Heat Pump

How Do Heat Pumps Work?

The working principle of heat pumps is based on the first law of thermodynamics which states that, energy can only be transmitted into the ambiance by heating, compression or mass addition. The  other way around, energy can be extracted from the ambiance by cooling, expansion and mass  subtraction. Theoretically energy can be transferred in every ambiance if and only if the temperature  is above absolute zero.(-273,15°C,  -459,67°F)

The direction of heat transfer is from hot atmosphere to the cold one. What heat pumps manage is changing heat transfer direction by consuming relatively small amount of electricity. A great amount of free energy, being spread from the Sun, is accumulated in seas, lakes, air and ground. The closer the temperature of heat source to the heated environment is,, the better the performance of heat pump is. Thus, the use of heat pumps are more beneficial where the climate is not that cold during winter.

The efficiency of heat pumps are defined with COP which is called as coefficient of performance.COP is calculated as dividing the amount of energy provided into the house to the consumed power by the compressor. Nowadays COP values changes between 3 to 4.In other words heat pumps consume one unit of energy while providing 4 units of energy to the house. By the aid of inverter technology heat pumps modulate themselves due to the need and minimize the energy consumption.

The operation cycle of heat pumps is separated into 4 main titles,

1-Evaporation: When Refrigerant in the closed loop circulates throughout the evaporator, it vaporizes with extracting heat from the heat source(air, water or soil).              

2-Compression: The pressure of the refrigerant is increased when refrigerant passes through the

compressor. This sudden pressure raise causes the temperature of refrigerant to go up to about 80° C.

3-Condensation: When refrigerant passes through the condenser, the refrigerant, at high pressure and temperature, transfers its energy to the heating water circulating inside the pipes. The heating water in the pipes then either releases the heat from the radiators and under floor heating pipes for heating or provides the domestic hot water.

4-Expansion: The pressure and temperature of refrigerant decreases when passing through the  expansion valve. Then refrigerant is ready to extract heat from heat source again and the cycle is  completed.

By the aid of a changeover valve the cycle works in reverse direction. Thus, the heat is extracted from the house and cooling occurs. When fan coils are used with heat pumps, cooling is provided into the house.

The outlet water temperature of heat pumps can reach approximately 65°C and water at that temperature is use full  When being used with radiators. However the length of the radiators have to be selected by using correction factors due to the outlet temperature of heat pump.

COP values is relatively less when heat pumps are used with radiators.

BENEFITS OF HEAT PUMPS

- Heat pumps use the stored energy in the environment so they are influenced by raise in the energy prices at a minimum level.

· Heat pumps are the cheapest way to get hot and domestic hot water together.

· The feedback time of heat pumps is approximately  5 years. This time period can be less or more due to the operation time.

·%25 of the total CO₂ emission is caused by the domestic energy use and %75 of domestic energy use is caused by heating and need of hot water. Thus, the use of heat pumps is the best solution to minimize the CO₂ emission caused by domestic energy consumption.The risk of explosion, poisoning or fire doesn’t exist in heat pump systems.

·In addition to heating operation by radiators or under floor heating pipes and providing domestic hot water , cooling operation is also possible by using fan coils. In other words heating, cooling and providing domestic hot water is possible with the same system which is heat pump.

· Heat pumps are based on “Install and Forget” principle which means heat pumps doesn’t need extra maintenance rather than simple periodic cleaning operation of filters.

Photos of Heat Pump applications are below: