1. Determine the heat flow rate through the composite wall as shown in the
figure below.
Take, $K_A$ = 150 W/m°C, $K_B$ = 30 W/m°C, $K_C$ = 65 W/m°C, $K_D$ = 50 W/m°C
400°C
10 cm
60°C
3 cm
B
C
D
7 cm
A
8 cm
3 cm
5 cm
2. A mild steel tank of wall thickness 10 mm contains water at 90°C. Calculate
the rate of heat loss per m² of tank surface area when the atmospheric
temperature is 15°C. The thermal conductivity of mild steel is 50 W/mK and
the heat transfer coefficients for inside and outside the tank are 2800 W/m²K
and
11 W/m²K respectively. Calculate also the temperature of the
outside surface of the tank.
3. A furnace wall consists of 250 mm fire brick, 125 mm insulation brick and 250
mm building brick. The inside wall is at temperature of 600°C and the
atmospheric temperature is 20 °C. Calculate the heat loss per m² of wall area
and the temperature of the outside wall surface of the furnace. The heat
transfer coefficient for the outside surface is 10 W/m²K and the thermal
conductivities of the fire brick, insulation brick and the building brick are 1.4,
0.2 and 0.7 W/mK respectively.
4. A vertical pipe 80 mm diameter and 2 m height is maintained at a constant
temperature of 120 °C. the pipe is surrounded by still atmospheric air at 30°C
. Find heat loss by natural convection.
