In order to obtain data for this paper, tests were run under laboratory conditionswith calibrated instruments. All tests were run with a +20F evaporatorand in a +32F room.

This discussion is predicated on the premise that the coil heat transfer surfaceis of the extended fin type with the air being forced over the extended finsurface and the refrigerant passing through a tube or series of tubes bondedto the extended surface. Further, since catalog ratings for air cooler equipmentby most manufacturers is without frost this discussion will be confinedto the effect on those ratings which determine the capacity of the air cooledequipment.