### Mechanical Operations - Semester Exam Question

5HB - Mechanical Operations - October 1999

Part A (20 x 2 = 40 Marks)

1. Give the sphericity of rasching ring whose length and diameter are equal
2. Define effectiveness of screen
3. Name the different methods of particle size measurement for fine particles
4. List out any three equipment used for storage of solids
5. Give the various methods of braking solids
6. What are crushers? Give any three
7. What do you mean by closed circuit grinding?
8. What is the disadvantage of choke crushing compared to free crushing?
9. Distinguish between 'Clasrifier' and 'Classifier'
10. Give any three types of centrifuge used in Industries
11. Define 'free settling'
12. Give the functions of flotation agents
13. What is filtration?
14. Give some commonly used filter media
15. What are the advantages of filter press?
16. Define compressibility coefficient of the filter cake
17. Define power number
18. What are the important properties that influence the mixing of fluids?
19. Where Banbury mixer is used?
20. Differentiate between agitation and mixing
21. Part B (5 x 12 = 60 Marks)

22. (a) (i) Define sphericity for spherical and non-spherical particles
23. (ii) Critically analyze the differential and cumulative methods of analysis to determine the average particle size

Or

(b) (i) What are the various types of industrial screens and how they are employed?

(ii) Explain the principle of electrostatic precipitation in gas cleaning

24. (a) Classify the size reduction equipment and discuss the principles of size reduction involved in each type of equipment. With the help of a neat sketch, discuss the hammer mill
25. Or

(b) A certain set of crushing rolls has rolls of 100 cm diameter by 38 cm width face. They are set so that the crushing surfaces are 1.25 cm apart at the narrowest point. The manufacturer recommends that they may be run at 50 to 100 rpm. They are to crush a rock having a specific gravity of 2.35, and the angle of nip is 30o. What are the maximum permissible size of the feed and the maximum actual capacity in tons per hour, if the actual capacity is 12 percent of the theoretical?

26. (a) (i) Derive an expression for calculating the minimum thickener area required for a gravity thickener.
27. (ii) Quartz particles (density = 2650 kg/m3) are settling in water at room temperature. What will be the maximum particle diameter so that Stoke's law can hold good in this case. Viscosity of water = 1004 x 10-6 kg/(m.sec)

Or

(b) Write the principles and applications of flotation. Explain any one of the commercial flotation equipment with the help of a neat sketch

28. (a) (i) Derive an expression between thickness of cake and volume of filtrate for filtration at constant pressure
29. (ii) Discuss any one filtration equipment with the help of a neat sketch

Or

(b) Explain the principle of centrifugal filtration. Derive an expression for calculating specific cake resistance for incompressible sludges from the basic fundamentals

30. (a) (i) Classify the mixing equipment used for dry powders and discuss them with sketches
31. (ii) Write short notes on the following:

(1) Scale up in agitator design

(2) Flow pattern in agitation vessel with turbine impeller

Or

(b) Discuss the following:

(i) Approximate dimensions of a turbine impeller and baffles used in a batch reactor based on reactor diameter

(ii) Power required for impeller mixers.

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