Glass curtain wall (hereinafter referred to as curtain wall) is one of the main outer structures of modern buildings, and its energy saving has become an important part of building energy efficiency in our country. In this paper, the energy saving of curtain wall is analyzed and calculated, and the energy saving effect is evaluated.

1, curtain wall building energy saving design principles

Our country is vast in territory, and when the north is still cold and snow, the south is the season of spring flowers. This paper proposes the following measures, such as building curtain wall design principles: (1) in cold area, cold region and temperate regions to the insulation design of curtain wall, winter, hot summer and cold winter and hot summer and warm winter areas to curtain wall design of heat insulation in summer. (2) there is no specific standard or specification of curtain wall thermal design, thermal design of curtain walls and windows according to the current national thermal design standards, specifications and reference of foreign related thermal design rules. (3) the complex heat transfer process and heat transfer mode must be analyzed and studied in the thermal design of curtain wall. The heat transfer process of the wall there are basically 3 ways: heat the outer surface and the surrounding air curtain wall and external environment between the air convection between the outer surface and the surrounding heat radiation, the outer surface of the external environment and the heat transfer between the outer surface, a variety of long wave and space (such as electromagnetic wave and long wave infrared etc. The) radiation heat transfer; heat transfer in the wall surface of the indoor environment and indoor air and the inner surface of the indoor air convection and heat transfer between, with the indoor environment of surface radiation heat transfer between the metal frame and wall heat transfer; heat flux: through single glass, through the metal frame through heat transfer the coating layer of glass to reduce heat radiation. (4) the heat transfer coefficient of the curtain wall is determined by the shape of the building, the climate conditions in the area, the heat transfer coefficient of the profile and the heat transfer coefficient of the glass.

2 、 thermal design of aluminum profile

Profile is the main force component of curtain wall. At present, most of the curtain wall adopts aluminum profiles and color plate profiles. In this paper, the aluminum profile is taken as an example for thermal analysis and calculation.

2. 1. Calculation of thermal insulation coefficient of aluminum profile

According to the "thermal design code for civil building" (hereinafter referred to as the "standard" provisions, thermal) aluminum thermal insulation coefficient R: R= / delta lambda type: R- material layer thermal insulation coefficient (M2 - K/W); delta material layer thickness (m); thermal conductivity of lambda materials 203W/ (M - K). A rectangular solid aluminum profile with a thickness of 100mm and a thermal insulation coefficient of R: R=0 is designed. 0005m2 K/W above calculation results did not consider the actual project is the use of hollow aluminum profiles. While the thickness of the rectangular hollow aluminum profile is 100mm thick, the wall thickness on both sides is generally 12mm. The thickness of the actual heat conduction of the hollow aluminum profile is only the thickness of the wall on both sides (24mm). The thermal insulation coefficient ratio of the solid aluminum profile and the hollow aluminum profile is 100 to 24, and the thermal insulation coefficient R of the hollow aluminum profile is R=0. 002m2 K/W

2. 2. Calculation of heat transfer and thermal insulation coefficient of aluminum profile

According to the "standard" thermal insulation aluminum profile, heat transfer coefficient R0: R0=Ri+R+Re type: Ri- aluminum inner surface heat transfer coefficient of thermal insulation (0. 11m2 K/W) (the same below); Re- aluminum surface heat transfer coefficient of thermal insulation (0. 04m2 K/W) (the same below); R- aluminum heat insulating coefficient (0. 002m2. K/W). R0=0.11+0. 04+0. 002=0. 152m2 K/W

2. 3. Calculation of heat transfer coefficient of aluminum profile

According to the code of thermal engineering, the heat transfer coefficient of aluminum profile is K0:

K0=1/R0

Formula: heat transfer coefficient of heat insulation of R0- aluminum profile, 0. 152m2 K/W.

K0=1/0. 152=6. 58W/ (m2. K)

The calculation results obtained on the upper form are the basic heat transfer coefficients of the non thermal aluminum profiles, which are in accordance with the thermal specifications, table 4. 4. The heat transfer coefficient of single window in 1 is 6. 4W/ (m2, K) is basically the same.

2. 4, the basic design requirements of hot broken aluminum profiles

The hot rolled aluminum section is also called heat insulated aluminum profile or insulated aluminum profile. It is made of aluminum and plastic (or other heat insulation material), and its intermediate plastic heat insulation layer mainly has embedded, extruding and filling type.

(1)

The heat transfer process of hot rolled aluminum profiles is very complex, and the heat transfer coefficients are difficult to calculate. Refer to DIN4108 "insulation of high-rise buildings" (1981. 8) (hereinafter referred to as "DIN4108 regulations") stipulates that the basic heat transfer coefficient K0 of the thermal aluminum section is not greater than 3. 5W/ (m2. K).

(2) the minimum thickness of the intermediate plastic layer of the hot rolled aluminum profile shall be specified according to the DIN4108 regulations, and the minimum shall be 7mm.

(3) the design of the middle plastic layer of the hot rolling aluminum profile must meet the requirements of the overall strength and rigidity of the profile.

3. Comparison of heat transfer coefficient of curtain wall glass

Cold area and cold area in winter, because of the single glass curtain wall (hereinafter referred to as the "single glass curtain wall") of the heat transfer coefficient is larger, resulting in lower temperature, and it is easy to form steam drops in the inner surface of the curtain wall and generate icing phenomenon. In order to effectively improve the heat transfer coefficient of curtain walls in these areas, it is an important measure to adopt the thermal insulating aluminum glass curtain wall (hereinafter called "broken thermal curtain wall"). DIN4108 regulations specify that the heat transfer coefficient K0 of the thermal curtain wall is not greater than 3. 5W/ (m2. K). The heat transfer coefficient of glass is calculated according to "thermal engineering standard".

3. Calculation of heat transfer coefficient of 1 monolayer glass (8mm)

(1) thermal insulation coefficient of single layer glass: R=0. 011m2 K/W

(2) thermal insulation coefficient of single layer glass: R0=Ri+R+Re=0. 11+0. 011+. 0. 4=0. 161m2 K/W

(3) the heat transfer coefficient K0 of single layer glass is K0=1/R0=6. 21W/ (m2. K)

3. 2, insulating glass