Research On Thermal Characteristics Of Insulating Glass And Its Application In Residential Buildings

In Yangtze River zone, it is very complex in the construction climate characteristics, hot in summer and cold wet in winter, especially long time in summer and huge of solar radiation intensity. Energy saving in window should focus on thermal insulation in summer and heat preservation in winter. Owing to the norm,"Design standard for energy efficiency of Residential Buildings in hot summer and cold winter zone"(JGJ134-2001), held out more strict standard for the heat transfer coefficient of window in the residential construction ,it is required to amply to use energy saving glazing in new buildings. It keeps good performances of insulating against heat, reducing cold radiation and non-moisture condensation. Therefore it will substitute for double-pain window and become the energy saving products that considered being to use at first in residential buildings. The thermal technology performance of the insulating glass will be mostly researched in the paper, especially the optical air-layer thickness of the insulating glass will be researched by the energy saving index of heat transfer coefficient.The energy saving principle of the insulating glass in the paper has been analyzed at first. And then the main factors has put forward for the energy saving index of the insulating glass, including original block of glass, the air-layer thickness, kinds of gas and the environmental condition inside and outside the room, etc. The paper analyses to calculate the thermal resistance of the insulating glass, especially of the air-layer.On the basis of the analysis of theory, the natural convection in the air-layer of the insulating glass is adopted a law of numerical simulation. In the numerical simulation, it is adopted to use the condition of ordinary wall temperature for the different structure of insulating glass and the different wall temperature. The simulation results show that the main factors include kinds of gas in the layer, the relative layer thickness and the temperature difference between cold and hot wall for the nature convection in air-layer. Among the factors, the relative layer thickness is the most influential. The main heat transfer is the radiation heat transfer while the heat conduction and convection are relatively small in proportion. The radiation heat transfer assumes constant in the air-layer. So the optical air-layer thickness is assumed the thickness to make the convection heat transfer reach the minimum. The temperature field, the velocity field and the pressure field in the air-layer have been analyzed and the convection heat transfer in the air-layer is found faint and could approximation be regarded as the pure conduction heat transfer. The heat transfer coefficient is calculated by the results of simulation, compared correctly with the calculated data by the maturate software. Then, the optical air-layer thickness has been simulated in the main cities in the Yangtze River zone.To verify the simulation results, the orthogonal test is adopted in the paper. It designs for the three factors of the air-layer thickness and height and the temperature difference between cold and hot wall. The hot wall tank method is used in the experiment and the heat transfer throng the air-layer, the temperatures in cold and hot wall and the air-layer area was measured to calculate the heat transfer coefficient by the forma Q = K (t_H - t_C)A. Because the losses of heat were big in the experimental apparatus, there were great difference in calculating the heat transfer coefficient between the simulation and experiment. However, it is still directive significant to determine the optical air-layer thickness.The paper analyzes the applicability of the insulating glass in buildings finally. And the energy consumption through the insulating glass and else glasses were proceeded contrastive analysis. The results show that it is obvious to reduce the energy consumption in buildings.