Chemical Engineering - Heat Transfer

1. 

The Grashoff number is defined as the ratio of the

A. buoyancy to inertial forces.
B. buoyancy to viscous forces.
C. inertial to viscous forces.
D. buoyancy to surface tension forces.

Answer: Option B

Explanation:

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2. 

According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor)

A. 2f
B. f
C. f/2
D. f/4

Answer: Option C

Explanation:

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3. 

The absorptivity of a body is equal to its emissivity

A. at a particular temperature.
B. for circular bodies.
C. under thermal equilibrium.
D. none of these.

Answer: Option C

Explanation:

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4. 

Absorptivity and refletivity of a perfect black body are respectively

A. 1 and 0
B. 0 and 1
C. 1 and ∞
D. 0 and 0.5

Answer: Option A

Explanation:

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5. 

In thermal radiation for a black body (where, ε is emissivity and α is absorptivity)

A. α = 1; ε ≠ 1
B. α ≠ 1, ε = 1
C. α ≠ 1, ε ≠ 1
D. α = 1; ε = 1

Answer: Option D

Explanation:

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