Mass Transfer

361.Pick out the wrong statement pertaining to the analogy between equations of heat and mass transfer operations.

1. Sherwood number in mass transfer is analogous to Nusselt number in heat transfer
2. Prandtl number in heat transfer is analogous to Schmidt number in mass transfer
3. Reynolds number in mass transfer is analogous to Grashoff number in heat transfer
4. Reynolds number remains the same in both heat and mass transfer

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362.Pick out the wrong statement pertaining to the cooling towers.

1. In case of induced draft cooling tower, the fan is placed at the top of the tower
2. Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and hot discharged air
3. A natural draft cooling tower is recommended to be used, when the air humidity is low and air temperature is also low
4. Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature

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363.Pick out the wrong statement pertaining to the rotary dryer.

1. Flights (located in the inside shell of rotary dryer) lift the material being dried and shower it down through the current of hot air/gases. It extends from the wall to a distance which is about 8-12% of the inside diameter of shell
2. Hold up of a rotary drier is defined as the fraction of the dryer volume occupied by the solid at any instant. The best performance for rotary drier is obtained, when the hold up is in the range of 0.05 to 0.15
3. Rotary dryer is suitable for drying sticky material
4. Recommended peripheral speed of a rotary drier is in the range of 10 to 30 metres/minute

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364.Pick out the wrong statement.

1. Mechanical agitation is required, if the system has low interfacial tension
2. Sieve tray towers are generally used for systems having low interfacial tension
3. When Henry's law constant is very small, then the mass transfer rate is controlled by the gas film resistance
4. Taylor-Prandtl analogy for heat and mass transfer considers the transfer through both laminar and turbulent layers

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365.Pick out the wrong statement.

1. Packed towers are preferred for vacuum operation, because the pressure drop through the packing is less and they (packings) also lessen the possibility of tower wall collapse
2. Packed towers are preferred over plate towers for handling corrosive and foamy liquids
3. Diameter of randomly packed tower is normally more than 1.2 metres
4. Due to uneven supply and improper distribution of liquid, problem of channelling, loading & flooding is generally encountered in packed towers

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366.Pick out the wrong statement. Generally for physical adsorption, a gas of

1. Higher molecular weight is adsorbed in preference to a gas of low molecular weight
2. High critical temperature is adsorbed in preference to a gas of low critical temperature
3. Low volatility is adsorbed in preference to a gas of high volatility
4. None of these

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367.Pick out the wrong statement. Raoult's law does not apply, when the

1. Size of component molecules are not equal
2. Attractive forces between like and unlike molecules in the solution are approximately equal
3. Component molecules are non-polar
4. Chemical combination or molecular association between unlike molecules takes place in the formation of solution

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368.Pick out the wrong statement:

1. Absorption factor is constant, when the equilibrium and operating lines are straight
2. In case of a stripper, the equilibrium curve is always below the operating line
3. In case of an absorber, the operating line is always above the equilibrium curve
4. In the absorption of low solubility gases, the liquid film is the controlling resistance

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369.Plate efficiency

1. Is a function of the mass transfer between liquid and vapour
2. Increases due to foaming
3. Both (A) & (B)
4. Increases due to weeping and dumping of liquid

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370.Plate efficiency in a distillation column is reduced due to the _________ of liquid.

1. Entrainment
2. Foaming
3. Weeping & dumping
4. All (A), (B) & (C)

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