Explore topic-wise MCQs in Mechanical Operations.

This section includes 4 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Operations knowledge and support exam preparation. Choose a topic below to get started.

1.

For a bed of small spherical particles that fluidizes at the rate of 1cm/s, the operating velocity should be less than which of the following? Consider porosity of the bed to 0.45.

A. 25 cm/s
B. 50 cm/s
C. 40 cm/s
D. 48 cm/s
Answer» C. 40 cm/s
Discussion
2.

A fluidized bed has small particles with Reynolds number 18 and diameter 2 mm. The fluid medium is water. The density of the particle is 2500 kg/m3. Consider viscosity of water to be 8.11 × 10-4 kg/ms. Assume the particles to be completely spherical. Porosity of bed is 0.45. Assume acceleration due to gravity as 9.8 m/s2.

A. 0.07
B. 0.004
C. 0.08
D. 0.04
Answer» D. 0.04
Discussion
3.

Which of the following is the correct equation for minimum fluidization velocity for large particles? Here, Dp is the diameter of the particle, ρP and ρF are the density of particle and fluid medium respectively, εmf is the porosity and ΦS is the shape factor.

A. Umf2 = \(\frac {Dp (ρP-ρF)g}{1.75ρF}\) × εmf3 × ΦS
B. Umf2 = \(\frac {Dp (ρP-ρF)g}{1.75ρP}\) × εmf3 × ΦS
C. Umf2 = \(\frac {Dp (ρP-ρF)g}{1.75ρP}\) × εmf2 × ΦS
D. Umf2 = \(\frac {Dp (ρP-ρF)g}{1.75ρF}\) × εmf2 × ΦS
Answer» B. Umf2 = \(\frac {Dp (ρP-ρF)g}{1.75ρP}\) × εmf3 × ΦS
Discussion
4.

Which of the following is the best condition for minimum fluidization?

A. Drag force imparted by the down flowing gas equals the weight of the particles, and void space in the bed increases slightly
B. Drag force imparted by the upward flowing gas equals the weight of the particles, and void space in the bed increases slightly
C. Drag force imparted by the upward flowing gas equals the weight of the particles, and void space in the bed decreases slightly
D. Drag force imparted by the down flowing gas equals the weight of the particles, and void space in the bed decreases slightly
Answer» C. Drag force imparted by the upward flowing gas equals the weight of the particles, and void space in the bed decreases slightly
Discussion