How to Calculate Heat Exchange Coefficient

Subtract the cold input temperature of the exchanger from the hot output temperature and the cold output temperature from the hot input temperature. Add the two values together and divide by two to get the average temperature difference. For example, a hot input temperature of 75 C, a cold output temperature of 70 C, a hot output temperature of 30 C and a cold input temperature of 25 C would be ((75-70) + (30-25))/2 = 5 C.

Multiply the average temperature difference between the input and output temperatures by the surface area within the heat exchanger. For example, a heat exchanger with 1 square meter of surface area equals 5 m^2 K. Note that the Kelvin and Celsius temperature units are the same size; they just have different zero points. With the temperature difference, you can switch between the two units without converting them.

Divide the heat transfer rate by the average temperature difference multiplied by the surface area to get the heat transfer coefficient. For example, a heat transfer rate of 1250 W would yield a heat transfer coefficient of 1250/5 = 250 W/ (m^2K).