1,Solar vacuum tube for solar energy water heater 2,ISO,CE 3,Available in various size 4.5days delivery 5.OEM available 1, Vacuum tube is ... the space between the two glass tubes to form a vacuum, so it eliminates heat loss.7, This why the tubes ... KW≥230/KWAverage Heat loss coefficient≤0.85W/(*)≤0.85W/(*)Solar irradiation under stagnation≤3.5MJ/≤3.5MJ/Hailstone resistancehailstone diameter25mmhailstone ...