Consider a $1\mathrm{.}2-$m$-$high and $2\mathrm{.}4-$m$-$wide double$-$pane$$window consisting of two $3-$mm$-$thick layers of glass$($k$=0\mathrm{.}78$ W$/$m$$K$)$ separated by a $2\mathrm{.}5-$cm$-$wide airspace.$$Determine the steady rate of heat transfer through this window$$and the temperature of its inner surface for a day during$$which the room is maintained at $20$C while the temperature of$$the outdoors is $0$C$.$ Take the heat transfer coefficients on the$$inner and outer surfaces of the window to be h$1=10$ W$/$m$2$K$$and h$2=25$ W$/$m$2$K$,$ respectively, and disregard any heat transfer by radiation.$$Evaluate air properties at a film temperature of $10$C and$1$ atm pressure. Use the temperature difference across the air gap as $15$C for the initial guess.

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The steady rate of heat transfer through this window is W$.$

The temperature drop across the air gap is