Tutorial 1 (Conduction and Convection) 1. Consider a composite structure shown on below. Conductivities of the layer are: k1 = k3 = 10 W/mK, k2 = 16 W/mK, and k4 = 46 W/mK. The convection coefficient on the right side of the composite is 30 W/m2K. Calculate the total resistance and the heat flow through the composite. (0. 46, 173. 9 W) 2. Consider a 1. 2-m high and 2-m-wide glass window whose thickness is 6 mm and thermal conductivity is k= 0. 78W/m. 0C.

Determine the steady rate of heat transfer through this glass window and the temperature of its inner surface for a day during which the room is maintained at 24 0C while the temperature of the outdoors is -5 0C. Take the convection heat transfer coefficients on the inner and outer surfaces of the window to be h1= 10 W/m2 . 0C and h2 = 25 W/m2 . 0C and disregard any heat transfer by radiation. (471W, 4. 40C) 3. Consider a 1. 2-m-high and 2-m-wide double-pane window consisting of two 3-mm-thick layers of glass (k=0. 78 W/m . 0C) separated by 12-mm-wide stagnant air space.

Determine the steady rate of heat transfer through this double-pane window and the temperature of its inner surface for a day during which the room is maintained at 24 0C while the temperature of the outdoors is -50C. Take the convection heat transfer coefficients on the inner and outer surfaces of the window to be h1=10 W/ m2 . 0C and h2 = 25 W/m2 . 0C and disregard any heat transfer by radiation. Given also k air = 0. 026 W/ m . 0C (114W, 19. 20C) 4. A cylindrical resistor element on a circuit board dissipates 0. 5W of power in an environment at 400C. The resistor is 1. 2 cm long, and has a diameter of 0. 3cm. Assuming heat to be transferred uniformly from all surfaces, determine (a) the amount of heat this resistor dissipates during a 24-h period, (b) the heat flux on the surface of the resistor, in W/m2 and (c) the surface temperature of the resistor for a combined convection and radiation heat transfer coefficient of 9 W/m2 . 0C. (3. 6 Wh, 1179 W/m2, 1710C) 5. Water is boiling in a 25-cm-diameter aluminum pan (k=237 W/ m . 0C) at 95 0C.

The thermal conductivities of various material used, in W/m. 0C, are kA=kF=3, kB=10, kC=23, kD=15 and kE=38. The left and right surface of the wall are maintained a uniform temperatures of 3000C and 1000C, respectively. Assuming heat transfer through the wall to be one-dimensional, determine (Given Rcond = x/kA and Rconv = 1/hA) a) The rate of heat transfer through the wall. b) The temperature at the point where the sections B, D and E meet. c) The temperature drop across the section F. (6453. 0075 W, 259. 59380C, 134. 22220C)