Contrastive Analysis of Energy Saving Characteristics of Building Glass

China is a major energy source, building energy consumption, industrial energy consumption and transportation energy consumption is the main source of energy consumption. According to statistics: building energy consumption accounts for about 30% of the total energy consumption, the proportion in the next 20 years may reach 35%; building energy consumption, through the glass doors and windows loss of energy consumption accounted for all building energy consumption 2/3, where the heat loss is 1/3. The data show that the energy lost by the glass accounts for 80% of the energy loss of doors and windows. Therefore, to improve the energy-saving performance of glass, has become the real key to building energy efficiency.

2, several terms

2.1, solar spectrum

The wavelength of the solar radiation is about 0.15μm ~ 4μm, and the energy is about 97% in the wavelength range of 0.3μm ~ 2.5μm. The ultraviolet wavelength is 280nm ~ 380nm, and the radiant energy is about the total solar energy 7%; visible wavelength range 380nm ~ 780nm, about 50% of the total solar radiation energy; near infrared light wavelength range of 780nm ~ 2500nm, about 43% of the total solar radiation energy. Which only visible light on the building lighting effect.

2.2, visible light transmission ratio Tvis

The visible light transmittance is the percentage of the ratio of the intensity of the transmitted light to the intensity of the incident light in the visible spectrum (380 nm to 780 nm). The higher the visible light transmittance of the glass, the better the luminous effect of the room, but the same amount of solar heat entering the room will increase accordingly, while maintaining the same low radiation performance.

2.3, the shielding coefficient of glass SC

According to the standard GB / T2680-94 "visible glass transmittance, solar direct transmission ratio, solar total transmittance, UV transmittance and the determination of the relevant window parameters," the shielding coefficient is defined as: under normal incidence conditions, The ratio of the total solar transmittance ratio of the solar system through the light transmission system to the same conditions, the same area of ​​standard glass (3mm thick ordinary transparent flat glass).

The shading coefficient of the glazing indicates that the glazing of the glazing is weakened in the absence of other shading measures.

2.4, heat transfer coefficient K

Heat transfer coefficient K is a measure of glass insulation properties of an important indicator in Europe and the United States also known as U value. Heat transfer coefficient is in the stable heat transfer conditions, the glass on both sides of the air temperature difference of 1 ℃, the unit time through 1m2 insulating glass heat transfer, with the unit W / (m2.K) said. The lower the heat transfer coefficient K, the better the thermal insulation performance of the glass, the less the heat loss, the more significant the energy saving effect when used.

3, comparative analysis

Insulating glass is made of two or more pieces of glass sandwiched between the air or inert gas (such as argon (denoted by A), krypton), with effective support evenly separated and sealed sealed products. Insulating glass mainly through the middle of the gas layer to reduce the heat transfer coefficient, to achieve the effect of thermal insulation. Commonly used insulating glass thickness of 3mm, 4mm, 5mm, 6mm, 10mm, 12mm, the middle of the gas layer thickness of 6mm, 9 ~ 12mm, 12 ~ 20mm.

We know that heat loss is achieved by conduction, convection and thermal radiation. The use of insulating glass, can effectively prevent the heat conduction and convection, play a certain role in energy conservation. By using Lambda950 UV / Vis / near infrared spectrophotometer and Fourier transform infrared spectroscopy, the ordinary monolithic transparent glass, transparent insulating glass and low-E (low-E) coated insulating glass were analyzed respectively. By comparing the visible light transmittance, Shielding coefficient and other parameters, analysis of three kinds of glass energy-saving performance.

3.1, ordinary single transparent glass, transparent insulating glass energy-saving detection and comparative analysis

6mm ordinary monolithic white glass and 6mm + 12Amm +6mm hollow glass using spectrophotometer and infrared spectrometer in the solar spectrum 280nm ~ 2500nm wavelength range of the test, the parameters shown in Figure 1 and Figure 2.

It can be seen from Fig. 1 that the visible light transmittance Tvis of 6mm plain white glass is 0.8797, about 88.0%; the value of shielding coefficient SC is 0.955; the heat transfer coefficient U value (K value) is 5.816; visible light reflectance is 8.24 %; Solar direct transmission ratio of 79.2%.

It can be seen from Fig. 2 that the thickness of visible glass is 0.4663, that is, 76.6%, and the shielding coefficient SC is 0.815, and the heat transfer The coefficient of U (k) is 2.538; the visible light reflectance is 14.6%; the direct solar transmission ratio is 62.6%.

Insulating glass compared with ordinary white glass, because two or more pieces of glass between the air or inert gas thermal conductivity is much smaller than the glass, thereby improving the thermal resistance, reducing the heat transfer coefficient. It can be seen from Fig. 1 and Fig. 2 that the heat transfer coefficient is reduced from 5.816 to 2.538, the hollow glass heat transfer coefficient is only 44% of the single layer glass, and the effective barrier to heat conduction and convection mode is achieved, and good heat insulation effect. However, ordinary insulating glass due to high heat radiation, the radiation to prevent the effect is not good. It can be seen from Figure 2, ordinary insulating glass shielding coefficient of up to 0.815, in the building energy-saving insulation effect is not prominent.

3.2 Low-E (Low-E) coating insulating glass energy-saving detection and analysis

The hollow glass of 6mmLow-E + 12Amm + 6mm was measured by spectrophotometer and infrared spectrometer in the wavelength range of 280nm ~ 2500nm, and the parameters were shown in Fig.

As can be seen from Figure 3, a thickness of 6mm Low-E glass and a 6mm ordinary white glass, the middle folder 12mm of argon, the resulting insulating glass visible light transmittance Tvis value of 0.5043, or 50.4%; shielding coefficient SC The value is 0.548; the heat transfer coefficient U value (ie K value) is 1.842; visible light reflectance ratio is 23.2%; solar direct transmission ratio is 31.0%, belongs to shade type Low-E glass. Compared to ordinary insulating glass, the heat transfer coefficient U value from 2.538 to 1.842, to obtain a better thermal insulation effect. The shielding coefficient SC reduced from 0.815 to 0.548, effectively preventing the solar thermal radiation into the room, thereby reducing the heat loss, play a building energy efficiency effect.

In addition, Low-E glass has a strong reflection effect on long-wave radiation compared to ordinary hollow glass, and the reflection ratio of low-E insulating glass is increased from 12.9% to 22.9%.

4 Conclusion

(1) ordinary insulating glass compared with ordinary white glass, more effective to achieve the heat conduction and convection way barrier, get a good insulation effect. But its shielding coefficient is high, in the building energy-saving insulation effect is not prominent.

(2) low-radiation (Low-E) coated insulating glass compared to ordinary insulating glass, get a better insulation effect. And the shading coefficient is reduced, the solar reflectivity increases, effectively preventing the solar heat radiation into the room, thereby reducing the heat loss, play a building energy efficiency effect.

(3) fully aware of the existing energy-saving glass products, continuous research and development of new superior performance of the glass, the building energy consumption to maximize energy conservation is of great significance.