Question

In a coal fired power plant, a furnance Wall consists of a 125 mm wide refractory brick and a 125 mm wide insulating firebrick separated by an air gap as shown in figure. The outside Wall is covered with a 12 mm thickness of plaster. The inner surface of Wall is at 1100 °C, and then room temp is 25 °C. The Heat transfer coefficient from the outside Wall surface to air in room is 17 W/m^2 K, resistance to heat flow of air gap is 0.16 K/W. The thermal conductivities of refractory brick, the insulating firebrick, and the plaster are 1.6, 0.3 and 0.14 W/m K, respectively. Calculate the rate of Heat loss per unit area of Wall surface.

Resistance per unit área

a) Rag = ? (Air gap)

b) Rrb = ? (Refractory brick)

c) Rfb = ? ( firebrick)

d) Rpl = ? (plaster)

e) Rconv = ? (convection)

f) Rtotal = ?

g) q = ?

Answer #1

Drawing the thermal resistance circuit we can solve this problem as below-

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