Analysis and current situation of influencing fact

2022-08-18
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Analysis of influencing factors and current situation of insulating glass UG value

Author: Li Saike glass technology (Shanghai) Co., Ltd. Ma Xiaohui Lu Hongkai

Abstract: This paper determines the best filling gas and thickness of insulating glass through the selection of different filling gas and gas layer thickness of insulating glass, and also compares the influence of different thermal emissivity values on insulating glass UG value, which is helpful for design Construction and engineering technicians provide some practical information

key words: insulating glass argon thermal emissivity energy saving

1. Preface

the dimensional tolerance of plastic formed parts with the most stable shrinkage characteristics can be selected from 110, 120 and 130 groups of "design standards for energy efficiency of public buildings" issued by the Ministry of construction and the General Administration of quality, technical supervision, inspection and quarantine, and officially implemented on July 1, 2005. This is a comprehensive national standard for energy efficiency design of leading public buildings approved and issued by China. Under the condition of ensuring the same indoor thermal environment comfort parameters, the standard requires that the total energy consumption of heating, ventilation, air conditioning and lighting throughout the year be reduced by 50% compared with the public buildings designed and built in the early 1980s. As public buildings such as large shopping malls, high-end hotels and guesthouses, their main energy consumption is in the air conditioning refrigeration and heating system, accounting for about 50% - 60% of the total energy consumption, and 20% - 50% of these consumed energy is consumed by the heat transfer of the outer envelope. Therefore, in the design requirements of new buildings proposed in the standard, the maintenance structure shares about 25% - 13% of the energy saving, and the air conditioning and heating system shares about 20% - 16% of the energy saving

as an important part of modern architecture, glass is the link with the largest heat loss in the whole external maintenance structure. 70% of the heat is lost through the heat conduction of glass. Therefore, with the introduction of energy-saving design standards, insulating glass, an energy-saving product with a very long history in Europe, has also begun to enter the stage of wide application in China

2. Insulating glass

insulating glass (Figure 1) is a relatively sealed glass product with a dry air layer and a spacer frame, which is sealed by two or more pieces of glass through the periphery. The energy-saving effect of hollow glass unit is mainly through the formation of a certain spatial structure between the glasses, that is, a certain gas layer is formed between the glass and the glass, because the thermal conductivity of the gas is far lower than that of the glass, thus reducing the thermal conductivity of the whole unit to achieve the purpose of energy saving. However, in the process of the booming development of the domestic insulating glass industry, we found that the domestic owners' understanding of insulating glass has deficiencies in theory and practice, and the existing problems have seriously affected the application of insulating glass itself. In particular, the UG value, one of the most important performance evaluation criteria of insulating glass, is not attached great importance. Or attention, but based on cost or other considerations, the most reasonable and effective UG value was not adopted, resulting in waste in design, manufacturing and later application. Although unreasonable insulating glass can also play a certain energy-saving effect, this effect is questionable. The final result is that the cost is increased, but the energy-saving effect is not as obvious as expected, and the waste caused by this is even greater

3. UG value of insulating glass

UG value of insulating glass refers to the heat transfer coefficient of insulating glass. Its heat transfer forms mainly include radiation heat transfer, conduction heat transfer and convection heat transfer. Among them, radiation heat transfer accounts for 60%, conduction heat transfer accounts for 38%, and convection heat transfer accounts for 2%. Therefore, the improvement of UG value of insulating glass unit is mainly to reduce the radiation heat transfer and conduction heat transfer, and at the same time, the influence of gas convection should be considered. 3.1 influence of conduction and heat transfer on UG value

different gas interlayer thickness has a great influence on the UG value of insulating glass. Similarly, different gases have different effects on UG value. At present, different gases and gas layer thickness are compared. We used two 4mm white glasses to simulate. By comparing the influence of the spacer size of different gases on the UG value, we find that xenon is the most ideal spacer gas, which can reach the minimum UG value of 2 at 9mm. 51, followed by krypton at 12mm, which can reach 2. 55, again 16mm 2 of argon. 62, then spacetime gas and SF6 are 2 respectively. 75 and 3. 04。

influence of different gas layer thickness on UG value

Table 1 best spacer layer for different gases

type SF6 xenon krypton argon nitrogen oxygen air

thickness/mm 7912161818 18

ug value (white glass) 3. 04 2。 51 2。 55 2。 62 2。 74 2。 73 2。 75

thickness/mm 5710161818 18

ug value (Low-E) 2. 11 1。 06 1。 16 1。 30 1。 55 1。 54 1。 56

from table 1, we can find that if air is used as the spacer gas, its thickness should reach about 18mm. Although SF6 reaches the thickness of 7mm when it reaches the UG value, its UG value is 3. 04。 Its UG value is 0 higher than that of air. 29。 It can't have the effect of heat insulation at all, The main function of SF6 is sound insulation ". for Low-E glass with a thermal emissivity value of 0.1, xenon and krypton can further reduce its thickness, reduce the impact of air convection on heat transfer, achieve a smaller UG value and reduce the use of sealant and other materials. However, xenon and krypton are very rare gases, and the cost of filling these gases is much higher than the cost of reduced sealing materials. Therefore, although their effect is very ideal, it is worth considering Considering the cost, raw material acquisition and other factors, it is not recommended to use

from table 1, we can also find that argon, as an inert gas, is also a fairly good filling gas to reduce the UG value. Although it is 0 higher than krypton. 14, but its cost is much lower than that of xenon and krypton. However, when Low-E glass is used together, its UG value is 0 lower than that of air filled glass. 26。 Therefore, the obvious advantage of argon as the filling gas of the interlayer is that after filling argon, the UG value of the insulating glass can be significantly reduced to achieve better insulation effect, while the cost is very small compared with the price of the whole insulating glass. European countries that have very strict requirements for energy conservation and environmental protection all adopt the method of filling argon in the interlayer to achieve a lower UG value. Table 2 Effect of argon with different amount of young people becoming the "main force" on UG value argon content 0%10%25%40%65%80%90%100%

ug value (white glass) 2. 76 2。 73 2。 72 2。 70 2。 67 2。 65 2。 63 2。 62

ug value (Low-E) 1. 57 1。 53 1。 49 1。 45 1。 39 1。 35 1。 32 1。 30

Table 2 shows the UG values of different argon contents, and the 16mm spacer layer is used as the reference basis for calculation. In the table, we can find that the amount of inflation has a great influence on the value of UG. In order to obtain an ideal UG value, the argon filling amount should be greater than 90%

3.2 influence of radiant heat transfer on UG value

radiant heat transfer mainly comes from two parts, one is solar radiation, the other is mid far infrared radiation. The solar radiation spectrum can be divided into three parts: ultraviolet (wavelength in nm), which accounts for 3% of the solar radiation energy; Visible light (wavelength range 400-700nm), which accounts for 48% of solar radiation energy; Near infrared (wavelength range in nm), accounting for 49% of solar radiation energy; The radiant energy of mid far infrared is basically equal to the total radiant energy of the sun

for building glass, one of the main indicators related to solar radiation is SC value, the indicator related to blackbody radiation is UG value, and the main part of blackbody radiation is mid far infrared heat transfer. The heat transfer process of the infrared part is mainly the process that the glass absorbs heat and radiates outward again through the glass surface. This important index is the surface thermal emissivity of the glass. Therefore, the effective way to reduce the UG value is to reduce the heat absorption of glass by reducing the thermal emissivity, so as to reduce the heat re radiated after glass absorption. Low-E glass is coated with metal or metal oxide on the surface of the glass to improve the far-infrared thermal reflection of the glass and reduce the thermal emissivity value, so as to reduce the heat transfer of the glass due to blackbody radiation

Figure 5 shows that the smaller the thermal emissivity value of the glass, the smaller the UG value of the insulating glass. Therefore, the selection of Low-E glass with different thermal emissivity values has a great impact on the UG value of insulating glass. Generally, two kinds of Low-E glass, Low-E glass and offline Low-E glass, are commonly seen in the market. Their thermal emissivity is generally 0. 18 and 0. About 1, so when they fill argon, the UG value can reach 1. 6 and 1. About 3. The coated glass on the domestic market and off-line can meet the ideal design requirements. Therefore, in order to obtain ideal energy-saving effect, Low-E insulating glass is a good choice

4. Summary

with the development of new materials and the application of various new technologies, the UG value of insulating glass is also further reduced. The use of window frames with lower UF value, the development of warm edge technology, glass coating, especially the development of low emissivity Low-E of double silver, can more effectively reduce the UG value of glass and achieve a more ideal effect of heat preservation and energy saving. However, according to the current situation and the development of insulating glass in China, it is an ideal choice to choose or offline single silver Low-E insulating glass filled with argon. Its UG value can reach 1. 3. It can fully achieve the national goal of 50% energy saving

references

analyzing the factors in addition of the IGU UG Value Abstract different kings of spacers with different gas influence the UG value largely. This article is written to find the better choice of the gas and spacer width。 We find that the IGu with the 16mm spacer and filled the Argon will get a better Ug value。 And we also simulate the Emissivity-Ug value curve to evaluate the low-e glass whether it can be used suitably。 So the designer, builder and engineer may find some information from this article。

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