1b.Consider a 1.2-m-high and 2-m-wide double-pane window consisting of two 3-mm-thick layers of glass (k = 0.78 W/m · °C) separated by a 12-mm-wide stagnant air space (k = 0.026 W/m · °C). Determine the steady rate of heat transfer through this double-pane window and the temperature of its inner surface for a day during which the room is maintained at 24°C while the temperature of the outdoors is _5°C. Take the convection heat transfer coefficients on the inner and outer surfaces of the window to be h1 = 10 W/m2 · °C and h2 = 25 W/m2 · °C, and disregard any heat transfer by radiation. The thermal conductivity of the glass and air are given to be kglass = 0.78 W/m⋅°C and kair= 0.026 W/m⋅°C.
1a.A copper slab ( k = 372 W/m .K ) is 3mm thick . it is protected from the corrosion on each side by a 2 mm thick layer of stainless steel ( k = 17 W/m .K ) . The temperature is 40oC on one side of this composite wall and 100oC on the other. Find the temperature distribution in the copper slab and the heat conducted through the wall.
Given: ksteel = 17 W/m .K kcopper = 372 W/m .K
Steel Copper Steel
T1 = 40oC T2 T3 T4 = 10oC
q
2mm 3mm 2mm
1b.Consider a 1.2-m-high and 2-m-wide double-pane window consisting of two 3-mm-thick layers of glass (k = 0.78 W/m · °C) separated by a 12-mm-wide stagnant air space (k = 0.026 W/m · °C). Determine the steady rate of heat transfer through this double-pane window and the temperature of its inner surface for a day during which the room is maintained at 24°C while the temperature of the outdoors is _5°C. Take the convection heat transfer coefficients on the inner and outer surfaces of the window to be h1 = 10 W/m2 · °C and h2 = 25 W/m2 · °C, and disregard any heat transfer by radiation. The thermal conductivity of the glass and air are given to be kglass = 0.78 W/m⋅°C and kair= 0.026 W/m⋅°C.
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