Illustration 2.3
Consider a composite wall containing 5-different materials as shown in the fig. 2.7. Calculate the rate of heat flow through the composite from the following data?
Solution 2.3
Assumptions:
1. Steady-state one-dimensional conduction.
2. Thermal conductivity is constant for the temperature range of interest.
3. The heat loss through the edge side surface is insignificant.
4. The layers are in perfect thermal contact.
5. Area in the direction of heat flow is 1 m2.
The height of the first layer is 4 m (h1 = h2 + h3 ).
The equivalent circuit diagram of the above composite is,
On calculating equivalent resistance with the given data (Note: thickness of layer 2 = thickness of layer 3 and thickness of layer 4 = thickness of layer 5, in the heat flow direction),
Fig. 2.7: Composite of illustration 2.3; (a) composite, (b) corresponding electrical circuit |
Thus the heat flow rate through the composite,
