Coaxial Heat Exchanger with copper is good heat conduction suitable air sourced heat pump water heater,water chiller and so on. Spiral twisted ... .High turbulence inside reduced fouling rate on water side.One heat exchanger tube promised the risk of inner leaking.Cost effcientVarious material ... ,cupronickel,aluminum,titanium,stainless steel to carbon steel. Weal Yield Coaxial Heat Exchanger