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DESCRIPTION OF DRYER OPERATION
Operating principal - The dryers described in this manual operate on the same principal. A refrigeration unit reduces
the temperature of a chamber called an evaporator or heat exchanger through which warm, moist, compressed air is
passed. As the air is passed through the chamber, it is cooled causing moisture in the air to condense.
The
condensate is collected and drained away via an automatic drain valve.
Air circuit - Warm, wet compressed air enters the dryer and passes through the air to air heat exchanger. Here, it is
cooled by cool, dry air leaving the evaporator. The pre-cooled air then enters the air to refrigerant heat exchanger
(evaporator ) where it is cooled to a temp of approximately 33-35 DEG F. Cooling in the evaporator causes water
vapor in the air to condense. Liquid water is entrained in the air stream where it enters a high efficiency water
separator and is removed from the system by means of an automatic drain.
Refrigerant circuit - Refrigerant (R-22) gas is pumped at high pressure by a compressor to an air or water cooled
condenser where it is cooled and condensed to a liquid form. The liquid is forced through a capillary tube or TXV
where the resulting pressure drop causes the boiling point of the refrigerant to drop. Low pressure liquid refrigerant
enters the evaporator where heat from the entering air is transferred causing it to boil and become a low pressure, cool
gas. A portion of the liquid may be bypassed through a liquid injection circuit that keeps the compressor cool under
conditions of high load and ambient temperatures. The low pressure gas is returned to the compressor, where it is re-
compressed and begins the cycle again.
CONDENSER
COMPRESSOR
HOT GAS
VALVE
HEAT
EXCHANGER
AIR IN
AIR to AIR HEAT
EXCHANGER
AIR OUT
DRAIN
Figure 1.2 Refrigeration Circuit
4
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