Quote:
Originally Posted by AirConditioner
I want to convert a 6500 BTU window air conditioner into a "water source" air conditioner. I've looked at various threads showing homemade heat exchangers, but I think I'd like to just use a flat plate heat exchanger from ebay. I want to plumb it so that both the evaporator and condenser on the original window unit become an evaporator and cold air comes out both sides.
How do I know what size heat exchanger I need for the condenser? Most of them do not have BTU or ton ratings. I can't post a link because I don't have enough posts, but I'm looking at a 14 plate SS heat exchanger on ebay for $48. It's rated for 725 PSI but I don't know if it would be big enough? Dimensions are 2.83"x7.36".
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Welcome to hell... (just kidding)
This is a great project that you want to do, and I hope that you completely succeed, and that your share your success (and errors/mishaps) with us through descriptions and photos that you record along the way.
Having said all that, your question is a frequently encountered problem for doing similar projects.
Part of the problem is that many cheap HXs found on ebay are meant for transferring heat from water-to-water, and the transfer capacities that they may list are completely different for refrigerants.
There are also differences in heat transfer rates amongst various refrigerants (thus the capacity of a particular HX) , but those differences are not as dramatic as it is for refrigerant-to-water. So, if you can find data that indicates what the transfer is for one refrigerant, you will be in the ball park.
I did a web search for "brazed plate exchanger sizing water refrigerant", and I turned up a number of promising links,
THIS_ONE in particular looked good.
So look through this area and the PDFs until you zero in on a unit that looks good.
It is a good idea to over-size your HX by about 150% to 200% , it will improve efficiency.
You will also want to be sure that your refrigerant-side fittings are for brazing, rather that any kind of threaded fitting. In the industry, various terms are used, but "sweat fitting" seems to be the most often used.
Lastly, you need to know that soldering refrigerant tubing and components is
not strong enough to survive refrigeration use. You will want to braze your tubing and fittings. The process is almost identical to soldering, but higher temperatures and stronger bonding alloy is used.
And just to make you life more confusing, technicians and repairmen in the refrigeration field often say, "solder up the system", when they actually mean to braze the system.
Let us know what you find.
Best,
-AC_Hacker