WO2007124386A2

WO2007124386A2 - Heat exchange devices and materials utilizing gas permeable membranes

Info

Publication number: WO2007124386A2
Application number: PCT/US2007/067017
Authority: WO
Inventors: Igor Touzov
Original assignee: Igor Touzov
Priority date: 2006-04-19
Filing date: 2007-04-19
Publication date: 2007-11-01
Also published as: WO2007124386A3

Abstract

This invention eliminates impact of hydrodynamic resistance of wicking material(s) while preserving high efficiency of capillary suction achievable by very harrow capillaries in design of heat transporting devices such as a heat pipe. It utilizes micro- or nano- porous membranes, in place of traditional wicks, placed across (normal to the vector of speed) the transport direction of the liquid. Elimination of the resistance is achieved by positioning the membrane on surface of the liquid that forms an interface between the liquid and the vapor allowing vapor to condense on liquid surface creating extensive capillary pressure.

Description

HEAT EXCHANGE DEVICES AND MATERIALS UTILIZING GAS PERMEABLE MEMBRANES

DESCRI PTION

RELATED APPLICATION DATA

[Para 1 ] This application is a continuation-in-part of each of:

(1 ) U.S. patent application Ser. No. 1 1 /308,663, filed Apr. 1 9, 2006, entitled "Grid and yarn membrane heat pipes", hereby incorporated by reference

(2) PCT application Ser. No PCT/US06/62591 filed Dec, 24, 2006, entitled "PERFORATED HEAT PIPE MATERIAL", hereby incorporated by reference

TECHNICAL FIELD

[Para 2] The invention provides essential improvement in field of heat transferring devices and materials. In particular it contributes to designs of devices and materials that rely on use of phase transitions of embedded substances such as gas and liquids. Fundamental advantage of instant invention is its ability to passively transport heat over high vertical transitions and extended distances.

BACKGROUND ART

[Para 3] Prior art accounts for wealth of designs addressing the problem of heat transfer and heat dissipation. In specific area of devices utilizing phase transitions of embedded substances, commonly referred as heat pipes, there are two principally different groups of solutions.

[Para 4] One utilizes narrow tube that contains both liquid and vapor of said liquid in form of bubbles occupying whole section of the tube. The bubbles and the liquid form a train of adjacent volumes arranged along the tube. Essential requirement for the tube is Closed

Profile, which means that beginning and the end of the tube are joint together creating a continuous loop. Gradient in temperature between two sections of the loop creates mechanical instability in the train and causes vibrations and movement of the liquid along the loop. This motion aids to transport of heat between a hot and a cold sections of the profile. Fundamental details of this solution group are described by Huang in US Patent 6,269,865. Drawback of this design is its high energy loses due to mechanical vibrations of liquid in the narrow capillary profile. These losses limit principal performance of similar designs.

[Para 5] Second group of solutions uses two continuous volumes one of which is filled with liquid and another with vapors of said liquid. Both volumes interface each other. This allows vapors to be transferred into the liquid and otherwise without forming bubbles. In this group of solutions vapor freely moves between a hot (evaporator) and a cold (condenser) segments of the designs thus transferring heat. Reverse flow of condensed liquid delivers to the evaporator segment for re-evaporation by means of wick or gravity. In order to aid the reverse flow all existing designs use one of tree following approaches:

(1 ) Use gravity to transport liquid from higher elevations to lower elevation toward a heat source(s). These designs are limited to applications where the heat source and evaporator are below the condenser section.

(2) Use of capillary forces inside of wicking material that absorbs condensed vapors in the condenser section and aid to the flow of liquid toward the evaporator section where liquid re-evaporates. These designs allow transport of heat from higher locations to lower locations acting in directions opposed to the gravity. Disadvantage of these designs comes from hydrodynamic resistance of the wicking material that limits throughput of the liquid. As a result, an increase in transfer distance drastically reduces allowable amount of transported heat. Fundamental problem this approach deals with lays in two facts: 1 ) effect of capillary forces increases with decrease in capillary area (use of denser wicks); 2) hydrodynamic resistance increases with decrease in capillary area (do not use dense wicks). That is why any design that deals with high height drop between the condenser and the evaporator segments inherently rely on dense wicking material with narrow capillary areas. This dramatically reduces throughput of the liquid and the heat throughput of such designs.

(3) Last group of known approaches utilizes hybrid designs that combine features of both previously described ones. Some portion of the volume usually assigned to the wicking material is replaced with clear passages or tubes that aid to reduction of hydrodynamic resistance of reverse liquid flow. This approach allows increased heat throughput of the designs as well as some increase in transport distance. Yet it has inherent limitations of both previous approaches that limit its ability to function against the gravity when source of the heat is positioned above the condenser section.

[Para 6] In invention of Zhou, et al. disclosed in US patent 6,994, 1 51 , author introduces a novel approach for micro-channel heat exchanges. He proposes use on hydrophobic membrane to extract vapors from evaporator region to reduce backpressure on a liquid pump as shown on A. To prevent vapor condensation in vapor chamber he suggests using a pump to reduce vapor pressure and thus make it unsaturated. Condensation inside the vapor channel 1 04 would cause blockage of membrane 1 1 2and render the design nonfunctional. While active approach can provide the only solution in many technical applications the field of instant invention focuses on completely passive designs. As another design inventor Zhou discloses use of hydrophobic membrane in heat pipes by applying it around wick structure 1 1 8 in evaporator segment as shown on B. Such approach might provide some benefits but do not resolve problem of hydrodynamic friction described above. Detailed description of can be found in referenced UP patent 6,994, 1 51 . DISCLOSURE OF INVENTION

[Para 7] The subject of instant invention is ability to eliminate the impact of hydrodynamic resistance of wicking material(s) while preserving high efficiency of capillary suction commonly achievable by very narrow capillaries. Concept of this approach was first disclosed in co-pending US patent application 1 1 /308,663 and cited here by reference. Instant invention utilizes micro- and/or nano- porous membranes that allow complete replacement of traditional wicks. Opposed to known designs where liquid flows along and through the wicking materials, this invention places capillary structure across the transport direction (normal to the vector of speed) of the liquid. Elimination of the resistance is thus explained by position of the membrane(s). While known prior art solutions place capillary wicking material inside the volume of the liquid, instant invention places its capillary membranes on surface of the liquid. This way the membrane forms an interface between the liquid and the vapor and avoids interference with the liquid flow.

[Para 8] Hydrophobic porous membrane creates permeable separator that allows vapors to pass, while preventing liquid from entering dedicated vapor chamber. Here and afterwards term hydrophobic will be used as substitution of the term "low affinity to selected liquid", and term hydrophilic will be used as a replacement for the term "high affinity to selected liquid". This is done to resolve common confusion, as it is obvious to one experience in surface properties of materials and liquids, that liquids other than water can be used in disclosed design. Present description is intended to disclose fundamental concept of the invention and do not limits itself to case of water. Instead, it intends to use broad range of available liquids and condensable gases and reference to those simply omitted to improve clarity of description.

[Para 9] Unlike prior art invention of Zhou role of membranes in instant invention is to create capillary pumping and to exclude unnecessary wicks and pumps, thus producing highly efficient passive deigns capable to operate on large distances and high gravitational drops.

[Para 1 0] Development in areas of purification (e.g. gas and liquid filtration) and popularity of these technologies made commercially available micro- and nano-membranes very affordable and available in variety of materials. The materials of membranes account for both hydrophilic and hydrophobic polymers with pore sizes as small as 30nm and up to hundreds of microns. Because of small pores and good uniformity typical 1 00 nm hydrophobic nylon membranes (e.g. product of General Electrics) have water breakthrough pressure of 246kPa and airflow of 6.4 SCCM/cm²/kPa. Instant invention does not intend to limit itself to any particular membrane type or source, as it is obvious that its concept is strictly independent on that. Instead, instant invention accounts for any type of porous material that is capable to transmit gases across its volume as a membrane. This includes porous ceramics, metals, textiles, sintered plastics, etc.

[Para 1 1 ] Primary concept of instant invention is illustrated on Figure 2. It utilizes two sealed volumes 1 and 2. Volume 2 is filled with liquid 7 and volume 1 with vapors 8 of said liquid. It is well known in related literature that more that one chemical can be used to form content of a vapor phase and a liquid phase in heat pipes. Present invention do not limit itself to cases when the liquid 7 or vapor 8 composed of a single chemical, instead it covers all cases when multiple chemical components are used to constitute liquid 7 and vapor 8. This also accounts for situations when some of the chemical components and not condensable.

[Para 1 2] The volumes 1 and 2 have interface segment(s) formed by membranes 5 and 6. This separation is done for initial disclosure only as it become obvious that the same physical membrane can be extended to form both membranes 5 and 6. Each of the interface segments may be formed by multiple of membranes stacked together. In fact, co-pending patent application US 1 1 /308,663 discloses composite membrane that has hydrophobic and hydrophilic membranes joint together to form amphophilic membrane that is still permeable to vapors and impermeable to liquid but has one side wetable by selected liquid while other side is not. The membrane stack can also use membranes with different thickness and different pore size. The advantage of such aggergation is ability to use ultrathin hydrophobic membrane with small pore size and high water breakthrough pressure but low mechanical strength. This membrane layer attached to thicker coarse membrane will have adequate mechanical stability.

[Para 1 3] The hydrophobic membrane films prevent liquid 7 from flowing across the interface segments 5 and 6, yet vapors 8 of said liquid can cross the interface. Important to notice that this membrane interfaces are associated with evaporator segment 3 and condenser segment 4 respectively.

[Para 14] The most challenging situation for all prior art designs is placement of heat source 3 at higher location than heat sink 4. In case of instant invention such angled of vertical placement of the design creates hydrostatic pressure within the volume occupied by the liquid. While this pressure remains below water breakthrough pressure of the lower membrane interface, the liquid 7 remains trapped inside volume 2. There is one critical factor that is fundamentally essential to instant invention: all inner volumes 1 and 2 have to be particle free, and all surfaces of vapor volume 1 must be hydrophobic. Detailed description of this requirement was disclosed in co-pending US patent application 1 1 /308,663 and briefly cited herein: any liquid volume constrained in sphere with curvature higher that curvature of meniscus of liquid 7 on membrane 6 is unstable and will form vapors inside volume 1 thus keeping volume 1 liquid-free. These conditions can be violated by presence of hydrophilic particles or surfaces within volume 1 that may render designs of instant invention nonfunctional. [Para 1 5] There are no restrictions on shape or area of volumes 1 and 2, and there is no hydrodynamic interaction between the liquid and the membranes. This gives a freedom to choose design geometry that keeps hydrodynamic limitations of the designs below considerable level. In fact traditional design of heat pipe with a wick structure has to account for volume and weight of wick when designing a pipe that must operate over large height and distance. In many cases volume and weight of required wick become unsurpassable limitation. Instant invention eliminates wick requirement completely and volumes of chambers 1 and 2 must satisfy trivial tube size criteria's to provide reasonable back pressure for sustained flow rate of liquid 7 and vapor 8.

[Para 1 6] Preferred design operates as following. Because complete volume of the design is sealed the liquid 7 always stays in balance with saturated vapor 8. Application of heat to evaporator region 3 causes liquid 7 to boil. Heat source in thermal connection with evaporator 3 boils liquid 7 and creates vapor bubbles in vicinity of membrane segment 5. The bubbles get adsorbed to hydrophobic membrane 5and create excessive pressure Pi of saturated vapor on liquid faced side of membrane 5. Membrane 5 is impermeable to liquid 7 and allows vapor 8 from the bubbles to pass through while blocking the liquid. In conditions total volume of the bubbles becomes so large that membrane segment 5 completely disengages from the liquid 7. In special designs membrane 5 can be purposely moved away from boiling surface of water 7 in segment of evaporator 3, thus vapor 8 will create dedicate volume below membrane segment 5 inside chamber 2. It is also possible to eliminate membrane segment 5 completely by placing interlaced fins in it place. The fins will prevent random drops of liquid from escaping evaporator 3 and reaching into chamber 1 . This alternative design will provide higher performance due to elimination of flow resistance that membrane segment 5 provides to passing vapor 8. The only requirement for such alternative design is static orientation, as evaporator 3 must be above condenser 4. [Para 1 7] . In preferred design pressure P2 of vapors 8 on other side of membrane 5 is less than pressure Pi This ensures that the vapor become unsaturated and will not condense in chamber 1 . Vapor 8 flows along chamber 1 toward condenser 4. Liquid 7 has lower temperature within the condenser volume 4. Membrane segment 6 blocks the liquid from crossing from chamber 2 to chamber 1 until total pressure across the membrane remains below the breakthrough pressure. As lower temperature of the liquid in condenser 4 the pressure P₄ of saturated vapors on liquid facing side of membrane 6 are lesser than pressure in chamber 1 . Because pressure P₄ is less than pressure P3 on opposite side of the membrane segment 6 vapor 8 will penetrate through the membrane and will be turned into the liquid inside condenser 4 segment of volume 2. Pressure gradients Pi >P2>P3>P₄ ensure directed circulation of vapor 8. Liquid 2 continues this circulation as pressure gradient Pi -P₄ is overcompensated by capillary pressure gradient. The capillary pressure in condenser region 4 is created by positive curvature of the liquid-vapor interface at lower temperature (higher surface tension). The capillary pressure created in evaporator region 3 is lower because of its higher temperature that lowers surface tension. Depending on orientation of the design and an amount of supplied heat, liquid in evaporator 3 may have a free surface (surface curvature zero) or may interface membrane 5 (common case). In addition membrane 5 may include a layer with high affinity to liquid 7 (in which case meniscus curvature will be negative).

[Para 1 8] Because the membrane segments 5 and 6 operate as a pump creating driving pressure gradients, to preserve their mechanical integrity some supporting mechanical elements could be necessary. Example of such support will be considered below. Nevertheless instant invention does not limit itself to those examples and covers all design cases that uses described operating principles regardless of peculiarities of mechanical support elements. [Para 1 9] It is obvious that cases when plurality of separate or interconnecting volumes form each of the volumes 1 and 2 belong to the scope of present invention. The cases when there is more than one evaporator 3 or more than one condenser 4 is integrated into disclosed design are trivial extension of disclosed concept and are covered by scope of this invention. In fact, preferred embodiment below describes modular approach where evaporator 3 and condenser 4 created as separate assembly. There will be shown that one evaporator is connected to one condenser by one pair of connecting vessels. It is obvious to one experience in art of thermal engineering that such modules can be used to complex thermal managing aggregate that employs plurality of condensers 4 connected with another plurality of evaporators 3 through plurality of connecting vessels that satisfy requirement of present disclosure and embodiments. Such engineering uses of disclosed embodiments are foreseeing and belong to the scope of present invention.

[Para 20] Figure 3 illustrates example of model data for design that employs two tubes

with areas of 1 cm² as each of said sealed volumes 1 and 2. One tube is coated from inside with hydrophobic polymer coat. Each end of tube 1 is connected to an end of tube 2 through hydrophobic membrane. The volume of tube 1 is evacuated, and uncoated tube 2 is filed with water. As shown on the plot, the change in length of the design causes only minor effect on overall heat transfer efficiency. In particular illustration increase in length to 100 meters only contributes 0.025 percent to increase in thermal resistance. [Para 21 ] The only limiting factor that truly constrains heat transport capacity of the designs

in present invention is flow of vapor through the membranes. Figure 4 shows modeled thermal resistance of the vertical design with evaporator 3 located 20 meters above condenser 4. The membranes 5 and 6 have areas of 1 cm² and effective pore size of 100 nm. The liquid is water. The plot shows that the resistance quickly decays with temperature increase. Yet selected membrane type shows very high resistance per 1 cm² compared to other available membrane types.

[Para 22] Dependency of thermal resistance from orientation is shown on Figure 5. With

angle changes from 0 degrees (horizontal) to 90 degrees (vertical: heat source is on top) the change in resistance is less than 0.1 percent. This shows virtual independency of thermal transfer characteristics from the orientation of the devices with respect to vector of acceleration. This is distinctive characteristic of instant invention that enables new areas of applications for passive heat transferring devices.

[Para 23] Although thermal resistance of invented designs decreases with raise in temperature, there is one efficient solution that allows dramatically decrease it. Models presented above have considered flat membrane geometry. At the same time corrugated membranes should be used instead. In alternative design the membrane is folded as it is done in traditional filters. In parameters of cited examples if thickness of the membrane is 65 micron, and density of folded fins is 25% by volume the membrane, and the fins height is 1 cm the resulting effect will give 38.5 fold reduction in thermal resistance compared to the flat membrane designs.

[Para 24] While flat and folded topology is the most common for membrane materials, this invention does not limit itself to such choice. It is obvious that plurality of alternative shapes of the membranes can be used providing increase in membrane's surface area. [Para 25] The porosity of the membrane is directly linked to its breakthrough pressure and to its resistance to the vapor flow. The breakthrough pressure limits maximum height difference between evaporator 3 and condenser 4. Increase in breakthrough pressure allows all invented designs to have higher height separation between evaporator 3 and condenser 4. At the same time it correlates with decrease in permeability of the membrane to vapors 8 and requires adequate increase in total area of the membrane. Selection of membrane material with proper breakthrough pressure thus allows optimization of the design performance. As an example 1 00 nm hydrophobic membrane allows placement of the heat source up to 24 meters above the heat sink. Yet when such height is not required 1 0 micrometer membrane can provide more compact solutions that will operate with heights below 1 .5 meter.

BRIEF DESCRIPTION OF DRAWINGS

[Para 26] shows prior art designs that employ gas separation membranes. A shows micro- channel design that employs external liquid pump. B shows proposed heat pipe design with improved evaporator.

[Para 27] Figure 2 shows schematic view of primary embodiment of instant invention.

[Para 28] Figure 3 shows usability of the invention at long passive heat transporting devices.

[Para 29] Figure 4 shows dependency of thermal resistance from temperature.

[Para 30] Figure 5 shows dependency of thermal resistance from angle of orientation

[Para 31 ] Figure 6 shows exploded view of preferred embodiment.

[Para 32] Figure 7 shows performance of the preferred embodiment with 20 m height differential.

[Para 33] Figure 8 shows exploded view of alternative embodiment utilizing integral membrane chamber in tubular geometry.

[Para 34] Figure 9 shows performance of the tubular design. Plot shows difference of evaporator and condenser temperatures in logarithmic scale. [Para 35] Figure 1 0 shows exploded view of alternative embodiment utilizing integral membrane chamber in planar geometry.

[Para 36] Figure 1 1 shows performance of the planar design.

MODES FOR CARRYING OUT THE INVENTION

[Para 37] Reference will now be made in detail to the preferred and alternative modes of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these modes. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and the scope of the invention as defined by appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a through understanding of the present invention. However, it should be noted that the present invention may be practiced without these specific details. In other instances, well known methods, procedures and components have not been described in detail as not to obscure aspects of the present invention.

THE PREFERRED MODE

[Para 38] Figure 6 illustrates one of possible implementation modes of the invention. This

mode will be best described on example of prototype developed to passively transfer 1 kW of heat from 20 meter elevation down to heat sink that dissipates said heat to some external media e.g. ground water. The prototype employs two identical modules one for evaporator segment 3 and one for condenser segment 4. Structure of condenser segment is shown as exploded view. [Para 39] Because both condenser 4 and evaporator 3 have identical construction in this prototype, herein only condenser 4 will be described. It has solid aluminum enclosure 9 with two threaded holes that holds compression fittings 10 and 1 1 . Fitting 10 connects to 1 /8 inch copper tube 2 filled with water 7. Fitting 1 1 connects to V≥ inch copper tube 1 filled with water vapor 8. Vertical wall of enclosure 9 has machined vertical fins on inner side (hidden on current view) that increase heat exchange efficiency between said wall and the liquid 7.

[Para 40] Membrane 6 is hydrophobic nylon membrane with embedded polyester support. It has effective pore size of 1 00 nanometers and can be purchased from General Electrics Inc. in commercial quantities. The membrane is folded to form 200 closely packed fins with profile height of 2.54 cm. The fins are separated from each other by means of spacers 1 4 that are made from coarse mesh of hydrophobic polymer (e.g. PTFE). The fin stack is pressed against supporting surface of adapter 1 3. The adapter is machined or (injection molded from hydrophobic nylon. This partial assembly then sealed by edge frame 1 2 that is formed by injection molding of hydrophobic nylon. Assembled part has membrane 6 hermetically attached to adapter 1 3.

[Para 41 ] The adapter 1 3 has one threaded port that hosts hose fitting 1 5. The fitting is made from hydrophobic plastic and deforms while forming hermetic seal when fitting 1 1 fits in. Assembly of enclosure 9 is sealed by lid 1 6 and metal 0.25 mm wire O-ring 1 7. The sealed assembly 4 has two volumes separated by the membrane 6. One volume is connected to fitting 1 1 and has all hydrophobic surfaces it constitutes a part of volume 1 . The second volume is connected to fitting 1 0 and has all metal surfaces it constitutes a part of volume 2.

[Para 42] Two assemblies 3 and 4 are connected by tubes 1 and 2. Tube 1 has hydrophobic inner coat. This coat can be created by various ways: e.g. deposition of water repelling paint on existing metal tube; or by use of thin wall PTFE tube inserted into flexible corrugated stainless steel gas pipe (commonly used in residential sector).

[Para 43] Total length of the prototype is 20.1 meters. It has thermal resistance virtually

independent from its orientation or shape of 1 and 2connecting tubes. Figure 7 shows data of heat transfer characteristics of this prototype with three different heat sources: 200, 1 000, and 5000 watts. The plot shows dependency between evaporator 3 and condenser 4 temperatures as a function of temperature of water that was used as a heat sink by means of immersing condenser 4 into it. When temperature increases the thermal resistance of the

prototype decreases as was expected from model data shown on Figure 4.

The method of assembly of the prototype may vary and is not essential to this invention.

One practical example consists of connecting tubes 1 and 2 to evaporator and condenser assemblies, evaluating assembly using T-coupler, filling tube 2 with degassed water, sealing the T coupler.

ALTERNATIVE MODE (TUBULAR DESIGN)

[Para 44] The same concept disclosed in instant invention can be implemented as an integral

heat pipe shown on Figure 8. This mode was described in co-pending US patent

application 1 1 /308,663 and will be recited here.

[Para 45] Membrane of this mode is heat sealed to form sleeve 1 7. Round spiral 1 8 with hydrophobic surface (polyester coated with hydrophobic nylon) is inserted into the sleeve

1 7 along its complete length. The spiral has a joint that connects all loops together, and a slit that breaks all loops. These modifications to the spiral allow it to have variable diameter and resist compression along its axis.

[Para 46] Before insertion the spiral 1 8 is wrapped with wadding 1 9 of hydrophobic fiber

(e.g. spun PTFE). The wadding is necessary for two purposes: first, it allows membrane 1 7 to be compressed against the spiral without mechanical damage; second, it creates layer of thermal insulation that prevents quick cooling of the vapor 8 in vicinity of condensing region 4 that in turn prevents condensation of vapors 8 within volume 1 .

[Para 47] The ends of the sleeve 1 7 are heat sealed resulting in sealed volume 1 . Copper tube 2 of diameter larger than the sleeve 1 7 is carefully placed around the sleeve and sealed on one end. This assembly then evacuated through open end of tube 2, and then filled with water until all volume around the sleeve is occupied, then sealed.

[Para 48] In working prototype of this mode tube 2 was Yi inch copper tube with length of 1 meter. Material of membrane 1 7 is GE hydrophobic nylon membrane with effective pore size of 10 micron, and breakthrough pressure of 1 8 kPa. As evaporator 3 top 1 0 centimeters of pipe 2 were used. As condenser 4 bottom 1 0 cm of the pipe 2 were immerse in water.

Figure 9 shows plots of performance for heat source supplying 20, 1 00 and 500 watts. As temperature of condenser gradually increases the difference at temperatures between the evaporator and the condenser ends of the pipe also decrease indicating gradual increase in performance.

[Para 49] Alternatively this mode can be implemented without use of wadding 1 9 and spiral 1 8. Membrane itself gas notable rigidity if bended in tubular shape of small diameter (e.g. 4mm) and heat sealed along axial direction forming profile of number eight(8). This membrane profile is heat sealed on both ends. Plurality of such membrane segments are placed inside of tube 2. Collection of inner volumes of the membrane profiles form vapor transport volume 1 . Plurality of other alternatives can be considered yet all of them belong to the scope of present invention.

ALTERNATIVE MODE (PLANAR DESIGN) [Para 50] The same concept disclosed in instant invention can be implemented as an integral

planar heat pipe shown on Figure 1 0. This mode was described in co-pending US patent application 1 1 /308,663 and will be recited here.

[Para 51 ] The present mode herein described as planar prototype. There are no dedicated evaporator 3 and condenser 4 regions, instead any location of the planar prototype can play role of the evaporator or the condenser. In fact it is possible to have more than one condenser 4 regions and more than one evaporator 3 regions.

[Para 52] Because of these peculiarities the membrane 20 functions as both the evaporator membrane region 5 and the condenser membrane region 6. Two sheets of membrane material 20 are stacked on opposite sides of hydrophobic wadding 1 . The wadding of present prototype is made of hydrophobic nylon fibers sintered to form a stable sheet. Any other breathable hydrophobic material with large porosity can be used instead (e.g. woven coarse mesh of hydrophobic fiber, woven or knitted textile, etc.)

[Para 53] Layer 1 is heat welded with membrane sheets 20 around the perimeter and plurality of inner profiles 21 . Resulting aggregate has sealed inner volume 1 that carries functions of the vapor transfer chamber 1 .

[Para 54] Two sheets 2 of thin metal foil are stack on each side of the membrane aggregate.

The foil sheets 2 are welded to each other through holes 21 and by outer perimeter. Volume between the foils 2 and the membranes 20 is evaluated first and then filed with water until the foil start to bulge out, and then the volume is sealed. The volume formed by foils 2 carries out functions of liquid transport volume 2 as water occupies sealed space around membranes 20.

[Para 55] This prototype has plurality of perforations 21 that are subject of co-pending PCT application US0662591 . Distinctive feature of present mode is soft shell design. This means that outer shell formed by foil 2 does not carry localized structural load. Instead it allows any externally applied pressure to slightly deform the foil surface. Advantage of such design approach is very high flexibility of the prototype, if fact it can be even folded like a sheet of paper without any damage.

[Para 56] Because all inner components of this prototype are thermoplastic (e.g. hydrophobic nylon), the initial assembly can be easily modified by addition of new perforations similar to 21 . In order to do that a location where perforation will be made compressed with heat seal equipment that creates a spot or a line or a closed profile seam in membranes 20 and wadding 1 without unsealing the vapor chamber 1 . This brings opposite layers of foils 2 into contact with each other and allows them to be welded together (by e.g. ultrasonic or spot welder).

[Para 57] The prototype of the present mode was created as l feet x 1 feet assembly. The material of membranes 20 is GE hydrophobic nylon with effective pore size of 200 nanometers. The foils 2 are 25 micron thick copper, and the wadding 1 is woven hydrophobic nylon mesh made from multifilament nylon yarn. The evaporator region 3 was created by placing two belt heater elements with combined area of 24x25.4x25.4 mm² near top edge of the assembly that were positioned vertically. The bottom edge was immersed into water and formed the condenser region 4 with area of 608 x25.4 mm². Performance

data are plotted on Figure 1 1 for heating power of 5, 20, and 1 00 Watts. [Para 58] Present mode can also be implemented using rigid foil 2 design at shown in co- pending US patent application 1 1 /308,663, in that case membranes material could use larger porosity and provides better heat transfer performance. Yet depending on particular practical application the soft shell design could be found more attractive. [Para 59] It is obvious that all listed modes can use corrugates or folded membranes that provide adequate increase in design performances due to increase in membrane surface area. INDUSTRIAL APPLICABILITY

[Para 60] Invented approach to design of passive heat transferring devices that can act at arbitrary gravity/acceleration vector has broad industrial applicability. Herein listed just few examples of such. Ability to convey heat from high elevations (20 meters or more) without use of pumps or other active components provides direct benefits to HVAC and energy harvesting applications. Compact tube and planar designs have attractive application in electronics cooling and energy efficient housing.

[Para 61 ] Because performance of invented devised does not change with acceleration or gravity vector, they are attractive component for heat management applications in avionics and aero-space equipment.

Claims

What i s clai med is :

[Clai m 1 ] A substantially hydrophobic vessel coupled with at least one gas permeable membrane for use in heat exchanging device, wherein at least one side of the membrane is hydrophobic, and the device utilizes condensable gases as a medium for heat exchange.

[Clai m 2] A heat exchanging device comprising at least one of the vessels of [Claim I ].

[Clai m 3] A heat exchanging device of [Claim 1 ] comprising at least one evaporator and at least one condenser.

[Clai m 4] A substantially hydrophobic vessel coupled with at least one gas permeable membrane of [Claim 1 ] for use in heat exchanging device, wherein at least one side of at least one membrane is hydrophilic.

[Clai m 5] A heat exchanging device of [Claim 1 ] comprising gas impermeable shell enclosing said membrane.

[Clai m 6] A heat exchanging device of [Claim 5] wherein said shell comprises at least one deformation that connects opposite surfaces of the shell without unsealing its inner volume.

[Clai m 7] A heat exchanging device of [Claim 5] wherein said shell comprises at least one perforation that joins opposite surfaces of the shell without unsealing its inner volume.

[Clai m 8] A substantially hydrophobic vessel formed by surface of gas permeable membrane for use in heat exchange device, wherein volume of said vessel sealed by adjacent essentially hydrophobic entity.

[Clai m 9] A substantially hydrophobic vessel of [Claim 8] for use in heat exchange device, wherein volume of said entity is seam.

[Clai m 1 0] A heat exchanging device comprising at least one of the vessels of [Claim 8].

[Clai m 1 I ] A heat exchanging device wherein vessels of [Claim 8] form a network of connected volumes. [Clai m 1 2] A heat exchanging device wherein vessels of [Claim 8] form a sequential array of separated volumes.

[Clai m 1 3] A textile comprising devices of [Claim 8].

[Clai m 1 4] A device of [Claim 8] comprising gas impermeable shell enclosing said vessel.

[Clai m 1 5] A device of [Claim 14] wherein said shell comprises at least one deformation that connects opposite surfaces of the shell without unsealing its inner volume.

[Clai m 1 6] A device of [Claim 14] wherein said shell comprises at least one perforation that joins opposite surfaces of the shell without unsealing its inner volume.

[Clai m 1 7] A device of [Claim 14] wherein said shell deforms transferring external pressure on structure of said vessel.