Portable isothermal heat transfer device and method

Abstract

A portable temperature regulation device comprising a working fluid reservoir comprising a first inner wall, an outer wall, a working fluid disposed between said inner wall and said outer wall, and a first cavity configured to accept a thermal container, and a thermal container disposed in said cavity comprising a second inner wall extending over the working fluid reservoir, a second cavity configured to accept a heat sink, a gap between said first inner wall and said second inner wall.

Description

PORTABLE ISOTHERMAL HEAT TRANSFER DEVICE AND METHODTECHNICAL FIELD

[0001] The present technology relates to mobile temperature regulation devices generally, and particularly isothermal cooling and heating devices.BACKGROUND

[0002] Environmental temperatures or other factors that increase core temperature can have a deleterious effect on both people and devices. For instance, temperatures outside of the physiologic human temperature range are known stressors of the human body. As a consequence, physical performance suffers at these temperatures. By way of examples for devices, at colder temperatures, batteries are less efficient, whereas at higher temperatures, electronic devices are prone to overheating. As another example, tissue, such as donor organs or blood, degrades and loses viability when exposed to inappropriate temperatures.

[0003] In persons, elevated core body temperature can be induced by the environment, exercise, stress, or medical conditions that affect thermoregulation. The use of a mobile temperature regulation device may be used to combat these effects.

[0004] For example, the concept of palmar cooling can be utilized to reduce core body temperature and combat heat exhaustion. In the palms of hands, there is a network of blood vessels that specialize in heat transfer called arteriovenous anastomoses (AVAs). In response to increase in core body temperature, AVAs vasodilate and blood flows rapidly to the periphery of the body (i.e., the palms). Through circulation, blood cools and in turn cools one’s core. To maximize this regulatory mechanism, certain criteria must be met. First, the temperature of a cooling interface needs to be within a desired temperature range.Additionally, there may be a benefit to maintaining the palm in a relaxed state, as contrasted to a fisted shape, to prevent mechanical restriction of blood flow through the AVAs. Similar benefits may also be achieved by warming or cooling glabrous skin surfaces such as the soles of the feet, palms of the hand, etc.

[0005] There is also a need for cooling or heating units maintained at a target temperature, to keep objects, such mechanical or electronics devices, or organic compounds, tissue samples, organs, or other materials, at optimal temperatures. Such objects may then be stored during transport within such units to ensure that they are kept at an optimal temperature.SUMMARY

[0006] The following aspects and embodiments thereof described and illustrated below are meant to be exemplary and illustrative, not limiting in scope.

[0007] In one exemplary aspect, provided is a device comprising a working fluid with a boiling point set within a fixed tolerance of a desired temperature. In some such embodiments, such tolerance may be three degrees Celsius or less. The working fluid flows in a closed-loop system through a condensation chamber. The working fluid vapor travels into the condensation chamber through buoyancy effects and condenses on the walls or portions thereof. The walls or portions of the condensation chamber are cooled by a thermal heat sink, which may be a cooling element, such as an ice pack or ice bath. During operation, the working fluid condenses along the sides or top of the condensation chamber and falls back to the liquid chamber for circulation. The working fluid is maintained under pressure through a vacuum or partial vacuum. The strength of the vacuum and / or the pressure of the working fluid may be changed to adjust the boiling point of the working fluid.

[0008] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following descriptions.

[0009] Additional embodiments of the present device and its method of use will be apparent from the following description, drawings and claims. As can be appreciated from the foregoing and following description, each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present disclosure provided that the features included in such a combination are not mutually inconsistent. In addition, any feature or combination of features may be specifically excluded from any embodiment of the present disclosure. Additional aspects and advantages of the present disclosure are set forth in the following description and claims, particularly when considered in conjunction with the accompanying examples and drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. l is a schematic of a prior art temperature regulation device.

[0011] FIG. l is a perspective view of the exemplary temperature regulation mechanism.

[0012] FIG. 3 shows a cut-away view of the exemplary temperature regulation mechanism.

[0013] FIG. 4 is an exploded view of the exemplary temperature regulation mechanism.

[0014] FIG. 5 is a flow chart of an exemplary cooling cycle.

[0015] FIG. 6 is a schematic of a temperature regulation device incorporating an exemplary mechanism.

[0016] FIG. 7 is a flow chart of an exemplary cooling cycle.

[0017] FIG. 8 is a schematic of a temperature regulation device incorporating an exemplary mechanism.DETAILED DESCRIPTIONI. Definitions

[0018] Various aspects now will be described more fully hereinafter. Such aspects may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art.

[0019] Where a range of values is provided, it is intended that each intervening value between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the disclosure. For example, if a range of 0° to 5° is stated, it is intended that 1°, 2°, 3°, 4°, and 5° are also explicitly disclosed, as well as the range of values greater than or equal to 0° and the range of values less than or equal to 5°.

[0020] The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a “chamber” includes a chamber as well as two or more chambers, and the like.

[0021] The term “about,” particularly in reference to a given quantity, is meant to encompass deviations of plus or minus five percent.

[0022] The compositions of the present disclosure can comprise, consist essentially of, or consist of, the components disclosed.

[0023] All percentages, parts and ratios are based upon the total weight of the compositions and all measurements made are at about 25 °C, unless otherwise specified.

[0024] By reserving the right to proviso out or exclude any individual members of any such group, including any sub-ranges or combinations of sub-ranges within the group, that can be claimed according to a range or in any similar manner, less than the full measure of this disclosure can be claimed for any reason. Further, by reserving the right to proviso out or exclude any individual substituents, analogs, compounds, ligands, structures, or groups thereof, or any members of a claimed group, less than the full measure of this disclosure can be claimed for any reason.

[0025] For convenience, certain terms employed in the specification, examples and claims are collected here. Unless defined otherwise, all technical and scientific terms used in this disclosure have the same meanings as commonly understood by one of ordinary skill in the art to which this disclosure belongs.II. Device

[0026] Existing palmar cooling systems operate by circulating a working fluid to a cooling pad worn by the user. The contact between the pad and the user’s palm causes the pad to extract heat from the user’s body and serves to cool the user’s blood, which also cools the user’s muscle temperature. The working fluid is typically cooled using ice packs or an ice bath, which are at 0°C. Extracting heat using a working fluid like water at the optimal temperature requires pumping the fluid with a pump. However, during use, ice packs and ice baths will rise in temperature, limiting the amount of time that the working fluid may be cooled effectively.

[0027] Such a prior art system is detailed in FIG. 1. The main unit 1 comprises a water reservoir 10, which is filled with water, or another suitable working fluid. Water reservoir 10 is fluidly connected to pump 11, which is fluidly connected to mechanical valve 12. Main unit 1 further includes ports 14 and 15 to provide fluid connections water reservoir 10 and mechanical valve 12, respectively. Mechanical valve 12 is configured to control the temperature of the working fluid that is output through port 15. Cooling element 13 is fluidly connected between pump 11 and mechanical valve 12. Cooling element 13 may be an ice bath or ice pack. Main unit 1 further comprises a battery 16 that powers pump 11. To operate the device, interface 2 is fluidly coupled to mechanical valve 12 and water reservoir 10 through ports 14 and 15, thereby creating a closed loop path for the working fluid.

[0028] During operation, mechanical valve 12 operates to mix fluid that has circulated through cooling element 13 with working fluid from reservoir 10 in order to keep the working fluid at a desired temperature. Because cooling element 13 becomes warmer over time during use, the amount of time valve 12 must operate in order to allow interface 2 to reach the desired temperature is dependent on, and related to, the temperature of cooling element 13 and its ability to cool the working fluid.

[0029] In an alternative prior art device, to ensure that the working fluid maintains a consistent temperature, the working fluid may be cooled using thermoelectric coolers, or a refrigeration cycle rather than by an ice pack or ice bath. However, existing methods are complex and require electrical energy to move the working fluid and remove heat from the system. Accordingly, there is a need for a cooling mechanism that is able to maintain a consistent optimal temperature of the working fluid without the need for electrical energy.

[0030] The present technology addresses these and other shortcomings by providing a temperature regulation device comprising a working fluid with a boiling point set within a fixed tolerance of a desired temperature range. In some embodiments, this tolerance may be within three degrees Centigrade of a desired temperature. The working fluid is maintained under pressure through a vacuum or partial vacuum. The pressure of the working fluid may be adjusted by adjusting the strength of the vacuum. By adjusting the pressure of the working fluid, the boiling point of the working fluid may also be changed.

[0031] With reference to FIGS. 2-4, the temperature regulation device as described in this specification is shown to include cannister 20. Cannister 20 comprises a working fluid reservoir 21 and thermal container 22. Working fluid reservoir 21 comprises a base 200, a first outer wall 201, and a first inner wall 202, and is configured to hold working fluid 23. First outer wall 201 may be non-insulative and comprises a thermally conductive material, such as stainless steel, ceramic, or similar material. Base 200 and first outer wall 201 may be manufactured as separate components that are later assembled, or as a single component. First inner wall 202 preferably comprises a thermally non-conductive material, such as, but not limited to plastic. Working fluid reservoir 21 further comprises a first cavity 203 configured to accept thermal container 22. Thermal container 22 comprises a base 204, and a second inner wall 205. Second inner wall 205 extends over the entirety of working fluid reservoir 21, including outer first wall 201 and first inner wall 202, forming an air-tight seal.Second inner wall 205 comprises a thermally conductive material, such as, but not limited to,aluminum, copper, or copper alloy. Other alternative materials will be apparent to those skilled in the art. Thermal container 22 further comprises a second cavity 206 configured to accept a heat sink (not shown) such as an ice pack or ice bath, or may be an object to be heated.

[0032] The space defined by base 200, first outer wall, 201, first inner wall 202, and second outer wall 205 defines an air-tight enclosure and contains working fluid 23. Working fluid 23 comprises acetone, methanol, or other fluid with a boiling point close to a desired target temperature (see Table 1). The gap 207 between inner wall 205 of thermal container 22 and inner wall 202 of working fluid reservoir 21 acts as an insulator between the working fluid and the heat sink. The insulation may be provided by vacuum or partial vacuum insulation, though the space may also contain an inert insulating gas, such as, but not limited to, argon, krypton, or a similar insulating gas, or thermally insulating material, such as, but not limited to, fiberglass.TABLE 1

[0033] The thermal conductivity of canister 20 combined with the efficient thermal transport of working fluid 23 creates a heat flux sufficient to cause vasoconstriction when placed in contact with a glabrous surface. In some embodiments, the exterior of canister 20 may be coated with a material of lower thermal conductivity than canister 20 in order to tune the heat flux of the system. In some embodiments, the exterior material may also be a soft material to increase comfort to the user. The exterior material may be, by way of example, TPU, silicone, rubber, urethane, or a similar material. In some embodiments, a portion of canister 20 not intended to be in contact with the heat source may be coated with an insulating material in order to facilitate thermal transfer to portions of canister 20 that are in contact with the heat source and thereby extend the effective duration of the cooling source and life span of the heat sink.

[0034] In an alternate embodiment, second inner wall 205 may comprise a portion of first inner wall 202 wherein the portion of inner wall 202 that comprises a thermally conductive material resides entirely above the working fluid in liquid form.

[0035] An appropriate working fluid and working pressure is selected prior to assembly based on a target temperature for the device. Such working fluids are well known in the art and may be selected with reference to a working fluid table, such as Table 1, which contains a list of exemplary working fluids, together with boiling points at different pressures. Other criteria for selection of a working fluid may include volatility, regulatory constraints, transport conditions, reactivity with the other materials of the device, or other exogenous factors. During assembly, the enclosure containing working fluid 23 is pressurized to a target pressure. In some embodiments, the amount of pressure to which the working fluid is subject may later be adjusted by a user, such as through a valve or pump. Adjustment of the pressurecauses the boiling point of the working fluid to change. Thus, a target boiling point temperature may be selected by adjusting the pressure that the working fluid is under.

[0036] In certain embodiments, during operation, a heat sink is placed in cavity 206. The heat sink may be at 0 °C, but may be at any temperature below the boiling point of the working fluid. While the heat sink is in contact with inner wall 205 of thermal container 22, heat will be transferred from working fluid 23, through thermal container 22, to the heat sink.

[0037] An exemplary cooling cycle is illustrated in FIG 5. The cooling cycle begins at step 301 when cannister 20 comes into contact with a heat source that is above the boiling point of working fluid 23. At step 302, heat is transferred from the heat source through outer wall 201, causing working fluid 23 to boil. At step 303, boiling of working fluid 23 causes working fluid 23 to change to working fluid vapor. Because the boiling process happens isothermally, working fluid 23 will be converted to working fluid vapor at a constant temperature. The isothermal boiling process lowers the temperature of outer wall 201 towards the boiling point of working fluid 23 and maintains the temperature at the boiling point while working fluid 23 continues to boil.

[0038] At step 304, the working fluid vapor rises up in working fluid reservoir 21 and makes contact with outer wall 205 of insulating layer 22. At step 305, the contact between the working fluid vapor and outer wall 205 causes heat to be transferred from the working fluid vapor to the heat sink, causing the working fluid vapor to condense back into a liquid. Through this convection cycle, cooling unit will continue to operate and maintain a constant temperature until the temperature of the heat sink exceeds the boiling point of the working fluid.

[0039] It will be appreciated that the shape of cannister 20 is not limited to a cylinder and may be a sphere, spheroid, prolate spheroid, torus, or any convex shape. In addition, to ensure that the convection cycle described above takes place in a variety of environments and positions, working fluid reservoir 21 may be permitted to move with respect to outer wall in order to ensure that the working fluid remains at the bottom of the reservoir. Proper orientation may be maintained using a gyroscope or magnet affixed to base 200, or by weighting base 200 to ensure that it remains oriented with working fluid 23 at the bottom of fluid reservoir 21. In another embodiment, a strap, which may be adjustable, is attached to cannister 20, allowing cannister 20 to be carried at a desired orientation. In an alternativeembodiment, a conductive wool, such as steel wool, aluminum wool, or a similar material, may be placed in working fluid reservoir 21. The conductive wool acts to prevent working fluid 23 in liquid form from splashing up while cannister 20 is in motion and making contact with thermally conductive second inner wall 205, while still allowing the working fluid in vapor form to reach second inner wall 205 and condense upon it. As will be readily apparent to one skilled in the art, alternative materials and configurations may be used to prevent working fluid 23 in liquid form from splashing up while cannister 20 is in motion.

[0040] As shown in FIG. 6, in an embodiment, the temperature regulation device as described in this specification may be integrated into a palmar cooling device, or a device that cools another glabrous surface. The device comprises a cavity 203 configured to accept a heat sink as described in this specification, as well as insulation 30. Insulation 30 may be vacuum or partial vacuum insulation, an inert insulating gas, including, but not limited to, argon, krypton, or a similar insulating gas, or thermally insulating material, including, but not limited to, fiberglass. The device further includes heat pipe 31, which contains the working fluid. Heat pipe 31 comprises a thermally conductive material, such as, but not limited to copper, and is in thermal contact with thermal container 22. The working fluid in heat pipe 31 may be under pressure through a vacuum or partial vacuum. Optionally, an interface 32 may be provided that provides a thermal connection between heat pipe 31 and a heat source. It will be appreciated that the shape of heat pipe 31 is not limited to a cylinder and may be any rigid shape configured to hold a working fluid, including, but not limited to an L-shaped pipe, a C-shaped pipe, a bracelet shape, or any other convex shape containing at least two ends.

[0041] An exemplary cooling cycle is illustrated in FIG. 7. To engage isothermal cooling, a heat sink is placed in the cavity of cooling unit 30. The heat sink may be at 0 °C, but may be at any temperature below the boiling point of the working fluid. The cooling cycle begins at step 401 when interface 2 comes into contact with a heat source. The thermal connection between interface 2 and heat pipe 31 causes heat to be transferred from interface 2 through heat pipe 31 to the working fluid within the heat pipe. At step 402, when the heat from the interface 2 is above the boiling point of the working fluid, the working fluid will boil. At step 403, the boiling of the working fluid causes the working fluid to change to working fluid vapor. Because the boiling process happens isothermally, the working fluid will be converted to working fluid vapor at a constant temperature. At step 404, the pressure difference between the heat source and the heat sink attracts the working fluid vapor towards the heat sink and, atstep 405, condense by thermal container 22 and return to liquid form when cooled by the heat sink. At step 406, the working fluid liquid moves back to the heat source through capillary action. The isothermal boiling process lowers the temperature of heat pipe 31 towards the boiling point of the working fluid and maintains the temperature at the boiling point while the working fluid continues to boil. Through this convection cycle, the cooling unit will continue to operate and maintain a constant temperature until the temperature of the heat sink exceeds the boiling point of the working fluid.

[0042] In an embodiment, temperature regulation device 22 may be used to cool a target liquid to a target temperature without the need to put ice in the target liquid or a powered cooling device. As shown in FIG. 8, cannister 20 is removably attached to liquid compartment 40 through a connector 41, such as, but not limited to a slide-on connector, a clip-on connector, or otherwise attachable connector. When cannister 20 is attached to liquid compartment 40, outer wall 201 is placed in thermal communication with liquid compartment 40, which acts as a heat source, thereby allowing for heat transfer to the heat sink within cannister 20. The isothermal temperature regulation process within cannister 20 causes heat to be removed from liquid compartment 40 towards the heat sink within cannister 20, thereby controlling the temperature of any target liquid contained within liquid compartment 40 towards the boiling point of the working fluid.

[0043] It will be readily apparent to those skilled in the art that the cooling mechanisms disclosed in this specification may also be adapted to provide a passive isothermal heating system. To provide isothermal heating, an object to be heated is placed into thermal container 22 and cannister 20 is exposed to a heat source. This causes the system to draw heat out of the heat source into the object in thermal container 22, which becomes warmer.

[0044] The foregoing is for purposes of illustration of the device and its use. It will be readily apparent to those skilled in the art that the devices and methods described in this specification may be modified or substituted in various ways without departing from the spirit and scope of the technology.

Claims

IT IS CLAIMED:

1. A portable temperature regulation device comprising: a working fluid reservoir comprising: a first inner wall; an outer wall; a working fluid disposed between said inner wall and said outer wall; and a first cavity configured to accept a thermal container; and a thermal container disposed in said cavity comprising: a second inner wall extending over the working fluid reservoir; a second cavity configured to accept a heat sink; and a gap between said first inner wall and said second inner wall.

2. The portable temperature regulation device of claim 1, wherein said gap comprises a vacuum.

3. The portable temperature regulation device of claim 1, wherein said gap comprises a partial vacuum.

4. The portable temperature regulation device of claim 1, wherein said gap comprises an inert gas.

5. The portable temperature regulation device of claim 4, wherein said inert gas comprises argon.

6. The portable temperature regulation device of claim 4, wherein said inert gas comprises krypton.

7. The portable temperature regulation device of claim 1, wherein said working fluid comprises acetone.

8. The portable temperature regulation device of claim 1, wherein said working fluid comprises water.

9. The portable temperature regulation device of claim 1, wherein said working fluid comprises ethanol.

10. The portable temperature regulation device of claim 1, wherein said working fluid comprises methanol.

11. The portable temperature regulation device of claim 1, wherein said working fluid comprises ethyl acetate.

12. The portable temperature regulation device of claim 1, wherein said working fluid comprises N-hexane.

13. The portable temperature regulation device of claim 1, wherein said working fluid comprises toluene.

14. The portable temperature regulation device of claim 1, wherein said working fluid comprises methylene chloride.

15. The portable temperature regulation device of claim 1, wherein said thermal container comprises a thermally conductive material.

16. The portable temperature regulation device of claim 15, wherein said thermally conductive material comprises copper.

17. The portable temperature regulation device of claim 15, wherein said thermally conductive material comprises copper alloy.

18. The portable temperature regulation device of claim 15, wherein said thermally conductive material comprises aluminum.

19. The portable temperature regulation device of claim 1, further comprising a strap attached to said outer wall.

20. A method for isothermal heat transfer comprising: providing a portable temperature regulation device comprising: a working fluid reservoir comprising: a first inner wall; an outer wall; a working fluid disposed between said inner wall and said outer wall; and a first cavity configured to accept a thermal container; andan thermal container disposed in said cavity comprising: a second inner wall extending over the working fluid reservoir; a second cavity configured to accept a heat sink; and a gap between said first inner wall and said second inner wall; disposing a heat sink into said second cavity; and exposing said working fluid reservoir to a heat source.

21. The method of claim 20, wherein the isothermal heat transfer comprises isothermal cooling.

22. The method of claim 20, wherein the isothermal heat transfer comprises isothermal heating.

23. The method as in any one of claims 20-22, further comprising adjusting the pressure of said working fluid.

24. The method as in any one of claims 20-22, further comprising adjusting the boiling point of said working fluid.

25. The method of claim 20, wherein said gap comprises a vacuum.

26. The method of claim 20, wherein said gap comprises a partial vacuum.

27. The method of claim 20, wherein said gap comprises an inert gas.

28. The method of claim 27, wherein said inert gas comprises argon.

29. The method of claim 27, wherein said inert gas comprises krypton.

30. The method of claim 20, wherein said working fluid comprises acetone.

31. The method of claim 20, wherein said working fluid comprises water.

32. The method of claim 20, wherein said working fluid comprises ethanol.

33. The method of claim 20, wherein said working fluid comprises methanol.

34. The method of claim 20, wherein said working fluid comprises ethyl acetate.

35. The method of claim 20, wherein said working fluid comprises N-hexane36. The method of claim 20, wherein said working fluid comprises toluene.

37. The method of claim 20, wherein said working fluid comprises methylene chloride.

38. The method of claim 20, wherein said thermal container comprises a thermally conductive material.

39. The method of claim 38, wherein said thermally conductive material comprises copper.

40. The method of claim 38, wherein said thermally conductive material comprises copper alloy.

41. The method of claim 38, wherein said thermally conductive material comprises aluminum.

42. The method of claim 38, wherein said portable temperature regulation device further comprises a strap attached to said outer wall.

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