Refrigerator / Heat Pump
A thermodynamic device operating in reverse that consumes mechanical work to extract heat from a cold region and reject it into a warmer region.
Governing formula
COP_ref = Q_cold / W, COP_hp = Q_hot / W
SI unit
Dimensionless (Coefficient of Performance)
In depth
Heat pumps and refrigerators do not violate the Second Law because external work W is supplied to drive the non-spontaneous heat transfer against thermal gradient.
Examples in the real world
Household refrigerators using electric compressors to pump heat out of the food compartment into room air.