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- Question
Sphericity of pulverised coal is
Options- A. 1
- B. <1
- C. >1
- D. ?
- Correct Answer
- <1
- 1. The important dimensional group involved in the power requirement calculation in mixing operation is the __________ number.
Options- A. Reynold's
- B. Froude
- C. both (a) & (b)
- D. neither (a) nor (b) Discuss
- 2. At low Reynold's number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied:
Po = ?/?N3 D5 : Power number
Re = ? N D2/?: Reynold's number
N is the impeller rotational speed, and D is the impeller diameter.
Options- A. Po ? Re-1.0
- B. Po ? Re0.0
- C. Po ? Re0.5
- D. Po ? Re1.0 Discuss
- 3. Critical Speed (Nc) of a ball mill is given by(where R1 and R2 are radii of ball mill and the ball respectively).
Options- A.
- B.
- C.
- D.
Discuss
- 4. Use of 'grinding aids' is done in __________ grinding.
Options- A. dry
- B. wet
- C. ultrafine
- D. intermediate Discuss
- 5. Which of the following is the hardest material?
Options- A. Calcite
- B. Quartz
- C. Corundum
- D. Gypsum Discuss
- 6. For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter (d) as
Options- A. d
- B. d
- C. d2
- D. 1/d Discuss
- 7. For a cyclone of diameter 0.2 m with a tangential velocity of 15 m/s at the wall, the separation factor is
Options- A. 2250
- B. 1125
- C. 460
- D. 230 Discuss
- 8. Grinding efficiency of a ball mill is of the order of __________ percent.
Options- A. 1-5
- B. 40-50
- C. 75-80
- D. 90-95 Discuss
- 9. Filtration capacity of a rotary drum vacuum filter depends upon the
Options- A. cake thickness.
- B. characteristics of the feed slurry.
- C. both (a) & (b).
- D. neither (a) nor (b). Discuss
- 10. For efficient grinding, ball mills must be operated
Options- A. at a speed less than the critical speed.
- B. at a speed more than the critical speed.
- C. at a speed equal to the critical speed.
- D. with minimum possible small balls. Discuss
Mechanical Operations problems
Search Results
Correct Answer: both (a) & (b)
Correct Answer: Po ? Re0.0
Correct Answer:
Correct Answer: dry
Correct Answer: Corundum
Correct Answer: d2
Correct Answer: 230
Correct Answer: 1-5
Correct Answer: both (a) & (b).
Correct Answer: at a speed less than the critical speed.
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