Question is Write true or false against each statement a) In the fixed and fluid

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Question is Write true or false against each statement a) In the fixed and fluidized bed: In a fluidized bed, as the superficial velocity of fluid is increased, bed height remains constant b) The water in a cooling tower is normally cooled below the wet bulb temperature of the entering air. c) In the cooling tower the driving force for evaporation is very neatly, the difference between the Water vapor pressure and vapor pressure at Wet- Bulb temperature of water. d) In the cooling fower: Approach to wet bulb is given by the difference between The wer bulb temperature of water leaving the tower and the temperature of the incorning air. e) In the Gas Absorption : For a dry tower the differential pressure drop (AP) depends significantly on the nature of the packing. Din the Gas Absorption: If the gas flow rate remains constant, the pressure drop will increase by decreasing the liquid flow rate. g) In the fixed and fluidized bed: The phenomenon of bubbling occurs in gas solid system when The gas velocity is less than to the velocity required for fluidization. h) Molecular diffusion in gases: the gas- phase diffusion coefficient, DAB, is an inverse function of total system pressure.

Explanation / Answer

a) False.

There are cases where when superficial velocity is increased , the bed continues to expand in height, but the pressure drop stays constant.

b)False.Water cannot be cooled below wet bulb temperature

Cooling Tower Efficiency =   (Hot Water Temperature – Cold water Temperature) x 100/ (Hot Water Temperature – Wet bulb temperature)

In the ideal case, the cold water temperature is equal to the wet-bulb temperature. But practically not possible to achieve. Normally efficiency of cooling tower may range from 70 to 75 %

c)True .Driving force of evaporation is the difference between vapor pressure of water & vapor pressure at wet bulb temperature

d)False .

Approach = Cold Water from the tower (Outlet)– Wet Bulb Temperature

e) True

f) False

If the gas flow rate remains constant, the pressure drop will increase with an increase in the liquid flow rate. This is due to liquid fills the voids in the column, as a result the cross-sectional area available for gas flow is reduced.

g) False

Solids can fluidize with fluidization at low gas velocities without the formation of bubbles. At higher gas velocity, bubbles start to form at a point .

h) True. Refer Hirschfelder Equation states it is inversly proportional to total system pressure

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