Solar water heater converts sunlight energy into heat energy and heats water from low to high temperature to satisfy people’s hot water use in production. Solar water heater is divided into vacuum tube solar water heater and flat plate solar water heater according to the structure form, and now vacuum tube solar water heater is the main type, occupying 95% of the market share in China. The vacuum tube type solar water heater is composed of a collector tube, a storage tank and related accessories, and the conversion of solar energy into heat energy mainly relies on the collector tube. The collector tube exercises the principle of hot water floating up and cold water sinking down to make the water micro-circulation and reach the required hot water.
【1】Heat absorption process
Solar radiation through the outer tube of the vacuum tube is absorbed by the collector coating and then transferred along the inner tube wall to the water inside the tube. The water inside the tube increases in temperature after heat absorption, and the specific gravity decreases and rises, forming an upward momentum and forming a thermo-siphon system. As the hot water keeps moving up and stored in the upper part of the storage tank, while the lower temperature water along the other side of the tube keeps making up for the cloud cycle, and eventually the whole tank of water is raised to a certain temperature. And flat plate water heater, as usual for the split water heater, the medium in the collector plate because of the natural cycle of thermal siphon, the heat of the sun’s radiation in the collector plate is transmitted to the tank in real time, the tank through the heat exchange (jacket or coil) will heat transfer to the cold water. The medium can also be circulated by pump to realize heat transfer.
【2】Circulation piping
Domestic solar water heaters usually circulate things in a natural way, without external power. Vacuum tube solar water heaters are inline structures, and hot water is powered by gravity. Flat-plate solar water heaters provide power through the pressure of tap water (called top water). And solar central heating systems all accept pump circulation. Because the solar water heater collects heat in a small area, taking into account the heat loss, as usual, do not accept the pipe circulation.
【3】The course of using top water type
Flat-plate solar water heater for the top water way things, vacuum tube solar water heater can also be implemented in the way of top water things, the tank can accept the jacket or coil way. The advantage of the top water thing is that the water supply pressure is the tap water pressure, which is greater than the natural gravity pressure, especially when the installation height is not high, and its characteristic is that the water temperature is first high and then low in the course of use, which is easy to grasp and the user can easily adapt, but the tap water is required to maintain the water supply capacity. The top water thing way of solar water heater than the gravity water heater cost big, high price.
