Patent Application
20100319381
The present invention relates generally to a body suit cooling system. More specifically, it relates to a body suit cooling system having an evaporative cooling system that utilizes a free air approach to remove body heat from a person.
A coolant fluid such as water has an advantage of high volume heat capacity and much higher thermal conductivity compared to air. The heat exchange coefficient for liquid such as water is orders of magnitude higher than for air, resulting in the possibility for compact and energy efficient cooling systems. It is difficult to use the human body's evaporative cooling system when a person is wearing multiple layers of clothing. Thus, the evaporative process should occur outside of the person's body suit and water should be supplied from an outside source. Since it takes only about ten milliwatts of power to provide an air flow in an open space, a free air evaporative system can have improved efficiency.
An example of an existing cooling system is provided by Med-Eng Systems Inc. of Ottawa, Canada. A sample water flow rate for the system would be 50 g/s (about 50 Gph). A water storage bottle would be positioned such that supplying the water volume against the force of gravity would require approximately 0.5 W (watts) of power. If the water pump efficiency is 50 percent, it means that about 1 W of power is lost. Furthermore, existing cooling systems are formed of a large number of capillary tubes, which collect heat from a large body area. This results in large power losses due to the viscose friction in small tubes and very complex and expensive tube connections. Instead of less than one watt of electric power to push the water volume through the tubes with small viscose losses, the system uses much more power.
The cooling system typically uses ice to cool the vest. In addition to the logistical problems of this approach, the heat of fusion of water is 6.013 kJ/mole. Heating water from 0° C. to 30° C., adds another 2.257 kJ/mole, resulting in a total heat adsorbing capacity of 8.27 kJ/mole or 459 kJ/l. In comparison, water heat of evaporation is 40.683 kJ/mole or 2260 kJ/l for evaporative cooling. Thus, approximately three hours of cooling at 200 watts of heat release by a human body can be supplied by one liter of water. Temperature differences in an evaporative cooling system depend on ambient air temperature and humidity. For example, in a dry climate, a standard rooftop evaporative cooler can result in 20-25 K temperature differences. For a closed looped evaporative cooler 6-7° C. temperature can be achieved unless humidity approaches 100 percent.
Latent heat of vaporization is an amount of energy released or absorbed by a chemical substance, such as water, during a phase transition such as between a liquid phase to a gaseous phase. In the process of evaporative cooling, the conversion of a substance from a liquid state to a gaseous state causes a decrease in temperature of the remaining liquid. For example, air is blown over water, which causes the liquid water's surface molecules to evaporate to water vapor. This liquid-to-vapor phase transition requires an input of energy to overcome molecular forces of attraction between water molecules; this necessary energy input results in a temperature drop at the water's surface.
Perspiration is the human body's natural mechanism to keep cool; however, the removal of excess heat depends on the perspired fluid's contact with air. In certain environments, persons wear attire which traps the perspired fluid in a gap formed between the garment and the skin. Heat stress becomes a concern for these persons wearing work suits, especially impermeable suits, in hot climates. Examples of such persons include military servicemen in combat, clean-up crews at toxic spill sites, health workers in quarantined outbreak sites, etc. Existing self-contained evaporative cooler systems were designed for these applications to maintain the person's body at healthy and safe temperatures.
Existing evaporative cooling systems depend on an external power source to draw air towards and blow air flow over the cooling media. Air must move into contact with the liquid to affect the cooling process. A problem with existing self-contained evaporative cooling systems is a reliance on a thin gap air approach, i.e., existing systems utilize schemes which direct air flow into a thin gap formed between the person's body to be cooled and the suit the person is wearing. The relatively short clearance (referred to as a “gap”) between the body and the suit requires an especially powerful, external blower to push air into the gap. As a result, this method requires a high consumption of energy.
Accordingly, there is a need for a body suit cooling system which overcomes the above-mentioned deficiencies and others in existing systems. The present disclosure utilizes a free air approach, wherein an external power device, such as a fan, moves air into a free atmosphere space adjacent the suit while requiring less energy.
The present disclosure is directed towards a body cooling system for utilization with a protective suit worn by a person. The body cooling system includes an evaporative cooling apparatus and a cooperative air flow source, both of which are situated external to the protective suit. The air flow source, which is a mechanical fan or blower, produces a flow of air and blows it in free atmosphere towards the cooling apparatus. An undersuit, situated between an innermost layer of the protective suit and the wearer's skin, includes at least one conduit formed thereon. A volume of fluid flows from a reservoir in the evaporative cooling apparatus to the conduit, and is circulated through the conduit by a pump, wherein heat from the body is transferred into the fluid. The fluid flows through the conduit to the evaporative cooling apparatus, wherein the heated fluid evaporates upon contact with the air current.
The undersuit includes both a heat conducting envelope, surrounding an outer surface of the conduit, and a heat conducting cloth layer, situated closest to the skin, to aid in a transfer of heat from the wearer's body to the fluid flowing in the conduit. The undersuit preferably includes a copper envelope surrounding the conduit and a copper cloth layer. A thin layer of biologically inert material can be situated between the copper cloth layer and the skin to prevent any irritative and abrasive contact between the copper cloth layer and the skin.
The apparatus utilizes an evaporative cooling process. Specifically, the apparatus includes a radiator body having at least two elongate, finger-like projections extending upwardly therefrom. The finger-like projections are oriented substantially in parallel across the same plane, which is transverse to a direction of an air flow path forced from the air flow source. A fluid channel extends along an internal length of the evaporative cooling apparatus and connects to the conduit. The fluid channel provides for egress of the heated fluid carried away from the undersuit. The fluid leaving the channel is directed toward the finger-like elongate projections by a wicking material. The air flow contacts the wicking material enveloping both the finger-like projections and the crevices formed therebetween, which aids in the evaporation.
The present disclosure aims to reduce or minimize a risk of heat stress, i.e., heat stroke, heat exhaustion, cramps, rashes, and dizziness, etc., in workers exposed to extreme heat and arid environments. More specifically, the disclosure minimizes or prevents symptoms of heat stress in workers covered in partial or full body suits, which have a tendency to generally trap perspiration in the area between the suit material and the person's skin.
Other aspects of the disclosure will become apparent upon a reading of the following detailed description.
The present disclosure is directed to a body suit cooling system. Specifically, it is directed to a self-contained system worn by a person to maintain body temperature at healthy levels.
For purposes of this disclosure, the terms “body armor” and “suit” (hereinafter collectively referred to as “suit” or “protective suit”) refer to any protective clothing worn by a person. The present disclosure is particularly useful when used in conjunction with military suits and other armor worn by soldiers in combat; however, its use is not strictly limited to garments worn by servicemen. The term “suit” can similarly refer to explosive ordinance disposal (EOD) suits. The term “suit” can further include environmental suits designed for particular hostile environments. These suits can include any material which protects the wearer from certain temperatures, climates, or pressures. The term “suit” can also refer to a contamination or a hazardous material (“hazmat”) suit, which protects its wearer from hazardous materials or substances. The term “suit” can further refer to demron suits, which include radiation-blocking fabric that shield its wearer from radiation. The term “suit” can further include any protective clothing made from materials that block chemical and biological threats to the wearer.
The term “portion suit” refers herein to any material which covers any portion of a human body or an entire body. Portion suits can include tactical vests, boots, pants, or any other tactical gear that covers only a designated body region. Entire suits include one-piece outfits that cover all body regions.
For purposes of this disclosure, the term “suit” or “undersuit” can refer to a layer of material situated between the protective suit and the person's skin. The protective suit is oftentimes gas or vapor tight. As a result, it thwarts a body's natural cooling process by trapping sweat or perspiration between the impermeable material layers and the skin. The undersuit acts as an additional layer of a heat spreading material made either part of or separate from a protective suit.
For purposes of this disclosure, the term “cooling system” refers to a system which utilizes an evaporative cooling process. Evaporative cooling processes rely on both an evaporative fluid and moving air. Air must come into direct contact with the fluid so that some of the fluid's molecules can mix with the air. The air removes heat from the fluid during evaporation, which results in cooling of the fluid.
Referring now to
The undersuit 12 is at least one layer of material having a body-conforming characteristic. It is designed to be worn adjacent to the person's skin. In the present disclosure, the undersuit 12 is a separate garment worn beneath the innermost layer of a protective suit 26. That is, the person puts on the undersuit first, then wears the protective suit over it. The undersuit 12 can also be removably attached to the protective suit at attachment points so that its position remains fairly constant relative to the evaporative cooler apparatus. It is alternatively contemplated that the undersuit 12 is made as part of the protective suit, i.e., the undersuit would actually form the protective suit's innermost layer.
The undersuit 12 shown in
Referring now to
The conduit or tubes (hereinafter collectively referred to as “conduit 18”) of the conduit system are preferably manufactured from a thermoplastic material. The heat exchange coefficient, used to measure heat transfer, is dependent on flux, i.e., the amount of fluid that flows through a unit area per a unit of time. Because plastic has a low thermal activity which does not allow for spreading of heat current, an outer surface of the conduit 18 is surrounded by a heat-conducting cloth envelope 22.
The conduit 18 is in direct thermal contact with a heat conducting cloth layer 20. Heat transfers through various metals at different rates, but it transfers most rapidly through copper; hence, in the preferred embodiment, both the cloth layer 20 and an envelope 22 are formed of copper. Other embodiments are contemplated, however, which utilize different metals. Either one or both the cloth layer 20 or the envelope 22 can be formed of aluminum, silver, brass, or any other material with a high thermal conductivity, so long as the metal selected both effectively transfers heat and prevents or minimizes risks to the wearer.
Spacing between surface portions of conduit 18 is also dependent on the metal selected for the cloth layer and the envelope. Because copper transfers heat most expeditiously, a cloth layer 20 made of copper and envelope 22 made of copper provide for an increase in the spacing between outer surfaces of conduit 18. Spacing, as used herein, refers to the distance between opposing outer surfaces of neighboring or adjacent lengths of conduit portions. It is envisioned that portions of the conduit 18 of the cooling system 10 are spaced about 5-10 centimeters from each other.
A further advantage provided by copper cloth layer 20 and copper envelope or mesh 22 is a decrease in the viscous surface friction area of the conduit. That is, the heat conducting cloth layer and envelope allow for the tubes of conduit 18 to have an enlarged diameter. It is envisioned that a cross-sectional area of the tubes of conduit 18 is at least twice as great as that of corresponding conduits in existing cooling systems. The diameter of the conduit 18 of the present disclosure is between 6-8 millimeters as compared to 2-3 millimeters in existing systems. The advantage of an enlarged diameter of the tubes of the conduit is that it has the effect of reducing flow resistance of the conduit, and fewer tubes are required than if the tubes had a smaller diameter.
Because heat transfers from the person's body to the fluid flowing within the conduit 18, the copper cloth layer 20 is situated closest to a person's skin 24 and farthest from the protective suit 26. The copper cloth layer 20 includes an inner surface 21, adjacent the conduit 18 and the envelope 22, and an opposite, outer surface 23, adjacent the skin 24. The outer surface 23 is coated with a thin layer of biologically inert material 28. Layer 28 is in direct contact with the person's skin 24, and its function is to prevent or minimize any irritative or abrasive contact between the copper cloth layer 20 and the skin. The disclosure contemplates that the thin layer of biologically inert material 28 is selected from a group including, but not limited to, for example, Capron, Nylon, and cotton, etc.
Body heat transfers to the fluid flowing within the conduit 18. A terminal end of the conduit 18 is separate from the copper cloth layer 20 for delivery of outgoing fluid to the evaporative cooling apparatus 14.
Referring now to
The preferred embodiment of the present disclosure includes a metal-formed radiator body 32, preferably formed of aluminum, including a plurality of surface fluid channels 36 extending along its internal length transverse to the fingers 34. A first end 37 of the fluid channel 36 connects to a first terminal or distal end 39 of the conduit 18 contained in the undersuit 12, while a second opposite end 41 of the channel connects to an opposing terminal or distal end 43 of the conduit. At least one nozzle 38 formed in the fluid channel 36 provides for egress of fluids carried away from the undersuit 12. Placement of the nozzle 38 is preferably on the fluid channel's surface 45 closest to the fingers 34. In other words, the nozzle 38 is preferably oriented such that all fluid moving through the nozzle is directed toward the fingers 34 and away from the undersuit.
An outer surface 47 of each finger 34 and crevices or recesses 40 formed between adjacent fingers are coated with a wicking material 42. The wicking material 42 can be selected from a group including but not limited to melamine, a thin porous cloth such as cotton or another porous coating, chalk, porous ceramics, etc. A polyurea coating is one such wicking material 42 utilized in the preferred embodiment. The wick material 42 is fluid wetted, i.e., it absorbs fluid and moisture delivered thereto from the channel 36. The fluid is transformed to a gaseous state, i.e., it evaporates, when the air flow contacts the fluid.
An advantage of the evaporative cooler 14 is that it greatly reduces electric power requirements to drive the air flow source 16 due to the use of the fingers 34. Efficacy of cooling is determined by both the area of the wet surface and the aridity of air contacting it. The fingers 34 increase the surface area of wick material 42 exposed to the moving air current. The fingers 34 also avoid saturation of the air with vapor from the wick. An air parcel can only contain a certain amount of moisture before it can no longer accommodate gaseous molecules. The fingers 34 create spaces between the fingers, which each act as small air parcels capable of containing a greater amount of gaseous molecules evaporated from the fluid contained in the wicking material 42.
The present cooling system 10 further includes a means 16 to force air current. Referring to
The blower 16 does not require a direct communicative relationship with the undersuit 12 and the evaporative cooler 14; rather, it can be a separately contained apparatus operated by the same or independent controls. Existing evaporative cooling systems, which utilize the free gap approach, consume great amounts of power to force air currents through the gaps. The free air flow approach of the present disclosure reduces electric power requirements as much as 5-to-10 times that compared to existing systems. It takes only about ten milliwatts of power to provide sufficient air flow to open space, so the free air flow approach makes the present system much more energy efficient than existing cooling systems.
It is contemplated that any self-contained solar or battery power source can also be utilized to push fluid volume through the conduit 18 and to drive the fan for production of air current. In the present disclosure, this fluid is preferably water, which transforms to water vapor upon contact with air; however, the evaporative cooling system 10 is not limited to only water; rather, any fluid which absorbs heat readily and releases it in atmospheric air can be similarly used in the system.
Referring to
Essentially, the fluid or water circulates in a circuit, i.e., in the closed loop formed by the conduit 18, the supply bottle 48 and pump 17. During each circulation, some fluid in the conduit 18 loop leaks out to the wicking material 42. In certain embodiments, a valve (not shown) in association with corresponding nozzles 38 can control release of the fluid from the conduit 18 to the fingers 34. More specifically, a one-way valve can regulate egress of fluid from the conduit, but it can prevent any return of that fluid (elevated in temperature) not immediately evaporated into the conduit.
Referring again to
The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
