Heat transfer coefficient of glass curtain wall

Building doors, Windows and glass curtain walls are the weakest link of building envelope energy saving and the key components of building energy saving. According to calculate the heat loss that passes door window accounts for 40%~50% of envelope structure, occupy about 1/4 of building energy consumption. Therefore, the thermal performance of the outer window is the key to energy conservation of the envelope structure. At present, the thermal insulation performance of building doors and Windows can only be measured in the laboratory by the calibrated hot box method based on the principle of stable heat transfer. The heat box simulates the indoor climate conditions of the heating building in winter, and the cold box simulates the outdoor climate conditions in winter. The heat output of the electric heater in the heat box is measured, and the heat loss through the outer wall of the heat box, the specimen window frame and the filling plate is subtracted, and the product of the specimen area and the air temperature difference on both sides is divided to obtain the heat transfer coefficient K value of the outer window part. The relevant ISO standard also uses the hot box method, the Japanese standard uses the calibration hot box method or the protective hot box method, the general requirements of the calibration hot box method. Limited by equipment, hot box method is difficult to be widely used in field tests of curtain wall structure.

There is no on-site test method for heat transfer coefficient of glass curtain wall of Windows and doors in China. The heat transfer coefficient of the envelope is mainly tested in the main part of the envelope, namely the wall. In the Test Standard for Energy Conservation in Public Buildings, the heat transfer coefficient of transparent envelope structure is only mentioned that "when no metal components are exposed on the outer surface of transparent curtain wall and lighting roof, the heat transfer coefficient can be tested by on-site heat flow meter method". In the corresponding instructions, it refers to the detection method of external walls and roofing. In the standard of inspection method for curtain wall building, only the heat flow meter method is put forward according to the current standard. It can be seen that there is no specific method for the field test of heat transfer coefficient of glass curtain wall of building doors and Windows in the main domestic standards.

The accurate and convenient measurement of the heat transfer coefficient of the curtain wall window is of great value to the detection and appraisal of the thermal insulation performance of the glass curtain wall of new building doors and Windows in China.