1. After the solar water tank is empty of water, the temperature of the vacuum tube will be higher during the day if water is added at that time, the tube will easily explode due to the big difference of temperature. , which is the most likely possibility.
2. When there is less water in the vacuum tube, due to the high temperature, the steam after the water boils rises to the mouth of the tube and condenses into water when it meets cold air. releases a lot of heat and the vacuum tube partially overheats, expands and bursts. But it's less likely.
3. The vacuum tube cannot be insulated due to air leakage, causing the water in the tube to freeze when there is no light, causing the vacuum tube to swell and crack .
Detailed information:
The structure of an all-glass vacuum tubeconsists of an inner glass tube, a selective solar absorption coating, a vacuum interlayer, a protective glass tube, a bracket (spring clip), a getter, etc.
The inner glass tube is used as a water flow pipe; Selective solar absorption coatings such as copper oxide, black nickel, black chrome, black zinc and black copper are manufactured using vacuum deposition, sputtering, and electrochemical processing and d 'other processes are applied evenly to the outer surface of the inner glass tube to absorb solar radiation energy;
The inner glass tube covered with a selective coating is sealed in the cover glass, then the inner and outer glass tubes are a vacuum is established between the two to form a vacuum interlayer with a vacuum degree of 0.05 Pa to reduce heat loss ccaused by convection and air conduction, which is similar to the principle of a thermos bottle;
The all-glass vacuum collecting tube adopts an open design at one end, the inner tubes and outer are ring sealed at one end and the other end of the inner tube is a closed hemispherical round head. Spring clip is used. to support the round head at the inner end of the cover glass tube, so that the inner glass tube absorbs the sun. When the temperature increases due to radiation, the round glass head forms a free end for thermal expansion, thus buffering the thermal stress at the open end of the vacuum collector tube when the water heater works; after the vacuum tube is heated, it is initially adsorbed on the tube. Trace gases (mainly water vapor) on the wall will be released, affecting the vacuum degree. The getter andThe film getter are used to absorb these released gases in order to maintain a high vacuum in the collector tube.
Reference documents:
Baidu Encyclopedia - Solar vacuum tube