A heat pump is a machine that extracts energy from the air to heat or cool a space. This process is referred to as space conditioning. Heat pumps function as a reverse heat engine, drawing heat from a cold area and transferring it to a warm area. This article will also help you find out about the working of a heat pump and types of heat pumps.

What is a heat pump?

A heat pump is a mechanical device that uses external work to extract heat from a cold reservoir and give heat to a hot reservoir. Since a heat pump is subject to the same limits set by the second law of thermodynamics, the Carnot cycle can be used to calculate maximum efficiency. Heat pumps are typically distinguished by a performance coefficient, which is the number of items of energy delivered to the hot reservoir per unit work input.

Working of heat pump

Heating cycle

• A liquid refrigerant absorbs heat from the outdoor air in an evaporator converting it to a gas.
• The refrigerant goes through a compressor, which boosts the pressure of the gas and raises its temperature.
• The warm gas goes through condenser coils inside the space to be heated, and because the gas is hotter than the room, it transfers heat into the room and condenses back into a liquid.
• Finally, the liquid flows back through a valve that reduces its pressure to cool it.

Cooling cycle

• The cold refrigerant in the evaporator absorbs heat from the hotter room, causing the room to cool.
• The temperature of the refrigerant is then raised by passing it through the compressor.

• It spreads through the condenser coils, transmitting heat to the outside air.
• Then, it widens to decrease pressure and cools down to lower the room’s temperature.

Coefficient of efficiency

The ratio of heat output to work required is used to express the performance of a heat pump. This value essentially represents how much cooling or heating is done. This ratio is referred to as the coefficient of performance (K), and it is represented by the equation:

K = heat / electricity,

which makes the heating coefficient as:

K = Q_H / W_in

and the equation for cooling is

K = Q_C / W_in

Where,

W is the input work as electricity

Q_His the heat input to a room to warm it

Q_C is the heat thrown out of the room to cool it.

The higher the value of the heat pump, the better the heat pump is at transferring energy.

Types of heat pump

Geothermal heat pump

A geothermal heat pump, also known as a ground-source heat pump, is often used to transfer heat fluid (water with antifreeze) from the soil or groundwater. Installation costs for geothermal heat pumps are rather high. This heat pump can be used to cool buildings by transmitting heat from hot regions into the soil through a ground loop of piping buried in the ground.

Water Source Heat Pump

This heat pump’s operation is similar to a ground-source heat pump. However, the heat is refilled from a body of water instead of the ground. The primary requirement for this pump is that the body of water should be large enough to endure the unit’s cooling effect and should not freeze or cause adverse effects.

Air source heat pump

Heat is transferred between two heat exchangers by air source heat pumps. Typically, one heat exchanger is mounted on the outside of a building with fins attached to allow air to be blown inside with the help of a fan.

Exhaust air heat pump

Exhaust air heat pumps are used for mechanical ventilation. There are two types of exhaust air heat pumps:

1. Exhaust air-air heat pumps are used to transfer heat from the exhaust to the intake.
2. Exhaust air-water heat pumps are used to transfer heat to a heating circuit that includes a tank of domestic hot water.

Solar assisted heat pump

Two systems are integrated into this type of heat pump. One system has a heat pump and the other has thermal solar panels. The solar thermal panel serves as the low-temperature heat source in this case. The heat generated is directed to the heat pump’s evaporator.

Conclusion

The heat pump is used to either heat or cool a place. These systems take energy from the air and convert it to change the temperature. This article explains the working of a heat pump. If the coefficient of efficiency of a heat pump is high while working, it is considered to be a good heat pump.