Diagram of working principle of solar water heater 1. Cold water enters the solar water heater through the pipe, passes through the heat collecting plate, and the heat collecting plate can collect the energy solar, convert solar energy into thermal energy, then heat cold water. Since the density of cold water is higher than that of hot water, the hot water will automatically increase and then form circulating power. The water will gradually heat up on the heat collecting plate. After reaching a certain temperature, it can enter. the hot water tank. Those who need hot water will be able to get hot water at any time. Heating Figure 2. In fact, the principle of solar water heaters mainly includes the following two principles: (1) The principle of water circulation, that is, the water flows automatically. This is based on the fact that cold wateris denser than hot water. Cold water flows and hot water rises, forming natural convection that gradually heats the water in the water tank until it reaches the set water temperature. When the intensity of the sun is not sufficient to meet circulation needs, a water pump can be added to the closed water circulation circuit to obtain forced circulation. (2) Collector heat absorption principle: There is a special coating on the collector surface of the solar water heater. This coating has a high absorption rate in the visible range of solar energy. After absorbing it in the form of heat, heat. the radiation from the collector will have the wavelength in the longwave range and the coating has low longwave emissivity, thus effectively retaining solar heat. This heat is then used to gradually heat the cold water into hot water.Solar collector tube Let's talk in detail about the collector tube on this collector. The collector tube is actually like an elongated hot water kettle liner. It is made of two glass tubes, one large and one small. the inner layer is covered with a spectrum-selective absorption coating, and a straight void is drawn between the inner and outer tubes. It forms the core of the solar water heater and is used to maximize the absorption of thermal energy after solar radiation. The vacuum glass tube is round, has the characteristics of naturally following the broad source of the sun, coupled with the reflection principle of the reflector, the glass tube can receive light from all sides, the heat collection effect lasts longer, the water temperature is higher. , and it can work normally all year round, even in alpine areas.
Solution: (1) ∵CE=76 cm, ∠CEH=60°,
∴sin60°==,
∴CH=38 cm.
(2) Suppose the length of the radius OC of the water tank is x cm, then HO=(38 +x) cm, OD=(150+x) cm,
∵∠ADH = 30°,
∴OH=DO,
38 +x=(150+x),
The solution is: x=150 -76 = 150-131.48≈18.5cm．