1. The surface is smooth and clean, and the tube body has no stains, no air ducts, no scratches, and no scratching phenomenon (this phenomenon will affect the heat collection efficiency
and aesthetics).
2. The color of the film layer is mainly blue and black, and the overall color difference is small. But black does not mean that the vacuum tube is of good quality, because some manufacturers often make the film layer completely black in order to mask the noise. In fact, some color errors of vacuum tubes are inevitable and do not affect the heat collection efficiency of vacuum tubes.
3. The fired mirror surface is complete, smooth and translucent, without blackening or blackening.
4. There are three best vacuum tubes on the market: high temperature tubes, high efficiency tubes and high temperature tubes. The film layerof high temperature tubes is longer than that of ordinary tubes (about 1 cm from the tube mouth). This tube is resistant to high temperatures and has strong resistance to attenuation. The film layer will not age, fall off or fade when exposed. in air at high temperatures of 400°C. The high-efficiency tubular film layer is about 2.5 cm from the tube mouth. This tube has ultra-high absorption, less heat loss, rapid temperature rise and high thermal efficiency. Alpine tubes feature the advantages of high efficiency tubes with high thermal efficiency and rapid temperature rise. At the same time, they have less heat loss and can still produce hot water at -30°C. Consumers can choose different vacuum tubes according to different areas.
5. To the naked eye, the color of the inner tube is dark red, indicatingant that its lower metallic layer is made of copper. This type of vacuum tube can also work normally under. severe cold conditions, -30℃ Discharge hot water as usual. High quality vacuum tubes are generally used for more than 15 years, which is directly related to the lifespan of the solar water heater. Nowadays, the quality of most manufacturers is uneven, so consumers need to open their eyes and identify them carefully.