Why is insulating glass insulated?


Insulating glass has a certain thermal insulation performance, which is what we have learned in practical applications. So, why is insulating insulated glass? The company makes a statement for this.
It should be noted that to understand the thermal insulation of insulating glass, it is first necessary to understand the thermal resistance of its components, glass and air.

1 glass thermal resistance

Ordinary glass has a thermal conductivity of 0.77 W/m2K, which is 27 times that of air. In order to increase the thermal resistance of the glass, it is not necessary to simply increase the thickness of the glass, but it is necessary to select some glasses of special properties. For example, low-emissivity glass has the same transmittance for visible light as ordinary glass, but it can reflect all infrared and far-infrared rays in the room to avoid heat loss in the room. It is suitable for use in cold regions; heat-reflecting glass can The solar energy is reflected back to prevent solar energy from entering the room. It is suitable for use in areas where air conditioning is required. The heat absorbing glass has a high absorption rate of heat. After absorbing the heat of sunlight, it can be released to both sides if it is on the side of the heat absorbing glass. Adding a layer of reflective film will prevent the solar heat from entering the room better.

2 air layer thermal resistance

The thermal conductivity of air is very small, 0.028W/m2K, and the air in the interlayer is not convected, thus increasing the thickness of the air layer and significantly increasing the thermal resistance. The relationship between the thickness D of the air layer and the thermal conductivity K of the insulating glass is that when D is less than 10 mm, there is no convection in the air layer, and as D increases, K decreases; when D is greater than 10 mm, convective heat transfer increases, with As D increases, the magnitude of the decrease in K decreases; when D is greater than 20 mm, the K value hardly changes. From the aspects of heat insulation effect and economy, the thickness of the air layer is preferably 12 mm. Replacing the air in the interlayer with a gas having a low thermal conductivity such as argon also enhances the insulating effect of the insulating glass.

3 Thermal resistance of insulating glass: thermal resistance of insulating glass R = RI + ∑ RG + ∑ RA + RO RI in the formula, RO is the thermal resistance of the outer surface of the hollow glass, for a certain use, it is a fixed value.

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