Water mist is the most intuitive impression of the solar energy collector, and it is also the most troublesome thing of solar collector. In fact, the water mist is only a representation, it is the essence of the existence of the solar heat collector in the cavity of water, will not disappear because of the evaporation of sunlight.
There are three sources of these moisture:
Residual moisture: heat collecting cavity material (especially insulation material) for equilibrium moisture absorbed and environmental humidity balance after being encapsulated into the cavity, in the humid areas (such as China Guangdong and Jiangsu and Zhejiang provinces) the residual water content will be more, while in the dry areas (such as the Northwest China and Inner Mongolia) will be relatively better.
Infiltration of water, such as rain, especially when it is violent, due to the lack of closure of a heat collecting chamber.
Damp water: in a humid environment due to internal and external humidity difference (external humidity, internal humidity) and internal moisture absorption material for the formation of water increased, but also for the actual equilibrium moisture balance moisture formed.
The harm of moisture in flat plate collector
Weaken the solar radiation in the cavity: the evaporation of the water collector in the flat transparent cover layer (glass) for condensation of water mist, the transmittance will be affected, the solar radiation energy received will be weakened, but also increased the convective heat loss at the top of the air layer.
Heat insulation: insulation material is porous material, easy to absorb moisture. The coefficient of thermal conductivity of water is 25 times that of air. The moisture content of the material occupies some of the original air filled pore space. The results show that the thermal conductivity coefficient of 0.03W/M / K is 1%, and the thermal conductivity increases by a factor of 25%.
Absorption surface recession: the study shows that the absorption surface will have different degrees of corrosion in salt fog experiment, different surface absorption of salt spray test is the ability to also have the difference, the black chromium coating of high quality can be resistant to 120 hours, while the radiation characteristics of blue titanium coating especially good even as only 6 hours; non professional users also have their own use of direct observation and experience. Some enterprises in the production of blue film balcony flat panel collector in Inner Mongolia stock after a winter, that is, the absorption of white spots appear on the surface.
The phenomenon of water mist and the problem is serious, this is the superposition of internal and external factors, external environment condition of rain and snow, a dangerous situation, or changes in temperature and humidity, harmful substances in the atmosphere, especially PM2.5 and fine dust, the flat plate collector cavity has become the object of invasion in acid-base salt fog different extent; the internal structure and material to set the heat from their own to find a flat. The flat plate collector is one of the leading products in the field of solar energy. The appearance of water mist has seriously affected the thermal performance and the life of the flat plate collector.
Finally, it is found that the influence of water mist is mainly due to three aspects, such as excessive moisture absorption, tight sealing and poor exhaust effect. These issues also need industry experts and manufacturers together to overcome technical difficulties, better solve the corrosion problem of water mist and the collector plate, flat plate solar produce quality products, in order to repay the majority of users.