Evaporator, Compressor & Condenser

The Evaporator

The purpose of the evaporator is to remove unwanted heat from the product, via the liquid refrigerant. The liquid

refrigerant contained within the evaporator is boiling at a low-pressure. The level of this pressure is determined by two

factors:

- The rate at which the heat is absorbed from the product to the liquid refrigerant in the evaporator

- The rate at which the low-pressure vapour is removed from the evaporator by the compressor

To enable the transfer of heat, the temperature of the liquid refrigerant must be lower than the temperature of the product

being cooled. Once transferred, the liquid refrigerant is drawn from the evaporator by the compressor via the suction line.

When leaving the evaporator coil the liquid refrigerant is in vapour form.



The Compressor

The purpose of the compressor is to draw the low-temperature, low-pressure vapour from the evaporator via the suction

line. Once drawn, the vapour is compressed. When vapour is compressed it rises in temperature. Therefore, the

compressor transforms the vapour from a low-temperature vapour to a high-temperature vapour, in turn increasing the

pressure. The vapour is then released from the compressor in to the discharge line.

The Condenser

The purpose of the condenser is to extract heat from the refrigerant to the outside air. The condenser is usually installed

on the reinforced roof of the building, which enables the transfer of heat. Fans mounted above the condenser unit are

used to draw air through the condenser coils.

The temperature of the high-pressure vapour determines the temperature at which the condensation begins. As heat has

to flow from the condenser to the air, the condensation temperature must be higher than that of the air; usually between -

12°C and -1°C. The high-pressure vapour within the condenser is then cooled to the point where it becomes a liquid

refrigerant once more, whilst retaining some heat. The liquid refrigerant then flows from the condenser in to the liquid line.

Source: http://www.europe.honeywell.com/70_refrigeration_control/EN5B-0024UK07%20R0505.pdf