A section of a composite wall with the dimensions shown below has uniform temperatures of 200°C and 50°C over the left and right surfaces, respectively. If the thermal conductivities of the wall materials are: kA = 70 W/(m K), kB = 60 W/(m K), kc = 40 W/(m K) and kD = 20 W/(m K), determine the rate of heat transfer through this section of the wall and the temperatures at the interfaces.

GIVEN

A section of a composite wall

Thermal conductivities

kA = 70 W/(mK)

kB = 60 W/(mK)

kC = 40 W/(mK)

kD = 20W/(mK)

Surface temperatures

Left side (TAs) = 200°C

Right side (TDs) = 50°C

ASSUMPTIONS

One dimensional conduction

The system is in steady state

The contact resistances between the materials isnegligible

TA-200C To 50C 3 cm -D 3 cm 2 cm 2,5 cm -6 cm - 4 cm 6 cm