Mass Transfer
Plate towers are preferred to packed towers, when large temperature changes are involved, because of the reason that the

Packing may be crushed due to thermal expansion/contraction of the components of the equipments
Viscosity variation of the fluids may cause channeling/flooding
Pressure drop in the equipment will be very high
None of these

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Mass Transfer
Use of raschig rings in place of crushed stones as packing in packed beds (other things being same)

Increases pressure drop, increases surface area
Increases pressure drop, decreases surface area
Decreases pressure drop, decreases surface area
Decreases pressure drop, increases surface area

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Mass Transfer
Blowdown in a cooling tower

Is undesirable
Increases the scale forming tendencies of water
All of these
Means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities

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