Repeat the Problem 1.32 but assume that instead of surface temperatures, the given temperatures are those of air on the left and right sides of the wall and that the convective heat transfer coefficients on the left and right surfaces are 6 and 10 W/(m2 K), respectively.

Problem 1.32: Repeat the Problem 1.31 including a contact resistance of 0.1 K/W at each of the interfaces. Problem 1.31: A section of a composite wall with the dimensions shown in the schematic diagram 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

Composite wall

Thermal conductivities

kA = 70 W/(mK)

kB = 60 W/(mK)

kC = 40 W/(mK)

kD = 20W/(mK)

Air temperatures

Left side (TA???) = 200°C

Right side (TD???) = 50°C

Contact resistance at each interface (Ri) = 0.1 K/W

Convective heat transfer coefficients

Left side ( hcA ) = 6 W/(m2 K)

Right side ( hcD ) = 10 W/(m2 K)

ASSUMPTIONS

One dimensional, steady stateconduction

To.- 50C 3 cm to TA- 200C 3 cm 6 cm - 2 cm ' 2.5 cm 4 cm