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Comparative analysis of characteristics of building energy-saving glass
- Apr 06, 2017 -

Chinese is a big energy consumption, building energy consumption, industrial energy consumption and transportation energy consumption is the main source of energy consumption at present. According to statistics, the building energy consumption accounted for about 30% of total energy consumption, the proportion in the next 20 years is likely to reach 35%; building energy consumption, building energy consumption accounted for all through the glass doors and windows of the loss of 2/3, the heat loss is 1/3. Relevant data show that the energy loss through the glass doors and windows of the energy loss accounted for 80%. Therefore, to improve the performance of energy-saving glass, has become the key to realize the building energy saving.

2, a few terms

2.1, the solar spectrum

The solar radiation energy out of the wavelength range of about 0.15 m ~ 4 m, in 0.3 m ~ 2.5 m wavelength range with the concentration of about 97% of the energy, the wavelength range of 280nm ~ 380nm, the radiation energy accounted for about 7% of the total solar radiation energy; visible light wavelength range is 380nm ~ 780nm total solar radiation, accounting for about 50% of energy; near infrared wavelength range of 780nm ~ 2500nm, accounting for about 43% of the total solar radiation energy. The only visible light on the lighting effect.

2.2, visible light transmittance of Tvis

The visible light transmittance is in the visible spectrum (380nm ~ 780nm) range, through GlassThe percentage of the light intensity and the incident light intensity ratio. In the same low radiation performance under visible light transmission glass is higher than that, the better the effect of indoor lighting, solar heat into the room but at the same time will also increase accordingly.

Shading coefficient SC 2.3, glass

According to the standard of GB/T2680-94 " Architectural glass The visible light transmittance, solar direct transmittance, total solar energy transmittance, and ultraviolet transmittance determination ", shading coefficient is defined as: in the normal incidence condition, through the solar light system total transmission ratio and the same conditions, the standard glass of the same size (3mm thick ordinary transparent Plate glass ) the ratio of the total solar energy transmittance.

Shading coefficient window glass windows that no other shading measures, reduced the level of solar radiation heat transmission.

2.4, the heat transfer coefficient of K

The heat transfer coefficient K is an important index to measure the performance of thermal insulation glass, also known as U in europe. The heat transfer coefficient is stable under heat transfer conditions, the glass on both sides of the air temperature difference is 1 degrees centigrade, per unit time by 1m2 Hollow glass The heat transfer unit (m2.K), W/ said. The heat transfer coefficient K value is low, indicating the glass insulation performance better, less heat loss, energy-saving effect is more significant when in use.

3, comparative analysis

Hollow glass is made between two or more pieces of glass with air or inert gas (such as argon (A), krypton), to effectively support the uniform product separated and sealing adhesive. Hollow glass is mainly through the middle of the gas layer to reduce heat transfer coefficient, achieve heat preservation energy-saving effect. Hollow glass thickness used for 3mm, 4mm, 5mm, 6mm, 10mm, 12mm and so on, the gas in the middle layer thickness in the 6mm, 9 ~ 12mm, 12 ~ 20mm.

We know that the loss of heat by conduction, convection and heat radiation to achieve. The use of hollow glass, conduction and convection can effectively prevent heat, play a certain role in energy-saving insulation. By using Lambda950 UV / Vis / NIR spectrophotometer and Fourier transform infrared spectrometer respectively on ordinary monolithic transparent glass, transparent glass and Low-E coated insulating glass (Low-E) were analyzed by comparing the visible light transmittance, shading coefficient and other parameters, energy performance analysis of three kinds of glass.

3.1, ordinary single glass, transparent hollow glass energy saving detection and analysis

Hollow glass of white 6mm ordinary monolithic glass and 6mm 12Amm using 6mm spectrophotometer and infrared spectrometer in the solar spectrum in the wavelength range of 280nm ~ 2500nm were tested, the obtained parameters are shown in Figure 1 and figure 2.

Figure 1 shows that the visible light transmission 6mm ordinary white glass than the Tvis value of 0.8797, about 88%; numerical shading coefficient of SC is 0.955; the heat transfer coefficient U value (K value) is 5.816; visible light reflectance is 8.24%; solar direct transmittance is 79.2%.

Figure 2 shows that the two film thickness are ordinary white glass 6mm, argon sandwiched 12mm, hollow glass visible light transmittance than that obtained Tvis value is 0.7663, which is 76.6%; numerical shading coefficient of SC is 0.815; the heat transfer coefficient U value (K value) was 2.538; the visible light reflectance ratio 14.6%; solar direct transmittance is 62.6%.

Compared with the ordinary white glass hollow glass, because the thermal conductivity of two or more pieces of glass between the air or inert gas is much smaller than the glass, so as to improve the heat resistance, lower heat transfer coefficient. From Figure 1 and Figure 2 shows that the heat transfer coefficient decreased from 5.816 to 2.538, hollow glass heat transfer coefficient is only a single glass of 44%, to achieve an effective barrier against heat conduction and convection, has good heat insulation effect. But the ordinary insulating glass due to thermal radiation is high, is not good for the preventing effect of radiation. Figure 2 shows that the shading coefficient of ordinary insulating glass up to 0.815, in the construction of energy-saving heat insulation effect is not prominent.

3.2, low radiation (Low-E) detection and analysis of coated hollow glass energy saving

The use of hollow glass spectrophotometer and infrared spectrometer on the 6mmLow-E 12Amm 6mm in the solar spectrum in the wavelength range of 280nm ~ 2500nm test, see Figure 3 parameters.

Figure 3 shows that the thickness of a piece of ordinary white glass 6mm Low-E glass and a piece of 6mm, argon sandwiched 12mm, hollow glass visible light transmittance than that obtained Tvis value is 0.5043, which is 50.4%; numerical shading coefficient of SC is 0.548; the heat transfer coefficient U value (K value) of 1.842 visible light reflectance; 23.2%; solar direct transmittance is 31%, which belongs to the type Low-E glass shade. Compared with ordinary insulating glass, heat transfer coefficient U value decreased from 2.538 to 1.842, get a better insulation effect. SC shading coefficient decreased from 0.815 to 0.548, effectively prevent the solar thermal radiation into the interior, thereby reducing the heat loss, play the effect of building energy efficiency.

In addition, compared with ordinary insulating glass, hollow glass solar light reflecting Low-E ratio increased from 12.9% to 22.9%, therefore, Low-E glass has a strong reflection effect of long wave radiation.

4, conclusion

(1) ordinary insulating glass compared with ordinary white glass, more effectively achieve the heat conduction and convection of the barrier, has obtained the good effect of heat insulation. But the shielding coefficient is higher, in the construction of energy-saving heat insulation effect is not prominent.

(2) low radiation (Low-E) coated hollow glass than ordinary insulating glass, better heat insulation effect. And the sun shading coefficient decreased, light reflectance increased, effectively prevent solar thermal radiation into the interior, thereby reducing the heat loss, play the effect of building energy efficiency.

(3) to fully understand the existing Energy saving glass Continuous research and development of new products, glass of superior performance, has important significance for building energy consumption to maximize.