Apply for two layers 3.3 high boronsilicon glass tube

Apply for two layers 3.3 high boronsilicon glass tubeThe two layers glass tube, with same axis is vacuumized between them, the vacuum degree can reach 5*10^-2 PaCoated with AL/N/AL selective absorbing coating materialHigh absorbing efficiency: the vacuum magnetic-control sputtering selective absorptive coatings on the heat-collecitng plates has a high absorption coefficient of more than 93%, and the emission coefficient around 6%.Long life: the life span can reach 15 years.High procticability: able to endure impact of hail less than 25mm in diameter with high heat efficiency throughout the year.