5. Center of Glass Heat Transfer in Vertical Double-Pane Windows

In this chapter, we will investigate center of glass heat transfer in vertical double pane windows. For contributions to total heat transfer from other parts of a window system such as edges of glass and window frames, see Ref [1]. It is assumed that vertical double panes are parallel, air tight and with no moisture condensation. Also, solar radiation strikes the panes at near normal incidence. In the present analysis, it will be assumed that the outer and the inner surfaces of the glass layer has the same temperature and they are isothermal, since the glass layers are thin, i.e. about 0.003 m thickness, and the thermal conductivity through the glass layer, i.e. about 300 W/(m²-K), which is two orders of magnitude higher than the overall conductivity through a double pane window, i.e. about 3 W/(m²-K). Steady-state heat transfer conditions are considered and heat flow is perpendicular to glass pane surfaces and it is one-dimensional. Radiation heat transfer ignores gas absorption between panes. Convective heat transfer assumes high aspect ratio panes. With above assumptions, center of glass heat transfer for a vertical double pane window is illustrated in Figure 5-1.