Solar Evacuated Glass Tube

Solar Evacuated Glass Tube Descriptions of Solar Evacuated Glass Tube A evacuated tube or vacuum tube, known as a main component of evacuated tube solar collector, is mainly made of double-walled glass, namely inner tube, outer tube. Two glass tubes are closed on one side and sealed with each other on the other side so that an evacuated space is formed. The inner tube is coated with aluminium nitrite, a special selective material, which serves to absorb radiation falling on it. To maintain the vacuum between the two glass tubes during manufacture, a barium getter (see below) is used at the bottom of the glass tube. High temperature produced during manufacture will cause tube bottom to be coated with a barium layer, which provides a visual indicator of the vacuum status. The silver coloured barium layer will turn white if the vacuum is lost. Based upon this, we can easily determine whether or not a tube is operating correctly. See right picture below. Left Tube: Good Right Tube: Faulty Main Advantages of Solar Evacuated Glass Tube -Good hail resistance: the rigid borosilicate glass outer tube can withstand impact from hail up to 30mm in diameter -The superior insulating properties of the vacuum enable it to absorb the radiations from the sun, even it works on cloudy days since the tubes are able to absorb the energy from infrared rays which can pass through clouds. -Superior absorption: the round profile of tube enables the rays to reach the collector directly and therefore the energy can be constantly absorbed; the inner tube is coated with a special selective coating featuring excellent soar heat absorption and minimal heat reflection properties. Main Applications of Solar Evacuated Glass Tube As an indispensable component of Glass Evacuated Solar Collector, it mainly serves to provide heat for domestic use. Technical Specification of Glass Evacuated Tube Material: borosilicate glass 3.3 of ISO3585:1991standard; Transmittance of borosilicate glass: τ≥0.92. Absorbance of solar selective absorptive coating: α≥0.92; Hemispherical emittance:ε≤0.08 Start-up temperature: ≤25℃. Start-up time: ≤2 minutes under normal sunshine. Low temperature resistance: Max -30℃ Heat impact resistance: over 3 times’ alternative impacts of cold water below 25℃ and hot water over 90℃. Pressure resistance: Max 0.8 Mpa. Hail resistance: max ? 25mm hailstone Absorber Area : the total of the 360% absorber surfaces of the inner coated vacuum tube Appearance standard: the selective absorptive coatings should be even and intact. The permissible tolerance of borosilicate glad tube’s diameter should follow by ISO4803:1978. The camber of the borosilicate glass tube should be less than 0.3%. The translation the borosilicate glass tube, a distance of 40-45mm away from flange end, should be round. The ratio of the longest to the shortest radial dimensions of the borosilicate glass tube should be no more than 1.02. Technical Parameters (TYY-AA series vacuum tubes) Model Glass vacuum tubes Glass Material High-quality borosilicate glass 33 Thermal Expansion 3.3x10-6 ℃ Glass Tube Diameter ?47mm / 58mm Inner Glass tube diameter 37mm / 47mm Thickness of Vacuum ?5mm Length 1500mm ,1800 mm Glass Wall thickness 1.6 mm / 1.8mm Single Tube weight 1.35kg ; 2.0kg High Vacuum, long-term stability 5×10-3 Pa Absorber Material Aluminum Absorptive Coating Aluminum Nitride Absorption Coefficient α 0.90-0.93 Wind Resistance 30m/s Emittance <8% (80℃) Heat Loss <0.8W/ ( m2℃ ) Maximum Strength 0.8MPa Freezing Tolerance -30 ℃ Hail Resistance ? 30mm hail Insolation Temperature 250 ℃ Start-up Temperature ≤25 ℃ Life Time (years) 15 years

heat pipe solar collector