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Heat Transfer Mastery

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Questions and Answers

In a composite wall with three different materials having thermal conductivities $k$, $2k$, and $4k$ respectively, the temperature drop across different materials will be in the ratio

1 : 1 : 1

1 : 2 : 4 (correct)

2 : 4 : 1

4 : 2 : 1

The thermal diffusivity of a substance is given by

$\frac{k}{\rho c}$

$\frac{d}{k\rho}$

$k c/\rho$

$\frac{\rho c}{k}$ (correct)

The total emissive power of a blackbody surface is related to its radiation intensity $I$ as

$E = 4\pi I$ (correct)

$E = \pi I$

$E = \pi^2 I$

$E = 2\pi I$

For free convection, the Nusselt number is a function of

Prandtl and Grashoff numbers Signup and view all the answers

The characteristic length in Biot number is the ratio of

volume of solid to its surface area Signup and view all the answers

What is the ratio of temperature drop across the different materials in a composite wall consisting of three different materials with thermal conductivities $k$, $2k$, and $4k$ respectively?

b) 1 : 2 : 4 Signup and view all the answers

How is the thermal diffusivity of a substance expressed?

a) $\frac{\rho c}{k}$ Signup and view all the answers

How is the total emissive power of a blackbody surface related to its radiation intensity $I$?

a) $E = 4\pi I$ Signup and view all the answers

What is the thickness of the thermal boundary layer for a fluid with Prandtl number unity compared to the velocity boundary layer?

b) more than velocity boundary layer Signup and view all the answers

What are the factors on which the Nusselt number for free convection is dependent?

a) Prandtl and Grashoff numbers Signup and view all the answers