Heat pump, device that simultaneously transports heat and increases its temperature. To heat an area, the heat pump absorbs outside heat and brings it inside the area. A fluid called a refrigerant circulates through the heat pump, absorbs the outside heat, and travels first into a compressor that increases its temperature, and then into a heat exchanger to release its heat to room air. The refrigerant is then filtered through a valve that lowers its temperature and allows the process to begin again. The process can also be reversed to cool an area by absorbing inside heat and discharging it outside the area, as with a refrigerator.
See also: Air conditioning.