Consider a plane composite wall that is composed of two materials of thermal conductivities kA = 0.1 W/mK and kB = 0.04 W/mK and thicknesses LA = 10 mm and LB = 20 mm. The contact resistance at the interface between the two materials is known to be 0.30 m2K/W. Material A adjoins a fluid at 200°C for which h = 10 W/m2K, and material B adjoins a fluid at 40°C for which h = 20 W/m2*K. (a) What is the rate of heat transfer thro

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Netta00 Netta00 · Answer 1 · 2019-10-15T09:05:12+02:00

Answer:

q=39.15 W/m²

Explanation:

We know that

Thermal resistance due to conductivity given as

R=L/KA

Thermal resistance due to heat transfer coefficient given as

R=1/hA

Total thermal resistance

[tex]R_{th}=\dfrac{L_A}{AK_A}+\dfrac{L_B}{AK_B}+\dfrac{1}{Ah_1}+\dfrac{1}{Ah_2}+\dfrac{1}{Ah_3}[/tex]

Now by putting the values

[tex]R_{th}=\dfrac{0.01}{0.1A}+\dfrac{0.02}{0.04A}+\dfrac{1}{10A}+\dfrac{1}{20A}+\dfrac{1}{0.3A}[/tex]

[tex]R_{th}=4.083/A\ K/W[/tex]

We know that

Q=ΔT/R

[tex]Q=\dfrac{\Delta T}{R_{th}}[/tex]

[tex]Q=A\times \dfrac{200-40}{4.086}[/tex]

So heat transfer per unit volume is 39.15 W/m²

q=39.15 W/m²