Heat Pump

Heat Pump:

                   A heat pump is a device which operating in a cyclic process to maintains the temperature of a hot body (heated space) at a temperature higher than the temperature of surrounding.

📌 It is an electrical device that extracts heat from one place and transfers it to another by using mechanical energy. Examples: air conditioner; refrigerator.

📌 A refrigerator is a special case of a heat pump.

📌 It is an essential parts of a heating and cooling system.

📌 Most heat pumps are driven by electrical power, natural gas, liquefied petroleum gas (LPG) can power certain systems that drive an internal combustion engine in place of a conventional electric motor.

How Does a Heat Pump Works:

i) Process stage 01: At the beginning of the cycle the refrigerant (such as Freon) is in a liquid form This liquid refrigerant is very cold.  It enters the evaporator coil.

ii) Process stage 02: After the refrigerant leaves the indoor evaporator coil it has absorbed heat and become gas. The refrigerant enters the compressor which mechanically pressurizes the gas.  That process will increase its temperature so the refrigerant will leave the compressor as hot gas.

iii) Process stage 03: The refrigerant next moves to the condenser coil located outside the house.  Because the temperature outside is lower than the temperature of the hot gas the heat is transferred or “rejected” from the refrigerant in the coil to the outside air.

iv) Process stage 04: The refrigerant leaves the outdoor condenser coil as warm liquid.  Now we need to make the warm liquid refrigerant cold so that it can absorb more heat. Again to repeat the cycle.

Main Components of a Heat Pump:

• Evaporator: It contains work fluid at lower temperature than environment. Heat is extracted from ground, air or water. So the work fluid evaporators.
• Compressor: It brings gas to higher pressure, temperature rises.
• Condenser: Gas temperature is higher than fluid temperature of heating system. Excess heat is transferred to fluid. The gas cools and condenses.
• Expansion Valve: It causes pressure reduction, the temperature drops and the cycle begins again.

Coefficient of Performance (COP):

The performance of a heat pump is judged by how much heat transfer Q_h occurs into the warm space compared with how much work input W is required.