A heat pump is a device that transfers heat energy from a source of heat to a heat sink. Heat pumps move thermal energy in the opposite direction of spontaneous heat transfers. This happens by absorbing heat from a cold space and releasing it to a warmer one. A heat pump uses a small amount of external power to operate.
The main components of a heat pump are a condenser, and expansion valve, an evaporator, and a compressor. The medium used to transfer the heat through all of the components is called refrigerant. Some examples of heat pumps are air conditioners and freezers, but also can be HVAC these are devices used for heating or cooling a space.
For heating spaces a heat pump, they are basically the same as a refrigerator and air conditioner but, run in the opposite direction. Meaning they release heat into the conditioned space rather than into the surrounding environment, drawing heat from the cooler external air or the ground.
The great advantage of using a heat pump to keep your home warm, rather than just burning fuel, is that a heat pump supplies . Heat transfer is from the outside air, even at a temperature below freezing, to the indoor space. You only pay for . The quality of a heat pump is judged by how much heat transfer occurs into the warm space compared with how much work input is required. In the spirit of taking the ratio of what you get to what you spend, we define a heat pump’s coefficient of performance () to be