HEAT EXCHANGER SIZING BASIC DEFINITION AND TUTORIALS

SIZE OF HEAT EXCHANGER


Transfer of heat through the walls of the evaporator and condenser requires a temperature difference, and the larger these heat exchangers are, the lower will be the temperature differences and so the closer the fluid temperatures will be to those of the load and condensing medium.

The closer this approach, the nearer the cycle will be to the ideal reversed Carnot cycle. (See Table Below.)

These effects can be summarized as follows.

Larger evaporator 

1. Higher suction pressure to give denser gas entering the compressor and therefore a greater mass of gas for a given swept volume, and so a higher refrigerating duty;

2. Higher suction pressure, so a lower compression ratio and less power for a given duty.

Larger condenser

1. Lower condensing temperature and colder liquid entering the expansion valve, giving more cooling effect;

2. Lower discharge pressure, so a lower compression ratio and less power.


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