To reduce the home heating requirements, modern building codes in many parts of the country require the

Question:

To reduce the home heating requirements, modern building codes in many parts of the country require the use of double-glazed or double-pane windows, i.e., windows with two panes of glass. Some of these so called thermopane windows have an evacuated space between the two glass panes while others trap stagnant air in the space.(a) Consider a double-pane window with the dimensions shown in the following sketch. If this window has stagnant air trapped between the two panes and the convective heat transfer coefficients on the inside and outside surfaces are 4 W/(m2 K) and 15 W/(m2 K), respectively, calculate the overall heat transfer coefficient for the system.(b) If the inside air temperature is 22?C and the outside air temperature is ??5?C, compare the heat loss through a 4 m2 double-pane window with the heat loss through a single-pane window. Comment on the effect of the window frame on this result.(c) The total window area of a home heated by electric resistance heaters at a cost of $.10/kWh is 80 m2. How much more cost can you justify for the double-pane windows if the average temperature difference during the six winter months when heating is required is about 15?C?GIVENDouble-pane window with stagnant air in gapConvective heat transfer coefficientsInside ( hci ) = 4 W/(m2 K)Outside ( hco ) = 15 W/(m2 K)Air temperaturesInside (Ti) = 22?COutside (To) = ??5?CSingle window area (Aw) = 4 m2During the winter months, (??T) = 15?CHeating cost = $.1.0/kWhTotal window area (AT) = 80 m2ASSUMPTIONSSteady state conditions prevailRadiative heat transfer isnegligible