Chapter 1, Problem 1.42P

1. (a)   Consider a room with a 1.8-m-high and 2.0-m-wide double-pane window consisting of two 4-mm-thick layers of glass separated by a 10-mm-wide stagnant air space. The convection heat transfer coefficients on the inner and outer surfaces of the window are 12 W/m2 K and 25 W/m2 K, respectively, while the average thermal conductivity of glass is 0.78 W/m K; and the air, 0.026 W/m K.   If the room is maintained at 22 oC, the outside temperature is -4 oC and heat transfer due to radiation can be neglected, determine:                 (i) Draw the sketch and thermal resistance network;                                                (ii) the total thermal resistance;                (iii) the steady rate of heat transfer through this double-pane window;                                                                              (iv) the temperature of the inner surface of the window.…

Circular fins of uniform cross section, with diameter of 10 mm and length of 50 mm, are attached to a wall with surface temperature of 350°C. The fins are made of material with thermal conductivity of 240 W/m·K, and they are exposed to an ambient air condition of 25°C and the convection heat transfer coefficient is 250 W/m2·K. Determine the heat transfer rate and plot the temperature variation of a single fin for the following boundary conditions: (a) Infinitely long fin (b) Adiabatic fin tip (c) Fin with tip temperature of 250°C (d) Convection from the fin tip

15. The wall of a building consists of a 360-mm thick layer A which has a thermal conductivity, kA - 4.9 W/m-K, followed by a 80-mm thick second layer, layer B, which has a thermal conductivity, kg = 0.9 W/m-K. The inside and outside convection coefficients are 20 W/m² K and 39 W/m2 K. At these conditions, what is the overall heat transfer coefficient for this composite wall? Express your answer in W/m^2 K.