The heat insulation principle of pyrolysis low e glass is explained
In the mid-1970s, it was discovered that most of the heat transfer from double-glazed Windows was caused by the exchange of infrared radiation from one layer of glass to another. Therefore, as long as the emission rate of any surface in the double layer glass is reduced, the transmission of radiant heat can be greatly reduced. That's where the pyrolysis of low e glass comes in.
For two pieces of white glass without any coating, the long wave radiation exchange between them is very high, about 60% of the total heat exchange through this layer. When coated with low-e coating on the glass surface, the long wave radiation exchange between two pieces of glass will be greatly reduced. It can be seen that the effect of low-e is good when it is made into double layer, and the effect of heat preservation is better than that of single layer glass, which is very suitable for the cold north in winter.
The data showed that the emissivity of white glass was 0.84. When coated with a coating with a emissivity of 0.2, the radiation exchange rate of white glass decreased by 3/4, so the value of heat transfer coefficient also decreased. When the glass thickness is 4mm and the air thickness is 12mm, the heat transfer coefficient of the double-layer glass is about 2.8w /(m2*k). If the low-e coating reduces the heat transfer coefficient to 1.8w /(m2*k).
The advantages of low-e are obvious. As the coated film is very thin, it is transparent to the base wood for short-wave radiation, which makes the ultraviolet ray and visible light basically pass through, and is opaque to the long-wave infrared radiation. That is to say, keep indoor heat energy in winter, make its hard to send out outward, and summer will send out a lot of heat radiation of outdoor high temperature to reflect back, make its hard to enter indoor, accomplish "winter warm summer cool".