solar water heater vacuum tubes

Specifications

solar vacuum tube,glass vacuum tube

Specification:
The marerial of glass tube: Hard borosilicate: 3.3
The thickness of inner and outer tube of: 1.6mm
Absorption coefficient: 93%
Absorptive coating: High efficient heat absorptive selective sputtering coating:
SS-C/CU&AL-N/AL
Emission coefficient: 10%(8%)
Evacuated: 5*10-3pa
Stagnation temperature: 220 degree celsius
Hail resistance: 25m
Freezing resistance: -35degree celsius

Structure		Dual concentric geometry tube
Material of glass		hard borosilicate:3.3
Diameter and thickness of outer tube		Ø58±0.5mm&1.6mm
Diameter and thickness of inner tube		Ø47±0.5mm&1.6mm
Length of vacuum tube		1800mm(±mm)
Properties of absorptive coating	Coating method	selective absorptive sputtering coating: SS-C/cu & AL/N
	Transmissivity t≥0.89(AM1.5)	0.913
	Absorptance α≥0.86(AM1.5)	0.930
	Emissivity  εh≤0.080(30degree±5degree)	0.026
Pressure of vacuum tube   p≤5×10-2 Pa		5×10-3Pa
Stagnation parameter Y>250sqm·degree/kW		246.3
Solar radiance   H<4.7MJ/sqm		4.59
Average heat loss coefficient: ULT<0.8W(sqm·degree)		0.721
Lifetime		15 years