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 composit

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