Category: Mass Transfer

Pick out the wrong statement ?

Mass Transfer 25/06/2021
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A. A horizontal line on the humidity chart indicates the temperature changes at constant molal
humidity
B. When water is cooled from 80 to 70°C by exposure to the air with a wet bulb temperature of
60°C, then both the approach & the range would be 10°C
C. For unsaturated air-water vapor mixture at atmospheric conditions, the wet bulb temperature
& adiabatic cooling lines are the same
D. Relative saturation of unsaturated mixture of water vapor & air cannot be increased by either
reducing the mixture temperature or by increasing the total pressure

A 25 cm × 25 cm × 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1m × 1m × 1cm flat sheet of the same material is to be dried from one side only. Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is ____________________?

Mass Transfer 25/06/2021
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A. 1000
B. 1500
C. 2000
D. 2500

Pick out the wrong statement ?

Mass Transfer 25/06/2021
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A. Co-current absorbers are usually used, when the gas to be dissolved in the liquid is a pure
substance
B. In case of gas absorption, HETP is equal to HTU, when both the operating line & the
equilibrium lines are parallel
C. Hatta number is important in case of gas absorption with chemical reaction
D. In actual practice, absorption is an endothermic process, while stripping is an exothermic
process

Pick out the wrong statement pertaining to the cooling towers ?

Mass Transfer 24/06/2021
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A. In case of induced draft cooling tower, the fan is placed at the top of the tower
B. Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and
hot discharged air
C. A natural draft cooling tower is recommended to be used, when the air humidity is low and air
temperature is also low
D. Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb
temperature

Pick out the wrong statement?

Mass Transfer 21/06/2021
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A. The binary diffusivity in liquids is of the order of 10-5 cm2/sec
B. Molecular diffusion in solid is much faster than that in liquids
C. Particles movement from higher concentration to lower concentration takes place in diffusion
process
D. According to Poiseuille’s law, the permeability decreases with increase in temperature for
flow of a gas through a given capillary