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Whoa.! Copper Heat Exchanger Calc
Folks, (a die hard do-it-yourself'r here) I've spent several weeks (or months?) installing a solar thermal system for our house.
Somewhat sheepishly, its only after the fact that I'm trying to do a basic calculation of btu gain.
I have a home-made copper heat exchanger. It is four 60' coils of 1/2" soft L copper in parallel with 1" supply and return lines running into the tank.
So I figure the system GPM is split four ways within the heat exchanger. Can I thus divide system GPM by 4, and then look up the ft head loss on a chart for 1/2 copper for that number??? Now, do I multiply the result by 4 because there are four loops the water is pushing through? This is where I'm confused.
Same goes for the solar panels. Do I divide the system GPM by eight, look that head loss up on their pressure loss tables, and then multiply the result by eight?
We have (8) 4x10 AE-40 panels, 150' of 1" coper (round trip) from the panels to a 500 gal storage tank. Inside I build a coper heat exchanger with (4) 1/2" soft L coper coils in parallel. A Wilo S 21 pumps Dowfrost through the system. I'm curious how many GPM I'm pumping at the three speed settings.
I have the pump curve for my circulator, but calculating the head loss across the heat exchangers has me stumped. It seems really difficult to know how many GPM I am moving at a given speed setting.
Any help is much appreciated. Yeah, I know I should have done these calculations before I built everything, but that would have taken the fun out of it!