Work out evaporator sizing instantly with clear inputs, formula shown and shareable results.
Coil area follows the basic heat exchanger relation Q = U x A x ΔTm, so the surface needed is the load divided by the product of the coefficient and the mean temperature difference. Face area is a separate constraint set by airflow and the velocity above which condensate is blown off the fins, usually about 500 fpm.
Surface area
A = Q / (U x ΔTm)
Face area
Face ft² = airflow CFM / face velocity fpm, airflow = tons x 400
A = Q / (U x ΔTm). Coil area follows the basic heat exchanger relation Q = U x A x ΔTm, so the surface needed is the load divided by the product of the coefficient and the mean temperature difference.
Above roughly 550 fpm on a wet coil, condensate is carried off the fins into the duct, causing water damage and microbial growth downstream.
This calculator takes 4 inputs: Cooling load, Coil overall heat transfer coefficient, Mean air-to-refrigerant difference, Design coil face velocity. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.