Experimental and numerical study of energy loss through double-glazed windows

A double-glazed window separating a small scale room and the cold environment outside it are modeled by such a window joining a hot box to a cold one. The effects of different parameters on the heat transfer from the hot box (room) to the cold box (outside) are investigated experimentally. These parameters include: the size of the air gap between the double-glazed window, installation of a curtain in the air gap, the curtain to window distance behind the double-glazed window and tilting the double-glazed window from its vertical position. Although the results of these investigations are qualitatively predictable, a comprehensive experimental study to quantify the share of each individual item on the heat loss through the window is a reasonable research. The results indicate that increasing the air gap from 12 to 21 mm, results in 5.1% less energy loss through the window. By installing the curtain in the middle of a 21 mm air gap, the energy loss reduces by 19.9% compared to the same air gap but without a curtain. Also, by installing the curtain at a distance of 0.4 to 4 cm behind the window on the hot side, a 22% to 33.9% reduction in energy loss is observed. A tilt angle of 10 ° from vertical position can decrease the energy loss by 6.5%. Numerical studies with the Ansys Fluent 16 software provide good agreement with the experimental data. These numerical studies are conducted for one case in each set of experiments and help to study parameters that changing them in experimental work is costly and time consumable.