Hot Tip #21 – Refrigerant Type Compressed Air Dryers

Question: I have a refrigerant air dryer after my compressor. The temperature of the exit air is only “slightly” colder than the inlet air, and yet the dryer seems to be working fine. How is this possible?

Within the compressed air dryer, there are two heat exchangers.

Exchanger # 1 is a compressed air to compressed air heat exchanger.

Exchanger # 2 is a compressed air to refrigerant heat exchanger.

The path of the compressed air flow is:

First, it enters side A of exchanger # 1, exits exchanger # 1, then enters side A of exchanger #2, exits exchanger # 2,

then enters side B of exchanger # 1, then exits exchanger # 1 and exits the dryer.

Approximate temperatures of the heat cycle are:

Entering # 1 A (100 F) Entering # 2 A (60 F)

Entering # 1 B (40 F) Exiting # 1 B (95 F)

When the compressed air exits exchanger # 2 its temperature has been reduced to below the dew point.

At this point, the water drops out and exits the dryer via the water separation trap.

The dry, cold compressed air then enters side B of exchanger # 1 where it absorbs heat energy from the air on side A.

It now exits the dryer at a temperature “slightly” cooler than the entering air.