Operating principle of heat pumps

Heat pumps are machines capable of transferring heat from a body at a lower temperature to a body at a higher temperature, using electrical energy. The sun's rays heat the air, water and earth.

Air/water heat pumps only extract free energy in the air and transfer it to water in the form of heat.

The only energy that the system requires is absorbed by the compressor and the fans, although it must be remembered that the electrical energy absorbed by the compressor is combined with the energy taken from the air, together providing the heat for heating.

Heat pumps are machines capable of transferring heat from a body at a lower temperature to a body at a higher temperature, using electrical energy. The sun's rays heat the air, water and earth.

Air/water heat pumps only extract free energy in the air and transfer it to water in the form of heat.

The only energy that the system requires is that absorbed by the compressor and fans, although it must be remembered that the electrical energy absorbed by the compressor is added to the energy taken from the air, together providing heat for heating.

1.condenser, 2.expasion valve, 3.evaporator, 4.compressor.

The condenser and evaporator are comprised of heat exchangers, i.e. tubes placed in contact with a medium (which can be water or air) in which the frigorific fluid flows.

• This transfers heat to the condenser and removes it from the evaporator.
• The circuit components can be grouped into a single unit or divided into two parts ("SPLIT" systems) joined together by tubes in which the frigorific fluid circulates.
• In operation, the frigorific fluid within the circuit undergoes the following transformations:
  
  • Compression: the frigorific fluid in its gaseous state and originating from the evaporator at low pressure is brought up to high pressure; in compression it heats up by absorbing a certain amount of heat.
  • Condensation: the frigorific fluid from the compressor goes from a gas state to a liquid state letting off heat to the outside.
  • Expansion: passing through the expansion valve, the liquid frigorific fluid is partially transformed into steam and cools.
  • Evaporation: the frigorific fluid absorbs heat from the outside and evaporates completely.

All of these transformations compose the heat pump cycle: providing energy with the compressor to the frigorific fluid (in the evaporator), the frigorific fluid absorbs heat from the surrounding air medium (through the condenser) and transfers it to the water medium to be heated.

The heat pump, however, can reverse its cycle and function as a chiller (air cooling).