Analysis on Energy Saving Technology of Glass Curtain Wall Building
The glass curtain wall (hereinafter referred to as the "curtain wall") is one of the main external protective structures of modern buildings, and its energy conservation has become an important part of building energy conservation in China. In this paper, the technical analysis and calculation of the energy saving of the curtain wall are carried out, and the energy-saving effect is economically evaluated.
1. Design principles for energy saving in curtain wall buildings
China has a vast territory. When the north is still ice and snow, the south is the spring season. This paper proposes the following measures as the design principles for energy conservation in curtain wall buildings: (1) Curtain walls in severe cold regions, cold regions and mild regions, for winter thermal insulation design, curtain walls for hot summer and cold winter regions and hot summer and warm winter regions. Summer heat insulation design. (2) There is no special standard or specification for curtain wall thermal design in China. The thermal design of curtain wall is based on the relevant national standards and specifications for exterior wall and window thermal design and reference to relevant foreign thermal design procedures. (3) When performing curtain wall thermal design, it is necessary to analyze and study its complicated heat transfer process and heat transfer mode. There are three ways to heat transfer the curtain wall: 1 heat exchange between the outer surface of the curtain wall and the surrounding air and the external environment: convective heat transfer between the outer surface and the surrounding air, radiation heat exchange between the outer surface and the external environment, the outer surface Radiation heat exchange with various long waves (such as long waves generated by electromagnetic waves, infrared rays, etc.); 2 heat exchange between the inner surface of the curtain wall and indoor air and indoor environment: convective heat transfer between the inner surface and the indoor air, inner surface and indoor Radiation heat transfer between environments; heat transfer of 3 curtain wall and metal sash: heat transfer through a single layer of glass, heat transfer through the metal sash, and radiation heat transfer through the coating layer of the glass. (4) The heat transfer coefficient of the curtain wall is determined by the shape of the building and the climatic conditions of the area in which it is located, the heat transfer coefficient of the profile, and the heat transfer coefficient of the glass.
2. Thermal design of aluminum profiles
The profile is the main force component of the curtain wall. At present, most of the curtain wall uses aluminum profiles and color plate profiles. In this paper, aluminum profiles are taken as an example for thermal analysis and calculation.
2. Calculation of thermal insulation coefficient of aluminum profiles
According to the "Code for Design of Thermal Design for Civil Buildings" (hereinafter referred to as "Thermal Code"), the thermal insulation coefficient R of aluminum profiles is: R = δ / λ where: thermal insulation coefficient of R-material layer (m2 · K / W); δ - thickness of the material layer (m); λ - thermal conductivity of the material [take 203 W / (m · K)]. A rectangular solid aluminum profile with a thickness of 100mm and a thermal insulation coefficient R of R=0.0005m2·K/W The above calculation results do not take into account the hollow aluminum profile used in the actual engineering. The rectangular hollow aluminum profile with a thickness of 100 mm has a wall thickness of 12 mm on both sides, and the actual heat conduction thickness of the hollow aluminum profile is only the wall thickness portion of both sides (24 mm in total). The ratio of thermal insulation coefficient between solid aluminum profile and hollow aluminum profile is 100:24, and the thermal insulation coefficient R of hollow aluminum profile is: R=0.002m2·K/W
2. 2. Calculation of heat transfer coefficient of heat transfer of aluminum profiles
According to the "Hot Work Specification", the heat transfer coefficient R0 of the aluminum profile is: R0=Ri+R+Re where: Ri-aluminum profile heat transfer coefficient of internal heat transfer (take 0.11m2·K/W) The same as below); Re-aluminum profile outer surface heat transfer thermal insulation coefficient (take 0. 04m2 · K / W) (the same below); R-aluminum profile thermal insulation coefficient (take 0. 002m2 · K / W). R0=0.11+0.04+0.002=0.152m2·K/W
2.3. Calculation of heat transfer coefficient of aluminum profiles
According to the "Hot Work Specification", the heat transfer coefficient K0 of the aluminum profile is:
K0=1/R0
Where: R0-aluminum profile heat transfer thermal insulation coefficient, taking 0. 152m2 · K / W.
K0=1/0.152=6.58W/(m2·K)
The calculation result obtained by the above formula is the basic heat transfer coefficient of the unbroken aluminum profile, which is basically the same as the heat transfer coefficient of the single-layer window in Table 4.4.1 of the Thermal Engineering Specification. 6.4W/(m2·K) the same.
2.4. Basic design requirements for heat-dissipating aluminum profiles
Heat-breaking aluminum profiles, also known as heat-insulating aluminum profiles or insulated aluminum profiles, are made of aluminum and plastic (or other insulating materials). The main production processes of plastic insulation are embedded, extruded and filled. .
(1)
The heat transfer process of the heat-dissipating aluminum profile is very complicated, and the heat transfer coefficient is difficult to calculate. Generally, only the data is obtained through the test. According to DIN 4108 "Insulation of high-rise buildings" (1981. 8) (hereinafter referred to as "DIN 4108 Regulations"), the basic heat transfer coefficient K0 of the heat-dissipating aluminum profile is not more than 3. 5 W / (m 2 · K).
(2) The minimum thickness of the intermediate plastic layer of the heat-dissipating aluminium profile shall be a minimum of 7 mm in accordance with DIN 4108.
(3) The design of the intermediate plastic layer of the heat-dissipating aluminum profile must meet the overall strength and stiffness requirements of the profile.
3. Comparison of heat transfer coefficient of curtain wall glass
In the cold winter and cold winters, the single-layer glass curtain wall (hereinafter referred to as “single-glass curtain wallâ€) has a large heat transfer coefficient, which causes the room temperature to decrease, and it is easy to form vapor water droplets and freeze on the inner surface of the curtain wall. . In order to effectively improve the heat transfer coefficient of the curtain wall in the above areas, the use of a heat-insulating aluminum hollow glass curtain wall (hereinafter referred to as "breaking heat curtain wall") is one of the important measures. According to the DIN 4108 regulations, the heat transfer coefficient K0 of the heat-insulating curtain wall is not more than 3. 5 W / (m 2 · K). The heat transfer coefficient of the glass is calculated according to the Thermal Code.
3. Calculation of heat transfer coefficient of single-layer glass (8mm)
(1) Thermal insulation coefficient of single-layer glass: R=0.011m2·K/W
(2) Heat transfer thermal insulation coefficient of single-layer glass: R0=Ri+R+Re=0.11+0.011+. 0. 4 = 0. 161 m 2 · K / W
(3) The heat transfer coefficient K0 of the single-layer glass is: K0=1/R0=6. 21W/(m2·K)
3. 2. Calculation of heat transfer coefficient of insulating glass (8+10+6)
(1)
The thermal insulation coefficient R of the insulating glass is: R=R1+Ra+R2=0.159m2·K/W where: R1 is the thermal insulation coefficient of the outer glass (take 0.011m2·K/W); R2-the inner glass is hot Insulation coefficient (taken 0.008 m2 · K / W); Ra - winter general air layer thermal insulation coefficient (take 0.14m2 · K / W);
(2)
The heat transfer coefficient R0 of the insulating glass is: R0=Ri+R+Re=0.11+0.159+0.04=0.309m2·K/W (3) The heat transfer coefficient K0 of the insulating glass is: K0=1/R0=3.24 W/(m2·K)
3.3. Comparison of heat transfer coefficients between single-layer glass and hollow glass
The above calculations show that the heat transfer coefficient of single-layer glass is 48% larger than that of insulating glass, indicating that the energy-saving effect of insulating glass is much greater than that of single-layer glass.
4. Economic evaluation of curtain wall building energy conservation
In China, people attach great importance to the control of construction costs, and it is easy to ignore the economic and social benefits brought about by the energy-saving effect of buildings generated by appropriately increasing construction costs. Below, we make a comprehensive evaluation of the building energy-saving effect of the curtain wall through calculation and analysis.
(1)
Located in a commercial building in the Beijing area, the curtain wall area is 10,000 m2, the building height is less than 4 m, and the annual heating days in Beijing is 129 d. Consider the actual daily heating for 10 h. The heat consumption is calculated according to the two schemes of using a single glass curtain wall and a heat-dissipating curtain wall. According to the "Code for Design of Heating, Ventilation and Air Conditioning" (GBJ19-87) (hereinafter referred to as "HVAC Code"), the basic heat consumption of the curtain wall is: Q = αFK (tn-twn): Q-the basics of the curtain wall Heat consumption (W); α-curtain wall temperature difference correction coefficient, take 1.0; F- curtain wall area, 10000m2; K-curtain wall heat transfer coefficient, single glass curtain wall take 6.4W / (m2 · K), heat-dissipating curtain wall 3.5W / (m2 · K); tn - winter indoor temperature calculation, take 19 ° C; twn - heating outdoor calculation temperature, take -9 ° C. For the simple calculation, the above formula is set: 1 the structure type of the curtain wall is type I; 2 the outdoor calculation temperature of the heating takes the outdoor temperature calculation (dry bulb) temperature value; 3 does not consider the window opening, hole or roof, ground intrusion through the curtain wall The heat consumption of the indoor cold air; 4 does not consider the heat consumption of the cold air that penetrates into the room through the gap of the curtain wall; 5 does not consider the orientation of the building; 6Q is only the theoretical calculation value. The basic heat consumption of the single glass curtain wall is Q1=1792kW; the basic heat consumption of the heat-dissipating curtain wall is Q2=980kW.
(2) The single-glass curtain wall converts the heat (heat energy) consumed by the annual heating to the electric energy E: E=(1792-980)×129×10=1047480kW·h
(3) Economic comparison of energy-saving effects between heat-dissipating curtain wall and single-glass curtain wall building
The unit cost of a single glass curtain wall is 1,300 yuan/m2, and the unit cost of a heat-insulated curtain wall is 1,800 yuan/m2, and the initial investment is increased by 5 million yuan. The electricity price in Beijing (assumed to be unchanged within 10 years) is 0.70 yuan / (kW · h), the power factor is 0.9, the annual cost of RMB is 820,000 yuan for the single-glass curtain wall than the heat-dissipating curtain wall. (Assume that it is unchanged within 10 years), the economic benefits of single-glass curtain wall and heat-dissipating curtain wall building energy saving are shown in Table 1. It can be seen from Table 1 that the heat-insulating curtain wall can recover all the increased construction costs in the seventh year. By the 10th year, the economic benefits of the heat-dissipating curtain wall building energy saving will be 2.56 million yuan more than the single-glass curtain wall. This shows that the economic benefits of building energy-saving buildings with broken heat curtain walls are very obvious.
5 Conclusion
(1)
The curtain wall is a new type of building material that integrates new technologies, new materials and new structures developed in China in the past 20 years. In China, millions of square meters of curtain walls are put into use every year and continue to grow at a rate of 10%. Therefore, the building energy-saving design of the curtain wall is very important.
(2)
According to the technical analysis, calculation and evaluation of building energy-saving economic benefits, the building energy-saving work of the curtain wall is very beneficial to the construction investors and the society. The investment for building energy conservation can be fully recovered and can be used in the curtain wall. Investors create good economic and social benefits.
(3) The structural form of the heat-dissipating curtain wall is the most effective way to save energy in the curtain wall building.
Threaded Globe Valve,B Type Globe Valve,B Type Threaded Globe Valve,Inner Threaded Globe Valve
Wenzhou KAIZHENG Valve Technology Co.,LTD. , https://www.kazevvalve.com