Experimental Study On Optical And Thermal Performance Of Exhaust Air Window Embedding Multilayer Films

Exterior windows are the weakest insulation of building envelope components.Under the background of energy conservation and emission reduction,improving the thermal insulation of exterior windows is one of the effective ways of building energy saving.This study proposes a new type of exhaust air window embedding multilayer films for building exterior window structure.The exhaust air window embedding multilayer films is an external window structure that utilizes exhaust air from conditioned room to conduct active heat insulation.It is composed of two glass panes,the cavity between the glass and the multilayer films embedded in the cavity.Ordinary exhaust windows allow exhaust air from conditioned room to flow through the cavity,making the inner surface of the indoor glass close to the indoor air temperature to reduce cooling/heating load through window,and the innovation of the exhaust air window embedding multilayer films is the multilayer films embedded in the cavity,which divide an exhaust cavity into several air flow cavities,increasing the flow of exhaust air inside the window to make full use of the low-grade energy of the exhaust air to further enhance the thermal insulation of the window.Windows have the important functions of lighting,ventilation,and thermal insulation.In this paper,the exhaust air window embedding multilayer films is studied from the optical and thermal insulation aspects by experimental means,and the following work is carried out:For the optical experiment,the optical model of the exhaust air window embedding multilayer films is established using the energy balance of each component to analyze the effect of the embedded films on the total radiation transmittance and visible light transmittance of the window.The embedded film is the core component of this window.In order to obtain the solar extinction coefficient and visible light extinction coefficient of the film,an experimental platform is built.Under real weather conditions,the total radiation transmittance and visible light transmittance of double-layer hollow glass embedding a layer of PVC film are measured.The error function is established and the golden section search is used to deduce the solar extinction coefficient and visible light extinction coefficient of PVC film in reverse based on the optical model and the measured total radiation transmittance and visible light transmittance as the source data.Using the obtained solar extinction coefficient and visible extinction coefficient of the film and the optical model of exhaust air window embedding multilayer films,the effects of the number of film layers,film thickness and incident angle on the total radiation transmittance and visible light transmittance of this window are studied.The experiment in this paper is only a preliminary study on the thermal insulation of this window.Utilizing the original experimental platform of the research group,the exhaust air window embedding two layers of film is tested under the real winter climatic in Wuhan.The thermal insulation of this window is studied and in order to explore the improvement of the insulation of the window by the exhaust air,a comparative experiment is conducted to test the comparison of this window before and after opening the exhaust port.The experimental data shows that the inside glass surface temperature of exhaust air window embedding multilayer films in winter is higher,which can improve the thermal comfort of indoor personnel.The difference between the average temperature of the inside glass surface and the indoor air temperature is lower,and the thermal insulation is better.The experimental results can also be used as verification data for the later simulation study of the exhaust air window embedding multilayer films.