Thermal performance indicators, the average daily efficiency as high as possible, the average heat loss coefficient as low as possible. Key components of domestic solar water heater system is the all-glass vacuum tube solar collectors (referred to as the vacuum tube), vacuum quality directly affects the performance of the entire domestic solar water heaters. Purchase should carefully observe the coating on the glass vacuum tube, the coating layer is called the solar selective absorbing coating, coating color will be different, due to the production process of the manufacturers, but are generally black, dark blue or dark gray, good quality coating color uniformity, the film no scratches, no peeling or shedding phenomenon, no stone or tumor on the glass, the supporting supporting pieces of glass placed in correct, not loose. It should also be noted. Purchase the pipe spacing between the vacuum tube, usually two center distance in about 70mm is appropriate. Stent design of domestic solar water heater should be reasonable, and should be of sufficient strength and stiffness (supplement: There corrosion resistance, do not use the two-year bracket down) in order to ensure that there is sufficient load-bearing capacity. Large areas in some of the daily wind, especially in coastal areas, in the purchase of domestic
solar heating systems should also note that the product is designed for wind resistance. Currently on the market, a variety of reflectors form of domestic solar water heaters, flat reflectors, curved reflectors, embossed aluminum reflectors purchase should pay attention to the product design can take full advantage of the vacuum tube heat absorbing surface, the vacuum can be the maximum extent by the light.