... alternative absorption coating on the inner surface of the vacuum tube,from the high-temperature environment super-conduction tubes,leads ... the solar energy,heat the water in the vacuum tube directly,through the cold and hot water convection,changes the solar ... manifold:stainless steel SUS304 2b,2) outer manifold: VPDF3)glass tube dimension:47X1500 mm4)heat preservation: 72 hours5) hail resistance: ...