Heat Transfer and Air-Source Heat Pumps
There are many different kinds of heat pumps, but they all operate on the same basic principle of heat transfer. Heat transfer means that rather than burning fuel to create heat, a device moves heat from one place to another. Heat naturally flows downhill, which means that it tends to move from a location with a high temperature to a location with a lower temperature. A heat pump uses a small amount of energy to switch that process into reverse, pulling heat out of a relatively low-temperature area and pumping it into a higher temperature area. In a heat pump, this heat is transferred from a heat source (e.g. the ground or air) into a heat sink (e.g. your home).
One of the most common types of heat pumps is the air-source heat pump, which takes heat from the air outside your home and pumps it inside through refrigerant-filled coils. Inside this basic heat pump, you’ll find two fans, refrigerator coils, a reversing valve and a compressor.
This system is more commonly known as an air-air heat pump, because it takes heat from outdoor air and transfers it to indoor air ducts. With the proper modification, air-source systems can also work with other types of indoor heating systems.