View Full Version : Help:with reflector design for black plastic hot water collector, etc.
August 2nd, 2006, 14:26 PDT
I have been heating water on a black aluminum roof in a tilted coil of black coiled plastic water line made for burial in a trench. I would like to get more BTUs on cloudy days. I thought a reflector underneath it along with an enclosure to trap heat may do.
I'd like to have some ideas of reflector designs and configuration of my black pipe. I prefer to use gravity flow, but have 60-watt circulators if needed.
Thanks in advance
August 2nd, 2006, 17:32 PDT
An insulated enclosure with tempered glass will allow sunlight to penetrate then trap the reradiated heat, so that's a good idea. Not sure if you need a reflector: you may be getting more heat through conduction from the roof through the plastic line. You could use aluminum flashing as a reflector to do a test.
Wayne from NS Cana
August 3rd, 2006, 4:31 PDT
If it won't melt, I would go with a black backing wherever the sunlight could reach it, however, where the backing is hidden from the sun by the collector, a reflector would re-direct heat radiated FROM the COLLECTOR, back to the collector.
What pressure do you have inside your black plastic water line? Be aware that this pipe wasn't meant for high temperatures, and will soften, perhaps to the point of bursting if enclosed under glass.
I built my own collector using copper pipe, painted flat black, under glass and insulated back and sides with styrofoam. It works great, but in the few places where the sun gets through to the styrofoam backing, the heat melted holes in it. I had painted it black where the sun could hit it, to "make" more heat and protect it from UV etc. I now know it would have been better for the styrofoam if I had used white paint, of aluminum foil to protect it from the sun.
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