WO2010107857A1

WO2010107857A1 - Personal cooling system for use under protective clothing

Info

Publication number: WO2010107857A1
Application number: PCT/US2010/027573
Authority: WO
Inventors: Charles A Howland
Original assignee: Warwick Mills, Inc.
Priority date: 2009-03-17
Filing date: 2010-03-17
Publication date: 2010-09-23

Abstract

A personal cooling system evaporatively cools a wearer of protective clothing, thereby avoiding heat stress, skin irritation due to unevaporated sweat, and excess water drinking. A heat-exchanging fluid such as water or ethylene glycol is circulated between a cooling garment worn under the protective clothing and externally worn cooling fabric that is moistened by water from a reservoir. In some embodiments the reservoir also supplies drinking water. The cooling fabric can be fire retardant, and can be a cape, a cylinder through which air is blown by a fan, or part of the protective clothing itself. Embodiments include a protective chemical barrier also moistened by the evaporation water. Under realistic conditions, more than 125 W/m² of heat can be dissipated by a cooling system that weighs less than 6 pounds, has a volume of less than 250 cubic inches, and can operate independently for more than 2 hours.

Description

PERSONAL COOLING SYSTEM FOR USE UNDER PROTECTIVE CLOTHING

Inventor:

Charles A. Howland

RELATED APPLICATIONS

[0001] This application claims priority to U. S . Provisional Application No. 61/160,774, filed March 17, 2009, incorporated herein by reference in its entirety for all purposes. In addition, this application also claims priority to U. S . Provisional Application No. 61/257,570, filed November 3 , 2009, incorporated herein by reference in its entirety for all purposes.

FIELD OF THE INVENTION

[0002] The invention relates to protective clothing, and more particularly to apparatus for cooling and decontaminating a wearer of protective clothing.

BACKGROUND OF THE INVENTION

[0003] Protective clothing of various types is worn by a wide variety of civilian and military personnel when working under conditions where harmful environmental factors are present or can be anticipated. Examples include fire protective clothing worn by fire fighters, chemical protective suits worn by HAZMAT workers, biologically protective clothing worn by communicable disease investigators, and MOPP garments worn by soldiers for protection against chemical and biological weapons.

[0004] While protective clothing can be critical to the safety of workers in hazardous environments, such clothing tends to be poorly ventilated, and can pose a significant overheating risk for the wearer. For example, MOPP 4 garments, which provide protection against dangerous chemical and biological (CB) agents, are made either from impermeable materials or from semi-breathable, heavy, multilayer, organic-absorbent materials. EOD blast suits are not intentionally un- vented, but in practice they are little different from MOPP 4 garments.

[0005] Such protective garments create a humid microclimate against the skin of a wearer that prevents sweat evaporation from occurring, and thus eliminates one of the body's most crucial heat dissipation mechanisms. Under these conditions, heat stress can develop in the wearer, because the ability to maintain an acceptable core body temperature is increasingly compromised. It is well documented that even small increases in core body temperature can have a very detrimental effect on job performance levels. Sustained increases in core body temperature can lead to heat-induced disorders such as fatigue, cramps, dehydration, dizziness, and heat stroke. A mortality rate of up to 40% can be expected from fully developed cases of heat stroke, as defined by a core temperature of 40 ⁰C or more.

[0006] In addition, the buildup of un-evaporated sweat against the wearer's skin can lead to significant discomfort and skin irritation.

[0007] One approach to avoiding heat stress while wearing protective clothing is to use breathable protective clothing that protects by absorption or destruction of harmful chemicals and pathogens, while allowing air and moisture to penetrate, thereby allowing the body's natural cooling mechanism to function. However, the broad spectrum of CB agents that pose threats to military and emergency response personnel makes it difficult to provide comprehensive and dependable protection without providing a sealed barrier, and a sealed barrier necessarily tends to interfere with the body's evaporative cooling.

[0008] Another approach to avoiding heat-related stress and discomfort while wearing protective clothing is to wear a personal cooling system under the protective clothing. One type of personal cooling system known in the art is a fluid-cooled garment that is worn under protective clothing. The skin-facing side of the fluid-cooled garment is attached to a refrigeration system that circulates chilled water, or another cooled fluid, through a series of tubes attached to or embedded within the garment, thereby cooling the wearer. However, because such refrigeration systems are heavy, and consume significant amounts of power, this approach has been mainly limited in practice to tethered applications such as transport vehicles and aircraft.

[0009] The use of sophisticated, compact vapor compressors for the individual soldier has shown some success. However, such systems require a demanding stand-alone power supply, whose sole purpose is to provide the energy needs of the cooling system. Such a power supply is a serious logistical challenge to supply and maintain. In general, for applications where mobility is imperative, such as for soldiers and for emergency response personnel, portability of the cooling unit is a principle consideration. The extent of the unit's portability is determined by its size, weight, level of component integration, and power requirements. Even in advanced refrigeration systems, the compressor and the power supply each weighs over five pounds. These systems are also quite complex and expensive to procure and to maintain.

[0010] So as to further protect a wearer of protective clothing, a chemical agent is sometimes applied to the outer surface of the protective clothing that deactivates pathogens and/or dangerous chemicals. Dry agents are problematic, due to diverse destruction rates and underlying chemical kinetics problems. Wet chemistries are a much more promising approach. However, these chemistries must typically rely on atmospheric moisture to contribute and maintain the needed water content, and since humidity is variable, and low humidity limits reaction rates, these wet chemistry approaches can be unreliable for the destruction of some agents, such as anthrax.

[0011] What is needed, therefore, is a personal cooling system for use under protective clothing that can remove sufficient heat to avoid any substantial increase in a wearer's core and skin temperatures, is sufficiently self-contained, small, and light in weight so as not to significantly impede the mobility of the wearer, can operate independently for more than 2 hours, and is simple in design and therefore easy to supply and maintain. What is further needed is a system that can maintain the moisture content of protective wet chemistry applied to the outer surface of a protective garment when ambient humidity alone is insufficient.

SUMMARY OF THE INVENTION

[0012] A personal cooling system is claimed that cools a wearer of protective clothing by mimicking the human body's evaporative cooling strategy, thereby avoiding the high weight, large volume, and high power consumption of vapor compression cooling systems. The claimed system thereby protects against heat stress while maintaining portability and simplifying logistical support. The present invention also reduces the tendency of the wearer to sweat, thereby reducing drinking water consumption by the user, as well as discomfort and skin irritation due to un-evaporated sweat. In some embodiments, the invention also provides moisture that maintains protective wet chemistry applied to the exterior of protective clothing.

[0013] The claimed personal cooling system includes cooling fabric that is exposed to the ambient environment surrounding the protective clothing and is moistened by water from a portable water reservoir. In some embodiments, the cooling fabric is at least a portion of the protective garment. In other embodiments, the cooling fabric is formed as a cylinder with a fan blowing air through the center of it. In still other embodiments, the cooling fabric is a cooling cape that is worn outside of the protective garment and exposed to the air on both its inner and outer surfaces, In various embodiments, evaporation water is transferred from the reservoir to the cape by wicking action, by gravity feed, and/or by a mechanical or electric pump. In some embodiments, a set of porous hoses controls the dispensing of water into the cooling fabric.

[0014] The cooling fabric includes a network of fluid-cooling tubes at least in thermal contact with the cooling fabric. Water, or another heat-exchanging fluid such as oil or ethylene glycol, is circulated through the fluid-cooling tubes so as to be cooled by evaporation of the evaporation water from the cooling fabric. The fluid-cooling tubes arc in fluid communication with a network of user-cooling tubes which are maintained in thermal contact with skin of the user by a cooling garment worn by the user under the protective clothing. Λs the heat-exchanging fluid passes through the cooling garment, it draws metabolic heat from the user and transports the heat to the cooling fabric, where the heat is dissipated into the environment as the heat-exchanging fluid is cooled in preparation for recirculation to the cooling garment, In various embodiments, the cooling garment includes user-coolin -"-tog tubes at least attached to a hood and/or a vest asscmblv.

[0015] The claimed system further includes a cooling pump configured to circulate cooling water through the fluid-cooling and user-cooling tubes of the cooling fabric and the cooling garment. In this regard, the heat-exchanging fluid and pump function in much the same way as the wearer's blood is moved by the heart through the lungs to the skin and back in normal metabolic thermal management. In various embodiments, the cooling pump is electrically driven by a small battery.

[0016] In certain embodiments, protective wet chemistry is applied to the cooling fabric, and the water content of the wet chemistry is maintained by distribution of the evaporation water onto the cooling fabric.

[0017] In various embodiments, under typical ambient conditions, the personal cooling system of the present invention can remove more than 125 Watts of heat from a wearer of protective clothing, weighs less than 6 pounds, has a volume of less than 250 cubic inches, can operate independently for more than 2 hours, and is simple in design and therefore easy to maintain.

[0018] In some embodiments, the cooling fabric is an evaporative cooling cape made of a flexible material that is worn outside of the protective clothing and moistened by evaporation water from a reservoir carried by the wearer. In some of these embodiments the cooling cape wicks the evaporation water throughout both surfaces of the flexible material, and the physical configuration of the cooling cape maximizes its movement through the air, exposing both surfaces of the cape to the air as the wind blows and/or as the wearer moves about. In other embodiments, the cooling fabric is formed into a hollow cylinder, through which a fan blows a stream of air. In still other embodiments the cooling fabric covers at least a portion of the outer surface of the protective garment.

[0019] In some embodiments, two networks of tubes are attached to and/or embedded within the cooling fabric. One of the tube networks is a "leaky" cape- moistening network that supplies the evaporation water to the cooling fabric for evaporative cooling. The second tube network is a non-leaky cooling network, and is used to circulate the heat-exchanging fluid between the cooling fabric and the cooling garment worn underneath the protective clothing. In some embodiments, a common reservoir supplies potable water both as the evaporation water and as user drinking water. A small pump circulates the heat-exchanging fluid between the cooling cape and the cooling garment. In various embodiments, water is supplied to the cape-moistening network by the same pump, by a separate pump, by gravity, and/or by capillary action. In some embodiments, the cooling fabric is flame resistant and retardant.

[0020] One general aspect of the present invention is a personal cooling system that includes a cooling garment wearable by a user beneath outer clothing and a user-cooling conduit through which a heat-exchanging fluid can be circulated, the user-cooling conduit being at least attached to the cooling garment and configured so as to be maintained in thermal communication with skin of the user when the user wears the cooling garment. The personal cooling system further includes cooling fabric wearable by the user so as to be exposed to air external to the outer clothing, and a fluid-cooling conduit at least in thermal communication with the cooling fabric, the fluid-cooling conduit being in fluid communication with the user-cooling conduit so as to enable the heat-exchanging fluid to circulate therebetween. In addition, the personal cooling system includes a cooling pump configured for circulating the heat-exchanging fluid between the user-cooling conduit and the fluid-cooling conduit, an evaporation water conduit configured for delivering evaporation water to the cooling fabric, so that evaporation thereof cools the heat-exchanging fluid as it passes through the fluid-cooling conduit, and a water reservoir in fluid communication with the evaporation conduit and configured to supply evaporation water thereto.

[0021] In some embodiments, the cooling fabric is at least attached to the outer clothing. In other embodiments the cooling fabric is incorporated into the outer clothing. Iin still other embodiments the cooling fabric is formed substantially into a hollow cylinder that can be worn by the user external to the outer clothing, the personal cooling system further including a fan configured to circulate air through the hollow cylinder. And in yet other embodiments the cooing fabric is a cape that can be worn external to the outer clothing.

[0022] Various embodiments further include a protective chemical barrier applied to the cooling fabric and configured so as to be moistened by the evaporation water when the evaporation water is delivered to the cooling fabric. In some of these embodiments the protective chemical barrier includes an N- halamine compound.

[0023] In certain embodiments the evaporative cooling conduit is an evaporative cooling tube that is configured to distribute water onto the cooling fabric through openings located along a length of the evaporative cooling tube. And in some of these embodiments the evaporative cooling tube is manufactured by extruding an elastomer powder with a limited volume of binder, so as to form water-permeable pores in walls of the evaporative cooling tube.

[0024] In various embodiments the fluid-cooling conduit is interwoven with the user-cooling conduit. In some embodiments the heat-exchanging fluid includes at least one of water, oil, and ethylene glycol.

[0025] In some embodiments the outer clothing includes protective clothing. In certain embodiments the cooling fabric is fire retardant. In some embodiments the cooling fabric includes a hydrophilic fiber which is able to wick the evaporation water throughout the cooling fabric. And in various embodiments the cooling fabric includes at least one of flame retardant meta-aramid hydrophilic fiber and Nomex fiber.

[0026] Certain embodiments further include an evaporation pump configured for distributing the evaporation water onto the cooling fabric. In other embodiments the cooling pump is configured to distribute the evaporation water onto the cooling fabric. In still other embodiments the cooling system is configured to distribute the evaporation water onto the cooling fabric by at least one of gravity and capillary action.

[0027] In various embodiments the water reservoir is configured to supply drinking water to the user as well as evaporation water to the cooling fabric, in some embodiments the personal cooling system weighs less than six pounds. In cetain embodiments the personal cooling system has a total volume of less than 250 cubic inches. And in various embodiments the personal cooling system is capable of independently operating for longer than two hours.

[0028] Another general aspect of the present invention is an evaporatively cooled protective garment system which includes a barrier garment configured to protect a user from contamination by at least one of chemicals and pathogens, and a cooling garment wearable by a user beneath the barrier garment. The system further includes a user-cooling tube through which a heat-exchanging fluid can be circulated, the user-cooling tube being at least attached to the cooling garment so as to be maintained in thermal communication with skin of the user when the user wears the cooling garment. The system also includes cooling fabric wearable by the user substantially outside of the barrier garment so as to be exposed to air external to the barrier garment, and a fluid-cooling tube at least attached to the cooling fabric and in fluid communication with the user-cooling tube so as to enable the heat-exchanging fluid to circulate therebetween. The system further includes a cooling pump configured for circulating the heat-exchanging fluid between the user-cooling tube and the fluid-cooling tube, an evaporative cooling tube configured so as to deliver evaporation water to the cooling fabric, and a water reservoir in fluid communication with the evaporative cooling tube and configured to supply evaporation water thereto.

[0029] The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a front view of a user wearing a cooling garment of the present invention;

[0031] Figure 2 is a transparent side view of the present invention illustrating a user wearing a cooling garment under protective clothing, with a cooling cape, a water reservoir, and a pump attached to the exterior of the protective clothing, the cape being shown in an unrealistic orientation for illustration purposes;

[0032] Figure 3 A is an opaque side view of the embodiment of Figure 2, the cape being shown in a realistic orientation;

[0033] Figure 3B is an opaque rear view of the embodiment of Figure 3 A;

[0034] Figure 3C is an opaque side view of an embodiment similar to Figure 3A, but including a cooling cylinder instead of a cooling cape;

[0035] Figure 3D is an opaque rear view of the embodiment of Figure 3C;

[0036] Figure 3E is a top view of the cooling cylinder of the embodiment of Figure 3C; [0037] Figure 4 is a functional side illustration of a cape embodiment that includes separate cooling water and heat-exchanging fluid reservoirs, wherein the illustration includes an expanded view of a section of the cape; and

[0038] Figure 5 is a diagram of a typical N-halamine compound applied to a surface of a cooling fabric in an embodiment of the present invention.

DETAILED DESCRIPTION

[0039] The present invention is a personal cooling system for cooling a wearer of protective clothing. The personal cooling system includes a cooling garment worn under the protective clothing, wherein the cooling garment removes heat from the wearer, and cooling fabric exposed to ambient air outside of the protective clothing, wherein the heat from the wearer is dissipated by evaporative cooling of the cooling fabric.

[0040] Figure 1 illustrates a user 100 wearing a cooling garment 102 included in an embodiment of the invention. The cooling garment 102 is worn under the protective clothing at least in thermal contact with the user 100, and in some embodiments in physical contact with the skin of the user. The skin of the user is cooled by circulation of a heat-exchanging fluid through a network of tubes 104 at least attached to the cooling garment 102. In various embodiments, the heat- exchanging fluid is water, ethylene glycol, oil, or a mixture thereof. In the embodiment of Figure 1 , the cooling garment 102 covers the shoulders, arms, chest, and head of the user 100. In other embodiments, the cooling garment covers only the head and chest, while in still other embodiments the cooling garment covers the legs of the user 100 as well as the head and chest.

[0041] Figure 2 is a transparent side view of a complete embodiment of the present invention. Protective clothing 200 is worn by the user 100 over the cooling garment 102. The protective clothing 200 is penetrated by tubes 206 that supply the heat-exchanging fluid to the cooling garment. In the embodiment of Figure 2, cooling fabric 202 is attached to the rear of the protective clothing 200 in the neck region, but is otherwise separate from the protective garment 200. In other embodiments, the cooling fabric 202 covers at least a part of the outer surface of the protective garment 200, and in some of these embodiments the cooling fabric 202 is incorporated into the outer layer of the protective garment 200. Note that the cooling fabric 202 in Figure 2 is shown detached from the protective garment 200 and rotated at an unrealistic angle so as to better show its structure and function. The cooling fabric 202 is illustrated in operative configurations in Figures 3A and 3B as a cooling "cape," and in Figure 3C and 3D as a cooling cylinder, as discussed in more detail below.

[0042] The cooling fabric 202 of Figure 2 includes a flexible fabric 203 at least attached to two networks of tubing 204, 206. One of the networks of tubing 204 is a "leaky" cape-moistening network that supplies evaporation water to the flexible fabric 203 in a manner similar to that used for drip irrigation. The evaporation water is pumped by a small pump 208 from an evaporation water reservoir 210, which in this embodiment is carried outside of the protective clothing on the back of the user 100. In similar embodiments, the evaporation water reservoir 210 is carried inside of the protective clothing 200. In still other embodiments, the evaporation water flows by gravity and/or by capillary action onto the flexible fabric 203. In the embodiment of Figure 2, the evaporation water is potable water that can also be consumed by the user 100 through a drinking tube 212.

[0043] In various embodiments, the cape-moistening tubes 204 are manufactured by extruding an elastomer powder with a limited volume of binder. The result is a tube that is mechanically solid, but has many small pores in its walls, resulting in a "leaky" tube. The flexible fabric 203 in the embodiment of Figure 2 contains a hydrophilic fiber which wicks the evaporation water throughout the cooling fabric 202 so as to keep both of its surfaces moistened.

[0044] With reference to figures 3A and 3B, in some embodiments the physical configuration of the cooling fabric 202 is a cooling cape 202 that maximizes its movement through the air, convectively exposing both surfaces of the cooling cape 202 to the air as the wind blows and/or as the wearer moves about. With reference to Figures 3C and 3D, in other embodiments the cooling fabric 202 is contained within a cooling cylinder 300 that includes a cooling fan 301 configured to blow air 302 through the cooling cylinder 300 and past the surface of the cooling fabric 202. In still other embodiments the cooling fabric 202 covers or is incorporated in at least a portion of the outer surface of the protective clothing 200.

[0045] In some embodiments, the flexible material 203 is a flame retardant meta-aramid hydrophilic fiber, such as Nomex fiber type 430, which has a good combination of intrinsic flame retardant properties and good wicking behavior.

[0046] Referring again to Figure 2, the other network of tubes 206 that is at least attached to the flexible fabric 203 is not leaky. It carries a heat-exchanging fluid such as water, oil, ethylene glycol, or a mixture thereof, that is circulated by a pump between the cooling fabric 202 and the cooling garment 102. In the embodiment of Figure 2, the same pump 208 is used to circulate both the evaporative cooling water and the heat-exchanging fluid. In other embodiments, the evaporative cooling water is supplied to the cooling fabric 202 by gravity and/or by capillary action. In certain embodiments, water from the reservoir 210 is used to supply both evaporation water and heat-exchanging water.

[0047] Figures 3A and 3B are opaque side and rear views respectively of an embodiment wherein the cooling fabric 202 is a cooling cape 202, which is shown in its operating configuration. Figures 3C and 3D are opaque side and rear views respectively of an embodiment wherein the cooling fabric 202 is contained within a hollow cooling cylinder 300 through which air 302 is blown by a cooling fan 301 , the embodiment being shown in its operating configuration. Figure 3E is a top view of the cooling cylinder 300 of Figures 3C and 3D, showing the cooling fabric 202 wrapped within the cylinder 300 and exposed to the hollow interior of the cylinder 300. The fan 301 is positioned to blow air 302 down the center of the hollow cylinder 300, thereby evaporating water deposited onto the flexible fabric 203 by the "leaky" cape-moistening tubes 204, which in this embodiment run vertically around the outer circumference of the flexible fabric 203. The heat exchanging fluid flows through heat-exchanging tubes 206 that are circumferentially coiled in this embodiment near the inner circumference of the flexible fabric 203. In the embodiment of Figures 3C through 3E, the water reservoir 210 is carried inside of the protective clothing 200.

[0048] Figure 4 is a functional illustration of an embodiment that includes a cooling cape 202, a cooling reservoir 400 which is distinct from the evaporation water reservoir 210, and a fluid pump 402 which is distinct from the evaporation water pump 208. An expanded detail 404 of a portion of the cooling fabric 202 is included in the figure, where it can be seen that the heat-exchanging fluid tubes 206 in this embodiment are interwoven and in close thermal contact with the evaporation water tubes 204. The heat-exchanging fluid tubes 206 and the evaporation water tubes 204 are at least attached to the flexible fabric 203. In various embodiments, the flexible fabric 203 includes a hydrophilic wicking fiber, and is fire retardant. In some embodiments the flexible fabric 203 is a meta- aramid such as Nomex fiber type 430. The evaporation water tubes 204 include hollow centers 406 with leaky walls through which the evaporation water flows onto the flexible fabric 203. In some embodiments, the inner diameter of the hollow center 406 is equal to or less than 1/16 inch. As the evaporation water 408 leaks out of the center tubes 406, it moistens a layer of absorbent material 410 that surrounds the tubes 406 and provides a high evaporation surface area. In some embodiments, the absorbent material 410 is made from woven Nomex.

[0049] In various embodiments, a protective wet chemistry is applied to the outer surface of the cooling fabric 202, and is maintained in a wet state by the evaporation water that is also used for cooling. It has been shown that both moisture and temperature contribute to the destruction, or inactivation, of pathogens such as anthrax spores. Reagents distributed with aqueous solutions provide multiple advantages over dry chemistry to defeat chemical and biological ("CB") threats, particularly when dealing with spore-form agents such as anthrax. Anthrax spores are extremely resilient, and require extended exposure to reagents for successful destruction. However, when exposed to moisture and a vegetative enzyme, the spores rapidly germinate, which makes them vulnerable to chemical destruction. The cooling fabric 202 of the present invention provides an ideal environment for destruction of CB threats using wet chemistry, since the cooling fabric 202 is kept moistened by the evaporation water, and is warmed by the heat- exchanging fluid, and ultimately by the body heat of the wearer.

[0050] In some embodiments, N-halamine compounds are applied to the cooling fabric 202 as protective wet chemistry. A typical N-halamine compound 500 is illustrated in Figure 5. N-halamine compounds have a unique molecular structure that binds chlorine to treated surfaces so as to provide extended, robust antimicrobial properties. A key feature for this chemistry is that the N-halamine molecule 500 can easily be recharged with chlorine in the field simply with a dilute solution of household bleach (sodium hypochlorite). N-halamine compounds are known to be effective in aqueous systems against mustard (HD) and carbamate pesticides. In some embodiments, chlorine is included in the evaporation water, so as to maintain the activation of an N-halamine compound applied to the cooling fabric 202.

[0051] In various embodiments, under realistic operating conditions, the present invention can remove more than 150 Watts of heat per square meter of cooling fabric 202 from a wearer 100 of protective clothing 200, and in some embodiments the cooling fabric 202 can remove up to 300 Watts of heat per square meter. Certain embodiments weigh less than 6 pounds, have a volume of less than 250 cubic inches, can operate independently for more than 2 hours, and are simple in design and therefore easy to maintain. Various embodiments circulate the heat-exchanging fluid at a circulation rate of 20 cπr/min through flexible tubing 206 having an inner diameter of 1/16 inch.

[0052] Like all cooling processes, the present invention is affected by ambient conditions. Because the present invention cools by evaporation, the "wet bulb" temperature is the most important ambient condition, since the wet bulb temperature is the minimum temperature that can be reached by evaporative cooling at a given ambient temperature and humidity, and is substantially the temperature that can be reached at the cooling surface of the cooling fabric 202.

[0053] Table 1 summarizes "worst case" ambient and wet bulb temperatures applicable to desert environments in which the US military is currently active. Also presented is a result under more "typical" conditions as might be encountered in parts of the United States, for example by a fire fighter. As can be seen in the table, even under the worst case conditions there is a differential of at least 18 ⁰F between the ambient temperature and the web bulb temperature, the differential being more than sufficient to achieve a target cooled skin temperature of 85 ⁰F. Even under the more "typical" conditions of 95 ⁰F and a non-desert humidity level of 44 %, there is a differential of 14 ⁰F that is sufficient to achieve a cooled skin temperature below 85 ⁰F.

Table 1

[0054] By cooling the user 100, the present invention also reduces the tendency of the user 100 to sweat, thereby reducing discomfort and skin irritation due to un- evaporated sweat. This approach is supported by the Army technical literature. The paper by Sawka, M.& Wenger, B. (US Army, Natick Lab, Physiological Responses to Acute Exercise-Heat Stress, 1988, herein incorporated in its entirety for all purposes), reviews in detail the regulatory mechanisms for sweating behavior. They point out that both skin temperature and core temperature affect the sweating response. If the cooling garment 102 is maintained at a temperature no greater than 85 ⁰F, the skin response triggers for sweating are typically avoided. In the same way, if the overall metabolic heat output from the user 100 is managed and the user's core temperatures does not rise, then the triggers for sweating should be avoided.

[0055] In various embodiments, between 3 and 3.5 pounds of water are required for 2 hours of cooling, and the total mass of the cooling tube assemblies, the pump, and the battery, is between 1.5 and 2 pounds. These weights combine to give an overall system weight of from 5 to 5.5 pounds. However, because evaporative cooling water can be supplied from the same reservoir as potable drinking water, and because cooling of the user 100 reduces the need for the user 100 to drink water, the net increase in water consumption due to the invention is actually much less than 3.5 pounds in two hours, thereby reducing the effective weight of the invention to much less than 5.5 pounds. [0056] The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.

Claims

CLAIMSWhat is claimed is:

1. A personal cooling system, comprising: a cooling garment wearable by a user beneath outer clothing; a user-cooling conduit through which a heat-exchanging fluid can be circulated, the user-cooling conduit being at least attached to the cooling garment and configured so as to be maintained in thermal communication with skin of the user when the user wears the cooling garment; cooling fabric wearable by the user so as to be exposed to air external to the outer clothing; a fluid-cooling conduit at least in thermal communication with the cooling fabric, the fluid-cooling conduit being in fluid communication with the user- cooling conduit so as to enable the heat-exchanging fluid to circulate therebetween; a cooling pump configured for circulating the heat-exchanging fluid between the user-cooling conduit and the fluid-cooling conduit; an evaporation water conduit configured for delivering evaporation water to the cooling fabric, so that evaporation thereof cools the heat-exchanging fluid as it passes through the fluid-cooling conduit ; and a water reservoir in fluid communication with the evaporation conduit and configured to supply evaporation water thereto.

2. The personal cooling system of claim 1 , wherein the cooling fabric is at least attached to the outer clothing.

3. The personal cooling system of claim 1 , wherein the cooling fabric is incorporated into the outer clothing.

4. The personal cooling system of claim 1 , wherein the cooling fabric is formed substantially into a hollow cylinder that can be worn by the user external to the outer clothing, the personal cooling system further including a fan configured to circulate air through the hollow cylinder.

5. The personal cooling system of claim 1 , wherein the cooing fabric is a cape that can be worn external to the outer clothing.

6. The personal cooling system of claim 1 , further comprising a protective chemical barrier applied to the cooling fabric and configured so as to be moistened by the evaporation water when the evaporation water is delivered to the cooling fabric.

7. The personal cooling system of claim 6, wherein the protective chemical barrier includes an N-halamine compound.

8. The personal cooling system of claim 1 , wherein the evaporative cooling conduit is an evaporative cooling tube that is configured to distribute water onto the cooling fabric through openings located along a length of the evaporative cooling tube.

9. The personal cooling system of claim 8, wherein the evaporative cooling tube is manufactured by extruding an elastomer powder with a limited volume of binder, so as to form water-permeable pores in walls of the evaporative cooling tube.

10. The personal cooling system of claim 1 , wherein the fluid-cooling conduit is interwoven with the user-cooling conduit.

11. The personal cooing system of claim 1 , wherein the heat-exchanging fluid includes at least one of water, oil, and ethylene glycol.

12. The personal cooling system of claim 1 , wherein the outer clothing includes protective clothing.

13. The personal cooling system of claim 1 , wherein the cooling fabric is fire retardant.

14. The personal cooling system of claim 1 , wherein the cooling fabric includes a hydrophilic fiber which is able to wick the evaporation water throughout the cooling fabric.

15. The personal cooling system of claim 1 , wherein the cooling fabric includes at least one of flame retardant meta-aramid hydrophilic fiber and Nomex fiber.

16. The personal cooling system of claim 1 , further comprising an evaporation pump configured for distributing the evaporation water onto the cooling fabric.

17. The personal cooling system of claim 1 , wherein the cooling pump is configured to distribute the evaporation water onto the cooling fabric.

18. The personal cooling system of claim 1 , wherein the cooling system is configured to distribute the evaporation water onto the cooling fabric by at least one of gravity and capillary action.

19. The personal cooling system of claim 1 , wherein the water reservoir is configured to supply drinking water to the user as well as evaporation water to the cooling fabric.

20. The personal cooling system of claim 1 , wherein the personal cooling system weighs less than six pounds.

21. The personal cooling system of claim 1 , wherein the personal cooling system has a total volume of less than 250 cubic inches.

22. The personal cooling system of claim 1 , wherein the personal cooling system is capable of independently operating for longer than two hours.

23. An evaporatively cooled protective garment system, comprising: a barrier garment configured to protect a user from contamination by at least one of chemicals and pathogens; a cooling garment wearable by a user beneath the barrier garment; a user-cooling tube through which a heat-exchanging fluid can be circulated, the user-cooling tube being at least attached to the cooling garment so as to be maintained in thermal communication with skin of the user when the user wears the cooling garment; cooling fabric wearable by the user substantially outside of the barrier garment so as to be exposed to air external to the barrier garment; a fluid-cooling tube at least attached to the cooling fabric and in fluid communication with the user-cooling tube so as to enable the heat-exchanging fluid to circulate therebetween; a cooling pump configured for circulating the heat-exchanging fluid between the user-cooling tube and the fluid-cooling tube; an evaporative cooling tube configured so as to deliver evaporation water to the cooling fabric; and a water reservoir in fluid communication with the evaporative cooling tube and configured to supply evaporation water thereto.