Anyone have a heated swimming pool?

[Paul Sandhu]

I have an above ground pool, about 12000 gallons. It's my intent to build a wood fired heater for it. I have about 200 hedgeapple trees in my yard, and about 800 other assorted trees so the wood supply is basically endless. I'm using a water tank from an RV as a fire pit. It's about 42" long and about 16" in diameter. I cut it in half the long way. For the heat exchanger I'm using 3/4" black pipe. The picture is what the first level looks like. The 3 pipes on the left are complete. The 3 on the right are in the picture for reference. I'm going to build 2 more layers of pipe with the pipe centered over the spaces between the layer below it. A sump pump will circulate water from the pool through the pipes. The top half of the water tank will be like a lid over the exchanger, and I'll drill a few holes in the top to allow the heat to flow around the pipes.

My main questions are this: Should I grind off the black layer of the pipe to allow better heat conduction? I have brazing wire to use in my mig welder, and the appropriate shielding gas. If I coated the bare pipe with the brazing material, would it improve the heat transfer?

I'm hoping to increase the temperature of the pool by 5-10 degrees in 2-4 days and maintain it. The fire and pump would be running 24/7. I was in Argentina on a dove hunt earlier this year. There was an outdoor below ground pool that was heated by circulating the water through a series of pipes in a fire pit next to the pool. The pool was 102 degrees, the air temperature was in the 60's at night.