1. Assume that one-dimensional heat transfer occurs through the composite wall s
ID: 3279805 • Letter: 1
Question
1. Assume that one-dimensional heat transfer occurs through the composite wall shown in the figure below. T = 500°C | A T = 100°C Material A has a thermal conductivity k 1-75 wm-1 K-, and a length of LA-20cm. Material B has a thermal conductivityk-Wm- K and a length of L 25cm. Material C has a thermal conductivity kc 'swm-1 K-1 and a length of Lc = 25 cm. Material D has a thermal conductivity ky, = 20wm-1 K-1 and a length of Lo-iocm. Materials A and D both have a cross sectional area of 2m2, while materials B and C have a cross sectional area of 1 m2 (a) Determine the heat transfer rate through the wall. (b) Determine the temperature of the right face of material A (c) Determine the temperature of the left face of material DExplanation / Answer
A) Conductance of A= 75*2/0.20 =750 W/K
Conductance of B = 60*1/0.25 = 240 W/K
Conductance of C = 58*1/25 = 232 W/K
Conductance of B and C =240+232 = 472 W/K
Conductance of D = 20*2/0.40 = 100 W/K
Total resistance =1/750 + 1/472 +1/100 = 0.01345 K/W
Heat transfer rate = deltaT/resistance
= 400 K /(0.01345 K/W)
= 29740 W
B) temperature at right face of A = 500 - 29740/750
= 460.35 K answer
C) temperature at left face of D = 100 + 29740/100
= 397.4 K answer
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