Mass Transfer (Set 1) Flashcards
As one of the transport phenomena, the concepts in mass transfer are crucial for design, operation, and maintenance of mass or heat & mass transfer equipment such as mixing and separation processes.
Mass transfer rate between two fluid phases does not necessarily depend on the ____ of the two phases.
chemical properties
In a solution containing 0.30 Kg mole of solute and 600 kg of solvent, the molality is
0.5
Fenske equation determines the
minimum number of theoretical plates.
The term “cooling range” in a cooling tower refers to the difference in the temperature of
hot water entering the tower and the cooled water leaving the tower.
Which of the following is the most suitable for extraction in a system having very low density difference?
Centrifugal extractor
Total reflux in a distillation operation requires minimum
number of plates
The amount of steam required per unit quantity of distillate in case of steam distillation will be reduced by
both (a) and (b).
The difference of wet bulb temperature and adiabatic saturation temperature of unsaturated mixture of any system is
(+)ve
Fenske’s equation for determining the minimum number of theoretical stages in distillation column holds good, when the
relative volatility is reasonably constant.
When the temperature and humidity of air is low, we usually use ____ draft cooling tower.
natural
Pick out the correct statement.
all (a), (b) and (c).
____ columns are used for liquid dispersion in a continuous gas phase.
Packed
Overall efficiency of the distillation column is
the ratio of number of ideal plates to actual plates.
On addition of solute in the solvent, the ____ of the solution decreases.
both (b) and (c)
Which is the controlling factor for a drum drier?
Heat transfer
Drying operation under vacuum is carried out to
reduce drying temperature.
Air initially at 101. 3 kPa and 40°C and with a relative humidity of 50%, is cooled at constant pressure to 30°C. The cooled air has a
higher relative humidity
Separation of two or more components of a liquid solution can not be achieved by
absorption
Stefan’s law describes the mass transfer by
both ‘a’ & ‘b’
At minimum reflux ratio for a given separation
number of plates is infinity.
Relative humidity is the ratio of the
partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.
In batch distillation with constant reflux, overhead product composition ____ with time.
decreases
Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the ____ of a fibre.
electrical resistance
Heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapour by 1°F is called the
specific heat
To increase the absorption factor, (where, G = gas flow rate, S = solvent flow rate)
increase ‘S’ and decrease ‘G’.
The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, NPr = NSc = ____
1
Dew point of a gas-vapour mixture
decreases with decrease in pressure.
In a packed absorption tower, if the equilibrium and operating lines are both straight lines, then the ratio, HETP/HTUOG ____ the absorption factor.
both (a) and (b)
Which of the following plays an important role in problems of simultaneous heat and mass transfer?
Lewis number
In case of an absorber, the operating
line always lies above the equilibrium curve.
As the reflux ratio in a distillation coloumn is increased from the minimum, the
total cost first decreases and then increases.
Absorption factor is defined as (where, S1 = slope of the operating line S2 = slope of the equilibrium curve)
S1/S2
A plait point is the point on the solubility curve, where the tie line reduces to a point. What is the number of plait point for a ternery system containing twopairs of partially miscible liquids?
0
Which of the following remains constant during sensible cooling process?
Both (a) and (b)
Physical absorption is
both (b) and (c)
Make up water is required in a cooling tower to replace the water lost by
all (a), (b) and (c)
Which of the following quantities need not be fixed before starting the design of a co-current absorber?
Flow rate of entering liquid
Mass transfer co-efficient of liquid is
affected more by temperature than that for gases.
Absorption accompanied with chemical reaction is exemplified by the absorption of
SO2 in alkaline solution.
Which of the following unit operations makes use of Thiele-Geddes equation?
Multicomponent distillation.