copper coil heat exchanger copper coil: 25-35m red copper as heat exchanger in water tank(Dia12*1.0mm) copper coil heat exchanger How it works1. Vacuum tube absorb heat ... into the copper coil, it absorbs heats from water in the water tank.Features 1,Cheap and reliable hot ... solution2,Simple structure, easy to assemble and install. 3,Strong wind, snow and hailstone resistant ability 4,Fresh water, ...