Heat collection principle of solar water heater. With the continuous improvement of living standards, every household has used water heaters, which can meet the use of hot water in people's daily life. So what is the heat collection principle of solar water heaters? Let's take a look.
The heat collection principle of solar water heater 1 Solar water heater converts solar light energy into heat energy and heats water from low temperature to high temperature to meet people's hot water use in life and production. Solar water heaters are divided into vacuum tube solar water heaters and flat plate solar water heaters according to their structural forms. At present, vacuum tube solar water heaters are the mainstay, accounting for 95% of the domestic market share. Vacuum tube household solar water heater consists of heat collecting tube, water storage tank and related accessories. The conversion of solar energy into heat energy mainly depends on the collector tube. The collector tube uses the principle of hot water floating and cold water sinking to make the water produce microcirculation and reach the required hot water.
1 endothermic process
Solar radiation passes through the outer tube of the vacuum tube, is absorbed by the heat collecting coating, and then passes along the inner tube wall to the water in the tube. After absorbing heat, the temperature of water in the pipe rises, and the specific gravity decreases and rises, forming upward power and forming a thermosyphon system. As the hot water moves upward, it is stored in the upper part of the water storage tank, and the water with lower temperature is continuously replenished along the other side of the pipeline, and finally the whole tank of water rises to a certain temperature. Flat water heaters are usually split water heaters. The medium naturally circulates in the heat collecting plate due to thermosiphon, and the heat irradiated by the sun on the heat collecting plate is transferred to the water tank in time, and the heat in the water tank is transferred to cold water through heat exchange (jacket or coil). The medium can also realize heat transfer through pump circulation.
2 circulating pipeline
Domestic solar water heaters usually work in natural circulation mode and have no external power supply. Vacuum tube solar water heater is in-line structure, and hot water is powered by gravity. Flat solar water heaters are powered by the pressure of tap water (called top water). The solar central heating system adopts pump circulation. Due to the small heat collection area of solar water heaters, considering the heat loss, pipeline circulation is generally not used.
3 Top Water Use Process
Flat solar water heater works in top water mode, vacuum tube solar water heater can also work in top water mode, and water tank can use jacket or coil. The advantage of jacking water is that the water supply pressure is tap water pressure, which is higher than the natural gravity pressure, especially when the installation height is not high. Its characteristic is that the water temperature is high first and then low in the process of use, which is easy to master and easy for users to adapt, but tap water is required to maintain its water supply capacity. The cost and price of solar water heater with top water working mode are higher than that of gravity water heater.
Heat collection principle of solar water heater 2 1 working principle of vacuum tube solar water heater: vacuum tube absorbs heat-micro-circulation-heat preservation water tank-metering control system-user vacuum tube solar water heater, which uses vacuum tube to collect heat to realize light-heat conversion to the maximum extent, and sends hot water to the heat preservation water tank through micro-circulation and to users through special pipelines. The control system sends tap water to solar energy through control valves and controllers to realize automatic control. Auxiliary electric heating is put in the water tank, which has been used in rainy days, rain and snow angels, saving electricity by 90%. And run it automatically.
2 Performance characteristics and technical parameters:
1 heat collecting element-specification for technical parameters of vacuum tube;
1200mm× 47mm1500mm× 47mm. At present, Al-N/Al vacuum sputtering selective coating has the best heat collection effect. This product adopts 1.2 and 1.5m glass vacuum coating tubes, with absorption rate ≥0.93, infrared emissivity ε≤0.6, average heat loss UCT 0.9w/m2 and vacuum degree P ≤ 5× 10.
2. Performance characteristics and technical parameters of thermal insulation materials:
The quality of thermal insulation materials is directly related to the thermal efficiency and the use at night and early morning, which is particularly important in the cold northeast. At present, the better insulation method is imported polyurethane insulation. If the ingredients, process, environment and temperature are not suitable, it will also lead to uneven foaming, too large foaming holes, slow leakage of working medium and gradual decline of heat preservation, which requires manufacturers to have special foaming machinery, standardized molds and high technological level. In addition, we should not only know the material technology of products, but also look at the organic cost of machinery, equipment and molds of manufacturers and the level of quality control. Product quality is directly related to the interests of consumers.
Polyurethane insulation layer thickness: 70mm closed porosity: 65.69; Thermal conductivity: 19.83mw/m. K, after high temperature curing.
3. Water tank lining and bracket
Water tank is an important part for storing hot water, and its material strength and corrosion resistance are very important. The high-quality material should be imported SUS304 plate, stainless steel plate with thickness of 0.6 mm-0.8 mm, argon protection and high-frequency automatic welding, which can improve the corrosion resistance of steel plate in various water quality or various environments. It is an advanced welding process.
The bracket is made of stainless steel (SUS304) with beautiful appearance and high strength. The bracket and the whole machine are connected by bolts, which have strong rigidity, convenient transportation and installation and strong corrosion resistance.
Working principle of heat pipe pressure-bearing solar water heater: vacuum tube absorbs heat-heat pipe conducts heat-heat preservation water tank-control system-users. (the price is higher)
Heat pipe pressure-bearing solar water heater uses vacuum tube to collect heat, and U-shaped fins are built in to transfer heat in high temperature environment to the heat pipe, which quickly transfers heat to the water tank, especially in cloudy weather with low radiation intensity. After continuous testing, the daily average thermal efficiency of the heat pipe solar water heater is as high as 56%.
Technical parameter specification of heat pipe of heat transfer element: φ8× 1520
1. There are many domestic heat pipe manufacturers. We tested all domestic heat pipes, and tested their performance and service life according to GB/T14812-1993, GB/14813-1993. Finally, the inorganic molecular heat pipe (patented technology of American -MACBLE Company) was selected, and it was proved to have excellent heat transfer performance through the long-term system test of Stanford Research Institute (SRI). Heat transfer does not need phase change of working medium, but depends on molecular thermal motion, which has the advantages of fast heat transfer and high heat transfer efficiency.
2. High bearing capacity
The water tank of heat pipe solar water heater adopts 2MM thick steel plate, arc head and automatic CO 2 welding. The pressure bearing capacity is 0.6MPa, and the sealing working pressure is as high as 1.2Mpa. The internationally advanced electroless nickel plating technology is selected, and the surface spraying has reached the international advanced level. The collector can withstand the pressure of tap water (the highest test pressure can reach 1.2MPa). The dimensions meet the requirements of TB3 1 1-74.
3. Strong frost resistance and bearing capacity
The heat pipe solar water heater adopts heat pipe heat transfer technology, and there is no water in the heat collecting pipe, so it will not freeze and crack the heat collecting pipe because of the low temperature in extremely cold areas, which will affect its use. Moreover, because there is no water in the pipe, if a heat pipe is damaged, it will not affect the work of the whole machine, so that the application scope of the water heater is wider. The bracket is made of stainless steel (SUS304) with beautiful appearance and high strength. The bracket is connected with the whole machine through bolts. The bracket and the whole machine have good rigidity, convenient transportation and installation and strong corrosion resistance.