A wall of dimensions 2.00 m by 3.50 m has asingle-panewindowof dimensions0.75 m by 1.20 m .Ifthe inside temperature is 20^(@)C and the outside temperatureis -10^(@)C, effective thermalresistanceof the opaque wall and windoware 2.10 m^(2) KW^(-1) and 0.21m^(2) K W^(-1) respectively. The heat flowthroughthe entirewall will be .

A wall of dimensions 2.00 m by 3.50 m has asingle-panewindowof dimensi

1.	A wall of dimensions 2.00 m by 3.50 m has asingle-panewindowof dimensions0.75 m by 1.20 m .Ifthe inside temperature is 20^(@)C and the outside temperatureis -10^(@)C, effective thermalresistanceof the opaque wall and windoware 2.10 m^(2) KW^(-1) and 0.21m^(2) K W^(-1) respectively. The heat flowthroughthe entirewall will be .
Answer» `215 W` `205 W` `175 W` `110 W` SOLUTION :The wall and the window are in parallel arrangement , so net heat flow is the sum of heat flow through the wall and the window. The temperature difference, `T_(H) - T_(C) = 30 K` Area of window, `A_(i) = (0.75) (1.20) = 0.90 m^(2)` Heat flow through window pane, `((dQ)/dt)_(1)= (T_(H) - T_(C))/(R_(1)) = (0.90)(30)/(0.21) = 128.6 W` The area of the wall, `A_(2) = (2.00)(3.50) - (0.75)(1.20) = 6.10 m^(2)` Heat flow through the wall, `((dQ)/dt)_(2) = (T_(H) - T_(C))/(R_(2)) = ((6.10)(30))/((2.10)) = 87 W` Net heat flo, `(dQ)/(dt) = 128.6 + 87 = 215.6 W`