EP1588113B1

EP1588113B1 - Heat transfer system

Info

Publication number: EP1588113B1
Application number: EP03779362.7A
Authority: EP
Inventors: Edward J. Kroliczek; Michael Nikitkin; David A. Wolf, Sr.
Original assignee: Swales and Associates Inc
Current assignee: Northrop Grumman Innovation Systems LLC
Priority date: 2002-10-28
Filing date: 2003-10-28
Publication date: 2013-12-25
Anticipated expiration: 2023-10-28
Also published as: BRPI0315812B1; BR0315812A; MXPA05004443A; AU2003285045A8; ES2453904T3; EP1588113A2; RU2371653C2; EP1588113A4; JP2006508324A; RU2005116246A; AU2003285045A1; WO2004040218A9; WO2004040218A2; JP4998933B2; WO2004040218A3

Description

This description relates to thermodynamic systems comprising a heat transfer system and a cyclical heat exchange system.
Heat transfer systems are used to transport heat from one location (the heat source) to another location (the heat sink). Heat transfer systems can be used in terrestrial or extraterrestrial applications. For example, heat transfer systems may be integrated by satellite equipment that operates within zero or low-gravity environments. As another example, heat transfer systems can be used in electronic equipment, which often requires cooling during operation.
Loop Heat Pipes (LHPs) and Capillary Pumped Loops (CPLs) are passive two-phase heat transfer systems. Each includes an evaporator thermally coupled to the heat source, a condenser thermally coupled to the heat sink, fluid that flows between the evaporator and the condenser, and a fluid reservoir for expansion of the fluid. The fluid within the heat transfer system can be referred to as the working fluid. The evaporator includes a primary wick and a core that includes a fluid flow passage. Heat acquired by the evaporator is transported to and discharged by the condenser. These systems utilize capillary pressure developed in a fine-pored wick within the evaporator to promote circulation of working fluid from the evaporator to the condenser and back to the evaporator. The primary distinguishing characteristic between an LHP and a CPL is the location of the loop's reservoir, which is used to store excess fluid displaced from the loop during operation. In general, the reservoir of a CPL is located remotely from the evaporator, while the reservoir of an LHP is co-located with the evaporator.
EP-A-0210337 discloses a capillary-assisted evaporator for heat absorption and for transport of a heat transfer medium from a heat source to a heat sink.
WO 2004/031675 , which was filed before but published after the filing date of the present application and thus is prior art according to Article 54(3) EPC relates to an evaporator for a heat transfer system. The evaporator includes a heated wall, a liquid barrier wall containing working fluid, a primary wick, a vapor removal channel located at an interface between the primary wick and the heated wall and a liquid flow channel located between the liquid barrier wall and the primary wick.
The invention provides a thermodynamic system as defined in claim 1. Preferred features of the invention are set out below.
Implementations may include one or more of the following aspects. For example, the condenser includes a vapor inlet and a liquid outlet and the heat transfer system includes a vapor line providing fluid communication between the vapor outlet and the vapor inlet and a liquid return line providing fluid communication between the liquid outlet and the liquid inlet.
The evaporator includes a liquid barrier wall containing the working fluid on an inner side of the liquid barrier wall, which working fluid flows only along the inner side of the liquid barrier wall, wherein the primary wick is positioned between the heated wall and the inner side of the liquid barrier wall; a vapor removal channel that is located at an interface between the primary wick and the heated wall, the vapor removal channel extending to a vapor outlet; and a liquid flow channel located between the liquid barrier wall and the primary wick, the liquid flow channel receiving liquid from a liquid inlet.
The working fluid is moved through the heat transfer system passively.
The working fluid Is moved through the heat transfer system without the use of external pumping.
The working fluid within the heat transfer system changes between a liquid and a vapor as the working fluid passes through or within one or more of the evaporator, the condenser, the vapor line, and the liquid return line.
The working fluid is moved through the heat transfer system with the use of the wick.
The heat transfer system further includes fins thermally coupled to the condenser to reject heat to an ambient environment.
In another general aspect, the thermodynamic system includes the cyclical heat exchange system and the heat transfer system coupled to the cyclical heat exchange system to cool the portion of the cyclical heat exchange system. The heat transfer system includes an evaporator including a wall configured to be coupled to a portion of the cyclical heat exchange system and a primary wick coupled to the wall and a condenser coupled to the evaporator to form a closed loop that houses a working fluid.
Implementations may include one or more of the following features. The evaporator is thermally coupled to the portion of the cyclical heat exchange system. The cyclical heat exchange system includes a Stirling heat exchange system. The cyclical heat exchange system includes a refrigeration system. The heat transfer system is coupled to a hot side of the cyclical heat exchange system. The thermodynamic system heat transfer system is coupled to a cold side of the cyclical heat exchange system.
The evaporator may be used in any two-phase heat transfer system for use in terrestrial or extraterrestrial applications. For example, the heat transfer systems can be used in electronic equipment, which often requires cooling during operation or in laser diode applications.
The annular evaporator may be used in any heat transfer system in which the heat source is formed as a cylindrical surface.
The heat transfer system may take advantage of gravity when used in terrestrial applications, thus making an LHP suitable for mass production. Terrestrial applications often dictate the orientation of the heat acquisition surfaces and the heat sink; the annular evaporator utilizes the advantages of the operation in gravity.
The heat transfer system provides a thermally efficient and space efficient system for cooling a cyclical heat exchange system because the evaporator of the heat transfer system is thermally and spatially coupled to a portion of the cyclical heat exchange system that is being cooled by the heat transfer system. Use of the heat transfer system enables exploitation of cylindrical cyclical heat exchange systems, which are capable of being used in a commercially practical application for cabinet cooling.
Integral incorporation of the evaporator not within the scope of the present invention or condenser with the heat source of the cyclical heat exchange system can minimize packaging size. On the other hand, if the evaporator or condenser is clamped onto the heat source, the deployment and replacement of parts is facilitated.
The heat transfer system is used to cool a cyclical heat exchange system having a cylindrical geometry, such as, for example, a free-piston Stirling cycle. A heat transfer system provides efficient fluid line connection (one vapor phase and on sub-cooled liquid return line connector) to and from an equally efficiently packaged annular condenser assembly.
The heat transfer system incorporates a condenser that is efficiently packaged as a flat plate condenser that is formed into annular sections to which are attached extended air heat exchange surface elements such as corrugated fin stock.
The heat transfer system combines efficient heat transfer mechanisms (evaporation and condensation) to couple the fluid of the Stirling cycle (helium) to the ultimate heat sink (ambient air). Consequently, a significant improvement in Stirling Cycle efficiency (for example, up to 50%) Is provided.
The evaporator and the condenser of the heat transfer system can be independently designed and optimized. This allows any number of attachment options to the cyclical heat exchange system. Moreover, the heat transfer system is insensitive to gravity orientation because a wick is incorporated into the evaporator.
The heat transfer system provides efficient cooling to a cabinet, such as a refrigerator or vending machine, in a small package at a commercially acceptable cost.
The annular evaporator is interference fit onto a cyclical heat exchange system to provide easy assembly with improved thermal efficiency.
The heat transfer system includes a condenser having finned inner and outer annular, portions to provide efficient heat transfer to the air in a reduced packaging space. The condenser may be roll bonded or formed by extrusion.
A loop heat pipe may provide for efficient packaging with a cylindrical refrigerator by adapting the traditional cylindrical geometry of a LHP evaporator to a planar "flat-plate" geometry that can be wrapped in an annular shape.
The packaging of the heat transfer system is described with respect to a few exemplary implementations, but is not meant to be limited to those exemplary implementations. Although described with respect to use for cooling a cabinet, such as a domestic refrigerator, vending machine, or point-of-sale refrigeration unit, one of skill in the art will recognize the numerous other useful applications of a compact, energy efficient and environmentally friendly refrigeration unit utilizing the heat transfer system as described herein.
Other features and advantages will be apparent from the description, the drawings, and the claims.
Certain preferred embodiments will now be described by way of example only and with reference to the accompanying drawings, in which:

Fig. 1A is a diagram of a three-port main evaporator.
Fig. 1 B is a cross-sectional view of the main evaporator taken along 5B-5B of Fig. 1 A.
Fig. 2 Is a cross-sectional view of a planar evaporator which is not part of an embodiment of the claimed invention.
Fig. 3 is an axial cross-sectional view of an annular evaporator.
Fig. 4 is a radial cross-sectional view of the annular evaporator of Fig. 3.
Fig. 5 is an enlarged view of a portion of the radial cross-sectional view of the annular evaporator of Fig. 4.
Fig. 6A is a perspective view of the annular evaporator of Fig. 3.
Fig. 6B is a top and partial cutaway view of the annular evaporator of Fig. 6A.
Fig. 6C is an enlarged cross-sectional view of a portion of the annular evaporator of Fig. 6B.
Fig. 6D is a cross-sectional view of the annular evaporator of Fig. 6B taken along line 14D-14D.
Figs. 6E and 6F are enlarged views of portions of the annular evaporator of Fig. 6D.
Fig. 6G is a perspective cut-away view of the annular evaporator of Fig. 6A.
Fig. 6H is a detail perspective cut-away view of the annular evaporator of Fig. 6G.
Fig. 7A is a flat detail view of the liquid barrier wall formed into a shell ring component of the annular evaporator of Fig. 6A.
Fig. 7B is a cross-sectional view of the liquid barrier wall of Fig. 7A taken along line 15B-15B.
Fig. 8A is a perspective view of a primary wick of the annular evaporator of Fig. 8A.
Fig. 8B is a top view of the primary wick of Fig. 8A.
Fig. 8C is a cross-sectional view of the primary wick of Fig. 8B taken along line 16C-16C.
Fig. 8D is an enlarged view of a portion of the primary wick of Fig. 8C.
Fig. 9A is a perspective view of a heated wall formed into an annular ring of the annular evaporator of Fig. 6A.
Fig. 9B is a top view of the heated wall of Fig. 9A.
Fig. 9C is a cross-sectional view of the heated wall of Fig. 9B taken along line 17C-17C.
Fig. 9D is an enlarged view of a portion of the heated wall of Fig. 9C.
Fig. 10A is a perspective view of a ring separating the heated wall of Fig. 9A from the liquid barrier wall of Fig. 7A.
Fig. 10B is a top view of the ring of Fig. 10A.
Fig. 10C is a cross-sectional view of the ring of Fig. 10B taken along line 18C-18C.
Fig. 10D is an enlarged view of a portion of the ring of Fig. 10C.
Fig. 11A is a perspective view of a ring of the annular evaporator of Fig. 6A.
Fig. 11B Is a top view of the ring of Fig. 11A.
Fig. 11C is a cross-sectional view of the ring of Fig. 11 B taken along 19C-19C.
Fig. 11 D is an enlarged view of a portion of the ring of Fig. 11C.
Fig. 12 is a perspective view of a cyclical heat exchange system that can be cooled using a heat transfer system.
Fig. 13 is a cross-sectional view of a cyclical heat exchange system such as the cyclical heat exchange system of Fig. 12.
Fig. 14 is a side view of a cyclical heat exchange system such as the cyclical heat exchange system of Fig. 12.
Fig. 15 is a schematic diagram of a first implementation of a cyclical heat exchange system including a cyclical heat exchange system and a heat transfer system.
Fig. 16 is a schematic diagram of a second implementation of a cyclical heat exchange system including a cyclical heat exchange system and a heat transfer system.
Fig. 17 is a schematic diagram of a heat transfer system using an evaporator designed in accordance with the principles of Figs. 2-5.
Fig. 18 is a functional exploded view of the heat transfer system of Fig. 17.
Fig. 19 is a partial cross-sectional detail view of an evaporator used In the heat transfer system of Fig. 17.
Fig. 20 is a perspective view of a heat exchanger used in the heat transfer system of Fig. 17.
Fig. 21 is a graph of temperature of a heat source of a cyclical heat exchange system versus a surface area of an interface between the heat transfer system and the heat source of the cyclical heat exchange system.
Fig. 22 is a top plan view of a heat transfer system packaged around a portion of a cyclical heat exchange system.
Fig. 23 is a partial cross-sectional elevation view (taken along line 31-31) of the heat transfer system packaged around the cyclical heat exchange system portion of Fig. 22.
Fig. 24 is a partial cross-sectional elevation view (taken at detail 3200) of the interface between the heat transfer system and the cyclical heat exchange system of Fig. 22.
Fig. 25 is an upper perspective view of a heat transfer system mounted to a cyclical heat exchange system.
Fig. 26 is a lower perspective view of the heat transfer system mounted to the cyclical heat exchange system of Fig. 25.
Fig. 27 is a partial cross-sectional view of an interface between an evaporator of a heat transfer system and a cyclical heat exchange system in which the evaporator is clamped onto the cyclical heat exchange system.
Fig. 28 is a side view of a clamp used to clamp the evaporator onto the cyclical heat exchange system of Fig. 27.
Fig. 29 is a partial cross-sectional view of an interface between an evaporator of a heat transfer system and a cyclical heat exchange system in which the interface is formed by an interference fit between the evaporator and the cyclical heat exchange system.
Fig. 30 is a partial cross-sectional view of an interface between an evaporator of a heat transfer system and a cyclical heat exchange system in which the interface is formed by forming the evaporator integrally with the cyclical heat exchange system.
Fig. 31 is a top plan view of a condenser of a heat transfer system.
Fig. 32 is a partial cross-sectional view taken along line 40-40 of the condenser of Fig. 31.
Figs. 33-35 are detail cross-sectional views of a condenser having a laminated construction.
Fig. 36 is a detail cross-sectional view of a condenser having an extruded construction.
Fig. 37 is a perspective detail and cross-sectional view of a condenser having an extruded construction.
Fig. 38 is a cross-sectional view of one side of a heat transfer system packaging around a cyclical heat exchange system.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Evaporator Design

Evaporators are integral components in two-phase heat transfer systems. For example, as shown in Figs. 1A and 1B, the evaporator 500 includes an evaporator body or container 515 that is in contact with the primary wick 540 that surrounds the core 510. The core 510 defines a flow passage for the working fluid. The primary wick 540 is surrounded at its periphery by a plurality of peripheral flow channels or vapor grooves 545. The channels 546 collect vapor at the interface between the wick 540 and the evaporator body 515. The channels 545 are in contact with the vapor outlet 550 that feeds into the vapor line that feeds into the condenser to enable evacuation of the vapor formed within the evaporator 115.
The evaporator 500 and the other evaporators often have a cylindrical geometry, that is, the core of the evaporator forms a cylindrical passage through which the working fluid passes. The cylindrical geometry of the evaporator is useful for cooling applications in which the heat acquisition surface is cylindrically hollow. Many cooling applications require that heat be transferred away from a heat source having a flat surface. In these sort of applications, the evaporator can be modified to include a flat conductive saddle to match the footprint of the heat source having the flat surface. Such a design is shown, for example, in U.S. Patent No. 6,382,309 .
The cylindrical geometry of the evaporator facilitates compliance with thermodynamic constraints of LHP operation (that is, the minimization of heat leaks into the reservoir). The constraints of LHP operation stem from the amount of subcooling an LHP needs to produce for normal equilibrium operation. Additionally, the cylindrical geometry of the evaporator is relatively easy to fabricate, handle, machine, and process.
However, as will be described hereinafter, an evaporator can be designed with a planar form to more naturally attach to a flat heat source. Such an arrangement does not fall within the scope of the claims.

Planar Design (not within the scope of the claims but provides explanatory background information)

Referring to Fig. 2, an evaporator 1000 for a heat transfer system includes a heated wall 1005, a liquid barrier wall 1010, a primary wick 1015 between the heated wall and the inner side of the liquid barrier wall 1010, vapor removal channels 1020, and liquid flow channels 1025.
The heated wall 1005 is in intimate contact with the primary wick 1015. The liquid barrier wall 1010 contains working fluid on an inner side of the liquid barrier wall 1010 such that the working fluid flows only along the inner side of the liquid barrier wall 1010. The liquid barrier wall 1010 closes the evaporator's envelope and helps to organize and distribute the working fluid through the liquid flow channels 1025. The vapor removal channels 1020 are located at an interface between a vaporization surface 1017 of the primary wick 1015 and the heated wall 1005. The liquid flow channels 1025 are located between the liquid barrier wall 1010 and the primary wick 1015.
The heated wall 1005 acts as a heat acquisition surface for a heat source. The heated wall 1005 is made from a heat-conductive material, such as, for example, sheet metal. Material chosen for the heated wall 1005 typically is able to withstand internal pressure of the working fluid.
The vapor removal channels 1020 are designed to balance the hydraulic resistance of the channels 1020 with the heat conduction through the heated wall 1005 into the primary wick 1015. The channels 1020 can be electro-etched, machined, or formed in a surface with any other convenient method.
The vapor removal channels 1020 are shown as grooves in the inner side of the heated wall 1005. However, the vapor removal channels can be designed and located in several different ways, depending on the design approach chosen. For example, according to other implementations, the vapor removal channels 1020 are grooved into the outer surface of the primary wick 1015 or embedded into the primary wick 1015 such that they are under the surface of the primary wick. The design of the vapor removal channels 1020 is selected to increase the ease and convenience of manufacturing and to closely approximate one or more of the following guidelines.
First, the hydraulic diameter of the vapor removal channels 1020 should be sufficient to handle a vapor flow generated on the vaporization surface 1017 of the primary wick 1015 without a significant pressure drop. Second, the surface of contact between the heated wall 1005 and the primary wick 1015 should be maximized to provide efficient heat transfer from the heat source to vaporization surface of the primary wick 1015. Third, a thickness 1030 of the heated wall 1005, which is in contact with the primary wick 1015, should be minimized. As the thickness 1030 increases, vaporization at the surface of the primary wick 1015 is reduced and transport of vapor through the vapor removal channels 1020 is reduced.
The evaporator 1000 can be assembled from separate parts. Alternatively, the evaporator 1000 can be made as a single part by in-situ sintering of the primary wick 1015 between two walls having special mandrels to form channels on both sides of the wick.
The primary wick 1015 provides the vaporization surface 1017 and pumps or feeds the working fluid from the liquid flow channels 1025 to the vaporization surface of the primary wick 1015.
The size and design of the primary wick 1015 involves several considerations. The thermal conductivity of the primary wick 1015 should be low enough to reduce heat leak from the vaporization surface 1017, through the primary wick 1015, and to the liquid flow channels 1025. Heat leakage can also be affected by the linear dimensions of the primary wick 1015. For this reason, the linear dimensions of the primary wick 1015 should be properly optimized to reduce heat leakage. For example, an increase in a thickness 1019 of the primary wick 1015 can reduce heat leakage. However, increased thickness 1019 can increase hydraulic resistance of the primary wick 1015 to the flow of the working fluid. In working LHP designs, hydraulic resistance of the working fluid due to the primary wick 1015 can be significant and a proper balancing of these factors is important.
The force that drives or pumps the working fluid of a heat transfer system is a temperature or pressure difference between the vapor and liquid sides of the primary wick. The pressure difference is supported by the primary wick and it is maintained by proper management of the incoming working fluid thermal balance.
The liquid returning to the evaporator from the condenser passes through a liquid return line and is slightly subcooled. The degree of subcooling offsets the heat leak through the primary wick and the heat leak from the ambient into the reservoir within the liquid return line. The subcooling of the liquid maintains a thermal balance of the reservoir. However, there exist other useful methods to maintain thermal balance of the reservoir.
One method is an organized heat exchange between reservoir and the environment. For evaporators having a planar design, such as those often used for terrestrial applications, the heat transfer system includes heat exchange fins on the reservoir and/or on the liquid barrier wall 1010 of the evaporator 1000. The forces of natural convection on these fins provide subcooling and reduce stress on the condenser and the reservoir of the heat transfer system.
The temperature of the reservoir or the temperature difference between the reservoir and the vaporization surface 1017 of the primary wick 1015 supports the circulation of the working fluid through the heat transfer system. Some heat transfer systems may require an additional amount of subcooling. The required amount may be greater than what the condenser can produce, even if the condenser is completely blocked.
In designing the evaporator 1000, three variables need to be managed. First, the organization and design of the liquid flow channels 1025 needs to be determined. Second, the venting of the vapor from the liquid flow channels 1025 needs to be accounted for. Third, the evaporator 1000 should be designed to ensure that liquid fills the liquid flow channels 1025. These three variables are interrelated and thus should be considered and optimized together to form an effective heat transfer system.
As mentioned, it is important to obtain a proper balance between the heat leak into the liquid side of the evaporator and the pumping capabilities of the primary wick. This balancing process cannot be done independently from the optimization of the condenser, which provides subcooling, because the greater heat leak allowed in the design of the evaporator, the more subcooling needs to be produced in the condenser. The longer the condenser, the greater are the hydraulic losses in a fluid lines, which may require different wick material with better pumping capabilities.
In operation, as power from a heat source is applied to the evaporator 1000, liquid from the liquid flow channels 1025 enters the primary wick 1015 and evaporates, forming vapor that is free to flow along the vapor removal channels 1020. Liquid flow into the evaporator 1000 is provided by the liquid flow channels 1025. The liquid flow channels 1025 supply the primary wick 1015 with the enough liquid to replace liquid that is vaporized on the vapor side of the primary wick 1015 and to replace liquid that is vaporized on the liquid side of the primary wick 1015,
The evaporator 1000 may include a secondary wick 1040, which provides phase management on a liquid side of the evaporator 1000 and supports feeding of the primary wick 1015 in critical modes of operation (as discussed above). The secondary wick 1040 is formed between the liquid flow channels 1025 and the primary wick 1015. The secondary wick can be a mesh screen (as shown in the Fig. 2), or an advanced and complicated artery, or a slab wick structure. Additionally, the evaporator 1000 may include a vapor vent channel 1045 at an interface between the primary wick 1015 and the secondary wick 1040.
Heat conduction through the primary wick 1015 may initiate vaporization of the working fluid in a wrong place -on a liquid side of the evaporator 1000 near or within the liquid flow channels 1025. The vapor vent channel 1045 delivers the unwanted vapor away from the wick into the two-phase reservoir.
The fine pore structure of the primary wick 1015 can create a significant flow resistance for the liquid. Therefore, it is important to optimize the number, the geometry, and the design of the liquid flow channels 1025. The goal of this optimization is to support a uniform, or close to uniform, feeding flow to the vaporization surface 1017. Moreover, as the thickness 1019 of the primary wick 1015 is reduced, the liquid flow channels 1025 can be space farther apart.
The evaporator 1000 may require significant vapor pressure to operate with a particular working fluid within the evaporator 1000. Use of a working fluid with a high vapor pressure can cause several problems with pressure containment of the evaporator envelope. Traditional solutions to the pressure containment problem, such as thickening the walls of the evaporator, are not always effective. For example, in planar evaporators having a significant flat area, the walls become so thick that the temperature difference is increased and the evaporator heat conductance is degraded. Additionally, even microscopic deflection of the walls due to the pressure containment results in a loss of contact between the walls and the primary wick. Such a loss of contact impacts heat transfer through the evaporator. And, microscopic deflection of the walls creates difficulties with the interfaces between the evaporator and the heat source and any external cooling equipment.

Annular Design

Referring to Figs. 2-5, an annular evaporator 1100 is formed by effectively rolling the planar evaporator 1000 such that the primary wick 1015 loops back into itself and forms an annular shape. The evaporator 1100 can be used in applications in which the heat sources have a cylindrical exterior profile, or in applications where the heat source can be shaped as a cylinder. The annular shape combines the strength of a cylinder for pressure containment and the curved interface surface for best possible contact with the cylindrically-shaped heat sources.
The evaporator 1100 includes a heated wall 1105, a liquid barrier wall 1110, a primary wick 1115 positioned between the heated wall 1105 and the inner side of the liquid barrier wall 1110, vapor removal channels 1120, and liquid flow channels 1125. The liquid barrier wall 1110 is coaxial with the primary wick 1115 and the heated wall 1105.
The heated wall 1105 intimately contacts the primary wick 1115. The liquid barrier wall 1110 contains working fluid on an inner side of the liquid barrier wall 1110 such that the working fluid flows only along the inner side of the liquid barrier wall 1110. The liquid barrier wall 1110 closes the evaporator's envelope and helps to organize and distribute the working fluid through the liquid flow channels 1125.
The vapor removal channels 1120 are located at an interface between a vaporization surface 1117 of the primary wick 1115 and the heated wall 1105. The liquid flow channels 1125 are located between the liquid barrier wall 1110 and the primary wick 1115. The heated wall 1105 acts a heat acquisition surface and the vapor generated on this surface is removed by the vapor removal channels 1120.
The primary wick 1115 fills the volume between the heated wall 1105 and the liquid barrier wall 1110 of the evaporator 1100 to provide reliable reverse menisci vaporization.
The evaporator 1100 can also be equipped with heat exchange fins 1150 that contact the liquid barrier wall 1110 to cold bias the liquid barrier wall 1110. The liquid flow channels 1125 receive liquid from a liquid inlet 1155 and the vapor removal channels 1120 extend to and provide vapor to a vapor outlet 1160.
The evaporator 1100 can be used in a heat transfer system that includes an annular reservoir 1165 adjacent the primary wick 1115. The reservoir 1165 may be cold biased with the heat exchange fins 1150, which extend across the reservoir 1165. The cold biasing of the reservoir 1165 permits utilization of the entire condenser area without the need to generate subcooling at the condenser. The excessive cooling provided by cold biasing the reservoir 1165 and the evaporator 1100 compensates the parasitic heat leaks through the primary wick 1115 into the liquid side of the evaporator 1100.
In another implementation, the evaporator design can be inverted and vaporization features can be placed on an outer perimeter and the liquid return features can be placed on the inner perimeter.
The annular shape of the evaporator 1100 may provide one or more of the following or additional advantages. First, problems with pressure containment may be reduced or eliminated in the annular evaporator 1100. Second, the primary wick 1115 may not need to be sintered inside, thus providing more space for a more sophisticated design of the vapor and liquid sides of the primary wick 1115.
Referring also to Figs. 6A-H, an annular evaporator 1400 is shown having a liquid inlet 1455 and a vapor outlet 1460. The annular evaporator 1400 includes a heated wall 1700 (Figs. 6G, 6H, and 9A-D), a liquid barrier wall 1500 (Figs. 6G, 6H, 7A, and 7B), a primary wick 1600 (Figs. 6G, 6H, and 8A-D) positioned between the heated wall 1700 and the inner side of the liquid barrier wall 1500, vapor removal channels 1465 (Fig. 6H), and liquid flow channels 1505 (Figs. 6H and 7B). The annular evaporator 1400 also includes a ring 1800 (Figs. 6G and 10A-D) that ensures spacing between the heated wall 1700 and the liquid barrier wall 1500 and a ring 1900 (Figs. 6G, 6H, and 11A-D) at a base of the evaporator 1400 that provides support for the liquid barrier wall 1500 and the primary wick 1600. The heated wall 1700, the liquid barrier wall 1500, the ring 1800, the ring 1900, and the wick 1600 are preferably formed of stainless steel.
The upper portion of the evaporator 1400 (that is, above the wick 1600) includes an expansion volume 1470 (Fig. 6H). The liquid flow channels 1505, which are formed in the liquid barrier wall 1500, are fed by the liquid inlet 1455. The wick 1600 separates the liquid flow channels 1505 from the vapor removal channels 1465 that lead to the vapor outlet 1460 through a vapor annulus 1475 (Fig. 6H) formed in the ring 1900. The vapor channels 1465 may be photo-etched into the surface of the heated wall 1700.
The evaporators disclosed herein can operate in any combination of materials, dimensions and arrangements, so long as they embody the features as described above. There are no restrictions other than criteria mentioned here; the evaporator can be made of any shape size and material. The only design constraints are that the applicable materials be compatible with each other and that the working fluid be selected in consideration of structural constraints, corrosion, generation of noncondensable gases, and lifetime issues.
Many terrestrial applications can incorporate an LHP with an annular evaporator 1100. The orientation of the annular evaporator in a gravity field is predetermined by the nature of application and the shape of the hot surface.

Cyclical Heat Exchange System

Cyclical heat exchange systems may be configured with one or more heat transfer systems to control a temperature at a region of the heat exchange system. The cyclical heat exchange system may be any system that operates using a thermodynamic cycle, such as, for example, a cyclical heat exchange system, a Stirling heat exchange system (also known as a Stirling engine), or an air conditioning system.
Referring to Fig. 12, a Stirling heat exchange system 2000 utilizes a known type of environmentally friendly and efficient refrigeration cycle. The Stirling system 2000 functions by directing a working fluid (for example, helium) through four repetitive operations; that is, a heat addition operation at constant temperature, a constant volume heat rejection operation, a constant temperature heat rejection operation and a heat addition operation at constant volume.
The Stirling system 2000 is designed as a Free Piston Stiling Cooler (FPSC), such as Global Cooling's model M100B (Available from Global Cooling Manufacturing, 94 N.
Columbus Rd., Athens, Ohio). The FPSC 2000 includes a linear motor portion 2005 housing a linear motor (not shown) that receives an AC power input 2010. The FPSC 2000 includes a heat acceptor 2015, a regenerator 2020, and a heat rejecter 2025. The FPSC 2000 includes a balance mass 2030 coupled to the body of the linear motor within the linear motor portion 2005 to absorb vibrations during operation of the FPSC. The FPSC 2000 also includes a charge port 2035. The FPSC 2000 includes internal components, such as those shown in the FPSC 2100 of Fig. 13.
The FPSC 2100 includes a linear motor 2105 housed within the linear motor portion 2110. The linear motor portion 2110 houses a piston 2115 that is coupled to flat springs 2120 at one end and a displacer 2125 at another end. The displacer 2125 couples to an expansion space 2130 and a compression space 2135 that form, respectively, cold and hot sides. The heat acceptor 2015 is mounted to the cold side 2130 and the heat rejector is mounted to the hot side 2135. The FPSC 2100 also includes a balance mass 2140 coupled to the linear motor portion 2110 to absorb vibrations during operation of the FPSC 2100.
Referring also to Fig. 14, in one implementation, a FPSC 2200 includes heat rejector 2205 made of a copper sleeve and a heat acceptor 2210 may of a copper sleeve. The heat rejector 2205 has an outer diameter (OD) of approximately 100 mm and a width of approximately 53 mm to provide a 166 cm² heat rejection surface capable of providing a flux of 6W/cm² when operating in a temperature range of 20-70°C. The heat acceptor 2210 has an OD of approximately 100 mm and a width of approximately 37 mm to provide a 115 cm² heat accepting surface capable of providing a flux of 5.2 W/cm2 in a temperature range of -30-5 °C.
Briefly, in operation an FPSC is filled with a coolant (such as, for example, Helium gas) that is shuttled back and forth by combined movements of the piston and the displacer. In an ideal system, thermal energy is rejected to the environment through the heat rejector while the coolant is compressed by the piston and thermal energy is extracted from the environment through the heat acceptor while the coolant expands.
Referring to Fig. 15, a thermodynamic system 2300 includes a cyclical heat exchange system such as a cyclical heat exchange system 2305 (for example, the systems 2000, 2100, 2200) and a heat transfer system 2310 thermally coupled to a portion 2315 of the cyclical heat exchange system 2305. The cyclical heat exchange system 2305 is cylindrical and the heat transfer system 2310 is shaped to surround the portion 2315 of the cyclical heat exchange system 2305 to reject heat from the portion 2315. In this implementation, the portion 2315 is the hot side (that is, the heat rejector)of the cyclical heat exchange system 2305. The thermodynamic system 2300 also includes a fan 2320 positioned at the hot side of the cyclical heat exchange system 2305 to force air over a condenser of the heat transfer system 2310 and thus to provide additional convection cooling.
A cold side 2335 (that is, the heat acceptor) of the cyclical heat exchange system 2305 is thermally coupled to a CO2 refluxer 2340 of a thermosyphon 2345. The thermosyphon 2345 includes a cold-side heat exchanger 2350 that is configured to cool air within the thermodynamic system 2300 that is forced across the heat exchanger 2350 by a fan 2355.
Referring to Fig. 16, in another implementation, a thermodynamic system 2400 includes a cyclical heat exchange system such as a cyclical heat exchange system 2405 (for example, the systems 2000, 2100, 2200) and a heat transfer system 2410 thermally coupled to a hot side 2415 of the cyclical heat exchange system 2405. The thermodynamic system 2400 includes a heat transfer system 2420 thermally coupled to a cold side 2425 of the cyclical heat exchange system 2405. The thermodynamic system 2400 also includes fans 2430, 2435. The fan 2430 is positioned at the hot side 2415 to force air through a condenser of the heat transfer system 2410. The fan 2435 is positioned at the cold side 2425 to force air through a condenser of the heat transfer system 2420.
Referring to Fig. 17, In one implementation, a thermodynamic system 2500 includes a heat transfer system 2505 coupled to a cyclical heat exchange system such as a cyclical heat exchange system 2510. The heat transfer system 2505 is used to cool a hot side 2515 of the cyclical heat exchange system 2510. The heat transfer system 2505 includes an annular evaporator 2520 that includes an expansion volume (or reservoir) 2525, a liquid return line 2530 providing fluid communication between liquid outlets 2535 of a condenser 2540 and the liquid inlet of the evaporator 2520. The heat transfer system 2505 also includes a vapor line 2545 providing fluid communication between the vapor outlet of the evaporator 2520, and vapor inlets 2550 of the condenser 2540.
The condenser 2540 is constructed from smooth wall tubing and is equipped with heat exchange fins 2555 or fin stock to intensify heat exchange on the outside of the tubing.
The evaporator 2520 includes a primary wick 2560 sandwiched between a heated wall 2565 and a liquid barrier wall 2570 and separating the liquid and the vapor. The liquid barrier wall 2570 is cold biased by heat exchange fins 2575 formed along the outer surface of the wall 2565. The heat exchange fins 2575 provide subcooling for the reservoir 2525 and the entire liquid side of the evaporator 2520. The heat exchange fins 2575 of the evaporator 2520 may be designed separately from the heat exchange fins 2555 of the condenser 2540.
The liquid return line 2530 extends into the reservoir 2525 located above the primary wick 2560, and vapor bubbles, if any, from the liquid return line 2530 and the vapor removal channels at the interface of the primary wick 2560 and the heated wall 2565 are vented into the reservoir 2525. Typical working fluids for the heat transfer system 2505 include (but are not limited to) methanol, butane, CO2, propylene, and ammonia.
The evaporator 2520 is attached to the hot side 2515 of the cyclical heat exchange system 2510. In one implementation, this attachment is integral in that the evaporator 2520 is an integral part of the cyclical heat exchange system 2510. In another implementation, attachment can be non-integral in that the evaporator 2520 can be clamped to an outer surface of the hot side 2510. The heat transfer system 2505 is cooled by a forced convection sink, which can be provided by a simple fan 2580. Alternatively, the heat transfer system 2505 Is cooled by a natural or draft convection.
Initially, the liquid phase of the working fluid is collected in a lower part of the evaporator 2520, the liquid return line 2530, and the condenser 2540. The primary wick 2560 is wet because of the capillary forces. As soon as heat is applied (for example, the cyclical heat exchange system 2510 is turned on), the primary wick 2560 begins to generate vapor, which travels through the vapor removal channels (similar to vapor removal channels 1120 of evaporator 1100) of the evaporator 2520, through the vapor outlet of the evaporator 2520, and into the vapor line 2545.
The vapor then enters the condenser 2540 at an upper part of the condenser 2540. The condenser 2540 condenses the vapor into liquid and the liquid is collected at a lower part of the condenser 2540. The liquid is pushed into the reservoir 2525 because of the pressure difference between the reservoir 2525 and the lower part of the condenser 2540. Liquid from the reservoir 2525 enters liquid flow channels of the evaporator 2520. The liquid flow channels of the evaporator 2520 are configured like the channels 1125 of the evaporator 1100 and are properly sized and located to provide adequate liquid replacement for the liquid that vaporized. Capillary pressure created by the primary wick 2560 is sufficient to withstand the overall LHP pressure drop and to prevent vapor bubbles from travelling through the primary wick 2560 toward the liquid flow channels.
The liquid flow channels of the evaporator 2520 can be replaced by a simple annulus, if the cold biasing discussed above is sufficient to compensate the increased heat leak across the primary wick 2560, which is caused by the increase in surface area of the heat exchange surface of annulus versus the surface area of the liquid flow channels.
Referring to Figs. 18-20, a heat transfer system 2600 includes an evaporator 2605 coupled to a cyclical heat exchange system 2610 and an expansion volume 2615 coupled to the evaporator 2605. The vapor channels of the evaporator 2605 feed to a vapor line 2620 that feed a series of channels 2625 of a condenser 2630. The condensed liquid from the condenser 2630 is collected in a liquid return channel 2635. The heat transfer system 2600 also includes fin stock 2640 thermally coupled to the condenser 2630.
The evaporator 2605 includes a heated wall 2700, a liquid barrier wall 2705, a primary wick 2710 positioned between the heated wall 2700 and the inner side of the liquid barrier wall 2705, vapor removal channels 2715, and liquid flow channels 2720. The liquid barrier wall 2705 is coaxial with the primary wick 2710 and the heated wall 2700. The liquid flow channels 2720 are fed by a liquid return channel 2725 and the vapor removal channels 2715 feed into a vapor outlet 2730.
The heated wall 2700 intimately contacts the primary wick 2710. The liquid barrier wall 2705 contains working fluid on an inner side of the liquid barrier wall 2705 such that the working fluid flows only along the inner side of the liquid barrier wall 2705. The liquid barrier wall 2705 closes the evaporator's envelope and helps to organize and distribute the working fluid through the liquid flow channels 2720.
In one implementation, the evaporator 2605 is approximately 2" (5 cm) tall and the expansion volume 2615 is approximately 1" (2.5 cm) in height. The evaporator 2605 and the expansion volume 2615 are wrapped around a portion of the cyclical heat exchange system 2610 having a 4" (10 cm) outer diameter. The vapor line 2620 has a radius of 1/8" (0.3 cm). The cyclical heat exchange system 2610 Includes approximately 58 condenser channels 2625, with each condenser channel 2625 having a length of 2" (5 cm) and a radius of 0.012" (0.3 mm) the channels 2625 being spread out such that the width of the condenser 2630 is approximate 40" (1 m). The liquid return channel 2725 has a radius of 1/16" (1.6 mm). The heat exchanger 2800 (which includes the condenser 2630 and the fin stock 2640 is approximately 40" (1 m) long and is wrapped into an inner and outer loop (see Figs. 22, 25, and 26) to produce a cylindrical heat exchanger having an outer diameter of approximately 8" (20 cm). The evaporator 2605 have a cross-sectional width 2750 of approximately 1/8" (0.3 cm) as defined by the heated wall 2700 and the liquid barrier wall 2705. The vapor removal channels 2715 have widths of approximately 0.020" (0.5 mm) and depths of approximately 0.020" (0.5 mm) and are separated from each other by approximately 0.020" (0.5 mm) to produce 25 channels per inch.
As mentioned above, the heat transfer system (such as system 2310) is thermally coupled to the portion (such as portion 2315) of the cyclical heat exchange system. The thermal coupling between the heat transfer system and the portion can be by any suitable method. In one implementation, if the evaporator of the heat transfer system is thermally coupled to the hot side of the cyclical heat exchange system, the evaporator may surround and contact the hot side and the thermal coupling may be enabled by a thermal grease compound applied between the hot side and the evaporator. In another implementation not according to the invention, if the evaporator of the heat transfer system is thermally coupled to the hot side of the cyclical heat exchange system, the evaporator may be constructed integral with the hot side of the cyclical heat exchange system by forming vapor channels directly into the hot side of the cyclical heat exchange system.
Referring to Figs. 22-24, a heat transfer system 3000 is packaged around a cyclical heat exchange system 3005. The heat transfer system 3000 includes a condenser 3010 surrounding an evaporator 3015. Working fluid that has been vaporized exits the evaporator 3015 through a vapor outlet 3020 connected to the condenser 3010. The condenser 3010 loops around and doubles back inside itself at junction 3025.
The cyclical heat exchange system 3005 is surrounded about its heat rejection surface 3100 by the evaporator 3015. The evaporator 3015 is in intimate contact with the heat rejection surface 3100. The refrigeration assembly (which is the combination of the cyclical heat exchange system 3005 and the heat transfer system 3000) is mounted in a tube 3205, with a fan 3210 mounted at the end of the tube 3205 to force air through fins 3030 of the condenser 3010 to exhaust channels 3035.
The evaporator 3015 has a wick 3215 in which working fluid absorbs heat from the heat rejection surface 3100 and changes phase from liquid to vapor. The heat transfer system 3000 includes a reservoir 3220 at the top of the evaporator 3015 that provides an expansion volume. For simplicity of illustration, the evaporator 3015 has been illustrated in this view as a simple hatched block that shows no internal detail. Such Internal details are discussed elsewhere In this description.
The vaporized working fluid exits the evaporator 3015 through the vapor outlet 3020 and enters a vapor line 3040 of the condenser 3010. The working fluid flows downward from the vapor line 3040, through channels 3045 of the condenser 3010, to the liquid return line 3050. As the working fluid flows through the channels 3045 of the condenser 3010 it loses heat, through the fins 3030 to the air passing between the fins, to change phase from vapor to liquid. Air that has passed through the fins 3030 of the condenser 3010 flows away through the exhaust channel 3035. Liquefied working fluid (and possibly some uncondensed vapor) flows from the liquid return line 3050 back into the evaporator 3015 through the liquid return port 3055.
Referring to Figs. 25 and 26, a heat transport system 3300 surrounds a portion of a cyclical heat exchange system 3302, that is surrounded, in turn, by exhaust channels 3305. The heat transport system 3300 includes an evaporator 3310 having an upper portion that surrounds the cyclical heat exchange system 3302. A vapor port 3315 connects the evaporator 3310 to a vapor line 3312 of a condenser 3320. The vapor line 3312 includes an outer region that circles around the evaporator 3310 and then doubles back on itself at junction 3325 to form an inner region that circles back around the evaporator 3310 in the opposite direction. The heat transport system 3300 also includes cooling fins 3330 on the condenser 3320.
The heat transport system 3300 also includes a liquid return port 3400 that provides a path for condensed working fluid from the liquid line 3405 of the condenser 3320 to return to the evaporator 3310.
Referring to Fig. 27, an evaporator 3500 slips over a heat rejection surface 3502 of a cyclical heat exchange system 3505. The evaporator 3500 includes a heated wall 3510, a liquid barrier wall 3515, and a wick 3520 sandwiched between the walls 3510 and 3515. The wick 3520 is equipped with vapor channels 3525 and liquid flow channels 3530 are formed at the liquid barrier wall 3515 in simplified form for clarity.
The evaporator 3500 is slipped over the cyclical heat exchange system 3050 and may be held in place with the use of a clamp 3600 (shown in Fig. 28) Which is not within the scope of the present invention. To aid heat transfer, thermally conductive grease 3535 is disposed between the cyclical heat exchange system , 3050 and heated wall 3510 of the evaporator 3500. In an alternate implementation not within the scope of the present invention, the vapor channels 3525 are formed in the heated wall 3510 instead of in the wick 3520.
Referring to Fig. 29, in another implementation, an evaporator 3700 is fit over a heat rejection surface 3702 of a cyclical heat exchange system 3705 with an Interference fit. The evaporator 3700 includes a heated wall 3710, a liquid barrier wall 3715, and a wick 3720 sandwiched between the walls 3710 and 3715. The evaporator 3700 is sized to have an interference fit with the heat rejection surface 3702 of the cyclical heat exchange system 3705.
The evaporator 3700 is heated so that its inner diameter expands to permit it to slip over the unheated heat rejection surface 3702. As the evaporator 3700 cools, it contracts to fix onto the cyclical heat exchange system 3705 in an interference fit relationship. Because of the tightness of the fit, no thermally conductive grease is needed to enhance heat transfer. The wick 3720 is equipped with vapor channels 3725. In an alternate implementation not within the scope of the present invention, the vapor channels are formed in the heated wall 3710 instead of in the wick 3720. Liquid flow channels 3730 are formed at the liquid barrier wall 3715 in a simplified form for clarity.
Referring to Fig. 30, in another implementation not within the scope of the present invention, an evaporator 3800 is fit over a heat rejection surface 3802 of a cyclical heat exchange system 3805 and features previously designed within the evaporator 3800 are now integrally formed within the heat rejection surface 3802. In particular, the evaporator 3800 and the heat rejection surface 3802 are constructed together as an integrated assembly. The heat rejection surface 3802 is modified to have vapor channels 3825; in this way, the heat rejection surface 3802 acts as a heated wall for the evaporator 3800.
The evaporator 3800 includes a wick 3820 and a liquid barrier wall 3815 formed about the modified heat rejection surface 3802, the wick 3820 and the liquid barrier wall 3815 being integrally bonded to the heat rejection surface 3802 to form a sealed evaporator 3800. Liquid flow channels 3830 are portrayed in a simplified form for clarity. In this way, a hybrid cyclical heat exchange system with an integrated evaporator is formed. This integral construction provides enhanced thermal performance in comparison to the clamp-on construction and the interference fit construction because thermal resistance is reduced between the cyclical heat exchange system and the wick of the evaporator.
Referring to Fig. 21, graphs 2900 and 2905 show the relationship between a maximum temperature of the surface of the portion of the cyclical heat exchange system that is to be cooled by the heat transfer system and a surface area of the interface between the heat transfer system and the portion of the cyclical heat exchange system to be cooled. The maximum temperature indicates the maximum amount of heat rejection. In graph 2900, the interface between the portion and the heat transfer system is accomplished with a thermal grease compound. In graph 2905, the heat transfer system is made integral with the portion.
As shown, at an air flow of 300 CFM, if the interface is a thermal grease interface, then the maximum amount of heat rejection would fall within a maximum heat rejection surface temperature 2907 (for example, 70 °C) with a heat exchange surface area 2910 (for example, 100 ft² (9.29 m²)). When the evaporator is constructed integrally with the portion by forming vapor channels directly in the heat rejection surface, that heat rejection surface would operate below the maximum heat rejection surface temperature of the thermal grease interface with significantly smaller heat exchange surface areas.
Referring to Fig. 31, a condenser 3900 is formed with fins 3905, which provide thermal communication between the air or the environment and a vapor line 3910 of the condenser 3900. The vapor line 3910 couples to a vapor outlet 3915 that connects the an evaporator 3920 positioned within the condenser 3900.
Referring to Figs. 32-35, in one implementation, the condenser 3900 is laminated and is formed with flow channels that extend through a flat plate 4000 of the condenser 3900 between a vapor head 3925 and a liquid head 3930. Copper is a suitable material for use in making a laminated condenser. The laminated structure condenser 3900 includes a base. 4200 having fluid flow channels 4205 (shown in phantom) formed therein and a top layer 4210 is bonded to the base 4200 to cover and seal the fluid flow channels 4205. The fluid flow channels 4205 are designed as trenches formed in the base 4200 and sealed beneath the top layer 4210. The trenches for the fluid flow channels 4205 may be formed by chemical etching, electrochemical etching, mechanical machining, or electrical discharge machining processes.
Referring to Figs. 36 and 37, in another implementation, the condenser 3900 is extruded and small flow channels 4400 extend through a flat plate 4405 of the condenser 3900. Aluminum is a suitable material for use in such an extruded condenser. The extruded micro channel flat plate 4405 extends between a vapor header 4410 and a liquid header 4415. Moreover, corrugated fin stock 4420 is bonded (for example, brazed or epoxied) to both sides of the flat plate 4405.
Referring to Fig. 38, a cross-sectional view of one side of a heat transfer system 4600 that is coupled to a cyclical heat exchange system 4605. This view shows relative dimensions that provide for particularly compact packaging of the heat transfer system. In this view, fins 4610 are portrayed as being 90 degrees out of phase for ease of illustration. To cool the heat rejection surface 4615 of the cyclical heat exchange system 4605 having a 4 inch diameter, the evaporator 4620 has a thickness of 0.25 inch and the radial thickness of the condenser is 1.75 inches. This provides on overall dimension for the packaging (the combination of the heat transfer system 4600 and the cyclical heat exchange system 4605 of 8 inches.
As discussed, the evaporator used in the heat transfer system is equipped with a wick. Because a wick is employed within the evaporator of the heat transfer system, the condenser may be positioned at any location relative to the evaporator and relative to gravity. For example, the condenser may be positioned above the evaporator (relative to a gravitational pull), below the evaporator (relative to a gravitational pull), or adjacent the evaporator, thus experiencing the same gravitational pull as the evaporator.
Other implementations are within the scope of the following claims. Notably, the terms Stirling engine, Stirling heat exchange system, and Free Piston Stirling Cooler have been referenced in several implementations above. However, the features and principals described with respect to those implementations also may be applied to other engines capable of conversions between mechanical energy and thermal energy.
Moreover, the features and principals described above may be applied to any heat engine, which is a thermodynamic system that can undergo a cycle, that is, a sequence of transformations which ultimately return it to its original state. If every transformation in the cycle is reversible, the cycle is reversible and the heat transfers occur in the opposite direction and the amount of work done switches sign. The simplest reversible cycle is a Camot cycle, which exchanges heat with two heat reservoirs.

Claims

A thermodynamic system (2500) comprising:
a cyclical heat exchange system (2510; 2610); and

a heat transfer system (2505; 2600) comprising:
an annular evaporator (2520; 2605) including a wall (2565; 2700) configured to be coupled to a portion of the cyclical heat exchange system and a primary wick coupled to the wall; and

a condenser (2540; 2630) coupled to the evaporator to form a closed loop that houses a working fluid,

wherein the annular evaporator is interference fit onto the cyclical heat exchange system.
The thermodynamic system of claim 1 wherein the condenser (2540; 2630) includes a vapor inlet and a liquid outlet;
further comprising:
a vapor line (2545; 2620) providing fluid communication between a vapor outlet and the vapor inlet (2550); and

a liquid return line (2530; 2635) providing fluid communication between the liquid outlet (2535) and a liquid inlet.
The thermodynamic system of claim 2 wherein the evaporator includes:
a liquid barrier wall (2570; 2705) containing the working fluid on an inner side of the liquid barrier wall, such that working fluid flows only along the inner side of the liquid barrier wall, wherein the primary wick is positioned between the heated wall and the inner side of the liquid barrier wall;

a vapor removal channel (2715) that is located at an interface between the primary wick and the heated wall, the vapor removal channel extending to the vapor outlet; and

a liquid flow channel (2720) located between the liquid barrier wall and the primary wick, the liquid flow channel receiving liquid from a liquid inlet (2520).
The thermodynamic system of claim 1 wherein the working fluid is moved through the heat transfer system (2505; 2600) passively.
The thermodynamic system of claim 4 wherein the working fluid is moved through the heat transfer system (2505; 2600) without the use of external pumping.
The thermodynamic system of claim 1 wherein the working fluid within the heat transfer system (2505; 2600) changes between a liquid and a vapor as the working fluid passes through or within one or more of the evaporator (2520; 2605), the condenser (2540; 2630), the vapor line (2545; 2620), and the liquid return line (2530; 2635).
The thermodynamic system of claim 1 wherein the working fluid Is moved through the heat transfer system (2505; 2600) with the use of the wick (2560; 2710).
The thermodynamic system of claim 1 further comprising fins thermally coupled to the condenser to reject heat to an ambient environment.
The thermodynamic system of claim 1 wherein the evaporator (2520; 2605) is thermally coupled to the portion of the cyclical heat exchange system (2510; 2610).
The thermodynamic system of claim 1 wherein the cyclical heat exchange system (2510; 2610) includes a Stirling heat exchange system.
The thermodynamic system of claim 1 wherein the cyclical heat exchange system (2510; 2610) includes a refrigeration system.
The thermodynamic system of claim 1 wherein the heat transfer system (2505; 2600) is coupled to a hot side of the cyclical heat exchange system (2510; 2610).
The thermodynamic system of claim 1 wherein the heat transfer system (2505; 2600) is coupled to a cold side of the cyclical heat exchange system (2510; 2610).
Use of the thermodynamic system (2500) of any of claims 1 to 12 for cooling the portion of the cyclical heat exchanger (2510; 2610).