fluidly connecting the second compression subchamber to a first heat exchanger; continuing to decrease the volume of the second compression subchamber to transfer the fluid flow out of the second compression subchamber and to a first heat exchanger; Including, 21. The method of claim 20, wherein these steps occur when the fluid flow is transferred from the first expansion subchamber to the second heat exchanger.

22. A method according to any preceding claim, wherein the apparatus is arranged to operate as a heat engine and heat is removed from the fluid as it passes through the second heat exchanger.

23. A method according to any one of the preceding claims, wherein the apparatus is configured to operate as a heat pump and heat is added to the fluid as it passes through the second heat exchanger.

24. 1. A thermodynamic device configured as a heat engine or heat pump, comprising: The device includes an expansion subchamber; forcing a fluid flow into the expansion subchamber at a suction pressure by increasing the volume of the expansion subchamber; fluidly isolating fluid within the expansion subchamber; and expanding the fluid in the expansion subchamber by further increasing the volume of the expansion subchamber to reduce the pressure of the fluid from the suction pressure; fluidly connecting the expansion subchamber to a heat exchanger; transferring fluid flow out of the expansion subchamber to said heat exchanger by decreasing the volume of the expansion subchamber; [0023] A thermodynamic apparatus, wherein the process of forcing the fluid flow from the first heat exchanger into the expansion subchamber at an inlet pressure is configured to be substantially isobaric.

25. A first heat exchanger; a second heat exchanger, where fluid is pumped from the first heat exchanger into the expansion subchamber and transferred from the expansion subchamber to the second heat exchanger; 25. The thermodynamic device of claim 24, comprising:

26. The thermodynamic device includes a compression subchamber, the device comprising:

26. The thermodynamic device of claim 25 configured to transfer the fluid flow out of the second heat exchanger and to the compression subchamber at a transfer pressure by increasing the volume of the compression subchamber.

27. The device is fluidly isolating the compression subchamber from the second heat exchanger; 27. The thermodynamic device of claim 26, configured to: compress the fluid in the compression subchamber by decreasing a volume of the compression subchamber to increase a pressure of the fluid.

28. The device is fluidly connecting the compression subchamber to a first heat exchanger; transferring the fluid flow out of the compression subchamber to the first thermal chamber by decreasing the volume of the compression subchamber; 30. The thermodynamic device of claim 27 configured to:

29. 29. A thermodynamic device according to any one of claims 24 to 28, wherein the device comprises an expansion chamber and a first piston, the expansion sub-chamber being an aspect of a variable volume defined by the expansion chamber and the first piston.

30. 30. The thermodynamic device of claim 29, wherein a volume of the expansion subchamber is configured to increase to force fluid flow from the first heat exchanger into the expansion subchamber during an intake phase of an intake stroke when there is relative movement in a first direction between the first piston and the expansion chamber.

31. 31. The thermodynamic device of claim 30, wherein the device is configured to further increase a volume of the expansion subchamber to reduce a pressure of the fluid during an expansion phase of the intake stroke where relative movement of the first piston and the expansion chamber continues to move in the first direction.

32. 32. The thermodynamic device of claim 30 or 31, wherein the first piston is configured to move relative to the expansion chamber in a second direction, opposite the first direction, during an exhaust stroke to reduce a volume of the expansion subchamber and transfer fluid flow out of the expansion subchamber to the second heat exchanger.

33. 33. A thermodynamic device as claimed in claim 31 or 32 when dependent on claim 27, wherein the device comprises a compression chamber and a second piston, the compression sub-chamber being an aspect of a variable volume defined by the compression chamber and the second piston, and wherein the volume of the compression sub-chamber is configured to be increased during an intake stroke when there is relative movement of the second piston and the compression chamber.

34. A thermodynamic device according to any one of claims 24 to 33, wherein the device is configured to function as a heat engine for driving a powertrain or for generating electricity.

35. A thermodynamic device according to any one of claims 24 to 33, wherein the device is configured to function as a heat pump, the device comprising a motor for driving the device.

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