- A heat pump is a device that uses fluid to transfer heat from one place to another. Refrigerators and air conditioners are both powered by heat pumps, which are used to transfer heat out of an area, thereby cooling it. Some buildings use reversible heat pumps to provide both heating and cooling depending on the season.
- Heat pumps uses a powerful pump called a compressor to move a fluid called refrigerant through a series of metal tubes. First, the refrigerant is pressurized and pumped into the condenser. When the refrigerant is compressed, it heats up. As the refrigerant flows through the condenser, its heat leaks out of the tubing. This heat is either used for warming or dispersed as waste heat, depending on the purpose of the pump.
- At the end of the condenser is a small valve that slowly sprays the refrigerant into the next chamber: the evaporator. The evaporator is kept at a low pressure by the valve. When the refrigerant sprays into it, it quickly expands, which cools it down. The refrigerant then flows through the evaporator tubing, which absorbs heat from the outside environment, warming the liquid inside. It then returns to the compressor to start the process again.
- In air conditioners, the condenser is kept outside of the house, where it spreads the waste heat into the air. A fan blows on the evaporator, cooling air and dispersing it around the house. Refrigerators work in much the same way, except the condenser is behind the fridge, and the waste heat is actually dispersed inside the house. Some modern heat pumps use the ground as a heat sink. A few feet underground, the air stays at nearly the same temperature all year round. In the summer, the heat pump can release waste heat into the ground, and in the winter, it can pull heat out of the ground and use it to warm the house.
