Number of evaporators which can be used in service in a multiple effect evaporat

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Question
Number of evaporators which can be used in service in a multiple effect evaporation system is limited by the
Options
A. practical limit reached, due to low heat transfer rate because of inadequate temperature difference.
B. economic limit reached, when the plant cost exceeds the saving of steam.
C. both (a) & (b).
D. neither (a) nor (b).

Correct Answer

both (a) & (b).

3. Spherical shaped pressure vessel is considered to be the most ideal, because it can
Options
A. withstand higher pressure for a given metallic shell thickness.
B. be fabricated very easily.
C. be designed without wind load considerations.
D. be supported very easily.

4. Pick out the wrong statement.
Options
A. Safety valves are provided in heat exchangers for removal of non-conden-sables.
B. Liquid metals and dowtherm are used for very high temperature heating.
C. In a shell and tube heat exchanger, high pressure fluid is generally routed through the tube.
D. A loop seal or U-seal is provided in a vertical condenser sub-cooler to prevent quick draining of the condensate.

5. With increase in gas flow rate to fabric surface area ratio (Nm3/hr/m2 fabric surface area), the size & the cost of a bag filter
Options
A. increases
B. decreases
C. remain unaffected
D. none of these

8. An adequate clearance between the tray and the shell wall of a distillation column is provided to
Options
A. drain the liquid from the tray when the unit is not in operation.
B. allow for thermal expansion and facilitate installation.
C. avoid back-trapping.
D. none of these.

10. Pick out the wrong statement about the design of a sieve plate column.
Options
A. An increased weir height improves the tray efficiency at the cost of high plate pressure drop; optimum wear height being 40-90 mm for column pressure above atmospheric and 6-12 mm for vacuum columns.
B. For segmental downcomers, the chord length is 60-80% of the column diameter. An initial value of downcomer area of 12% is taken in the design.
C. Width of the calming section provided at the inlet and outlet sides of the plate is 75 mm for column diameter below 1.5 metres and 100 mm for larger diameter columns.
D. Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is about 20 seconds.

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