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Old 06-18-19, 07:11 PM   #2
CrankyDoug
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I can offer some observations from my experience with air dryers. Perhaps it will give you a place to start.

All of the refrigeration cycle air dryers I've worked with use flooded evaporators to tightly regulate the temperature above the freezing point of the condensate. All of them remove water from the high pressure side of the air compressor. This is more efficient because water condenses more readily as pressure rises.

The dryer manufacturers all stipulated that the dryer should be placed after the primary air tank (receiver) and never between the compressor and the tank. One employer violated this rule and had endless problems (which they never learned from). The receiver provides most of the cooling and generally removes most of the water. The dryer removes enough additional water so that what remains cannot condense during subsequent air expansion in your plasma gun.

Most dryer manufacturers recommend a secondary receiver after the dryer so that the air flow through the dryer is somewhat continuous. At least two dryers I worked on had small internal receivers, probably because the designers knew the purchasers of their equipment would be too cheap to install the secondary receiver.

Years ago there were attempts to remove moisture prior to the compressor in the railroad industry. This was done to reduce moisture problems in the compressor itself. It wasn't very successful and I don't think it is used anymore.

The refrigerant/air interface is usually a coiled tube-in-tube heat exchanger. The largest one I worked on was tube-in-shell - can't remember if the refrigerant was in the shell or in the tubes. Air velocity in the heat exchanger must be slow enough to prevent condensate from being carried in the airstream.

Your aquarium chiller should be adequate if you follow the basic principles outlined above. You will need some form of condensate drain. Float drains are very reliable as long as you prevent them from freezing and keep them free of compressor oil. Without these two requirements, timed solenoid drains are preferable.
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