a) A house walls that are 20 cm thick and have an average thermal conductivity four times that of glass wool. Assume there are no windows or doors. The walls' surface area is 1000000 cm² and their inside surface is at 23° Çwhile their outside surface is at 4°C (Thermal conductivity of glass wool is 0.042 W/m°C) (i) Calculate the rate of heat conduction through house walls? (ii) How many 150W room heaters would be needed to balance the heat transfer due to conduction? (approximate number)

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a) A house walls that are 20 cm thick and
have an average thermal conductivity four
times that of glass wool. Assume there are no
windows or doors. The walls' surface area is
1000000 cm² and their inside surface is at
23° Çwhile their outside surface is at 4° C
(Thermal conductivity of glass wool is 0.042
W/m°C)
(i) Calculate the rate of heat conduction
through house walls?
(ii) How many 150W room heaters would be
needed to balance the heat transfer due to
conduction? (approximate number)
b) A spherical infrared heater of radius 6.05
cm has an emissivity of 0.74. What
temperature must it run at if the required
power is 0.42 kW? Neglect the temperature
of the environment. (Stefan's constant =
5.67*10-8 Wm¯-2K-4)
The temperature of the heater in Celsius =
Transcribed Image Text:a) A house walls that are 20 cm thick and have an average thermal conductivity four times that of glass wool. Assume there are no windows or doors. The walls' surface area is 1000000 cm² and their inside surface is at 23° Çwhile their outside surface is at 4° C (Thermal conductivity of glass wool is 0.042 W/m°C) (i) Calculate the rate of heat conduction through house walls? (ii) How many 150W room heaters would be needed to balance the heat transfer due to conduction? (approximate number) b) A spherical infrared heater of radius 6.05 cm has an emissivity of 0.74. What temperature must it run at if the required power is 0.42 kW? Neglect the temperature of the environment. (Stefan's constant = 5.67*10-8 Wm¯-2K-4) The temperature of the heater in Celsius =
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