These are not scientific definitions but are included for the intent of allowing one to better understand potential phase change cooling vests.
Heat always travels to cold.
Understanding this basic principle is important to being able to understand basic body cooling.
Convective cooling is when heat is exchanged via air.
Common examples include refrigerator cooling and air conditioned room cooling.
Conductive cooling is when heat is exchanged via physical contact with a cooling substance.
Common examples include water immersion (jumping into a cold swimming pool) and ice pack therapy for medical purposes.
Evaporative cooling is when heat is exchanged via energy generated by the change of phase of a liquid to a gas.
Common examples include body sweat evaporating during physical exertion and misting fans.
The most energy effective cooling process is conductive heat transfer.
To help illustrate this point, imagine being very hot and needing to cool down quick, you have the choice of:
Walking into an air-conditioned room with a temperature of 65° F. (Convective)
Standing in front of a misting fan. (Evaporative)
Jumping into a swimming pool at 65° F. (Conductive)
The choice is obvious; your body would sharply lower it’s core temperature if you stayed in the pool too long.
Also consider the fact that you can put your hand into the freezer and keep it there for quite a long time even though the air temperature is around 20° F.
Now see how long you can keep your hand in a bucket of ice water with a temperature around 38° F.
Easy to understand and illustrate.
Evaporative cooling is the least effective of these due to the fact that the energy exchange is very low.
In the above scenario, you would choose the misting fan as the last option.
ΔT (pronounced delta t) is quite simply the difference in temperature of 2 relateditems.
Perfect example is the ΔT of an outside temperature of 100° F and an air-conditioned room of 65° F would be termed as “the ΔT of 35° F”.