Discussion on the energy-saving auxiliary design m

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Discussion on the energy-saving auxiliary design method of double-layer glass curtain wall

paper Abstract: compared with the traditional glass curtain wall, the double-layer glass curtain wall can improve the thermal function of the building to a certain extent. However, whether its upper wind can be exerted depends on whether the design of the building and curtain wall is reasonable. At present, the research progress of the energy-saving design of double-layer glass curtain wall in the world is still based on basic research, and there is still a gap compared with the direct guidance of engineering design. Based on the review of the current situation of theoretical and experimental research at home and abroad, according to the current cooperation mode and process of this kind of architectural design at home and abroad, this paper proposes to adopt the corresponding auxiliary design method according to the different tasks in the three stages of scheme design, preliminary design and construction drawing design, Exaggeration should strengthen the summary of past design experience, so as to guide architects to accurately grasp the combination of double-layer glass curtain wall and architectural design in the scheme design stage, and realize effective energy conservation

1 background

nowadays, the popularity of glass curtain wall in modern buildings, especially high-rise office buildings, is increasing, and it is almost the consistent choice of the facade of office buildings in major cities in the world. One of the main reasons is that people's aesthetic tendency is still affected by the modernist style, and the glass curtain wall not only has a simple, transparent and modern appearance, but also can symbolize the strength and image of the enterprise. Therefore, it is favored by many owners and architects. However, people have also paid a heavy price for this unique appearance, because the thermal insulation and heat insulation functions of traditional glass curtain walls are far inferior to those of traditional walls, and there is a lack of reasonable measures to reduce the overheating of the sun in summer, which greatly increases the energy consumption of air conditioning and heating in such buildings. Recently, China has introduced energy-saving standards for public building design, which puts forward stricter thermal requirements for glass curtain walls

compared with traditional glass curtain walls, the unique sandwich design of double skin FaLaDe (hereinafter referred to as DSF) not only provides more possibilities for improving the thermal insulation function of curtain walls, but also provides a living place for sun shading components, so that they can effectively shade the sun without damaging the appearance of the building. In addition, it can also reduce building energy consumption by strengthening ventilation and cooling, so it is highly respected by architects. However, adopting DSF will not only increase the initial investment and sacrifice considerable building area, but also its maintenance cost is higher than that of general curtain walls. Moreover, we cannot simply assume that DSF must have better thermal functions such as thermal insulation, heat insulation and ventilation, At present, "most types of DSF can't reduce the shore hardness tester of Jinan new era assay instrument Co., Ltd. at the same time. This hardness tester (rubber hardness tester) is widely used in the hardness measurement of rubber and plastic. Only by combining different types or changing the system settings according to the details, can it be substantially improved compared with the traditional heat-insulating glass plus external shading scheme". For example, the most prominent problem is how to reasonably design the size of the interlayer. Because its space is too small, it will directly affect the ventilation and cooling effect of DSF in summer and transition seasons. Too large a cooling effect will reduce the space efficiency. If mechanical ventilation is completely relied on, the width of the interlayer can be reduced, but there is also a problem of how to optimize the cooling effect of ventilation and wind energy consumption. In addition, natural ventilation of the interlayer is also greatly affected by outdoor wind speed and direction. At present, there is no satisfactory set of methods to guide the selection of design premise, guess the operation effect, and guide the node structure design. There are many unsuccessful examples in the practice of countries all over the world. It can be seen that the decision-making and planning process of DSF selection and design is affected by two factors: aesthetics, thermal tranquility and energy conservation (Figure L), which is not a simple "just use it"

2 relevant research status abroad

dsf's energy-saving research has been carried out abroad, especially in Europe, for more than 20 years, mainly focusing on heat transfer process research, research combined with building operation mode, and full life cycle analysis. Among them, the first two aspects have achieved more research results. As the most powerful basis for guiding the project decision plan, the whole life cycle analysis is the ultimate goal of the whole research, and the research combined with the building operation mode is the link between the micro heat transfer research results and the macro large model of the curtain wall system, building and air conditioning system, which is very important to realize the annual energy consumption simulation of the building

The study of heat transfer process mainly includes theoretical and experimental studies. Among them, theoretical research is divided into node control volume method and computational fluid dynamics simulation method. The purpose of experimental research is to explore the empirical formula of heat transfer coefficient or convection heat transfer coefficient,. These research results can assist in the establishment of numerical models. For example, grabe research found that the resistance coefficient of natural activities in the interlayer cannot be used as the resistance coefficient under mechanical activities given in the manual. The heat transfer coefficient of the glass surface and the heat transfer coefficient of the whole window change linearly with the temperature difference between the inner and outer glass, but the former changes significantly, and the latter can be ignored in mild weather areas

The research on the combination of

and building operation mode includes the research on natural passage improvement under the premise of specific building layout and the research on the combination of air conditioning system. The calculation methods mainly include the use of trade energy consumption simulation software and the secondary development based on the calculation principle of network method. The research results of the Dutch scholar paassen show that the simple mechanical ventilation at night can reduce the installed capacity and energy consumption by 40%. If the controllable windows and the sky color prediction system are considered, the energy-saving potential will reach 70%. According to the simulation of gratia in Belgium, it is found that there will be significant pressure loss only when the curtain wall spacing is less than 40cm. In most curtain walls, the main pressure loss appears at the air outlet; For the South curtain wall, the natural ventilation opening size has a great influence on the temperature in the interlayer, but it has little influence in the front. It is very feasible to use draught at night, but be very careful during the day to prevent hot air from entering the room. The use of pull-out chimney can ensure that even if there is no wind pressure, the top-level building can achieve ventilation effect, but it is necessary to adjust the size of the opening to balance the ventilation volume of each floor. In his doctoral thesis, Li Baofeng made a lot of experimental research on the thermal function of DSF under the premise of cold winter and hot summer in China, and proposed that the outer wheel return type is more suitable for this kind of weather, and the interlayer width is 400mm. In summer, the ventilation should be dominated by wind pressure rather than hot pressure. The ideal materials for sunshade louvers and inner and outer curtain walls are perforated aluminum alloy and high-permeability glass respectively

at the same time, the measured results of some buildings provide valuable experience for designers. Pasquav's test results in the Siemens Building in Germany show that if a short-term high temperature is allowed, the whole building can adopt natural ventilation throughout the year. If there is no ceiling, the effect of night ventilation can be greatly improved. The building adopts ground source heat pump system for cooling, which can meet the requirements of the whole year. At the same time, the author points out that DSF is not energy-saving anywhere and in any building. First, in practice, the boundary prerequisites of some simulation assumptions need to be carefully considered. For example, the temperature around the curtain wall is often several degrees higher than the observed temperature of the scene image; For DSF with partition on each floor, the air exchange volume in the curtain wall depends more on the wind speed and direction, rather than the chimney effect. In the design, the double-layer curtain wall space should be separated from the air vent to prevent the backflow of hot air in summer, or the DSF with small area should be designed instead of the whole surface, or the exterior curtain wall should be completely opened in the hot season like dehi in Germany. However, the cost of this design is high, and the insulation function in winter will be reduced

there are few studies on DSF from the perspective of full life cycle analysis, especially the analysis of annual building energy consumption. The main research indicators include full life cycle economy and full life cycle greenhouse gas emissions. The representative is the analysis of Turkish scholar cetiner on the mild weather in Istanbul. The results show that the double-layer curtain wall can save up to 23% energy than the most energy-saving scheme of single-layer curtain wall, and the cheapest single-layer curtain wall is 25% cheaper than the cheapest double-layer curtain wall. In the double curtain wall system, the most energy-saving scheme can be reduced by 33. 9% energy consumption, and the most expensive scheme saves 7% in the whole life cycle. 7% of the funds

based on the above research status, there are already departmental conclusions in the existing research results that can be used to guide the design, but they cannot meet the actual needs. Due to the complex heat transfer process of DSF, different standards in one day and throughout the year, and the difficulty in obtaining the correct outdoor boundary premise, there is no correct and reliable method to simulate the annual energy consumption of DSF buildings. At the same time, the existing calculation methods are complex to operate and have high requirements for engineers. They are not suitable for guiding the work in the scheme design stage in engineering applications, but suitable for deepening the design stage

3 combination with architectural design process

at present, the research on DSF energy conservation is mainly concentrated in European and American universities, scientific research institutions and a few powerful engineering design companies. The scientific researchers engaged in this field have deep thermal knowledge background, and the research ideas are basically based on the analysis of the heat transfer process of DSF, with the goal of exploring reasonable mathematical models and computer simulation methods, and have made some achievements, such as energy consumption simulation software, CFD (comututlonalrudlfluid dynamics) simulation software and other recognized methods that can assist energy consumption research. However, these methods are generally complex, and not only can they not be grasped by architects, but also engineers with general thermal engineering background need special training to grasp them. In other words, the energy-saving research of DSF is still in the cutting-edge field, and there is still a long way to go to apply it to practical projects, especially to guide architects to do design

however, engineering practice will not rest because they can ensure the exact properties and quality of materials. Scientific research has not been fully developed. In fact, in recent years, some luxury office buildings and apartments in Beijing, Shanghai and other major cities in haineite have successively adopted DSF. However, there is a gap in varying degrees between the actual operation effect of these projects and the publicity. The use of DSF in some real estate projects is not entirely for energy-saving effects and economic considerations, but for the purpose of real estate speculation. After all, DSF has a fashionable appearance and the concept of improving its predecessors. It is expected that a large number of such buildings will emerge in the future. Engineering practice urgently needs the guidance of experience and theoretical research, but so far, many basic questions about the energy-saving effect of DSF have not been solved satisfactorily, such as: ① is DSF suitable for the weather in Beijing, Shanghai and Shenzhen? Is the energy saving effect significant? ② Is DSF applied to facades with different orientations at the same time? Is its structure the same? ③ What type of building is DSF most suitable for? Is the house worth using These questions seem simple and basic, but in fact they are very sharp. For any project that plans to adopt DSF to realize the three closed-loop control of force, deformation and displacement, we have to answer these questions at the beginning of the work. Although a large number of foreign practices have accumulated some experience, the actual operation performance of DSF varies greatly due to the weather conditions in different cities and even the surrounding conditions of a single building. Therefore, it is not easy to give full play to its advantages, create a quiet indoor environment, avoid overheating in the interlayer in summer and truly save energy. Only in design

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