Optimal design of double insulating glass spacing

Northeast China is located in the high latitude region of China, the temperature in winter is very low, the temperature difference between indoor and outdoor is very big, in order to meet the living requirements of residents in winter, it is necessary to carry out good insulation design for buildings. Among them, the thermal insulation performance of Windows is a very important link in the thermal insulation performance of buildings. The glass design is particularly important in the composition of Windows, which is the key link of window insulation performance.

Building doors and Windows are the weak part of the thermal insulation performance of the building external protection structure. Its long-term energy consumption accounts for about 50% of the long-term energy consumption of the whole building. Therefore, improving the thermal insulation performance of doors and Windows is an important way to reduce the long-term energy consumption of the building. The thermal insulation performance of Windows not only obviously affects the heating energy consumption of buildings, but also has an obvious influence on indoor thermal environment, comfort and indoor health conditions. If the insulation quality of the window is not good, the heat loss of heat transfer through the window and the heat loss of air penetration through the window gaps will increase significantly, which will lead to a significant increase in heating energy consumption. Double-layer insulating glass, which is widely used at present, is a kind of new building material with heat insulation, sound insulation, beautiful application, and can reduce the weight of buildings. The purpose of this project is to study the design scheme of double insulating glass spacing, and strive to find out the optimal spacing scheme that can make the insulation performance reach a higher level, and carry out experimental verification, to provide a certain scientific reference for the future building window insulation design in Northeast China.

1 Experimental scheme

The thermal insulation performance of glass Windows is directly reflected by the value of heat transfer coefficient K. The lower the heat transfer coefficient is, the less heat dissipation is, and the better the thermal insulation performance of Windows is. Therefore, this experiment mainly explores the combination of glass spacing to make the heat transfer coefficient Z small under the existing technology conditions. By drawing up the gradually prepared spacing combination, the test of heat transfer coefficient was carried out, and the image of the change of spacing combination and heat transfer coefficient was drawn. According to the image, the relationship between the spacing combination and the heat transfer coefficient was studied, and the Z-optimal spacing combination satisfying the better insulation performance was proposed to complete the research. After the study of combination, the orientation of δ1 and δ2 is studied, namely the orientation in the process of glass installation, and the influence of different orientations on the thermal insulation performance of Windows is studied. After determining the combination of Z rear spacing, further explore the Z optimal orientation, so as to further improve the thermal insulation performance of the Windows, and provide a basis for the installation of Windows in the process of building construction. According to the previous experimental data, when the double glass spacing is less than 10mm, the spacing and thermal resistance are almost in a linear relationship; When the distance between the two glasses is 10mm ~ 30mm, the relationship between the distance and the thermal resistance curve; When the spacing exceeds 30mm, the thermal resistance of the air layer increases very slowly due to the combined action of convection and radiation heat exchange.

The design should be based on the needs of the thermal resistance and the economic scale of the frame, appropriate to determine the spacing of the glass, generally not less than 9mm. At present, there are two glass Windows widely used on the market, including plastic Windows, wood Windows, aluminum Windows and aluminum-plastic composite Windows. The heat transfer coefficient is 2.4 ~ 2.5W·m-2·K-1, and the quality is up to 2.8W·m-2·K-1. Coupled with the error of winter heating and other conditions, the living environment of ordinary residents certainly does not have the good conditions of the laboratory. In practice, the figure is sure to be higher. We also visited the student dormitories on campus and measured the indoor temperature. In some places, the indoor temperature was only 15℃. It is not difficult to find that most of the heat is lost through the Windows, resulting in greater heating pressure and more waste of resources. Window glass from a single glass into a double glass or three glass, glass insulation performance will be significantly improved. This is not the effect of glass thermal resistance, but the air layer between the glass is the main reason for the increase in thermal resistance, because the heat transfer coefficient of stationary air is lower than that of any material.

Therefore, with the improvement of glass window technology development level, in order to better improve the insulation performance of doors and Windows, three-glass glass Windows can be made. According to the relationship between the thermal resistance of the sealed air layer and the thickness of the air layer, the net spacing thickness satisfying the better insulation performance is studied, and the orientation of different spacing of glass is studied to complete the research of this project.

2. Experimental process and results

According to the influence of air flow, glass thickness and other factors on the heat transfer coefficient of glass Windows, the spacing of equal fractions can achieve the best insulation effect. If one of the two spacing is too large and the other is too small, according to the change trend of the K value of the double glass, it can be seen that the too large spacing undertakes most of the heat preservation tasks, but the heat transfer coefficient will not be greatly reduced when the glass spacing is too large, and the reduction will be smaller and smaller, so the too large spacing can only be a waste, and the too small spacing is too sensitive to the insulation effect. A little increase in the distance will cause a substantial reduction in the heat transfer coefficient, so it is not appropriate to use too small spacing, too large or too small spacing Z will eventually lead to the deterioration of thermal insulation performance, so it is assumed that equal spacing makes the heat transfer coefficient of the window reach Z low.

According to the survey, 3mm+3mm, 6mm+6mm, 9mm+9mm and 12mm+12mm three-glass Windows are widely used in the market at present. Glass Windows with smaller spacing are mainly used for smaller openings in auxiliary rooms such as toilets, while glass Windows with larger spacing are mainly used for larger openings in main rooms such as living rooms and bedrooms with high requirements for warmth.

At the same time, the author conducted a survey on Heilongjiang Dryland Scientific Research Institute, participated in the experiment of heat transfer coefficient measurement, and obtained part of the experimental data. The general three glass Windows of these specifications have low thermal conductivity Z of 12mm+12mm, and the thermal conductivity coefficient of the main material is plastic window is 1.7 ~ 1.8W·m-2·K-1. Three glass wood window :1.7 ~ 1.8W·m-2·K-1, aluminum composite glass :2.0 ~ 2.1W·m-2·K-1.

Common on the market is the combination of equal spacing of three glass Windows, then unequal spacing? Because the heat transfer coefficient decreases linearly when the glass spacing is before 10mm, so excluding the possible combination of 3mm, it can not play the advantage of very low thermal conductivity of static air. At the same time considering too thin three glass Windows will also make the thermal conductivity close to two glass, according to 12mm+12mm, several groups of combinations :6mm+18mm, 9mm+15mm, and the two groups of spacing combination experiments. The experiment agrees with the hypothesis basically. The heat transfer coefficient of the 6mm+18mm spacing combination is 2.2W·m-2·K-1. The heat transfer coefficient of the 9mm+15mm combination is 2.0W·m-2· k-1. Comparing the heat transfer coefficient with the 12mm+12mm three-glass Windows, it is not difficult to see that the heat transfer coefficient of the 12mm+12mm combination of three-glass Windows is low in these combinations, so it can be concluded that the optimal spacing combination is the equal spacing combination. Imagine a wide spacing combination, such as 15mm+15mm, but according to the current thermal resistance needs, technical level and economic size of the frame, the total spacing combination is 24mm, 15mm+15mm such spacing combination or even higher spacing combination is not in line with the economic principle, because at the current level of technology will lead to a sudden increase in the cost of window frame production, So rule that out.

3 Closing remarks

According to the investigation, experiment, analysis and data sorting, it is concluded that the spacing combination of 12mm+12mm three-glass Windows is the spacing combination of Z economic Z insulation. Such Windows should be widely used with large openings in various buildings to replace two-glass Windows with much lower heat transfer coefficients or other spacing combinations of three-glass Windows. The insulation performance requirements do not have the living room, bedroom and other main room high bathroom, storage room, kitchen, corridor and other auxiliary rooms, can use 9mm+9mm or lower spacing combination. Although they do not have 12mm+12mm distance insulation, but these rooms are not as high as the requirements of the main room, such a distance can meet the insulation requirements of these auxiliary rooms, and higher than the insulation performance of two glass Windows, more economic.