... exchanger in the tank to heat the water.1.The inner tank is made of SUS304-2B stainless steel (thickness: ... : Outer: Aluminum alloy or stainless steel, inner: Rock wool with red copper pipe. 8.The standards of vacuum tubes with ... heat pipe: 14, 16, 18, 20, 24, 30, or 36 units ... all glass evacuated solar collector tube by 15 Heat pipe split pressure solar water heater