Abstract: A heat exchanging system for exchanging heat with contaminated water includes a housing having a coaxial tube exchanger assembly with return passages in the housing ends for the outer tubes and return tube bends for the inner tubes. A filter at the inlet of the coaxial tube assembly is formed of a number of passages in parallel with right angle bends defined by parallel fins between a bottom plate and transparent top plate. For cleaning there is a pressure chamber, a fill valve and an air valve intermittently activated. There is also a drain valve and a vacuum release valve. Heat exchanger tube is manufactured by rotatably and axially feeding tubing through a repeating impacting pointed power hammer that forms sharp edge craters on the exterior of the tube and sharp peaks on the interior. An impact tool driven by a powered impact hammer strikes the tubing passing through a tube pathway defined by variable direction rollers. A power drive roller has its axis askew to the axis of the tube.

Abstract: A multiplicity of parallel heat transfer tubes each sealed with refrigerant are journaled for rotation at each end and in a bulkhead that separates the air flow channel in a counterflow heat exchanger into ingoing and outgoing parallel channels. Each heat transfer element has closely spaced circular fins extending radially outward from each tube, the spacing between adjacent fins being less than the fin radius. A motor and transmission cause each heat transfer element to rotate about its longitudinal axis.