Ratio of tube length to shell diameter for a shell and tube heat exchanger is________________?

8 : 1 to 12 : 1 for both liquid-liquid and gas-gas heat exchangers

4 : 1 to 8 : 1 for liquid-liquid exchanger

Rate of filtrate delivery is inversely proportional to the___________________?

Filtering area & the pressure difference driving force

Cake & filter medium resistance

Practical dividing line between a ductile and brittle materials is suggested, when the ultimate elongation is about 5%. Generally, larger the knuckle radius, stronger is the corner torus section of a head. The knuckle radius provided should be less than ______________ of the head?

Either A. or B., whichever is smaller

Either A. or B., whichever is larger

Either A. or B., whichever is smaller

Power required for agitation depends upon the______________________?

Height & properties of the liquid

Agitator type & speed of agitation

Ponchon Savarit method is based on the use of enthalpy concentration diagram, which contains the bubble point curve (saturated liquid curve), dew point curve (saturated vapour curve) and equilibrium tie lines. As compared to McCabe-Thiele’s method, this method_________________?

is more accurate in finding the number of equilibrium stages

accounts for the enthalpy changes in the process

Facilitates direct calculation of heat load on reboiler & condenser from, the diagram used in this method

Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column ?

Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapour flow rates) and thus provide the maximum flexible ope

Bubble cap trays though most expensive are the best in situations, where low vapour rates is to be handled and a positive liquid seal is essential at

Murphree efficiency of all the three trays are nearly equal, however the peak efficiency is generally higher for sieve and valve trays than the bubble

Maintenance cost for valve and sieve trays are comparatively more than bubble cap tray due to their relatively complicated construction features

Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapour flow rates) and thus provide the maximum flexible ope

Pick out the wrong statement pertaining to the design of a long tube vertical evaporator ?

Tube dia is 3-6 cms, while tube length in 3-6 metres

Steam is fed to the shell, whereas the liquor is filled inside the tube

Liquor level is maintained at 1/3rd to 1/2 of the height of the tube

Pick out the wrong statement pertaining to the design of the distillation column?

Generally, a skirt clearance of 0.5″ to 1.5′ is recommended to prevent plugging of the slots by residue build up

The purpose of the slot is to disperse the gas into the liquid in the form of small bubbles

If sufficient slot area is not provided, the gas may pass through the skirt clearance

Pick out the wrong statement pertaining to the design of a horizontal tube evaporator ?

It is unsuitable for concentrating those liquids, which form a scale or deposit salt

It is suitable for process, in which the final product is a liquor instead of solid

Its usual dimensions are: tube dia = 2-3 cms; evaporator body dia = 1-4 metres and evaporator height = 2.5-4 metres

Liquor flows inside the tube, while the steam is outside submerging the tube

Pick out the wrong statement pertaining to the design of a basket type evaporator ?

The tube bundle is suspended on bracket

It is used for high viscosity liquor having large rate of scaling

The tube bundle is suspended on bracket

Downtake is formed by the annular space between the bundle and the shell

Pick out the wrong statement pertaining to the comparative evaluation of performance of the packed tower and the plate tower ?

In operations involving large temperature changes. (e.g. distillation), plate towers are preferred over packed towers as the packing may be crushed du

Plate tower is preferred, if interstage cooling is required to remove heats of reaction or solution

Plate tower is preferred over packed tower, if the operation involves liquids containing dispersed solids

The total weight of a dry plate tower is usually much more than that of a dry packed tower designed for the same duty

In operations involving large temperature changes. (e.g. distillation), plate towers are preferred over packed towers as the packing may be crushed du

Pick out the wrong statement pertaining to shell and tube heat exchanger_______________?

Clearance between shell & baffles and between tube & baffles should be minimum to avoid by-passing of the fluid, but it should be enough to permit the

Baffles are supported independently of the tubes by tie rods and positioned by spacers

Tie rods are fixed at one end in the tube sheet by making blind holes and the minimum number of tie rods is 4 with at least 10 mm diameter

Bracket supports are used for horizontal shell, while saddle support is used for vertical shell

Pick out the wrong statement pertaining to ‘Horton sphere’ used for the storage of liquid ammonia ?

Diameter of Horton sphere is normally 6 to 25 metres and it is supported by 6 to 12 nos. tubular or rolled section column

Thickness of spherical shell is half that of the cylindrical vessel under same operating pressure condition. Besides, the ratio of surface area to vol

Horton sphere is used for the storage of gases and volatile liquid at a moderate pressure of 1 to 10 kg/cm2

Horton sphere is used for the storage of liquid at sub-zero temperature at very high pressure upto 200 kg/cm2

Pick out the wrong statement pertaining to a shell and tube heat exchanger ?

The minimum value of baffle spacing is 50 mm

The maximum value of baffle spacing is equal to the I.D. of the shell

The maximum unsupported tube span is generally about 75 times tube diameter, but is reduced to about 60 times for aluminium, copper & alloys of these

Disk and doughnut baffle is the most commonly used baffle

Pick out the wrong statement. In an agitated vertical cylindrical reaction vessel, the___________________?

Ratio of liquid depth to tank diameter (i.e. the filling ratio) recommended for most purposes is 1

Filling ratio for dispersing gas in a liquid is 2 for sufficiently long contact period

Flat bottom and conical bottom vessels have low agitation efficiency for agitation of heavy solids in liquids

Dished bottom vessel has very high power consumption

Pick out the wrong statement about the design of sieve plate column and the bubble cap column ?

Weir height in case of a bubble cap plate ranges from 50 to 150 mm and is higher than the sieve plate

The downcomer design and the residence time in the downcomer is almost same for sieve plate and bubble cap columns

Weir length for a bubble cap plate is the same as that for the sieve plate

Weir height for a bubble cap plate column is the same as that for a sieve plate column

Weir height in case of a bubble cap plate ranges from 50 to 150 mm and is higher than the sieve plate

Pick out the wrong statement about the design of a sieve plate column ?

An increased weir height improves the tray efficiency at the cost of high plate pressure drop; optimum wear height being 40-90 mm for column pressure

For segmental downcomers, the chord length is 60-80% of the column diameter. An initial value of downcomer area of 12% is taken in the design

Width of the calming section provided at the inlet and outlet sides of the plate is 75 mm for column diameter below 1.5 metres and 100 mm for larger d

Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is

Pick out the wrong statement about routing of fluids in a shell and tube heat exchanger ?

The corrosive and fouling fluid should be preferably routed through the tubes

The viscous fluid should be routed through the shell side

Lower flow rate fluid should be routed through the shell side

Higher pressure fluid stream should be routed through the shell side

Pick out the wrong statement about distillation operation__________________?

Distillation under vacuum is a substitute for steam distillation

In differential (simple) distillation, the vapour is removed as soon as it is formed without appreciable condensation

In flash (equilibrium) distillation, a definite fraction of liquid is vaporised in such a way that the evolved vapour & residual liquids are in equili

Flash distillation, differential distillation & steam distillation are all continuous distillation processes

Pick out the correct statement___________________?

A riveted joint made in overlapping plates is called butt joint

Centre to centre distance between two consecutives rivets in a row is called the pitch

A riveted joint made in overlapping plates is called butt joint

Hole size drilled in riveted plates is less than the actual size of the rivet

Overall tray efficiency of a distillation column is the ratio of the number of ___________________?

Real trays required to the number of ideal trays required

Overall gas transfer units to the number of ideal trays required

Ideal trays required to the number of real trays required

Real trays required to the number of ideal trays required

Optimum reflux ratio in a continuous distillation column is determined by the__________________?

Maximum permissible vapour velocity

Total cost consideration (fixed cost of the column plus the cooling water & steam cost)

Optimum economic pipe diameter for fluid flow is determined by the____________________?

Total cost considerations (pumping cost plus fixed cost of the pipe)

Number of evaporators which can be used in service in a multiple effect evaporation system is limited by the__________________?

Practical limit reached, due to low heat transfer rate because of inadequate temperature difference

Economic limit reached, when the plant cost exceeds the saving of steam

Normally, the plate thickness of the bottoms and roofs of vertically cylindrical storage vessels as compared to that of the cylindrical shell is____________?

More or less depending upon the pressure & temperature inside the vessel and the nature of the fluid contained therein

Needle valves are generally not used for___________________?

High pressure throttling service

Movement of pipeline caused by thermal expansion is taken care by providing ___________________?

Change in the shape of pipeline

Most of the storage vessels/tanks are made cylindrical, because of the fact that a cylinder _________________?

Has greater structural strength

Mc Cable Thiele method used for finding theoretical stages in a distillation column assumes that the_____________________?

Sensible heat differences are small, because the temperature changes from tray to tray is small

Liquid/vapor loading across the column remains constant

324 + Mcqs in Process Equipment & Plant Design for Chemical in Chemical Engineering Page 3 McqOptions

101.	Reflux ratio variation in a distillation column is between___________________?
A.	Zero and infinity
B.	Zero and one
C.	Minimum and infinity
D.	None of these
Answer» D. None of these

102.	Ratio of tube length to shell diameter for a shell and tube heat exchanger is________________?
A.	8 : 1 to 12 : 1 for both liquid-liquid and gas-gas heat exchangers
B.	4 : 1 to 8 : 1 for liquid-liquid exchanger
C.	< 4 : 1 for gas-gas exchangers
D.	Both B. & C.
Answer» E.

103.	Rate of filtrate delivery is inversely proportional to the___________________?
A.	Filtering area & the pressure difference driving force
B.	Viscosity of filtrate
C.	Cake & filter medium resistance
D.	Both A. and B.
Answer» E.

104.	Pressure drop per tray in the atmospheric distillation column is about ________________ psi?
A.	0.01 – 0.5
B.	0.07 – 0.12
C.	0.5 – 1.0
D.	1 – 3
Answer» C. 0.5 – 1.0

105.	Pressure drop due to pipe fittings can be estimated by the equation, ΔP/ρ = 4f, (Le/D) (V2/2gc) where, Le = equivalent length of straight pipeline which will incur the same frictional loss as the fitting and D = diameter of the fitting. The value of (Le/D) (dimensionless) for 45° elbow and 180° close return bends would be respectively around______________________?
A.	5 and 10
B.	45 and 75
C.	180 and 300
D.	300 and 500
Answer» C. 180 and 300

106.	Pressure drop (Δp) and the superficial gas mass velocity (G) in case of packed absorption tower operating in the preloading range are related as_________________?
A.	Δp = G
B.	Δp = G0.5
C.	Δp = G2
D.	Δp = 1/G0.6
Answer» D. Δp = 1/G0.6

107.	Pressure differential maintained across a continuous rotary vacuum filter is in the range of _______________ mm Hg column?
A.	50 to 100
B.	100 to 150
C.	250 to 500
D.	600 to 700
Answer» D. 600 to 700

108.	Practical dividing line between a ductile and brittle materials is suggested, when the ultimate elongation is about 5%. Generally, larger the knuckle radius, stronger is the corner torus section of a head. The knuckle radius provided should be less than ______________ of the head?
A.	6% of I.D.
B.	3 times the thickness
C.	Either A. or B., whichever is larger
D.	Either A. or B., whichever is smaller
Answer» D. Either A. or B., whichever is smaller

109.	Power required for agitation depends upon the______________________?
A.	Height & properties of the liquid
B.	Agitator type & speed of agitation
C.	Size of agitator & the tank
D.	All A., B. and C.
Answer» E.

110.	Ponchon Savarit method is based on the use of enthalpy concentration diagram, which contains the bubble point curve (saturated liquid curve), dew point curve (saturated vapour curve) and equilibrium tie lines. As compared to McCabe-Thiele’s method, this method_________________?
A.	is more accurate in finding the number of equilibrium stages
B.	accounts for the enthalpy changes in the process
C.	Facilitates direct calculation of heat load on reboiler & condenser from, the diagram used in this method
D.	All A, B. & C.
Answer» E.

111.	Poisson’s ratio of a material is the ratio of unit lateral strain to the unit axial elongation within its elastic limit. The value of Poisson’s ratio for structural and pressure vessel steel may be taken as ____________________?
A.	0.01
B.	0.3
C.	0.75
D.	0.95
Answer» C. 0.75

129.	Overall distillation column efficiency for most of the refinery columns can be given by (for μ = 0.07 – 1.4 cp and relative volatility < 4) (where ε = overall column efficiency, % μ = molal average viscosity of feed at average column temperature and pressure, cp Δp = pressure drop per tray, psi) ?
A.	η = 17 – 61.1 log μ
B.	η = 24.6 (Δp/μ)
C.	η = 1.66 – 0.25 log μ
D.	η = 0.25 log μ – 1.67
Answer» B. η = 24.6 (Δp/μ)

132.	______________ of water makes it a widely used coolant in heat exchangers?
A.	Low corrosiveness
B.	Low dirt factor
C.	High specific heat
D.	Low viscosity
Answer» D. Low viscosity

112.	Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column ?
A.	Bubble cap trays though most expensive are the best in situations, where low vapour rates is to be handled and a positive liquid seal is essential at
B.	Murphree efficiency of all the three trays are nearly equal, however the peak efficiency is generally higher for sieve and valve trays than the bubble
C.	Maintenance cost for valve and sieve trays are comparatively more than bubble cap tray due to their relatively complicated construction features
D.	Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapour flow rates) and thus provide the maximum flexible ope
Answer» D. Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapour flow rates) and thus provide the maximum flexible ope

113.	Pick out the wrong statement pertaining to the design of a long tube vertical evaporator ?
A.	Tube dia is 3-6 cms, while tube length in 3-6 metres
B.	Steam is fed to the shell, whereas the liquor is filled inside the tube
C.	Liquor level is maintained at 1/3rd to 1/2 of the height of the tube
D.	None of these
Answer» E.

114.	Pick out the wrong statement pertaining to the design of the distillation column?
A.	Generally, a skirt clearance of 0.5″ to 1.5′ is recommended to prevent plugging of the slots by residue build up
B.	The purpose of the slot is to disperse the gas into the liquid in the form of small bubbles
C.	If sufficient slot area is not provided, the gas may pass through the skirt clearance
D.	None of these
Answer» E.

115.	Pick out the wrong statement pertaining to the design of a horizontal tube evaporator ?
A.	It is unsuitable for concentrating those liquids, which form a scale or deposit salt
B.	It is suitable for process, in which the final product is a liquor instead of solid
C.	Its usual dimensions are: tube dia = 2-3 cms; evaporator body dia = 1-4 metres and evaporator height = 2.5-4 metres
D.	Liquor flows inside the tube, while the steam is outside submerging the tube
Answer» E.

116.	Pick out the wrong statement pertaining to the design of a basket type evaporator ?
A.	It is used for high viscosity liquor having large rate of scaling
B.	The tube bundle is suspended on bracket
C.	There is no central downtake
D.	Downtake is formed by the annular space between the bundle and the shell
Answer» B. The tube bundle is suspended on bracket

117.	Pick out the wrong statement pertaining to the comparative evaluation of performance of the packed tower and the plate tower ?
A.	Plate tower is preferred, if interstage cooling is required to remove heats of reaction or solution
B.	Plate tower is preferred over packed tower, if the operation involves liquids containing dispersed solids
C.	The total weight of a dry plate tower is usually much more than that of a dry packed tower designed for the same duty
D.	In operations involving large temperature changes. (e.g. distillation), plate towers are preferred over packed towers as the packing may be crushed du
Answer» D. In operations involving large temperature changes. (e.g. distillation), plate towers are preferred over packed towers as the packing may be crushed du

118.	Pick out the wrong statement pertaining to shell and tube heat exchanger_______________?
A.	Clearance between shell & baffles and between tube & baffles should be minimum to avoid by-passing of the fluid, but it should be enough to permit the
B.	Baffles are supported independently of the tubes by tie rods and positioned by spacers
C.	Tie rods are fixed at one end in the tube sheet by making blind holes and the minimum number of tie rods is 4 with at least 10 mm diameter
D.	Bracket supports are used for horizontal shell, while saddle support is used for vertical shell
Answer» E.

119.	Pick out the wrong statement pertaining to ‘Horton sphere’ used for the storage of liquid ammonia ?
A.	Diameter of Horton sphere is normally 6 to 25 metres and it is supported by 6 to 12 nos. tubular or rolled section column
B.	Thickness of spherical shell is half that of the cylindrical vessel under same operating pressure condition. Besides, the ratio of surface area to vol
C.	Horton sphere is used for the storage of gases and volatile liquid at a moderate pressure of 1 to 10 kg/cm2
D.	Horton sphere is used for the storage of liquid at sub-zero temperature at very high pressure upto 200 kg/cm2
Answer» E.

120.	Pick out the wrong statement pertaining to a shell and tube heat exchanger ?
A.	The minimum value of baffle spacing is 50 mm
B.	The maximum value of baffle spacing is equal to the I.D. of the shell
C.	The maximum unsupported tube span is generally about 75 times tube diameter, but is reduced to about 60 times for aluminium, copper & alloys of these
D.	Disk and doughnut baffle is the most commonly used baffle
Answer» E.

121.	Pick out the wrong statement. In an agitated vertical cylindrical reaction vessel, the___________________?
A.	Ratio of liquid depth to tank diameter (i.e. the filling ratio) recommended for most purposes is 1
B.	Filling ratio for dispersing gas in a liquid is 2 for sufficiently long contact period
C.	Flat bottom and conical bottom vessels have low agitation efficiency for agitation of heavy solids in liquids
D.	Dished bottom vessel has very high power consumption
Answer» E.

Explore topic-wise MCQs in Chemical Engineering.

Reflux ratio variation in a distillation column is between___________________?

Ratio of tube length to shell diameter for a shell and tube heat exchanger is________________?

Rate of filtrate delivery is inversely proportional to the___________________?

Pressure drop per tray in the atmospheric distillation column is about ________________ psi?

Pressure drop (Δp) and the superficial gas mass velocity (G) in case of packed absorption tower operating in the preloading range are related as_________________?

Pressure differential maintained across a continuous rotary vacuum filter is in the range of _______________ mm Hg column?

Practical dividing line between a ductile and brittle materials is suggested, when the ultimate elongation is about 5%. Generally, larger the knuckle radius, stronger is the corner torus section of a head. The knuckle radius provided should be less than ______________ of the head?

Power required for agitation depends upon the______________________?

Ponchon Savarit method is based on the use of enthalpy concentration diagram, which contains the bubble point curve (saturated liquid curve), dew point curve (saturated vapour curve) and equilibrium tie lines. As compared to McCabe-Thiele’s method, this method_________________?

Poisson’s ratio of a material is the ratio of unit lateral strain to the unit axial elongation within its elastic limit. The value of Poisson’s ratio for structural and pressure vessel steel may be taken as ____________________?

Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column ?

Pick out the wrong statement pertaining to the design of a long tube vertical evaporator ?

Pick out the wrong statement pertaining to the design of the distillation column?

Pick out the wrong statement pertaining to the design of a horizontal tube evaporator ?

Pick out the wrong statement pertaining to the design of a basket type evaporator ?

Pick out the wrong statement pertaining to the comparative evaluation of performance of the packed tower and the plate tower ?

Pick out the wrong statement pertaining to shell and tube heat exchanger_______________?

Pick out the wrong statement pertaining to ‘Horton sphere’ used for the storage of liquid ammonia ?

Pick out the wrong statement pertaining to a shell and tube heat exchanger ?

Pick out the wrong statement. In an agitated vertical cylindrical reaction vessel, the___________________?

Pick out the wrong statement about the design of sieve plate column and the bubble cap column ?

Pick out the wrong statement about the design of a sieve plate column ?

Pick out the wrong statement about routing of fluids in a shell and tube heat exchanger ?

Pick out the wrong statement about distillation operation__________________?

Pick out the correct statement___________________?

Overall tray efficiency of a distillation column is the ratio of the number of ___________________?

Overall mass transfer co-efficient in case of absorption of __________ in water is based on the gas film co-efficient only, as the mass transfer process is gas film (phase) controlling ?

Optimum reflux ratio in a continuous distillation column is determined by the__________________?

Optimum economic pipe diameter for fluid flow is determined by the____________________?

______________ of water makes it a widely used coolant in heat exchangers?

Number of evaporators which can be used in service in a multiple effect evaporation system is limited by the__________________?

Normally, the ratio of the total riser area to the tower cross sectional area (for bubble cap towers of diameter more than 3 ft) is around_______________?

Normally, the plate thickness of the bottoms and roofs of vertically cylindrical storage vessels as compared to that of the cylindrical shell is____________?

Normally, the length to diameter ratio of rotary dryers varies from 4 to 10 and for its economic operation; the number of transfer units (NTU) for such dryers varies from ?

Normal screwed fittings are used for pipes upto a diameter of _______________ inches?

Nominal size of a pipe is an indication of its _______________ diameter?

Needle valves are generally not used for___________________?

n the agitators, the power required will be changed with the increase of diameter of agitator D. as ____________________?

Multiple blade paddle agitator is used for mixing high viscosity liquids/paste in which the paddle diameter is commonly 0.8 times the tank diameter. However, the width of the blade is in the range of ______________ times the paddle diameter?

Movement of pipeline caused by thermal expansion is taken care by providing ___________________?

Most of the storage vessels/tanks are made cylindrical, because of the fact that a cylinder _________________?

Minimum tube pitch recommended for shell and tube heat exchangers is about _______________ times the outside diameter of the tube?

Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter) ?

Minimum baffle spacing recommended in a shell and tube heat exchanger is equal to _____________________?

Mc Cable Thiele method used for finding theoretical stages in a distillation column assumes that the_____________________?

Maximum size of the raschig rings used in a packed tower is about _______________ of the column diameter?

Maximum plate efficiency is achieved in case of ______________ flow?

Maximum allowable vapour velocity in a bubble cap tower is determined by the ____________________?

122.	Pick out the wrong statement about the design of sieve plate column and the bubble cap column ?
A.	The downcomer design and the residence time in the downcomer is almost same for sieve plate and bubble cap columns
B.	Weir length for a bubble cap plate is the same as that for the sieve plate
C.	Weir height for a bubble cap plate column is the same as that for a sieve plate column
D.	Weir height in case of a bubble cap plate ranges from 50 to 150 mm and is higher than the sieve plate
Answer» D. Weir height in case of a bubble cap plate ranges from 50 to 150 mm and is higher than the sieve plate

123.	Pick out the wrong statement about the design of a sieve plate column ?
A.	An increased weir height improves the tray efficiency at the cost of high plate pressure drop; optimum wear height being 40-90 mm for column pressure
B.	For segmental downcomers, the chord length is 60-80% of the column diameter. An initial value of downcomer area of 12% is taken in the design
C.	Width of the calming section provided at the inlet and outlet sides of the plate is 75 mm for column diameter below 1.5 metres and 100 mm for larger d
D.	Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is
Answer» E.

124.	Pick out the wrong statement about routing of fluids in a shell and tube heat exchanger ?
A.	The corrosive and fouling fluid should be preferably routed through the tubes
B.	The viscous fluid should be routed through the shell side
C.	Lower flow rate fluid should be routed through the shell side
D.	Higher pressure fluid stream should be routed through the shell side
Answer» E.

125.	Pick out the wrong statement about distillation operation__________________?
A.	Distillation under vacuum is a substitute for steam distillation
B.	In differential (simple) distillation, the vapour is removed as soon as it is formed without appreciable condensation
C.	In flash (equilibrium) distillation, a definite fraction of liquid is vaporised in such a way that the evolved vapour & residual liquids are in equili
D.	Flash distillation, differential distillation & steam distillation are all continuous distillation processes
Answer» E.

126.	Pick out the correct statement___________________?
A.	Centre to centre distance between two consecutives rivets in a row is called the pitch
B.	A riveted joint made in overlapping plates is called butt joint
C.	Hole size drilled in riveted plates is less than the actual size of the rivet
D.	None of these
Answer» B. A riveted joint made in overlapping plates is called butt joint

127.	Overall tray efficiency of a distillation column is the ratio of the number of ___________________?
A.	Overall gas transfer units to the number of ideal trays required
B.	Ideal trays required to the number of real trays required
C.	Real trays required to the number of ideal trays required
D.	None of these
Answer» C. Real trays required to the number of ideal trays required

128.	Overall mass transfer co-efficient in case of absorption of __________ in water is based on the gas film co-efficient only, as the mass transfer process is gas film (phase) controlling ?
A.	CO2
B.	SO2
C.	NH3
D.	None of these
Answer» D. None of these

130.	Optimum reflux ratio in a continuous distillation column is determined by the__________________?
A.	Maximum permissible vapour velocity
B.	Flooding limit of the column
C.	Total cost consideration (fixed cost of the column plus the cooling water & steam cost)
D.	None of these
Answer» D. None of these

131.	Optimum economic pipe diameter for fluid flow is determined by the____________________?
A.	Viscosity of the fluid
B.	Density of the fluid
C.	Total cost considerations (pumping cost plus fixed cost of the pipe)
D.	None of these
Answer» D. None of these

133.	Number of evaporators which can be used in service in a multiple effect evaporation system is limited by the__________________?
A.	Practical limit reached, due to low heat transfer rate because of inadequate temperature difference
B.	Economic limit reached, when the plant cost exceeds the saving of steam
C.	Both A. & B.
D.	Neither A. nor B.
Answer» D. Neither A. nor B.