Heat transport system

A system includes a heat transfer system and a priming system coupled to the heat transfer system. The heat transfer system includes a main evaporator having a core, a primary wick, and a secondary wick, and a condenser coupled to the main evaporator by a liquid line and a vapor line. A heat transfer system loop is defined by the main evaporator, the condenser, the liquid line, and the vapor line. The priming system is configured to convert fluid into a liquid capable of wetting the primary wick of the main evaporator. The priming system includes a priming evaporator coupled to the vapor line, and a reservoir in fluid communication with the priming evaporator and coupled to the secondary wick of the main evaporator by a secondary fluid line.

TECHNICAL FIELD

This description relates to a system for heat transfer.

BACKGROUND

Heat transport systems are used to transport heat from one location (the heat source) to another location (the heat sink). Heat transport systems can be used in terrestrial or extraterrestrial applications. For example, heat transport systems may be integrated by satellite equipment that operates within zero or low-gravity environments. As another example, heat transport 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 transport 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 transport 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.

SUMMARY

In one general aspect, a system includes a heat transfer system and a priming system coupled to the heat transfer system. The heat transfer system includes a main evaporator having a core, a primary wick, and a secondary wick, and a condenser coupled to the main evaporator by a liquid line and a vapor line. A heat transfer system loop is defined by the main evaporator, the condenser, the liquid line, and the vapor line. The priming system is configured to convert fluid into a liquid capable of wetting the primary wick of the main evaporator. The priming system includes a priming evaporator coupled to the vapor line, and a reservoir in fluid communication with the priming evaporator and coupled to the secondary wick of the main evaporator by a secondary fluid line.

Implementations may include one or more of the following features. For example, the reservoir may be cold biased relative to an operating temperature of the heat transfer system. The reservoir may be mounted to a heat sink thermally connected to the condenser.

The secondary fluid line may insulate the liquid line from parasitic heat input. For example, the secondary fluid line may be coaxial with and surround the liquid line.

The priming system may be configured to reduce the temperature of the heat transfer system. The main evaporator may include a three-port evaporator. The reservoir may be coupled to the secondary wick of the main evaporator through a secondary condenser and a liquid line coupled to the core of the main evaporator.

The priming system may be configured to convert fluid that has a critical temperature above an operating temperature of the heat transfer system into a liquid. The operating temperature of the heat transfer system may be a cryogenic temperature or a sub-ambient temperature.

The heat transfer system may be used to cool an apparatus operating in an extra-terrestrial environment. The heat transfer system may be used to cool an apparatus operating in a terrestrial environment. The heat transfer system may be used to cool an electronic apparatus or an apparatus in a medical application. The heat transfer system may be used to cool one or more of a vending machine, a computer, a component in a transportation device, a display for a computer, and an infrared sensor.

The heat transfer system may include another reservoir operating at a temperature higher than the temperature of operation for the reservoir of the priming system to reduce a fill pressure of the system. The priming evaporator may include a core, a primary wick surround the core, and a secondary wick within the core. The main evaporator may include a bayonet tube extending through the core to guide fluid into the core.

In another general aspect, a method of transporting heat includes priming a heat transfer system that includes a main evaporator, a vapor line, a condenser, and a liquid line connected in a loop and reducing heat conditions within the heat transfer system. Priming the heat transfer system includes wetting a primary wick of a priming system evaporator, applying power to the priming system evaporator, converting fluid received from the priming system evaporator into a liquid, and wetting the main evaporator of the heat transfer system with the liquid through the liquid line. Reducing heat conditions within the heat transfer system includes at least one of sweeping vapor bubbles within the main evaporator into a reservoir in fluid communication with the priming evaporator or reducing parasitic heat gains on the liquid line.

Implementations may include one or more of the following features. For example, application of power to the priming evaporator may enhance circulation of fluid within the heat transfer system. Enhancing circulation of fluid within the heat transfer system may include enhancing circulation of fluid from the main evaporator, through the vapor line, through the condenser, through the liquid line, and returning into the main evaporator.

The method may further include reducing power to the priming system evaporator once the priming system evaporator is wetted. The method may include reducing power to the priming system evaporator once the priming system evaporator reaches a temperature below a critical temperature of the fluid.

The method may also include cold biasing the reservoir relative to a temperature of the heat transfer system. Cold biasing the reservoir may include mounting the reservoir to a heat sink that is in fluid communication with the condenser.

Wetting the primary wick of the priming system evaporator may include cold-biasing the reservoir to a temperature below the critical temperature of the fluid. Wetting the primary wick of the priming system evaporator may include pumping liquid formed within the reservoir into the priming system evaporator using capillary pressure.

The method may also include coupling the reservoir to a secondary fluid line in communication with a core of the main evaporator. Sweeping vapor bubbles within the main evaporator into the reservoir may include sweeping bubbles through a secondary wick of the main evaporator, through a secondary fluid line, through a secondary condenser, and into the reservoir. Reducing parasitic heat gains on the liquid line may include forming the secondary fluid line coaxially around the liquid line such that the secondary fluid line insulates the liquid line from parasitic heat gains. Reducing parasitic heat gains on the liquid line may include sweeping vapor bubbles formed within the secondary fluid line due to the parasitic heat gains into the secondary condenser, where the vapor bubbles are cooled and pushed into the reservoir.

The method may also include insulating the liquid line from parasitic heat gains. The method may further include operating the heat transfer system to transport heat from a heat source. The method may include operating the heat transfer system at a cryogenic temperature or a sub-ambient temperature.

The method may include using the heat transfer system to transport heat from an apparatus operating in an extra-terrestrial environment or from an apparatus operating in a terrestrial environment. The method may include using the heat transfer system to transport heat from an electronic apparatus, from an apparatus within a medical device, from an infrared sensor, from a vending machine, from a computer, from a component in a transportation device, or from a display device.

Aspects of the system and method can include one or more of the following advantages. For example, system and method permit startup from a supercritical state, which is a state in which the temperature of the system is above the critical temperature of the working fluid. The system and method is designed to enable cooling of the reservoir and the evaporator to temperatures below the critical temperature of the working fluid up and to enable the evaporator to be primed with liquid.

Other features will be apparent from the description, the drawings, and the claims.

DETAILED DESCRIPTION

As discussed above, in a loop heat pipe (LHP), the reservoir is co-located with the evaporator, thus, the reservoir is thermally and hydraulically connected with the reservoir through a heat-pipe-like conduit. In this way, liquid from the reservoir can be pumped to the evaporator, thus ensuring that the primary wick of the evaporator is sufficiently wetted or “primed” during start-up. Additionally, the design of the LHP also reduces depletion of liquid from the primary wick of the evaporator during steady-state or transient operation of the evaporator within a heat transport system. Moreover, vapor and/or bubbles of non-condensable gas (NCG bubbles) vent from a core of the evaporator through the heat-pipe-like conduit into the reservoir.

Conventional LHPs require that liquid be present in the reservoir prior to start-up, that is, application of power to the evaporator of the LHP. However, if the working fluid in the LHP is in a supercritical state prior to start-up of the LHP, liquid will not be present in the reservoir prior to start-up. A supercritical state is a state in which a temperature of the LHP is above the critical temperature of the working fluid. The critical temperature of a fluid is the highest temperature at which the fluid can exhibit a liquid-vapor equilibrium. For example, the LHP may be in a supercritical state if the working fluid is a cryogenic fluid, that is, a fluid having a boiling point below −150° C., or if the working fluid is a sub-ambient fluid, that is, a fluid having a boiling point below the temperature of the environment in which the LHP is operating.

Conventional LHPs also require that liquid returning to the evaporator is subcooled, that is, cooled to a temperature that is lower than the boiling point of the working fluid. Such a constraint makes it impractical to operate LHPs at a sub-ambient temperature. For example, if the working fluid is a cryogenic fluid, the LHP is likely operating in an environment having a temperature greater than the boiling point of the fluid.

Referring toFIG. 1, a heat transport system100is designed to overcome limitations of conventional LHPs. The heat transport system100includes a heat transfer system105and a priming system110. The priming system110is configured to convert fluid within the heat transfer system105into a liquid, thus priming the heat transfer system105. As used in this description, the term “fluid” is a generic term that refers to a substance that is both a liquid and a vapor in saturated equilibrium.

The heat transfer system105includes a main evaporator115, and a condenser120coupled to the main evaporator115by a liquid line125and a vapor line130. The condenser120is in thermal communication with a heat sink165, and the main evaporator115is in thermal communication with a heat source Qin116. The system105may also include a hot reservoir147coupled to the vapor line130for additional pressure containment, as needed. In particular, the hot reservoir147increases the volume of the system100. If the working fluid is at a temperature above its critical temperature, that is, the highest temperature at which the working fluid can exhibit liquid-vapor equilibrium, its pressure is proportional to the mass in the system100(the charge) and inversely proportional to the volume of the system. Increasing the volume with the hot reservoir147lowers the fill pressure.

The main evaporator115includes a container117that houses a primary wick140within which a core135is defined. The main evaporator115includes a bayonet tube142and a secondary wick145within the core135. The bayonet tube142, the primary wick140, and the secondary wick145define a liquid passage143, a first vapor passage144, and a second vapor passage146. The secondary wick145provides phase control, that is, liquid/vapor separation in the core135, as discussed in U.S. application Ser. No. 09/896,561, filed Jun. 29, 2001, which is incorporated herein by reference in its entirety. As shown, the main evaporator115has three ports, a liquid inlet137into the liquid passage143, a vapor outlet132into the vapor line130from the second vapor passage146, and a fluid outlet139from the liquid passage143(and possibly the first vapor passage144, as discussed below). Further details on the structure of a three-port evaporator are discussed below with respect toFIGS. 5A and 5B.

The priming system110includes a secondary or priming evaporator150coupled to the vapor line130and a reservoir155co-located with the secondary evaporator150. The reservoir155is coupled to the core135of the main evaporator115by a secondary fluid line160and a secondary condenser122. The secondary fluid line160couples to the fluid outlet139of the main evaporator115. The priming system110also includes a controlled heat source Qsp151in thermal communication with the secondary evaporator150.

The secondary evaporator150includes a container152that houses a primary wick190within which a core185is defined. The secondary evaporator150includes a bayonet tube153and a secondary wick180that extend from the core185, through a conduit175, and into the reservoir155. The secondary wick180provides a capillary link between the reservoir155and the secondary evaporator150. The bayonet tube153, the primary wick190, and the secondary wick180define a liquid passage182coupled to the fluid line160, a first vapor passage181coupled to the reservoir155, and a second vapor passage183coupled to the vapor line130. The reservoir155is thermally and hydraulically coupled to the core185of the secondary evaporator150through the liquid passage182, the secondary wick180, and the first vapor passage181. Vapor and/or NCG bubbles from the core185of the secondary evaporator150are swept through the first vapor passage181to the reservoir155and condensable liquid is returned to the secondary evaporator150through the secondary wick180from the reservoir155. The primary wick190hydraulically links liquid within the core185to the heat source Qsp151, permitting liquid at an outer surface of the primary wick190to evaporate and form vapor within the second vapor passage183when heat is applied to the secondary evaporator150.

The reservoir155is cold-biased, and thus, it is cooled by a cooling source that will allow it to operate, if unheated, at a temperature that is lower than the temperature at which the heat transfer system105operates. In one implementation, the reservoir155and the secondary condenser122are in thermal communication with the heat sink165that is thermally coupled to the condenser120. For example, the reservoir155can be mounted to the heat sink165using a shunt170, which may be made of aluminum or any heat conductive material. In this way, the temperature of the reservoir155tracks the temperature of the condenser120.

FIG. 2shows an example of an implementation of the heat transport system100. In this implementation, the condensers120and122are mounted to a cryocooler200, which acts as a refrigerator, transferring heat from the condensers120,122to the heat sink165. Additionally, in the implementation ofFIG. 2, the lines125,130,160are wound to reduce space requirements for the heat transport system100.

Though not shown inFIGS. 1 and 2, elements such as, for example, the reservoir155and the main evaporator115, may be equipped with temperature sensors that can be used for diagnostic or testing purposes.

Referring also toFIG. 3, the system100performs a procedure300for transporting heat from the heat source Qin116and for ensuring that the main evaporator115is wetted with liquid prior to startup. The procedure300is particularly useful when the heat transfer system105is at a supercritical state. Prior to initiation of the procedure300, the system100is filled with a working fluid at a particular pressure, referred to as a “fill pressure.”

Initially, the reservoir155is cold-biased by, for example, mounting the reservoir155to the heat sink165(step305). The reservoir155may be cold-biased to a temperature below the critical temperature of the working fluid, which, as discussed, is the highest temperature at which the working fluid can exhibit liquid-vapor equilibrium. For example, if the fluid is ethane, which has a critical temperature of 33° C., the reservoir155is cooled to below 33° C. As the temperature of the reservoir155drops below the critical temperature of the working fluid, the reservoir155partially fills with a liquid condensate formed by the working fluid. The formation of liquid within the reservoir155wets the secondary wick180and the primary wick190of the secondary evaporator150(step310).

Meanwhile, power is applied to the priming system110by applying heat from the heat source Qsp151to the secondary evaporator150(step315) to enhance or initiate circulation of fluid within the heat transfer system105. Vapor output by the secondary evaporator150is pumped through the vapor line130and through the condenser120(step320) due to capillary pressure at the interface between the primary wick190and the second vapor passage183. As vapor reaches the condenser120, it is converted to liquid (step325). The liquid formed in the condenser120is pumped to the main evaporator1,15of the heat transfer system105(step330). When the main evaporator115is at a higher temperature than the critical temperature of the fluid, the liquid entering the main evaporator115evaporates and cools the main evaporator115. This process (steps315–330) continues, causing the main evaporator115to reach a set point temperature (step335), at which point the main evaporator is able to retain liquid and be wetted and to operate as a capillary pump. In one implementation, the set point temperature is the temperature to which the reservoir155has been cooled. In another implementation, the set point temperature is a temperature below the critical temperature of the working fluid. In a further implementation, the set point temperature is a temperature above the temperature to which the reservoir155has been cooled.

If the set point temperature has been reached (step335), the system100operates in a main mode (step340) in which heat from the heat source Qin116that is applied to the main evaporator115is transferred by the heat transfer system105. Specifically, in the main mode, the main evaporator115develops capillary pumping to promote circulation of the working fluid through the heat transfer system105. Also, in the main mode, the set point temperature of the reservoir155is reduced. The rate at which the heat transfer system105cools down during the main mode depends on the cold biasing of the reservoir155because the temperature of the main evaporator115closely follows the temperature of the reservoir155. Additionally, though not required, a heater can be used to further control or regulate the temperature of the reservoir155during the main mode. Furthermore, in main mode, the power applied to the secondary evaporator150by the heat source Qsp151is reduced, thus bringing the heat transfer system105down to a normal operating temperature for the fluid. For example, in the main mode, the heat load from the heat source Qsp151to the secondary evaporator150is kept at a value equal to or in excess of heat conditions, as defined below. In one implementation, the heat load from the heat source Qspis kept to about 5 to 10% of the heat load applied to the main evaporator115from the heat source Qin116.

In this particular implementation, the main mode is triggered by the determination that the set point temperature has been reached (step335). In other implementations, the main mode may begin at other times or due to other triggers. For example, the main mode may begin after the priming system is wet (step310) or after the reservoir has been cold biased (step305).

At any time during operation, the heat transfer system105can experience heat conditions such as those resulting from heat conduction across the primary wick140and parasitic heat applied to the liquid line125. Both conditions cause formation of vapor on the liquid side of the evaporator. Specifically, heat conduction across the primary wick140can cause liquid in the core135to form vapor bubbles, which, if left within the core135, would grow and block off liquid supply to the primary wick140, thus causing the main evaporator115to fail. Parasitic heat input into the liquid line125(referred to as “parasitic heat gains”) can cause liquid within the liquid line125to form vapor.

To reduce the adverse impact of heat conditions discussed above, the priming system110operates at a power level Qsp151greater than or equal to the sum of the head conduction and the parasitic heat gains. As mentioned above, for example, the priming system can operate at 5–10% of the power to the heat transfer system105. In particular, fluid that includes a combination of vapor bubbles and liquid is swept out of the core135for discharge into the secondary fluid line160leading to the secondary condenser122. In particular, vapor that forms within the core135travels around the bayonet tube143directly into the fluid outlet port139. Vapor that forms within the first vapor passage144makes it way into the fluid outlet port139by either traveling through the secondary wick145(if the pore size of the secondary wick145is large enough to accommodate vapor bubbles) or through an opening at an end of the secondary wick145near the outlet port139that provides a clear passage from the first vapor passages144to the outlet port139. The secondary condenser122condenses the bubbles in the fluid and pushes the fluid to the reservoir155for reintroduction into the heat transfer system105.

Similarly, to reduce parasitic heat input to the liquid line125, the secondary fluid line160and the liquid line125can form a coaxial configuration and the secondary fluid line160surrounds and insulates the liquid line125from surrounding heat. This implementation is discussed further below with reference toFIGS. 8A and 8B. As a consequence of this configuration, it is possible for the surrounding heat to cause vapor bubbles to form in the secondary fluid line160, instead of in the liquid line125. As discussed, by virtue of capillary action affected at the secondary wick145, fluid flows from the main evaporator115to the secondary condenser122. This fluid flow, and the relatively low temperature of the secondary condenser122, causes a sweeping of the vapor bubbles within the secondary fluid line160through the condenser122, where they are condensed into liquid and pumped into the reservoir155.

As shown inFIG. 4, data from a test run is shown. In this implementation, prior to startup of the main evaporator115at temperature410, a temperature400of the main evaporator115is significantly higher than a temperature405of the reservoir155, which has been cold-biased to the set point temperature (step305). As the priming system110is wetted (step310), power Qsp450is applied to the secondary evaporator150(step315) at a time452, causing liquid to be pumped to the main evaporator115(step330), the temperature400of the main evaporator115drops until it reaches the temperature405of the reservoir155at time410. Power Qin460is applied to the main evaporator115at a time462, when the system100is operating in LHP mode (step340). As shown, power input Qin460to the main evaporator115is held relatively low while the main evaporator115is cooling down. Also shown are the temperatures470and475, respectively, of the secondary fluid line160and the liquid line125. After time410, temperatures470and475track the temperature400of the main evaporator115. Moreover, a temperature415of the secondary evaporator150follows closely with the temperature405of the reservoir155because of the thermal communication between the secondary evaporator150and the reservoir155.

As mentioned, in one implementation, ethane may be used as the fluid in the heat transfer system105. Although the critical temperature of ethane is 33° C., for the reasons generally described above, the system100can start up from a supercritical state in which the system100is at a temperature of 70° C. As power Qspis applied to the secondary evaporator150, the temperatures of the condenser120and the reservoir155drop rapidly (between times452and410). A trim heater can be used to control the temperature of the reservoir155and thus the condenser120to −10° C. To startup the main evaporator115from the supercritical temperature of 70° C., a heat load or power input Qspof 10 W is applied to the secondary evaporator150. Once the main evaporator115is primed, the power input from the heat source Qsp151to the secondary evaporator150and the power applied to and through the trim heater both may be reduced to bring the temperature of the system100down to a nominal operating temperature of about −50° C. For instance, during the main mode, if a power input Qinof 40 W is applied to the main evaporator115, the power input Qspto the secondary evaporator150can be reduced to approximately 3 W while operating at −45° C. to mitigate the 3 W lost through heat conditions (as discussed above). As another example, the main evaporator115can operate with power input Qinfrom about 10 W to about 40 W with 5 W applied to the secondary evaporator150and with the temperature405of the reservoir155at approximately −45° C.

Referring toFIGS. 5A and 5B, in one implementation, the main evaporator115is designed as a three-port evaporator500(which is the design shown inFIG. 1). Generally, in the three-port evaporator500, liquid flows into a liquid inlet505into a core510, defined by a primary wick540, and fluid from the core510flows from a fluid outlet512to a cold-biased reservoir (such as reservoir155). The fluid and the core510are housed within a container515made of, for example, aluminum. In particular, fluid flowing from the liquid inlet505into the core510flows through a bayonet tube520, into a liquid passage521that flows through and around the bayonet tube520. Fluid can flow through a secondary wick525(such as secondary wick145of evaporator115) made of a wick material530and an annular artery535. The wick material530separates the annular artery535from a first vapor passage560. As power from the heat source Qin116is applied to the evaporator500, liquid from the core510enters a primary wick540and evaporates, forming vapor that is free to flow along a second vapor passage565that includes one or more vapor grooves545and out a vapor outlet550into the vapor line130. Vapor bubbles that form within first vapor passage560of the core510are swept out of the core510through the first vapor passage560and into the fluid outlet512. As discussed above, vapor bubbles within the first vapor passage560may pass through the secondary wick525if the pore size of the secondary wick525is large enough to accommodate the vapor bubbles. Alternatively, or additionally, vapor bubbles within the first vapor passage560may pass through an opening of the secondary wick525formed at any suitable location along the secondary wick525to enter the liquid passage521or the fluid outlet512.

Referring toFIG. 6, in another implementation, the main evaporator115is designed as a four-port evaporator600, which is a design described in U.S. application Ser. No. 09/896,561, filed Jun. 29, 2001. Briefly, and with emphasis on aspects that differ from the three-port evaporator configuration, liquid flows into the evaporator600through a fluid inlet605, through a bayonet610, and into a core615. The liquid within the core615enters a primary wick620and evaporates, forming vapor that is free to flow along vapor grooves625and out a vapor outlet630into the vapor line130. A secondary wick633within the core615separates liquid within the core from vapor or bubbles in the core (that are produced when liquid in the core615heats). The liquid carrying bubbles formed within a first fluid passage635inside the secondary wick633flows out of a fluid outlet640and the vapor or bubbles formed within a vapor passage642positioned between the secondary wick633and the primary wick620flow out of a vapor outlet645.

Referring also toFIG. 7, a heat transport system700is shown in which the main evaporator is a four-port evaporator600. The system700includes one or more heat transfer systems705and a priming system710configured to convert fluid within the heat transfer systems705into a liquid to prime the heat transfer systems705. The four-port evaporators600are coupled to one or more condensers715by a vapor line720and a fluid line725. The priming system710includes a cold-biased reservoir730hydraulically and thermally connected to a priming evaporator735.

Design considerations of the heat transport system100include startup of the main evaporator115from a supercritical state, management of parasitic heat leaks, heat conduction across the primary wick140, cold biasing of the cold reservoir155, and pressure containment at ambient temperatures that are greater than the critical temperature of the working fluid within the heat transfer system105. To accommodate these design considerations, the body or container (such as container515) of the evaporator115or150can be made of extruded6063aluminum and the primary wicks140and/or190can be made of a fine-pored wick. In one implementation, the outer diameter of the evaporator115or150is approximately 0.625 inches and the length of the container is approximately 6 inches. The reservoir155may be cold-biased to an end panel of the radiator165using the aluminum shunt170. Furthermore, a heater (such as a kapton heater) can be attached at a side of the reservoir155.

In one implementation, the vapor line130is made with smooth walled stainless steel tubing having an outer diameter (OD) of 3/16″ and the liquid line125and the secondary fluid line160are made of smooth walled stainless steel tubing having an OD of ⅛″. The lines125,130,160may be bent in a serpentine route and plated with gold to minimize parasitic heat gains. Additionally, the lines125,130,160may be enclosed in a stainless steel box with heaters to simulate a particular environment during testing. The stainless steel box can be insulated with multi-layer insulation (MLI) to minimize heat leaks through panels of the heat sink165.

In one implementation, the condenser122and the secondary fluid line160are made of tubing having an OD of 0.25 inches. The tubing is bonded to the panels of the heat sink165using, for example, epoxy. Each panel of the heat sink165is an 8×19 inch direct condensation, aluminum radiator that uses a 1/16-inch thick face sheet. Kapton heaters can be attached to the panels of the heat sink165, near the condenser120to prevent inadvertent freezing of the working fluid. During operation, temperature sensors such as thermocouples can be used to monitor temperatures throughout the system100.

The heat transport system100may be implemented in any circumstances where the critical temperature of the working fluid of the heat transfer system105is below the ambient temperature at which the system100is operating. The heat transport system100can be used to cool down components that require cryogenic cooling.

Referring toFIGS. 8A–8D, the heat transport system100may be implemented in a miniaturized cryogenic system800. In the miniaturized system800, the lines125,130,160are made of flexible material to permit coil configurations805, which save space. The miniaturized system800can operate at −238° C. using neon fluid. Power input Qin116is approximately 0.3 to 2.5 W. The miniaturized system800thermally couples a cryogenic component (or heat source that requires cryogenic cooling)816to a cryogenic cooling source such as a cryocooler810coupled to cool the condensers120,122.

The miniaturized system800reduces mass, increases flexibility, and provides thermal switching capability when compared with traditional thermally-switchable, vibration-isolated systems. Traditional thermally-switchable, vibration-isolated systems require two flexible conductive links (FCLs), a cryogenic thermal switch (CTSW), and a conduction bar (CB) that form a loop to transfer heat from the cryogenic component to the cryogenic cooling source. In the miniaturized system800, thermal performance is enhanced because the number of mechanical interfaces is reduced. Heat conditions at mechanical interfaces account for a large percentage of heat gains within traditional thermally-switchable, vibration-isolated systems. The CB and two FCLs are replaced with the low-mass, flexible, thin-walled tubing used for the coil configurations805of the miniaturized system800.

Moreover, the miniaturized system800can function of a wide range of heat transport distances, which permits a configuration in which the cooling source (such as the cryocooler810) is located remotely from the cryogenic component816. The coil configurations805have a low mass and low surface area, thus reducing parasitic heat gains through the lines125and160. The configuration of the cooling source810within miniaturized system800facilitates integration and packaging of the system800and reduces vibrations on the cooling source810, which becomes particularly important in infrared sensor applications. In one implementation, the miniaturized system800was tested using neon, operating at 25–40 K.

Referring toFIGS. 9A–9C, the heat transport system100may be implemented in an adjustable mounted or Gimbaled system1005in which the main evaporator115and a portion of the lines125,160, and130are mounted to rotate about an elevation axis1020within a range of ±45° and a portion of the lines125,160, and130are mounted to rotate about an azimuth axis1025within a range of ±220°. The lines125,160,130are formed from thin-walled tubing and are coiled around each axis of rotation. The system1005thermally couples a cryogenic component (or heat source that requires cryogenic cooling)1016such as a sensor of a cryogenic telescope to a cryogenic cooling source such as a cryocooler1010coupled to cool the condensers120,122. The cooling source1010is located at a stationary spacecraft1060, thus reducing mass at the cryogenic telescope. Motor torque for controlling rotation of the lines125,160,130, power requirements of the system1005, control requirements for the spacecraft1060, and pointing accuracy for the sensor1016are improved. The cryocooler1010and the radiator or heat sink165can be moved from the sensor1016, reducing vibration within the sensor1016. In one implementation, the system1005was tested to operate within the range of 70–115 K when the working fluid is nitrogen.

The heat transfer system105may be used in medical applications, or in applications where equipment must be cooled to below-ambient temperatures. As another example, the heat transfer system105may be used to cool an infrared (IR) sensor, which operates at cryogenic temperatures to reduce ambient noise. The heat transfer system105may be used to cool a vending machine, which often houses items that preferably are chilled to sub-ambient temperatures. The heat transfer system105may be used to cool components such as a display or a hard drive of a computer, such as a laptop computer, handheld computer, or a desktop computer. The heat transfer system105can be used to cool one or more components in a transportation device such as an automobile or an airplane.

Other implementations are within the scope of the following claims. For example, the condenser120and heat sink165can be designed as an integral system, such as, for example, a radiator. Similarly, the secondary condenser122and heat sink165can be formed from a radiator. The heat sink165can be a passive heat sink (such as a radiator) or a cryocooler that actively cools the condensers120,122.

In another implementation, the temperature of the reservoir155is controlled using a heater. In a further implementation, the reservoir155is heated using parasitic heat.

In another implementation, a coaxial ring of insulation is formed and placed between the liquid line125and the secondary fluid line160, which surrounds the insulation ring.