 The refrigerant is then allowed to expand, and hence cool, and absorb heat from the outdoor temperature in the outside evaporator, and the cycle repeats.This is a standard refrigeration cycle, save that the "cold" side of the refrigerator (the evaporator coil) is positioned so it is outdoors where the environment is colder.In cold weather, the outdoor unit of an air source heat pump needs to be intermittently defrosted.