What is the principle of solar water heater?

Working schematic diagram of solar water heater 1. Cold water enters the solar water heater through the pipeline, and passes through the heat collecting plate, which can collect solar energy, convert it into heat energy, and then heat the cold water. Because the specific gravity of cold water is greater than that of hot water, hot water will automatically rise, thus forming a circulating power. Water will gradually heat up on the heat collecting plate. After reaching a certain temperature, it can enter the hot water storage tank and supply hot water when necessary. Heat Figure 2. In fact, the principle of solar water heater mainly includes the following two principles: (1) water circulation principle, that is, water will automatically flow, and the density of cold water is greater than that of hot water, so that cold water sinks and hot water rises, forming a natural convection cycle, and the water in the water tank will gradually heat up until it reaches the set water temperature. When the intensity of the sun is not enough to meet the needs of circulation, a water pump can be added to the closed loop of water circulation to realize forced circulation. (2) The heat absorption principle of the collector: The surface of the collector of the solar water heater has a special coating, which has a great absorption rate in the visible range of solar energy. After being absorbed as heat, the thermal radiation wavelength of the collector is in the long wave range, and the emissivity of the coating on the long wave is very low, thus effectively retaining the heat of solar energy. Then the cold water is gradually heated into hot water by this heat. The solar collector tube will be described in detail below. The collector tube is actually like a slender inner container of a hot water kettle, which consists of two glass tubes, one large and one small. The outer layer is transparent, the inner layer is coated with a spectrally selective absorption coating, and the inner tube and the outer tube are evacuated. It is the core of solar water heater, which is used to absorb the heat energy radiated by sunlight to the maximum extent. Because the vacuum glass tube is round and has the characteristic of naturally tracking the solar light source, combined with the reflection principle of the reflector, the glass tube can receive light from all directions, and the heat collection effect is more lasting, and the water temperature is higher, even in the alpine region, it can run normally all year round.