Study On Thermal Insulation Properties Of Multi-cavity Double-pane Glasses With Built-in Transparent Films

Glass is one of the weakest links of building insulation,whose application and development with better thermal performance is an irreplaceable part of building energy and efficiency research.Double-pane glasses are still the most widely used energy-saving glasses,despite their limited energy-saving potential.Thus,it will a helpful choice for energy-saving to improve Double-pane glasses'thermal performance and to exert their origin advantages of simple technology and high practicability,if some innovation can be carried on the basis of their origin design.This paper focuses on thermal performance of a new multi-cavity double-pane glass with a transparent film,an innovative insulating glass,which was proposed by Professor Qinglin Meng from SCUT.The paper firstly summarizes a current development and shortcomings of insulating glasses in domestic and foreign researches,and proposes two improvement targets to overcome those shortcomings.Then a construction of multi-cavity double-pane glasses with built-in transparent films is elaborated,which had responded the improvement targets.And FLUENT is used to simulate heat transfer processes of multi-cavity glasses and ordinary double-pane glasses.The results have showed differences of convective heat transfer processes in their interlayers and illustrated positive effects due to those innovative methods.Further,three kinds of plastic films(PC,PET,PVC)are selected as inter partitions of double-pane glasses,and their thermal parameters of various thicknesses have been measured then introduced into the WINDOW7.5 software of Lawrence Berkeley Laboratory.Subsequently thermal performance of multi-cavity double-pane glasses has been calculated by WINDOW7.5 and following 3 main conclusions are obtained:When films dividing the whole interlayer cavity equally,the overall K value of the glasses is the smallest.When changing the position of films,there is only a slight impact on their transmittance of visible light,their shading coefficient and their solar heat gain coefficient;(2)With increasing of number and thickness of the cavity,heat transfer coefficient of the glasses reduce gradually,from the initial maximum of 2.696 W/(m~2·K)reduces to 0.778 W/(m~2·K)(four films and five cavities),and their optical parameters also weaken,which change less than their heat transfer coefficients;(3)Differences of thickness and materials of built-in films have little influence on thermal performance of multi-cavity glasses,whose heat insulation will enhance obviously by changing filling gas only when the thickness of interlayers is small.When interlayers are thickened,positive effects of filling inert gas will be less obvious.What's more,in order to verify the reliability of the calculation of heat transfer coefficients of multi-cavity glasses produced by WINDOW7.5,the author has made some physical samples and conducted a physical measurement.The difference between measured values and calculated values of the heat transfer coefficient do not exceed 10%of the measured value,which indicates that the calculated values produced by WINDOW 7.5 is reliable.Due to the improvements,thermal performance of the glasses has been significantly improved comparing to ordinary insulating glass.Finally,three advantages of multi-cavity double-pane glass with built-in transparent films,including low cost,small glass weight,and better sound insulation,have been figured out through some simple calculation and verification,which indicates the glasses is cost-effective.