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Old 06-19-17, 07:06 AM   #10
jeff5may
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That's a water to air heat exchanger. Plumbed way different than a refrigerant to air exchanger. It's rather tiny as well.

The main plumbing issue is that most all evaporator exchangers​ are a long, series connected path. This gives the refrigerant the most time to pick up heat before it exits. The shotgun exchanger you cited has multiple short paths. This is good for water that is really hot, as the inlet pressure is pretty much constant in the header pipe. The flow divides equally between all the paths because the pipes are all flooded. Naturally, if the water enters at temperatures that could burn you, more heat goes into the air.

With refrigerant, what happens is the entering fog or frothy spray falls straight to the bottom of the header. Some liquid could make it through the bottom before it completely vaporizes. Either way, the oil will tend to collect in the bottom and could stagnate there. So this heat exchanger could potentially trap most of your compressor oil and let liquid refrigerant through to the compressor inlet. Both conditions are not good for the longevity of the compressor.

Since you're using the heat exchanger as an evaporator, you have a limited amount of heat transfer available before the thing starts making ice. Maybe 30 or 40 degF of gradient. Making ice isn't a bad thing, as it takes a lot of heat flow to do so. But whenever it happens, your airflow goes way down. The limited amount of surface area (frozen or not) will limit the heat flowing into the piping from the supplied air. This can be calculated if the design parameters of the heat exchanger are known. If not, hope for good luck.

Last edited by jeff5may; 06-19-17 at 08:58 AM..
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