outer diameter and inner diameter (mm): ??47/37; ??58/47 length of tube (mm): 1200, 1500, 1600, 1800, 2000, 2100 thickness of tube (mm): 1.60± 0.15 material: borosilicate glass 3.3 thermal expansion: 3.3*10-6/k maximum strength: 0.6 mpa selective absorbing surface: al-n-al sediment method: three target magnertron sputtering plating absorption of selective coating: α =90% -93% (am1.5) emission of selective coating: ξ =5%-7.5%(80 º c± 5º c) stagnation temperature: 220-260m2º c/kw solar irradiation for water temperature rise: ??4.0mj/ m2 coefficient of average heat loss: 0.6-0.7w/(m2 º c) vacuum: p??3.0*10-3pa