Application of vacuum glass on curtain wall
As a new generation of energy-saving glass, vacuum glass has developed rapidly since Beijing xinliji vacuum glass Technology Co., Ltd. put it into the domestic market for the first time. At present, more than ten completed projects such as Beijing Sky Plaza, Tsinghua University ultra-low energy consumption demonstration building, and Lelan Bao di club have used the vacuum glass produced by the company. Among them, Beijing Sky Plaza is a high-grade office building project. 22 floors above the floor of the building, the total construction area is more than 57,000 square meters, the vacuum glass curtain wall is more than 7000 square meters, the vacuum glass window is 2500 square meters, the heat transfer coefficient of the vacuum glass used is less than 1.2 Wm-2k-1, and the weighted sound insulation is higher than 36dB. It is the world's first all-vacuum glass building and the world's first building with large-area vacuum glass curtain wall.
Compared with other curtain walls, glass curtain walls have many advantages. At the same time, problems such as poor thermal insulation performance and light pollution have emerged in the early stage of development. With the development of science and technology, especially the rapid rise of glass deep processing industry, these problems are being gradually solved, among which, beijing xinliji vacuum glass Technology Co., Ltd. devotes itself to the development of vacuum glass series products, which provide a high-quality material for glass curtain wall and a new choice for architectural designers.
I. Performance advantages of vacuum glass applied to curtain wall
The most basic type of vacuum glass is standard vacuum glass, that is, a piece of ordinary float glass and a piece of low-radiation coated glass (Low-E glass). At present, there are three kinds of Low-E glass in the domestic market that can be used in the production of standard vacuum glass. Table 1 shows the K values of standard vacuum glass produced with three Low-E glasses.
Table 1
Serial Number
Category
Low-E film emissivity
K value (Wm
-2
k
-1
)
1
4L 0.15V 4
0.20
1.12
2
4L 0.15V 4
0.17
1.03
3
4L 0.15V 4
0.10
0.82
Note 0.15V: 0.15mm vacuum layer
4L: 4mm Low-E glass
4: 4mm white glass surface emissivity 0.84
As can be seen from Table 1, the thermal insulation performance of vacuum glass has obvious advantages compared with existing glass on the market. At present, the k value of ordinary hollow glass on the market is about 3.0 Wm-2k-1, and the K value of ordinary Low-E hollow glass is about 2.0 Wm-2k-1. The K value of Low-E hollow glass filled with inert gas can reach 1.4~1.6 Wm-2k-1.
In addition to the lower heat transfer coefficient than hollow glass, vacuum glass also has the following advantages:
1. Due to the high thermal resistance, the anti-condensation and frost formation performance is better.
2. Because the interval is vacuum, it has the following advantages:
The sound insulation performance is good, especially the sound insulation performance of low frequency band is better than that of hollow glass with the same thickness.
There is no internal fog condensation problem existing in hollow glass
There is no problem of gas thermal conductivity change when hollow glass is placed horizontally.
There is no swelling problem of hollow glass transported to low pressure area of plateau
3. As two pieces of glass form rigid connection, the wind pressure resistance strength is higher than that of hollow glass formed by glass of the same thickness. For example, vacuum glass composed of 4mm glass has a wind pressure resistance higher than 8mm thick glass, which is more than one and a half times that of hollow glass composed of 4mm glass.
4. Because it is sealed by all glass materials and air-absorbing agent is added inside, the Low-E film used is "hard Film", not offline "soft film" which is easy to oxidize and deteriorate and change color. As long as the manufacturing process and equipment are advanced, the service life of vacuum glass is much longer than that of hollow glass sealed with organic materials.
5. The thickness is more than twice as thin as that of hollow glass, which can not only save window frame materials, but also be used as a piece of glass combined with other glass deep processing technology groups to synthesize "sandwich vacuum", "vacuum Hollow", "Self-cleaning vacuum" and other "combined vacuum glass" with various properties ". This compatibility with other deep processing technologies can not only promote the development of other technologies, but also make up for the shortcomings of vacuum glass. For example, toughened vacuum glass cannot be manufactured at present, but combined technology can be used to solve the safety problem.
The above advantages of vacuum glass make it have comprehensive performance advantages.
II. Safety of vacuum glass
1. Solutions to vacuum glass safety problems
Since the production of vacuum glass needs to heat the glass to above 450℃ in a high-temperature furnace, tempered glass and laminated glass cannot be directly used in the production of vacuum glass. Then, the vacuum glass made of two sheet glass original pieces does not meet the requirements of building safety glass, and its application is greatly limited.
How can vacuum glass become building safety glass? The above-mentioned method of "combined vacuum glass" can just solve this problem. For example 1, the vacuum glass is regarded as a piece of original piece, and tempered glass or laminated glass is used to combine insulating glass on the two surfaces of the vacuum glass to form a hollow vacuum hollow structure, as shown in Figure 1. In example 2, the vacuum glass is regarded as a piece of original glass, and the two surfaces of the vacuum glass are respectively integrated with laminated glass, whose structure is equivalent to the vacuum glass made of two laminated glass, as shown in figure 2.
The two projects of Beijing sky Plaza and Tsinghua University ultra-low energy consumption demonstration building use the "combined vacuum glass" of the structure shown in Figure 1, and the laminated vacuum glass of the structure shown in Figure 2 is ready to be used in an office building project in Beijing. Comparing the two structures, we think that the outer tempered glass of the structure in figure 1 protects the inner vacuum glass. Usually, the combined glass has safety protection performance and required wind pressure resistance performance. However, since its interior still contains ordinary glass that can break and hurt people, whether it can be considered as safety glass still needs to be determined when formulating standards. The laminated vacuum glass of Fig. 2 structure is a kind of safety glass which conforms to the current standard.
Common laminated glass manufacturing processes include grouting method and Film method. Grouting method, also known as wet method, is to pour glue between two pieces of glass and form laminated glass after the glue is solidified. Due to the limitation of glue quality and equipment, the quality of laminated glass cannot be guaranteed by grouting method. Film method is also called dry method, and there are usually two processes. One is to use PVB film, through the pressure process, and finally at 130 ℃, 12kg/cm2 pressure under the action of molding method. Because vacuum glass supports two pieces of glass through tiny supports, and the two pieces of glass have the structure of vacuum layer in the middle, which makes the glass bear the effect of an atmospheric pressure (about 1kg/cm2), if PVB film forming process is used, it is equal to the pressure of 12kg/cm2 applied on the glass, vacuum glass will be crushed under such high pressure, so, it is difficult to synthesize vacuum laminated glass by PVB high pressure forming method. The other is to use EVA film (also called EN film) made by vacuum one-step molding process. The so-called vacuum one-step molding process is to place the glass with EVA film directly in a special silicone bag, and vacuum the silicone bag so that the outside air can exert an atmospheric pressure on the silicone bag, silicone bag a method to put pressure on the glass, and then put silicone bag into the heating furnace to raise the temperature to 100 ~ 115℃. In this method, the force acting on the glass is still an atmospheric pressure, which is the same as that before the vacuum glass is processed, so it will not be damaged.
At present, EVA vacuum laminated glass has passed the performance test.
The test in table 2 determines the safety performance of EVA vacuum laminated glass.
Table 2
Test sample
4 0.38EVA 4 0.15 vacuum layer 4 0.38EVA (sheet glass is ordinary float glass)
Test standard
GB9962-1999 laminated glass
Test Unit
National safety glass and quartz glass quality supervision and inspection center
Test results
Qualified to meet the requirements of class II-2 laminated glass
Because the curtain wall has the distinction between open frame and hidden frame. Hidden frame curtain wall has higher safety requirements for glass. We have improved the structure of combined vacuum glass in figs. 1 and 2 according to the applied patent, and the new structure is shown in Fig. 3.
There is a hidden danger in the structure of Figure 1 and Figure 2, that is, once the vacuum glass is broken due to strong external impact force, after losing the atmospheric pressure force of 10 tons per square meter, it is difficult to avoid the danger that part of the glass falls off due to the cracking of the vacuum glass along the edge only by the surrounding glass solder.
The structure of Figure 3 and Figure 4 is similar to that of hollow glass, which avoids the risk of edge cracking caused by direct bearing of external force by vacuum glass solder and makes the overall safety performance of glass higher.
2. Performance characteristics of safety vacuum glass
Safety vacuum glass not only meets safety requirements, but also has the following performance characteristics.
(1) thermal performance
In addition to the thermal resistance of the vacuum glass, the thermal resistance of the two-layer hollow glass is also increased in the thermal performance of the safety vacuum glass with the structure of figs. 1 and 3.
Table 3 theoretical calculation of K value for this structural glass.
Original k value of standard vacuum glass
Standard vacuum glass with a 6mm hollow K value on both sides
Standard vacuum glass is added with a layer of 6mm hollow on both sides. One of the glass is the k value of low-E glass with an emissivity of 0.17.
1.12
0.85
0.80
1.03
0.80
0.75
0.81
0.67
0.63
Note: unit Wm of K value
-2
k
-1
It can be seen from Table 3 that the K value of vacuum glass of this structure is further reduced on the basis of standard vacuum glass.
The safety vacuum glass with the structure of figs. 2 and 4 only adds Glass and glue layer, which does not contribute much to thermal resistance, so the k value is only slightly reduced.
(2) sound insulation performance
"Combined vacuum glass" adds Glass and glue layer. Due to the law of mass and the elastic damping effect of glue layer, the weighted sound insulation increases by 5~12 decibels on the basis of standard vacuum glass. For example, the "sandwich vacuum hollow" combined vacuum glass made for a music teaching building in Beijing has a structure of 6 0.38EVA 4L 0.15V 4 12A 6 with a total thickness of 32.5mm, measured by the architectural Physics Laboratory of Tsinghua University, the weighted sound insulation is 42dB, which is only 3 dB away from the highest level of sound insulation performance of the national standard for glass curtain wall.
(3) water resistance and UV resistance
Because EVA film has better water resistance and ultraviolet absorption performance than PVB film, EVA laminated glass is more suitable for outdoor use than PVB laminated glass, it is also more conducive to protecting the standard vacuum glass combined in it.
(4) combine new functions
Various structures in figs. 1 to 4 can use various functional glasses on the outer glass for performance superposition.
For example, use self-cleaning glass to make the glass curtain wall have self-cleaning function, and use fire-proof glass to make the glass curtain wall have fire resistance. In the structure of figure 2 and figure 4, two layers of EVA film can be used on one or both sides of the vacuum glass, and a layer of pc board or pet board can be placed in the middle of the two layers of film to enhance the impact resistance and anti-theft performance of the glass. In addition, a layer of light adjusting LCD film can be inserted between the two EVA films to make dimming vacuum laminated glass.
III. Application prospect of vacuum glass on curtain wall
The application of vacuum glass on curtain wall is still in its infancy, and there are still many problems to be solved. However, we cannot ignore the great potential of vacuum glass in the field of glass curtain wall.
For glass materials, the thermal insulation performance of vacuum glass has been in a leading position. In the long run, this leading edge will continue to expand.
With the progress of science and technology, in the near future, we can use Low-E glass with lower emissivity and make the thermal conductivity of vacuum glass supports smaller. After calculation, if we use Low-E glass with an emissivity of 0.05 and reduce the thermal conductivity of the existing support by half on the existing basis, the k value of the standard vacuum glass can be less than 0.5 Wm-2k-1; if two pieces of Low-E glass with an emissivity of 0.05 are used, and a piece of white glass is added as double vacuum glass, its K value can be less than 0.3 Wm-2k-1, while its thickness can be less than 10mm.
In the future, it is possible to directly process vacuum glass with tempered glass. On the one hand, it is beneficial to further reduce the k value of vacuum glass, on the other hand, it makes the safety performance of vacuum glass higher.
In short, the development of vacuum glass may mean a revolution for glass curtain wall.
