heat transfer

# heat transfer - E234 Thermodynamics A Really Nice Way to...

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E234 Thermodynamics A Really Nice Way to Solve Heat Transfer Problems Courtesy Prof. Gerald Rothberg To have a concrete problem to work with consider typical double pane windows, sometimes called thermopane. Imagine a room with a 2 m 2 window consisting of two sheets of 3 mm thick glass separated by a 1 cm thick air layer. Convective heat transfer through the thin air layer is negligible due to friction at the glass surfaces. On a typical winter day in Hoboken when the room temperature is 22 o C and the outside air temperature is 0 o C heat will be lost through the window. A typical air convection coefficient is 10 W/m 2 –K. The goal of this problem is to compare the heat losses through a single pane window and through the double pane window and estimate the economic value of the double pane window. Starting from the room, label the glass surfaces 1, 2, 3 and 4. T 1 = 22 o C. The outside air temperature is T 0 = 0 o C. The other temperatures are unknown at this point. T 4 is not equal to T 0 as will be seen below. ROOM 1 T1 =22 o C 23 4 T 0 =0 o C The rate of heat conduction is k t L H t cond R T T L A k L T T A k Q = = = (1) In equation (1) I have introduced the conduction thermal resistance R k

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heat transfer - E234 Thermodynamics A Really Nice Way to...

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