Question
Download Solution PDFA wall of a furnace is made up of inside layer of silica brick 119 mm thick covered with a layer of magnesite brick 240 mm thick. The temperatures at the inside surface of silica brick wall and outside surface of magnesite brick wall are 780 °C and 102 °C respectively. The contact thermal resistance between the two walls at the interface is 0.003 °C/W per unit wall area. Thermal conductivities of silica and magnesite bricks are 1.7 W/m °C and 6 W/m °C. The rate of heat loss per unit area of the wall is
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept:
To determine the rate of heat loss per unit area through a composite wall, we use the concept of thermal resistance in series.
Calculation:
Given:
- Thickness of silica brick,
- Thickness of magnesite brick,
- Temperature at the inside surface of silica brick,
- Temperature at the outside surface of magnesite brick,
- Thermal conductivity of silica brick,
- Thermal conductivity of magnesite brick,
- Contact thermal resistance,
Calculation:
First, calculate the thermal resistance of the silica brick layer:
Next, calculate the thermal resistance of the magnesite brick layer:
Then, calculate the total thermal resistance:
Finally, calculate the rate of heat loss per unit area:
Therefore, the rate of heat loss per unit area of the wall is:
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