... 4) 3 years warranty for evacuated tube solar collector 2012 hot sell heat pipe evacuated tube solar thermal collector (CE, ISO9001,CGC ... capacity:135,150,165,200,250,300Liter StructureAll-glass double-tube co-axial structureGlass materialHigh borosilicate 3.3 glassExtermal pipe ... .4~0.6W/(m2. °C) 2012 hot sell heat pipe evacuated or vacuum tube solar thermal collector (CE, ISO9001,CGC,Keymark )