Ice Box Heat ExchangerThe Ice Box is a safe and effective way to water cool the air leaving your reflectors without adding A C or more fans. It uses an air to water heat exchanger to water cool the hot air your reflectors produce. Water cooling is much more effective and efficient than air cooling, and here's some science to prove it: Water has a thermal conductivity of 0. 6 W (m*K) which is much higher than the thermal conductivity of air which is only 0. 03 W (m*K).