Question

Heat Loss Through Thermopane Double Window. A double window called thermopane is one in which two layers of glass dry stagnant air. In a given window, each of the glass layers is 6.35 mm thick separated by a 6.35 mm space of stagnant air. The thermal conductivity of the glass is 0.869 W/m K and that of air is 0.026 over the temperature range used For a temperature drop of 27.8 K over the system, calculate the heat loss for a window 0.914 m x 1.83 m. (Note: This calculation neglects the effect of the convective coefficient on the one outside surface of one side of the window, the convective coefficient on the other outside surface, and convection inside the window.) are used separated by a layer of

Answer 1

Glass 1 Glass 2 6.35 mm 6.35 mm 6.35 mm Given : AT = 27.8 x = 0.869 0.026 window (A)= - Ax Air = 10 Heat Area of Axe glass case of wlmik wlmin 0.914 x 1.83 m² 6.35 mm = (6.53 x 10- 3 conduction. m This is Heat loss as :- by conduction is given Temperature Difference - To sun of Individual Resistances AT + / Resistance due Resistance to Glass due due 1 due) + / Resistance due) + / Resistance due (Resistance (to Glass 2 : 0 - AT R & R2 + R3 Here Ri= = ax Agrass A 6.53 x 103 0.869 x (0.914x 1.83) 4.492583X105 Klw

Page No. Date R2 = = Similarly Sx Air Hair XA 6.53 x 10-3 0.026 x (0.914 x 1.83) 0.150 156 niw = Rz = - Sx glass 2 Marass 2 6.53 x10-3 0.869 x (0.914 x 1083) A = 4.492583 x 10-3 uw w substituting au values in ea ① 27.8 Helq2583 x 103 + 0.150156 + 4.493583 x 100 174.69 W Heat Loss - 8 = 174.69 watt 1