7HF - October 1999

Part A (20 x 2 = 40 Marks)

1. Floating head Heat exchanger is used for large temperature differentials
2. Why triangular pitch is preferred than square pitch in tube layout in heat exchanger?
3. Differentiate between evaporation and drying
4. Fourier's law applies to _________
5. Fruit juice can be concentrated in _________ evaporator
6. The most common standard size of a bubble cap is marketed with _________ inches diameter cup and _________ inches riser
7. Azeotropic distillation is employed to separate _________ mixture
8. Leaching is applicable to _________ system
9. Flooding occurs in a column due to _________
10. Reboiler is considered as one theoretical plate because _________
11. Relative humidity is the ratio of vapor pressure of high volatile component, vapor pressure of low volatile component
12. Milk is dried to powder in _________ dryer
13. For continuous drying of granular materials we use _________ dryer
14. Crystal size in a continuous crystallizer depends upon _________, _________, and _________
15. In case of cooling towers the ratio of rates of heat and mass transfer is indicated by Lewis number
16. Reaction vessels with the same thickness of shell but smaller in diameter withstands higher pressure
17. Write an equation for power requirements for an agitator
18. Draw a diagram of a concrete vessel for storing solids
19. Under what conditions of liquids, vacuum drum filters are used?
20. What is meant by maximum yield stress of a metal?
21. Part B (5 x 12 = 60 Marks)

22. (a) A shell and tube heat exchanger having 2 shell passes and four tube passes is being used for cooling. The shell side fluid enters at 400oF and leaves at 200oF and the tube side fluid enters at 100oF and leaves at 200oF. Calculate the mean temperature difference between hot fluid and cold fluid
23. Or

(b) Draw a neat sketch of an evaporator showing the parts such as calenderia and steam heating arrangements

24. (a) A gas mixture containing 6% SO2 and 94% dry air is to be scrubbed with fresh water in a tower packed with 1" rasching ring. The exit concentration of SO2 is 0.10 mole%. The tower is to treat 1000 lb/hr of gas mixture and is to be designed using 50% flooding velocity which is approximately 435 lb/(hr.sqft). The water flow is twice the minimum requirement. x1* at the optimum operating condition 0.00174 mole fraction calculated from equilibrium curve. Calculate the tower diameter and height
25. Or

(b) Draw a neat sketch of a distillation column with all the necessary accessories shown. The column is operated using bubble cap tray. Show separately the arrangement of trays and bubble caps

26. (a) Raw seeds of 0.7 g/cc density is to be dried in a batch tray drier from a moisture content of 1 lb H2O per lb of dry solids to 0.1 lb H2O per lb of dry solids. Trays are 2 ft.square each and 1/2 inch depth. Drying occurs only from the top surface of the seeds using a hot air at 160oF with a wet bulb temperature of 120oF. Mass flow of air is 500 lb/(hr.sqft). Critical moisture content is 0.4 lb H2O per lb of dry solids. The equilibrium moisture content is 0.04 lb H2O per lb of dry solids assuming constant rate of drying. The surface tension (l ) for contact between liquid and gas phase is 1026 lbf/inch. The relative humidity was found to be 31.8% at the operating condition. Calculate the drying time required
27. Or

(b)Draw a neat sketch of an Industrial type cooling tower to handle large quantity of process water. Show all the important parts of the tower.

28. (a) A turbine agitator is to be designed for the use of a reaction vessel of 2000 mm diameter. The diameter of the agitator is 750 mm. The maximum allowable speed of the agitator is 40 revolution per second. The maximum number of blades allowed are six. The specific gravity of the fluid is 1.3 and viscosity is 600 cP. The power function is obtained from a chart of Reynolds number Vs power function j and was found to be 4.5 for this fluid. Calculate the power required for the agitator motor in horse power taking into account the following losses: (i) Gland losses 10% and (ii) Transmission loss of 20%.
29. Or

(b) Draw a neat sketch of a reaction vessel with external jacketed arrangement for cooling. Agitator is provided to stir the reactants. Entry for liquid and outlet for the product are provided. Show also the stuffing box arrangements for the agitator shaft.

30. (a) A Plate and Frame filter press with 20 frames of 2.5 inches thick each is used to filter a CaCO3 slurry containing 0.0723 wt fraction of CaCO3. The effective filter area is 9.4 sqft per frame and Ve is assumed to be 0.3271 lit. Calculate the volume of the slurry, weight of the solids in the cake and the time required for filtering the slurry. Porosity of the cake = 0.453.
31. Or

(b) Draw a neat sketch of a centrifuge (top driven) filter showing all the essential parts.