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1. calculate the quantity of heat conducted through a brick wall of 2m^2 and thickness 12 cm in 1 hour. the surface temperatues of the brick wall are 8 C and 28 C. the thermal conductivity of the brick wall 0.13 W/mK.2.radius =30mm, surface temperature =40 C , pipe length =10m , film coefficient = 20 W/m^2K,... 顯示更多 1. calculate the quantity of heat conducted through a brick wall of 2m^2 and thickness 12 cm in 1 hour. the surface temperatues of the brick wall are 8 C and 28 C. the thermal conductivity of the brick wall 0.13 W/mK. 2.radius =30mm, surface temperature =40 C , pipe length =10m , film coefficient = 20 W/m^2K, surrounding air temperature = 28 C find the rate of heat transfer by convection

最佳解答:

1) The rate of heat transfer along the wall is 0.13 x (28 - 8) x 2/0.12 = 43.3 W Hence quantity of heat conducted in 1 hour = 43.3 x 3600 = 156000 J 2) Surface area of the pipe = 2π x 0.032 x 10 = 0.0565 m2 Hence the rate of heat transfer by convection is: 20 x 0.0565 x (40 - 28) = 13.57 W

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