[China Aluminum Network] glass curtain wall is a new type of contemporary wall, which gives the building's larger features is the organic integration of architectural aesthetics, architectural functions, building energy efficiency and architectural structure, building from different perspectives Different colors, with the sun, moonlight, light changes give people a dynamic beauty. Glass curtain wall is the product of modern science and technology development, and it is also a prominent feature of modern high-rise buildings. The energy-saving approach of glass curtain walls is usually through the use of coated glass, LOW-E glass, heat-reflecting glass, hollow glass and thermal break bridge aluminum to reduce the structural heat transfer coefficient, eliminate the structural system "thermal bridge" and reduce the heat loss of air permeability. Improve the sealing performance to achieve. The project uses heat-insulating aluminum profiles and hollow glass structures filled with argon to achieve thermal insulation and energy saving, reducing heat loss through conduction, and reducing the possibility of indoor moisture condensation on aluminum profiles due to over-saturation. Therefore, the use of aluminum alloy glass curtain walls in high-rise buildings has attracted wide attention from the industry. 1. Application and development of aluminum alloy glass curtain wall in high-rise buildings The ventilation curtain wall composed of two glass curtain walls inside and outside is also called a double curtain wall, a respiratory curtain wall, and a heat tunnel curtain wall. A ventilation and ventilation layer is formed between the inner and outer curtain walls. Because of the circulation or circulation of air in the ventilation layer, the temperature of the inner curtain wall is close to the indoor temperature, and the temperature difference is reduced. It saves energy compared with the traditional curtain wall heating. 42 % ~ 52%, saving energy when cooling 38% to 60%. With the continuous development of China's economic construction, building curtain wall as a high-tech product in China's construction industry has made rapid progress. With the development of aluminum alloy hidden frame curtain walls, aluminum curtain walls have also emerged. With the use of aluminum alloy glass curtain walls in the curtain wall project, China's high-rise buildings have become more radiant and beautiful, forming various colors, and various material combinations form a beautiful curtain wall pattern. The curtain wall made of aluminum plate is a form of the building curtain wall. It is mostly used for the wall protection and non-lighting walls, instead of mosaics and glazed tiles to spray the exterior wall. At present, aluminum plates that can be used for curtain wall engineering in the domestic construction market are generally classified into single-layer aluminum plates, composite aluminum plates, and honeycomb aluminum plates. Composite aluminum plates are currently widely used. The heat transfer process of a glass curtain wall can be roughly divided into three ways: First, heat transfer between glass and aluminum alloy (stainless steel) metal grids: heat transfer through a single layer of glass, heat transfer through a metal grid, and radiation reduction through a coating of glass. Heat exchange; Second, heat exchange between the inner surface of the curtain wall and the indoor air and indoor environment: convection heat transfer between the inner surface and the indoor air, radiation heat exchange between the inner surface and the indoor environment; third, the outer surface of the glass curtain wall and the surrounding air The heat exchange between the external environment; the convection heat transfer between the external surface and the surrounding air, the radiation heat exchange between the external surface and the external environment, and the long-wave radiation heat exchange between the external surface and the space. Fourth, ordinary glass curtain walls use single-layer glass and aluminum alloy beam column structure, and energy-saving glass curtain walls should be considered from the above three ways: by the previous approach (heat conduction) has a greater impact on the design of the node, the thermal conductivity of the glass The design uses insulating glass; for the thermal conductivity of the aluminum frame, the design uses nylon 66 and other structural plastics to form a "broken bridge", which can increase the thermal resistance and reduce the heat conduction, thus designing the thermal insulation curtain wall. On this basis, consider the second route (thermal convection) and the third route (thermal radiation). Double LOW-E glass is used in the structure and the upper and lower end convection openings are designed to design a dynamic curtain wall. The building curtain wall is an integral part of the building envelope structure. It is a part of the building where heat exchange, heat conduction is active and sensitive, glass is an important part of the building curtain wall, and various materials of the building facade are thin and easy to transmit. Thermal materials, so to save energy, we must change the thermal performance of glass. Hollow glass is composed of two or more pieces of glass. The glass is insulated with a hollow aluminum tube filled with a desiccant. The hollow part is filled with dry air or inert gas and sealed with butyl rubber, polysulfide rubber or structural adhesive. After being processed, under certain conditions, the thermal insulation performance of the hollow glass is better than that of the general concrete wall. The thermal conductivity coefficient of the ordinary double-walled hollow glass is smaller than that of the single-layer glass by 30%, and the thermal conductivity of the reflective hollow glass is smaller than that of the single-layer glass. About %, while hollow glass has excellent sound insulation performance, generally can reduce the noise 39 to 40 decibels. For example, hollow glass made of two glass sheets with different thicknesses will have better sound insulation due to reduced resonance. At this stage, most of the major measures to improve the energy-saving and heat-insulating properties of glass curtain walls are the use of coated glass, Low-E glass, heat-reflecting glass, hollow glass, and heat-insulating aluminum profiles to reduce the structural heat transfer coefficient K and eliminate the structural system's heat. Bridges, reduce heat loss from air infiltration, reduce the area of ​​window sashes, and improve its sealing performance. The smart curtain wall is an extension of the ventilation curtain wall. It is based on the intelligent building and controls the building supporting technology (warm, hot, light, and electricity). The computer can effectively adjust the indoor air, temperature, and light, and its building energy consumption is only quite 30% of traditional curtain walls. The basic unit of the photovoltaic curtain wall is a photovoltaic panel. The photovoltaic panel is a battery array composed of a plurality of photoelectric cells in series and in parallel. The battery array is placed in two layers of glass and is thermoset with a cast film resin on the back of the photovoltaic panel. Junction box and wire, so that solar energy can be converted into electricity for people to use. Under normal circumstances, this type of curtain wall columns and beams are insulated aluminum profiles. In order to reduce the heat loss and energy consumption of heating and heating in winter, in order to reduce the thermal invasion and energy consumption of air-conditioning refrigeration in summer, the development trend of thermal design for glass curtain walls is: to achieve the greenhouse effect for the curtain wall with heating and heating as its main goal. For the pursuit of the cold room effect of the air-cooled curtain wall, no matter what kind of curtain wall will pursue the rational use of solar energy. Dynamic curtain wall (also called hot aisle curtain wall and double ventilation curtain wall) is a good development direction. Photovoltaic curtain wall composed of photovoltaic panel system and curtain wall system is also an application development direction of active use of solar energy. Comprehensive utilization of light energy and heat energy Intelligent glass curtain wall of electric energy is an ideal development direction. China's building energy consumption is 2-3 times the building energy consumption of developed countries with the same climatic conditions. In the process of building a well-off society in an all-round way, the task of energy conservation and emission reduction is very arduous. Building energy efficiency is the basis for improving residential comfort and reducing the cost of use. It is also an urgent requirement for sustainable development. Only by placing resource conservation and reducing energy consumption in a prominent position can we better promote the construction of a harmonious society. 2. Thermal performance and energy-saving measures of glass curtain walls The glass curtain wall is used as a building envelope structure, and the heat loss caused by the heat transfer and the cold wind penetration heat loss accounts for 40% to 50% of the total building energy consumption. If the glass curtain wall is of reasonable structure, the energy loss can be greatly reduced. The influence of glass curtain wall on the energy consumption of existing buildings mainly has two aspects: First, the thermal performance of glass curtain wall affects the heating in winter and the indoor and outdoor air-conditioning temperature difference heat transfer in summer. The second is that the transparent material (such as glass) of the curtain wall is affected by solar radiation and the heat in the building is caused. The thermal properties of glass curtain walls mainly include: heat transfer coefficient K, shading coefficient Sc, and anti-condensation coefficient. The K value of heat transfer coefficient refers to the air-to-air heat transfer rate due to the heat transfer of glass and the temperature difference between indoor and outdoor. The heat transfer process includes convection and heat conduction. The heat transfer coefficient is an important aspect of the thermal performance of glass curtain walls. The insulation performance in China's "Classification of Physical Properties of Building Curtain Walls" is divided accordingly. The lower the K value, the lower the heat transfer through the glass. The shading coefficient of a glass curtain wall refers to the ratio of the amount of solar radiation energy passing through the curtain wall glass to the amount of heat transmitted through the 3 mm transparent glass under the same conditions. The smaller the Sc value, the better the performance of blocking direct sunlight radiation. So lower K values ​​and smaller Sc values ​​can effectively reduce the three heat transfer. According to the experimental results, the heat transfer and convective heat transfer capacity can be measured by the heat transfer coefficient. The radiation heat transfer capability can be controlled by the shading system. The heat transfer of the building is the result of the combined effects of the above three methods. The energy-saving design of glass curtain walls focuses on designing reasonable control measures to achieve energy-saving purposes. The thermal performance of glass curtain walls can be achieved by controlling heat transfer and increasing shielding. According to energy-saving design standards, the thermal performance requirements of transparent glass curtain walls are the same as those of windows. The heat transfer coefficient and the shading coefficient should be determined according to the proportion of the area occupied by the outer walls. The larger the area occupied by transparent glass, the smaller the heat transfer coefficient and shading coefficient requirements. Since the area of ​​transparent glass shall not be greater than 70% of the area of ​​the external wall, the glass curtain wall behind the building structure beams, but also to meet the requirements of the fire safety requirements of the glass curtain wall between the lower layers need to set 800mm high firewall. We can design two glass curtain walls to be opaque glass or other materials. If we meet the area of ​​two parts and less than 30% of the entire glass curtain wall, we can adopt appropriate calculations and designs in the design process of the architect. Increase the proportion of non-transparent glass curtain walls, so as to adjust the proportion of the entire virtual wall system to meet the energy saving requirements of the entire glass curtain wall. With the increase in the ratio of window to wall (area ratios of the transparent and non-transparent parts of the curtain wall), the heat gain from the transparent glass curtain wall increases sharply, and the cooling load of the air conditioner also increases sharply. Due to different processing techniques, glass can be divided into ordinary flat glass, endothermic glass, heat reflective glass, low-emissivity glass, and some special-purpose functional glasses. The heat transfer coefficients of various glasses are different. The effect of curtain wall profiles on the thermal performance of curtain walls: whether it is open frame, hidden frame, hanging type, point supported type or unit type glass curtain wall, the performance of the structural frame, especially the connection point profile, is related to the thermal performance of the glass curtain wall. Have a certain influence. The transparency of the glass can be used as indoor lighting and heating. The total amount of radiant energy transmitted through the glass window is determined by the intensity of local solar radiation, the angle of incidence of sunlight and glass, and the nature of the glass material. When the incident angle of light and the normal angle of the glass exceeds 60 degrees, the reflectivity will increase significantly. Thermal radiation in summer increases air-conditioning load in winter. Air permeability is caused by the air pressure difference between inside and outside the building caused by wind pressure and hot pressure, and the gaps or holes existing in the external protective structure of the building are necessary conditions for air penetration. For existing curtain wall buildings, air infiltration occurs due to loose parts aging. Hot air infiltration in summer increases air conditioning load. Winter cold wind infiltration will increase the heat load. For the hot summer and cold winter regions, the outdoor air design temperature in winter is 0°C, and the indoor and outdoor temperature difference is 20°C. The increased heat load cannot be ignored. Reducing the window-to-wall ratio of a building is a relatively straightforward and effective way to reduce building energy consumption. In practical projects, consideration should be given to the appearance and lighting requirements. According to the requirements of the design specifications, the performance of the glass curtain wall should be selected as appropriate. The use of energy-saving glass to increase the thermal resistance of glass and reduce the heat transfer coefficient of glass is a relatively straightforward method of reducing the energy consumption of glass. In order to improve the thermal resistance of the frame, the thermal cut bridge type energy-saving profile is selected, the glass curtain wall shading system is set, the sunshade system shields the solar radiation, and the influence of solar radiation on the indoor environment is reduced, and the building facade is enriched; all types of glass with substantially the same heat transfer coefficient are used. Curtain walls, improving the airtight performance of curtain walls, and reducing air convection heat transfer are also crucial for reducing the energy consumption of building curtain walls. Reducing the air leakage of various uncontrollable envelope structures and adopting controlled ventilation measures will help increase the supply of fresh air, improve indoor air quality, and reduce building energy consumption. In addition to the glass panels, the metal profiles of the glass curtain wall are also two important factors affecting the appearance and energy saving of the entire curtain wall system. In the frame glass curtain wall, the weighted average heat transfer coefficient in the glass and curtain wall structure should be taken as the heat transfer coefficient of the glass curtain wall. From this point of view, the heat transfer coefficient of the full hidden glass curtain wall is closer to the heat transfer coefficient of the glass panel, because although there is a structural frame, but due to hidden behind the glass panel, it has little effect on the heat transfer coefficient of the entire curtain wall, but From the point of view of the safety of the curtain wall, the open frame is relatively reliable, and through the heat-type open frame, the thermal bridge of the metal frame type is reduced. The glass curtain wall thermal bridge is a part of the structure, because its thermal conductivity is too good to cause the overall structure to reduce the thermal insulation capacity. In the ordinary glass curtain wall, the aluminum alloy frame is a thermal bridge of the glass curtain wall, and its thermal conductivity is more than 100 times that of the glass. The cold bridge is a unique thermal bridge, which is an unstructured structure or component that conducts heat away faster than the surrounding area and the inside surface of the bridge. Therefore, its temperature is lower. This type of thermal bridge, Commonly known as "cold bridge." The aluminum profiles without heat treatment during the winter are cold bridges. The indoor water vapor forms on the same surface of the cold bridge and the surrounding condensate water. The presence of condensate water increases the difficulty of structural treatment and provides moldy interior surfaces at the edge of the curtain wall. condition. In today's public buildings, exhibition buildings and sports buildings generally use large-area glass curtain walls because of their display function and aesthetic requirements. Since glass is a good conductor of heat, hollow glass or LOW-E glass is used for energy conservation. If an aluminum alloy frame with an ordinary glass curtain wall is used, the heat transfer coefficient is 203.00 W/m2.K, and the aluminum alloy frame will generate thermal energy for energy consumption. The shading system of the glass curtain wall is one of the direct ways to directly reduce the shading coefficient of the curtain wall. In addition to the glass material with different material characteristics, the shading system can also be used to reduce the shading coefficient. This has also become an important form of facade. Such a system of glass curtain walls can be divided into three types, ie, an external shading system, a double-glazed curtain wall interfacial shading system, and a built-in shading system. Glass curtain wall is more and more widely used in today's buildings. With the further development and improvement of glass curtain wall technology application, its position in architectural design will be more important. The architect should use the appropriate design form to consider the current form of glass while taking into account its thermal performance, provide energy efficiency according to the building, in order to comply with China's "energy-saving emission reduction" policy and the general trend of energy conservation. 3. Existing problems and countermeasures in the application of heat insulation aluminum profiles in the construction of curtain wall The building curtain wall is an integral part of the building envelope structure and is a part of the building where the heat exchange, the heat conduction is more active and more sensitive, and the aluminum profile is an important part of the building curtain wall. It is the easier heat transfer among the various materials of the external wall of the building. Materials, so to ensure that the entire building walls save energy, we must change the thermal performance of aluminum profiles. Heat-dissipating aluminum profiles consist of aluminum profiles and insulating material in the middle. The central insulation material mainly prevents heat conduction. The foreign “cold-bridging bridge†technology is to remove part of the heat conduction path of high-heat-conductivity aluminum profiles and to replace them with low-thermal conductivity materials in series and separate the aluminum profiles at the two ends of different ambient temperatures. The overall thermal conductivity of the composite material will certainly be greatly reduced, the thermal resistance value will be greatly increased, and the heat loss from the aluminum profile will be greatly reduced. This isolation method is called "cold-brake bridge" or simply "bridging bridge". The aluminum alloy section to which this isolation method is applied is called "insulation bridge aluminum section" or simply "bridge bridge aluminum section". It is called "heat-absorbing (cold) bridge material" or simply "disconnected (cold) bridge" or "broken bridge". Due to the adiabatic effect of the adiabatic cold bridge, when the outdoor end of the profile is already below freezing, the indoor end remains at room temperature. There is a cohesive force between the adiabatic cold bridge and the aluminum alloy so that the two can interact (transfer forces and deformations to each other). This guarantees that the cold-abrade bridge in the component under load can coordinate deformation and co-stress with the aluminum alloy profiles that are engaged on both sides. In other words, aluminum alloy profiles that can cut off on both sides of the hot and cold cold bridge will not undergo relative displacement under the action of the load. The temperature linear expansion coefficient of the cold-aluminum cold bridge and the aluminum alloy is relatively close. When the temperature changes, there will not be a large relative deformation between the two, so that the adhesive force is destroyed. This is a prerequisite for the existence of this composite material. The hot-air-cooled cold bridge aluminum profile has effectively improved the thermal insulation performance of the curtain wall. Heat-resistant cold bridge aluminum profiles are also highly resistant to high temperatures. However, it cannot be sprayed with fluorocarbons, so the cold bridges that need to be sprayed should be sprayed and then compounded. At present, the use of heat-insulating aluminum profiles in the field of curtain walls has become more and more widespread, but glass curtain walls also have some limitations, such as light pollution, large energy consumption and other issues. However, with the continuous emergence of new materials and new technologies, these problems are gradually being incorporated into the comprehensive research system of architectural modeling, building materials, and building energy conservation, as an overall design issue. There are three methods to prevent the reflection of the glass curtain wall. First, the rougher materials such as frosted glass should be selected instead of the full reflective glass. Second, attention should be paid to the installation angle of the glass curtain wall. Try not to use glass on concave or slanted buildings. The third is to install double glass in the glass curtain wall and black light-absorbing material on the inner glass so that it can absorb light in large quantities and prevent reflected light from affecting the public. The heat-dissipating aluminum-plastic composite architectural aluminum profiles solve the problem of high heat transfer coefficient of common architectural aluminum profiles, and fundamentally improve the moisture-retaining and heat-insulating properties of aluminum doors and windows and aluminum curtain walls. The promotion and application of high-efficiency, energy-saving, high-end luxury aluminum doors and windows has become possible, and new market development space has been opened up. However, the quality and safety problems of heat-insertion aluminum-plastic composite architectural aluminum profiles are very prominent. Mainly manifested in: the safety and reliability of the quality of the insulation layer engineering plastics, and the stability of the mechanical properties and mechanical strength of the two after the aluminum-plastic composite. At present, the research on the heat-insulating plastic composite profiles processed by the injection molding method or the embedded strip method is still deepening. The influence of the heat insulation layer on the properties of the architectural aluminum profiles and the combined mechanical mechanical properties of the composite materials will be improved. The heat-insulating aluminum profiles are applied to windows and bright-frame glass curtain walls. In order to achieve the equivalent heat insulation and heat insulation effects, heat-insulating aluminum profiles are generally used together with insulating glass. For the bright-framed glass curtain wall, the aluminum alloy has a large thermal conductivity due to the indoor or outdoor aluminum alloy as an integral or direct contact, and the heat insulation and heat insulation effects are not good. Therefore, the open-framed glass curtain wall is made of insulating glass with a heat-insulating aluminum profile, which has obvious insulation and heat insulation effects. For the hidden glass curtain wall, the direct contact of the curtain wall structure with the outdoor is the hollow glass, and the glass and the aluminum profile are the silicone structural adhesive, and the inner side of the structural adhesive is the aluminum profile. The general coating hollow glass thermal conductivity 2.3 ≤ K ≤ 3.2, such as the use of offline LOW-E coating made of hollow glass 1.4 ≤ K ≤ 1.8, insulation, heat insulation effect is very good, and the structure of plastic is also a low thermal conductivity material, there are good Thermal insulation. The theoretical analysis and experimental results show that the hidden frame glass curtain wall does not need to use heat-insulating aluminum alloy profiles. At present, in order to reduce the cost of some engineering projects, a PVC heat-break strip is used instead of a nylon 66 heat-break strip. Because of the difference between the linear expansion coefficient of PVC and the linear expansion coefficient of aluminum alloy, and its low strength (only about 30N/mm2), poor heat resistance (80°C), poor resistance to aging, and many other defects lead to the use of PVC insulation strips. The heat-insertion aluminum profiles after being compounded by the strips may cause looseness or even detachment of the PVC heat-break strips in the aluminum profiles due to thermal expansion and contraction after actual assembly and use, and the looseness and deformation may cause looseness and damage to the airtightness. And the watertight nature causes the whole to be loose and detached. Heat break is also a function of the insulation glass curtain wall. While carrying the stress, the heat-breaking strip also bears the function of sealing and transmitting. If the thermal expansion coefficient of the rolled strips rolled together by the mechanical composites is not consistent with the thermal expansion coefficient of the aluminum profile matrix, under the condition of non-uniform heating and cooling, deformation will inevitably occur, and the aluminum profiles and the hot strips cannot be guaranteed. A completely independent combined part "stretch and synchro" will inevitably lead to either loosening of the heat-breaking strip in the aluminum profile groove or deformation stress on the heat-insulating aluminum profile. In addition, the broken heat strip as an important part of the aluminum heat-dissipation profile, its dimensional accuracy directly determines the dimensional accuracy of the composite formed heat-dissipating aluminum profile. The assembly precision of the glass curtain wall is 0.2-0.3mm. To ensure the wind pressure resistance, airtightness and watertightness of the heat-insulating glass curtain wall, consider the margin of cumulative error. If the thermal breakage strip itself cannot be strictly controlled at 0.1 With an accuracy of less than mm, it is difficult to ensure the assembly accuracy of the entire glass curtain wall. The aluminum alloy building profile GB5237-2004 has been implemented, and the new standard has increased the standard for the hot-junction profile, and the construction industry standard for the broken-heat strip will also be introduced. With reference to standardized production and operation, all aspects will give full attention to the manufacture and installation of heat-insulating glass curtain walls, and will further promote the standardized development of the heat-insulating glass curtain wall market. 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