Mass Transfer

131.Drying of a solid involves _________ transfer.

1. Only heat
2. Only mass
3. Both heat and mass
4. None of these

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132.Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant

1. Humidity
2. Velocity
3. Temperature
4. All (A), (B) & (C)

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133.Drying of refractory is normally carried out in a _________ dryer.

1. Open pan
2. Tray
3. Rotary vacuum
4. Truck/tunnel

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134.Drying operation under vacuum is carried out to

1. Dry those materials which have very high unbound moisture content
2. Reduce drying temperature
3. Increase drying temperature
4. Dry materials having high bound moisture content

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135.During bottling of cold drinks (e.g. Pepsi), the main resistance to mass transfer for the absorption of carbon dioxide in water lies in the

1. Gas film
2. Liquid film
3. Liquid-gas interface
4. None of these

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136.During constant rate drying period, vaporisation rate per unit drying surface area

1. Decreases with time
2. Increases with time
3. Does not change with time
4. Does not affect the moisture content of the wet solid

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137.During constant rate period, the rate of drying decreases with the

1. Decrease in air temperature
2. Increase in air humidity
3. Both (A) and (B)
4. Neither (A) nor (B)

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138.During dehumidification of unsaturated air wet bulb temperature & partial pressure of vapor are not constant. However, during evaporative cooling process with recirculated water supply, the _________ remains constant.

1. Wet bulb temperature
2. Partial pressure of water vapor
3. Relative humidity
4. None of these

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139.During drying operation, it is easier to remove the _________ moisture.

1. Equilibrium
2. Critical
3. Unbound
4. Bound

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140.During sensible cooling process

1. Relative humidity decreases
2. Relative humidity increases
3. Wet bulb temperature decreases
4. Both (B) and (C)

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