Patent Publication Number: US-2021180920-A1

Title: Liquid cooled body armor

Description:
FIELD OF THE INVENTION 
     The present invention relates to liquid cooled body armor system. More specifically, it relates to a body armor comprising flexible metallic heat exchangers that allow for a cooling fluid to be circulated through it. 
     BACKGROUND OF THE INVENTION 
     Liquid cooled garments have been used to regulate the temperature of the body, dating back to the 1950s and their first uses in space to regulate the body-temperatures of astronauts inside of space suits. The operating principle of liquid-cooled-garments (LCGs) is that cooled fluid is circulated around the body through a network of thin flexible polymer tubes, which are tightly pressed against the skin. The physical contact of these tubes against the skin leads to a conductive heat transfer to the tube, and the fluid carries away the heat through a convective heat transfer with the inside walls of the tube. Thus, heat is removed from the body and the person wearing it stays cool. 
     The approach of using polymer tubes for heat transfer from the cooling fluid to the skin allows for good comfort to the wearer, as the tubes are typically made from flexible plastic or rubber and can move and stretch along with the body while the wearer is in motion. However, the thermal conductivity of flexible plastics and rubbers is low. This low thermal conductivity of the tube wall acts as an insulator, and requires a high temperature difference between the heat transfer fluid inside the tube and the skin, in order to transfer heat. For reference, nominal body temperature is approximately 37 degrees Celsius, and the water temperature inside a liquid-cooled-garment must typically be provided in a range of 15 to 20 degrees Celsius for the wearer to feel cool. Supplying cold water is not a problem in space applications, but for portable terrestrial applications where the water chilling apparatus must be carried by the user, the task of supplying cold water in high ambient temperature conditions becomes difficult: the water chilling apparatus is larger, heavier, and more power-consuming to provide colder water in high-ambient-temperature conditions. Improving the heat transfer from the body to the cooling fluid reduces the need for such cold water, therefore reducing power consumption and making the cold-water-supply apparatus smaller and lighter. 
     The ideal heat exchanger for skin-to-fluid heat transfer has high thermal conductivity and is also flexible. The polymer tubes typically used in liquid-cooled garments have a thermal conductivity ranging from 0.1 to 0.3 watts per meter Kelvin. Research has been done on improving the thermal conductivity of flexible polymers, with the best commercially available thermally conductive polymers achieving thermal conductivities of up to 3 watts per meter Kelvin. Metals have far better thermal conductivity than polymers; for reference, aluminum has a thermal conductivity of 205 W/mK and copper is at 401 W/mK. Copper has over 1,000 times better thermal conductivity than commonly used tubing in liquid cooled garments, and more than  100  times better conductivity than the current state-of-the-art polymers. 
     The challenge with using metals, such as copper, in liquid-cooled garments, is that metals are far less flexible than polymers and this lack of flexibility causes discomfort for the wearer while moving about. If it is possible to create a flexible heat exchanger that conforms to the shape of the body while still allowing fluid to pass through it, the numerous benefits of having a better heat transfer coefficient could be realized. This flexibility also allows it to assume the shape of the body armor that is worn on top of it. 
     Most importantly, better heat transfer allows for a lower total temperature difference between the cold-side and the hot-side of the refrigeration system that provides the cooling fluid which is pumped through the liquid-cooled garment. This lower total temperature difference improves the coefficient of performance of the refrigeration system, leading to a smaller, lighter, cold water supply system that also consumes less power, which also leads to a lighter energy storage system to run it. 
     Further, the applications of liquid-cooled garments are endless; however one of the most important domains of application is defense. The bullet proof or bullet resistant vests always were heavy and cumbersome, until a breakthrough fiber poly-p-Phenylene-terephthalate and polybenzamide were discovered. Such fibers are preferred as it provides high strength and low weight with extra protection from cuts, scrapes, or burns. Moreover, its application in personal protective equipments has increased high tensile modulus and low breakage elongation combined with very good resistance to chemicals making it the right choice for different composite structural parts in various applications. However, a major drawback of these fibers is that the fibers tend to absorb moisture; hence moisture resistant materials like epoxy are applied. Hence to sum it up, many layers of fiber are wrapped in thick plastic to keep it dry and effective. This makes the body armor temperature and moisture management very difficult. 
     Although there are body armor cooling systems available which work on the principle of evaporation and ventilation, available as padding, like in Armorvent™. However, none of these systems have been found effective as these systems do not cool the body directly and rather facilitate natural body mechanism of cooling by sweating. In a combat situation, this could mean severe mineral loss and fatigue. 
     Therefore, there is a technological need for making a comfortable, wearable, flexible metallic heat exchanger, that can be bonded to existing body armor and reduce the number of layers that a person has to wear thereby reducing the wearing time or application time in case of emergency. 
     Alternately, a body armor cooling systems with flexible metallic heat exchanger that can be latched onto existing body armor systems, which are reversible and quickly attachable. 
     OBJECT OF THE INVENTION 
     The main object of the present invention is to provide a liquid cooled body armor system comprising an existing body armor vest with plurality of armor plates, an adhering layer and plurality of heat exchangers. 
     Yet another object of the present invention is to provide a liquid cooled body armor system with plurality of armor plates attached with plurality of heat exchangers via the adhering layer. 
     Yet another object of the present invention is to provide a plurality of heat exchangers comprising plurality of metallic plates preferably copper or aluminium with pipes brazed to the back-side of the metallic plates. 
     Yet another object of the invention is to provide a liquid cooled body armor system for obviating the weight of the vest fabric and additional components as it is integrated into the existing body armor. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present invention, the invention provides a liquid cooled body armor system comprising an existing body armor vest with a plurality of armor plates, an adhering insulation layer and a plurality of heat exchangers wherein said plurality of armor plates is attached with said plurality of heat exchangers via said adhering layer; the plurality of heat exchangers comprises plurality of metallic plates made preferably of copper or aluminium with pipes brazed to the back-side of the metallic plates. The insulation layer is placed on an inner surface of the armor plates to prevent cooling of the armor plate, to avoid condensation. Further, an insulation material such as foam is used between the armor plates and the metallic plates to improve the overall efficiency of the system. 
     In an alternate embodiment, the present invention provides a liquid cooled body armor system comprising an existing body armor vest with a plurality of armor plates, a plurality of latching provisions and a plurality of heat exchangers wherein said plurality of armor plates is attached with said plurality of heat exchangers via said latching provisions; the plurality of heat exchangers comprises plurality of metallic plates made preferably of copper or aluminium with pipes brazed to the back-side of the metallic plates. The insulation layer is placed on an inner surface of the armor plates to prevent cooling of the armor plate, to avoid condensation. Further, an insulation material such as foam is used between the armor plates and the metallic plates to improve the overall efficiency of the system. 
     In yet another embodiment of the present invention the latching or fastening provision includes but is not limited to magnetic latches, mechanical latches, Velcro® fastener, clipped fasteners, etc. 
     In yet another embodiment, the present invention provides a plurality of heat exchangers, preferably, a thin flexible metal sheet having thickness between 0.05 mm and 10 mm, to which a series of thin flexible metal tubes having outer diameter between 0.5 mm and 10 mm, that are soldered, brazed, or bonded to it. 
     In yet another embodiment, the present invention provides a fluid that flows through the series of thin flexible metal tubes, which exchanges heat with the walls of the thin flexible metal tube through convection, which in turn exchanges heat with the thin flexible metal sheet through conduction, which in turn exchanges heat with the skin of the wearer through conduction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A complete understanding of the method of the present invention may be obtained by reference to the following drawings: 
         FIG. 1  illustrates the liquid cooled body armor system, front plate and back plate, including a cooling layer, being worn around the human body; 
         FIG. 2  shows the body armor assembly, in isolation; 
         FIG. 3  is a transparent view of the body armor, cooling plate and tubing assembly; 
         FIG. 4  is an exploded view of the liquid cooled body armor system; and 
         FIG. 5  illustrates the liquid cooled body armor system along with an external coolant pumping device in accordance with an embodiment of present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough, and will fully convey the scope of the invention to those skilled in the art. 
       FIG. 1  illustrates the liquid cooled body armor system with front armor plate and back armor plate, which includes a cooling layer (not shown), worn around the human body. Water circulates through the flexible tubes shown. 
       FIG. 2  shows liquid cooled body armor system, in isolation. 
       FIG. 3  is a transparent view of the body armor vest  10 , armor plates  12 ,  14 , an adhering layer and heat exchangers  20 ,  22 . The heat exchangers  20 ,  22  comprising metallic plates preferably made of copper or aluminium with metallic pipes brazed to the back-side of the metallic plates  12 ,  14 . Water flows through the flexible polymer tubes  16 ,  18  that go above the shoulders. The metallic pipes  24 ,  26  that are in between the armor plates  12 ,  14  and heat exchangers  20 ,  22  are metallic, and it is brazed to the heat exchange plate  20 ,  22  that is closest to the skin. The armor plate  12 ,  14  is the bulletproof steel strike plate or other polymer used in bulletproof equipments. In between the armor plates  12 ,  14 , and the metallic pipes  24 ,  26  is an insulation layer (not shown), which prevents heat transfer from the cooling circuit to the steel bulletproof plate. This prevents the bulletproof plate from getting cooled, and water condensing. The flexible polymer tubes  16 ,  18  deliver water to the metallic pipes  24 ,  26  that are sandwiched between the armor plates  12 ,  14  and the heat exchange plate  20 ,  22 . Preferably, the armor plates  12 ,  14  made of steel or other polymer used in bulletproof equipments having thickness from 2 mm to 4 mm and the heat exchange plate  20 ,  22  is metallic (e.g. copper or aluminum), having thickness from 0.1 mm to 2 mm, with a preferable thickness of 0.2 to 0.4 mm as ideal for most applications. Foam or insulation is used to fill the gaps between the armor plates  12 ,  14  and the heat exchange plate  20 ,  22 , to prevent water from condensing in these gaps, and to also provide insulation for the colder heat-transfer plate. This improves the energy efficiency of the system, by preventing the cooling of the bulletproof plate, which the person would never feel. 
       FIG. 4  is an exploded view of the liquid cooled body armor system comprising armor plates  12 , an insulation layer  28 , metallic pipes  24  and heat exchanger  20 . 
       FIG. 5  shows an engagement of the liquid cooled body armor system along with an external coolant pumping device  34 . The liquid cooled body armor system having provision such as, but not limited to quick connector, etc. at the distal end of tubes  30 ,  32  to connect it with an external coolant pumping device  34  which circulates coolant at a rate of up to 400 ml/min i.e. in and out of the liquid cooled body armor system. The coolant is pumped into the system at a temperature of 15.1° C. and pumped out of the system at 15.6° C. 
     The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principals of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. 
     Many modifications and other embodiments of the invention set forth herein will readily occur to one skilled in the art to which the invention pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.