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Heat Injury and Cooling as Explained by an Engineer

ΔT and the

Roll in Heat Casualties

Δ (delta) T is what the scientific community defines as the difference in temperature between two objects or thermal masses. Now you are asking what ΔT has to do with heat casualties. Heat related injuries happen when there is not enough ΔT between the human body and the environment it is in for the body to shed excess heat. Let us look at a typical summer outside work scenario. You are outside doing yard work and the temperature outside is 99 degrees F (Fahrenheit). Your body is doing its thing which is to help get rid of the heat that is building up inside it, this consists of sweating and increasing blood flow to the skin surface. Sweating is the body’s way of using evaporation to help cool the skin/blood down which works amazingly well in the desert but not so well in the southern states with high humidity. When this evaporative cooling loses some effectiveness, the result is the body's temperature starts to rise and rise, eventually getting to an overheated state. This is where PolarSkin Cooling products come in and take advantage of ΔT to quickly drop the body temperature, but how does it do it?

PolarSkin Cooling products are stored in the freezer to maintain the low temperature of the cooling media. The cooling sheets never freeze solid and remain flexible and pliable. So, when someone is in an overheated state the PolarSkin product is deployed on to the heat victim. The sheets are 35 degrees F where the overheated human body is 103 degrees F, this is a large ΔT (68 degrees F). Science has shown that the larger the ΔT the faster heat can move, from high to low temperature. To aid in this heat transfer the PolarSkin Ice Sheets utilize a fluid that increases contact with the body and therefore increases heat conduction. So now our thermal system has three heated "bodies", the human over heated body, the PolarSkin Ice Sheet, and the environment around the human. If we look at the temperatures of each, we see that the PolarSkin Ice Sheet will also want to absorb heat from the environment. Engineers at PolarSkin have developed a system that limits this heat transfer from the outside environment. Allowing the sheets to absorb more heat from the human body than from the surrounding air. Speeding up the cooling of the body is a critical factor in saving a person's life!

Understanding ΔT and how PolarSkin exploits a large temperature differential to cool an overheated person quickly. Increasing survivability of heat related injuries and mitigating damage that is caused by prolonged time in an overheated state.

Justin Stacy, Ph.D.


Short Fuse Engineering

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