The inner wall of a furnace is at a temperature of 700¬∞C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.¬∞C-1 respectively. The ambient air is at 30¬∞C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.¬∞C-1. The rate of heat loss from the outer surface in W.m-2is$

The inner wall of a furnace is at a temperature of 700¬∞C. The comp

1.	The inner wall of a furnace is at a temperature of 700¬∞C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.¬∞C-1 respectively. The ambient air is at 30¬∞C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.¬∞C-1. The rate of heat loss from the outer surface in W.m-2is$
A.	165.4
B.	167.5
C.	172.5
D.	175
Answer» B. 167.5

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