Quote:
Originally Posted by AC_Hacker
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Reducing the velocity reduces the BTU output.
You will have an increase in efficiency but nothing like 2X.
Sincerely,
-AC_Hacker
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This is absolutely true. You cannot transfer more heat than what is available. What I am hoping for, at best, is a small increase in HX efficiency.
If I am moving 10 GPM of water through one heat exchanger, installing two will cut the flow down to about 5 GPM per heat exchanger (not accounting for head-loss). The water will be exposed longer (due to 1/2 the velocity) and thus it will reach a slightly higher temperature. As the water becomes hot, the heat will not be absorbed from the refrigerant as quickly because HX depends on a substantial Delta-T.
In a perfect world, double the surface area per given quantity of water combined with water moving at a lower velocity means that the Delta-T in the system should be slightly less than a single HX. That combined with the fact that the same quantity of water is flowing with less head-loss may net a tiny increase in system efficiency.
I will not have a control for this experiment, I have never run this system with a single heat exchanger and most likely never will. That means ultimately any data I collect will be meaningless in terms of comparison of 1 vs 2 heat exchangers.
I started this thread to see if anyone had any good input on why
NOT to build the system this way.
The only negative aspect I could come up with on my own was fouling. If the water velocity is too low to create turbulent flow in the HX, it could cause excess fouling. I decided that since this is the heated side of a closed loop system, I shouldn't have any major fouling issues provided that I use clean distilled water and the proper anti-freeze / coolant mix. Furthermore, I have selected a pump that should maintain flow through each HX that is well within the manufacturer's design envelope.