Consider a multi-layered walls of a storage building (no windows) that is made of three layers as shown in the figure. The inside layer is a gypsum material that is 1.0 cm thick and has a thermal conductivity of 0.5 W/m.K. We then have a dense brick layer that is 15.0 cm thick and has a thermal conductivity of k = 5 W/m.K The outside wall is made of a wood panel that is 2.0 cm thick and has a thermal conductivity of k = 1.0 W/m.K In a cold day, the outside can be at -10oC and the convective heat transfer coefficient can be hout = 25 W/m2.K due to wind. Inside air of the building is kept at 10oC and the convective heat transfer coefficient over the inside surfaces is rather low with hin = 5 W/m2.K a) Show the thermal resistance diagram with all the temperature nodes. b) What is the rate of heat loss in kW per m2 under these conditions? c) What would be the temperature of the inside surface of the wall? d) What is the temperature at the interface between the brick wall and the plywood? e) If the cost of energy is $0.15 per kWh, how much would the ‘Monthly’ heating cost be if the total exposed wall is of the building is 600 m2? f) If we want to reduce our heat loss to half, what thickness of insulation with k = 0.1 W/m.K should we add to the wall?
Consider a multi-layered walls of a storage building (no windows) that is made of three layers as shown in the figure. The inside layer is a gypsum material that is 1.0 cm thick and has a thermal conductivity of 0.5 W/m.K. We then have a dense brick layer that is 15.0 cm thick and has a thermal conductivity of k = 5 W/m.K The outside wall is made of a wood panel that is 2.0 cm thick and has a thermal conductivity of k = 1.0 W/m.K
In a cold day, the outside can be at -10oC and the convective heat transfer coefficient can be hout = 25 W/m2.K due to wind. Inside air of the building is kept at 10oC and the convective heat transfer coefficient over the inside surfaces is rather low with hin = 5 W/m2.K
a) Show the thermal resistance diagram with all the temperature nodes.
b) What is the rate of heat loss in kW per m2 under these conditions?
c) What would be the temperature of the inside surface of the wall?
d) What is the temperature at the interface between the brick wall and the plywood?
e) If the cost of energy is $0.15 per kWh, how much would the ‘Monthly’ heating cost be if the total exposed wall is of the building is 600 m2?
f) If we want to reduce our heat loss to half, what thickness of insulation with k = 0.1 W/m.K should we add to the wall?
a) The thermal resistance diagram is given below-
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