Specifications

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6720649497 SM HP270-1 2012/09 en
The compressor and condenser are needed to enable the same refrigerant to be used several times. The cost of
compressing and condensing the vaporized refrigerant is far less than the cost of often renewing of the refrigerant.
To maintain the difference in pressure between the condenser and the evaporator caused by the compressor, an
expansion valve is needed. The expansion valve separates the high pressure from the low pressure side in the
system. Only a small amount of refrigerant liquid flows through the valve. In fact, the valve is adjusted so that the
liquid flow rate is the same as the evaporation rate.
The refrigerant boils in the evaporator at a constant low pressure and temperature. Heat is removed from the air,
cooling it. After leaving the evaporator, the vaporized refrigerant flows through the compressor, where the pressure
of the vaporized refrigerant is raised to a point at which it can be condensed by some relatively warm fluid (water at
normal conditions).
The compressor removes the refrigerant vapour and this creates such a low pressure in the evaporator that the
evaporation temperature is kept below the surrounding temperature. After being compressed, the vapour enters the
condenser and is condensed at constant pressure and temperature. Heat is transferred from the condensing
vapour through the walls of the condenser to the water in the tank.
The expansion valve has two functions: maintain the pressure difference between the condenser and the
evaporator, together with the compressor and regulate the volume of refrigerant going to the evaporator, in order to
ensure a correct evaporation and allow the absorption of energy by the gas.
Pict.21 – Schematic representation of heat pump principle
Heat exchange
(Air/R134)
Compressor
Heat exchange
(R134/Air)
Expansion