7HF - April 2000

Part A
  1. A pump operating under specified conditions delivers insufficient quantity of fluid. How it can be set right?
  2. Differentiate between the efficiency of venturi meter and orifice meter
  3. Define overall heat transfer coefficient in heat transfer
  4. Define HTU and NTU
  5. What is meant by weeping in a distillation column? How it can be eliminated?
  6. What is meant by unbound and bound moisture in a solid?
  7. Draw a line sketch of a top-driven centrifuge
  8. Why cooling towers are used in process industries?
  9. Suggest a suitable type of storage vessel for storing liquid ammonia. Give reasons for such recommendation.
  10. What is meant by steam economy in the design of evaporators?
  11. What is meant by filter cake resistance? How it affects filtration?
  12. Give an equation for the calculation of power requirement for an agitator
  13. Mention various types of commercially available crystallizers
  14. Mention why different packings are used in a distillation or absorption tower
  15. Define adsorption phenomenon
  16. Why steam traps are used in heat transfer apparatus?
  17. What type of closures are used for pressure vessels? Why?
  18. What are the differences between condenser and a reboiler?
  19. Why low pressure steam is used in evaporators?
  20. What is meant by induced draft in cooling tower?
  21. Part B

  22. (a) A soap kettle is 1.25 m in dia and its cylindrical height is also 1.25 m. It has a conical bottom, the height of which is 0.6 m. The kettle is made of 6 mm mild steel. The liquid in the kettle is filled up to a depth of 0.35 m from the top. A 50 mm outlet is provided at the tip of the conical bottom. It is required to install a steam heating coil made of 50 mm i.d. in the kettle. The coil is in the cylindrical section of the kettle. The total length of heating coil is 16 m. A paddle stirrer made with 4 arms is also installed with a suitable gear drive. Draw an half-sectional elevation and plan of the kettle. The top of the kettle is open to the atmosphere.
    Or

    (b) The following design details of a top suspended centrifuge are available:

    Diameter of basket: 75 cm

    Height of basket: 45 cm

    Stirrer shaft dia: 3 cm

    Thickness of basket: 1 cm

    Draw a sectional elevation of the centrifuge showing details of stirrer connection, arrangement for the cake removal and washing and solids discharge.

  23. (a) A double pipe heat exchanger uses 5 cm outer dia and 3 cm inner dia pipe. Draw a sectional elevation showing the return bends.
  24. Or

    (b) A solution of CS2 and CCl4 containing 50% (weight) each is to be continuously fractionated at atmospheric pressure at the rate of 1800 kg/hr. The distillate is to contain 95% (weight) CS2 and the residue contains 0.5% (weight). The feed will be 30 mole % vaporized before it enters the tower. A total condenser at the top is used and the reflux is returned at bubble point. Determine the number of theoretical plates and the position of the feed tray at a reflux ratio twice the minimum. Give a neat sketch of the tower showing a section of a tray.

    Data: The equilibrium data at 1 atm pressure of CS2(1) - CCl4(2)

    Temp oC

    76.7 74.9 73.1 70.3 68.6 63.8 59.3 55.3 52.3 50.4 48.5 46.3

    Mole % of CS2 in liquid (x1)

    0 2.96 6.15 11.06 14.35 25.85 39.08 53.18 66.3 75.74 86.04 100

    Mole % of CS2 in vapor (y1)

    0 8.23 15.55 26.6 33.25 49.5 63.4 74.7 82.9 87.8 93.2 100

    Specific heats of CS2 and CCl4 in liquid state are 0.98 and 0.88 kJ/kg.oC respectively. Latent heats of vaporisation of both CS2 and CCl4 can be assumed to be 127.8 kJ/kg.

  25. (a) Benzene is to be condensed in a 1-1 vertical condenser at a rate of 6000 kg/hr at atmospheric pressure. Benzene condenses on the shell side while water flows through the tubes. A unit having the following data is available.
  26. No. of tubes

    118

    Tube OD

    25 mm

    Tube ID

    22 mm

    Tube length

    3 m

    Thermal conductivity

    0.045 kW/m.K.

    Cooling water is available at 303 K. Scale factor at shell side is 0.176 and water side is 0.26 m2.K/kW respectively. Check whether this condenser is suitable for the required duty.

    Or

    (b) A thick walled vessel having an inside dia of 25 cm and an outside dia of 40 cm is subjected to an internal pressure of 15000 psi. Calculate the maximum induced stress according to the

    (i) maximum principle stress theory

    (ii) maximum shear stress theory

    (iii) maximum strain theory

    (iv) maximum strain energy theory

  27. (a) A solution is to be concentrated from 10% to 65% solids in a vertical tube evaporator. The solution has a negligible elevation of boiling point and its specific heat can be taken same as that of water. Steam is available at 203.6 kPa and the condenser operates at 13.33 kPa. The feed enters the evaporator at 295 K. The total evaporation is to be 25000 kg/hr of water. Calculate the heat transfer area required and the steam consumption in kg/hr if overall heat transfer coefficient is 2800 W/m2.K.
  28. Or

    (b) Draw a neat sketch of a triple effect evaporation with all accessories.

  29. (a) Write notes on
  30. (i) Design consideration for rotary driers

    (ii) Selection criteria for a pump and its design

    (iii) Design of high pressure vessels - certain important considerations.

    Or

    (b) Write design notes on the following:

    (i) Design of a solid-liquid extraction unit

    (ii) Volatile liquid storage vessel

    (iii) Design of cooling tower