Determine the overall conduction heat transfer rate per unit area occurring acro

Question

Determine the overall conduction heat transfer rate per unit area occurring across a furnace wall made of fire clay. Furnace wall has a thickness of 12-inches. The wall is insulated from outside. Thermal conductivity values for the wall and insulation materials are 0.2 W/m middot K and 0.02 W/m middot K, respectively. The furnace operates at 650 degree C. Average ambient temperature outside the furnace wall is 30 degree C and allowable temperature on the outer side of insulation is 80 degree C. If the air side heat transfer coefficient is 0.8 W/m2 middot K, calculate the minimum insulation thickness requirement. The roof of an electrically heated home is 6 m long, 8 m wide, and 0.25 m thick, and is made of a flat layer of concrete whose thermal conductivity is 0.8 W/m middot degree C. The temperatures of the inner and the outer surfaces of the roof one night are measured to be 15 degree C and 4 degree C, respectively, for a period of 10 hours. Determine (a) the rate of heat loss through the roof that night and (b) the cost of that heat loss to the home owner if the cost of electricity is $0.08/kWh Consider two houses that are identical, except that the walls are built using bricks in one house, and wood in the other. If the walls of the brick house are twice as thick, which house do you think will be more energy efficient?

Explanation / Answer

The answer of the following questions are as follows

a) The rate of heat loss through roof that night is 758 W.

b)The cost of electricity is 45000 rupees.

The house with the walls of wood would be more efficient.

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