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2. A furnace wall 28 cm thick is made of two materials bounded together. The “hot side
material is 20 cm thickness and has a thermal conductivity of 1.4 W/mK; the “cold

side” material is 8 cm thickness and has a thermal conductivity of 0.50 W/mK. The
0
inner surface is exposed to a hot gas at an average temperature 880 C, and the outer
0
surface is exposed to air at an average temperature of 35 C. Determine the heat transfer
2
through a wall area of 2.0 m , if the gas and air convective heat transfer coefficients are
2
65 and 6.0 W/m K, respectively. (3.5 kW)

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