A steady heat transfer model of hollow double glazing under entire wave length heat radiation

• A transparent heat radiation model on hollow double glazing is reported.
• Solar and long-wave radiation, convection and conduction are considered.
• Effective transmittance of hollow double glazing is defined and evaluated.
• Long-wave transparence radiation of glass cannot be ignored.
• Position of single low-E film on glazing surfaces affects heat gain and loss.

This paper presents a mathematical model of heat transfer between inside room surfaces and the outside environmental surface through hollow double glazing. It includes convective heat transfer on the inside and outside surfaces of hollow double glazing, the conduction heat transfer between the two glass sheets, and the radiation heat transfer (solar and long-wave radiation) through the sheets. Based on the total heat transferred through hollow double glazing, effective transmittance is identified as an important parameter for indicating the effect of the transparence radiation of hollow double glazing. The model evaluated the effects of three different combinations of hollow double glazing on the overall heat flux, the effective transmittance and the solar heat gain coefficient. The heat flux increment due to the long-wave transparence radiation of glass cannot be ignored in the overall heat flux. When a single low-E film is positioned on the outer surface of the indoor-side sheet of glass, it contributes to efficient heat preservation in winter. When positioned on the inner surface of the sheet on the outdoor side, the low-E film is more effective for heat insulation and the shading of sunshine in summer.