chemical engineering Mcqs
3801. For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it__________________?
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A. Decreases the outlet temperature of cooling medium

B. Decreases the pressure drop

C. Increases the overall heat transfer coefficient

D. None of these

3802. Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because___________________?
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A. Radiation becomes important

B. Sub-cooled boiling occurs

C. Conduction becomes important

D. Convection becomes important

3803. The ratio of lateral strain to linear strain is termed as the___________________?
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A. Poissons ratio

B. Bulk modulus

C. Shear modulus

D. Modulus of elasticity

3804. Liquid gradient over a tray can be minimised by________________?
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A. Providing a higher skirt clearance or a higher weir

B. Decreasing the number of rows of caps through which the liquid flows or by decreasing the

C. All A., B. and C.

D. Using split flow, radial flow or cascade flow for column diameter large than 4 ft

E. ocity of liquid flow past the caps or by reducing the distance along the tray through which

F. liquid must flow

3805. Indirect contact heat exchangers are preferred over direct contact heat exchangers, because_________________?
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A. There is no mist formation

B. Cost of equipment is lower

C. Heat transfer co-efficient are high

D. There is no risk of contamination
3806. In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass _____________ through the heat exchanger ?
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A. Twice

B. Thrice

C. Four times

D. Once

3807. Nusselt number is a function of Prandtl number and ______________ number of fluid in natural convection heat transfer?
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A. Reynolds

B. Biot

C. Grashoff

D. Stanton

3808. In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is_________________?
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A. Hyperbolic

B. Parabolic

C. Linear

D. None of these

3809. At constant temperature, the thermal conductivities of gases _____________ with rise in pressure?
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A. Remain unchanged

B. Decrease

C. Increase

D. May increase or decrease; depends on the pressure

3810. Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the________________?
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A. Flexibility possible in the baffle arrangement

B. High heat transfer co-efficient

C. Low pressure drop

D. Less corrosion problems

3811. (Le/D) for a Tee (used as elbow, entering branch) would be ____________________?
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A. Less than that for Tee (used as elbow, entering run)

B. More than that for Tee (used as elbow, entering run)

C. Around 90

D. Both B. and C.
3812. With increase in temperature, the total emissivity of conductors____________________?
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A. Remain same

B. Decreases

C. Decreases linearly

D. Increases
3813. Forced circulation evaporators are normally used for concentrating liquids having ___________________?
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A. Scaling characteristics

B. High viscosity

C. Both A. & B.

D. Neither A. nor B.

3814. The absorptivity of a grey body at a given temperature _____________ with increasing wavelength of radiation?
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A. Remain constant

B. Increases

C. May increase or decrease; depends on the material

D. Decreases

3815. Electro-magnetic spectrum range, which is important for radiation varies from _____________ microns?
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A. 10 to 100

B. 100 to 1000

C. 0.5 to 50

D. 1 to 100

3816. LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________?
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A. Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)

B. Outlet temperature of both the hot and cold fluid are same

C. Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid

D. None of these

3817. It is not recommended to use a 1-2 shell and tube heat exchanger for a particular heat duty, whenever the LMTD correction factor is___________________?
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A. > 0.75

B. < 0.75

C. < 0.50

D. < 0.25

3818. The average velocity in the tubes of a 1-4 heat exchanger is ______________ times that in 1-1 heat exchanger having the same size & number of tubes and operated at same liquid flow rate ?
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A. 4

B. 2

C. 4-Jan

D. 2-Jan

3819. In a multiple effect evaporator system having n effects, the amount of water evaporated per unit surface area in approximately equal to _____________ times that in a single effect?
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A. 0.5 nth

B. nth

C. (1/n)th

D. 1.5 nth

3820. The centre to centre distance between two consecutive baffles in a shell and tube heat exchanger is called the baffle pitch or baffle spacing, which is more than 1/5th the I.D. of the shell. Which of the following is not a function of the baffles ?
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A. To increase the tube side heat transfer co-efficient by inducing turbulence

B. To reduce the induced vibration in the tubes

C. To increase the residence time of shell side fluid

D. To provide support to the tube bundle

3821. LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counter-flow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the ______________ flow?
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A. Mixed

B. Counter flow

C. Parallel

D. Same in either A , B. or C.
3822. Shortest distance between two tubes is___________________?
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A. Called tube clearance

B. Called tube pitch

C. None of these

D. More in case of triangular pitch as compared to square pitch of tube layout

3823. When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is _______________?
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A. Free convection

B. Entry length problem in laminar forced conduction (developing thermal boundary layer)

C. Mixed convection (both free and forced)

D. Forced convection

3824. In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is _____________ the outlet temperature of the cold fluid?
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A. Either more or less than (depending upon the fluid)

B. Less than

C. Equal to

D. More than

3825. The unit of conductance in SI unit is_______________?
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A. W/m2

B. W/mK

C. W/K

D. W/m

3826. Corrosiveness of steam condensate is due to the presence of________________?
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A. CO2

B. Dissolved O2

C. Both A. & B.

D. Neither A. nor B.

3827. With increase in temperature, the thermal conductivity of most liquids_________________?
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A. Remain same

B. Decreases

C. Increases

D. First increases upto a certain temperature and then becomes constant

3828. Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ?
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A. Triangular pitch

B. Diagonal square pitch

C. None of these

D. Square pitch

3829. The normal range of velocity of water in pipes is _______________ m/sec?
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A. Oct-50

B. 15-30

C. 0.1-0.5

D. 1-2
3830. The ratio for the rate of washing to the final rate of filtration in a washing type of plate and frame filter is____________________?
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A. 0.25

B. 0.75

C. 1.25

D. 0.5

3831. For hot feed, forward feeding as compared to backward feeding results in ______________ economy?
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A. No effect on

B. None of these

C. Decreased

D. Increased
3832. Dittus-Boelter equation used for the determination of heat transfer co-efficient is valid ___________________?
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A. For liquid metals

B. For fluids in turbulent flow

C. When Grashoff number is very important

D. For fluids in laminar flow

3833. LMTD cant be used as such without a correction factor for the_________________?
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A. Condensation of mixed vapour in a condenser

B. Multipass heat exchanger

C. All A. B. and C.

D. Baffled heat exchanger

3834. Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8. Pr n, is not valid, if the value of __________________?
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A. Reynolds number for the flow involved is > 10000

B. Reynolds number for the flow involved is < 2100

C. n = 0.3 is used for cooling

D. n = 0.4 is used for heating

3835. Normal screwed fittings are used for pipes upto a diameter of _______________ inches?
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A. 9

B. 5

C. 1.5

D. 3
3836. A multiple effect evaporator as compared to a single effect evaporator of the same capacity has _________________?
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A. Lower heat transfer area

B. Higher steam economy

C. Lower steam economy

D. Higher solute concentration in the product

3837. The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the________________ ?
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A. Solution has an elevation of boiling point

B. Evaporators operate at atmospheric pressure

C. Evaporators operate under vacuum

D. None of these

3838. Which of the following has the lowest overall heat transfer co-efficient ?
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A. Molten sodium

B. Air

C. Water

D. Dowtherm

3839. Multipass heat exchangers are used______________________?
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A. To obtain higher heat transfer co-efficient and shorter tube

B. Because of simplicity of fabrication

C. To reduce the pressure drop

D. For low heat load

3840. In most of the shell and tube heat exchangers, the tube pitch is generally ______________ the tube diameter?
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A. one-fourth of

B. 1.25-1.50 times

C. 2.5 times

D. Less than

3841. 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?
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A. 0.65 to 0.80

B. 0.3 to 0.5

C. 0.1 to 0.25

D. 0.5 to 0.6

3842. In the design of a paddle agitator, the ratio (paddle dia/tank dia) is normally taken as___________________?
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A. 0.5

B. 0.8

C. 0.25

D. 0.1

3843. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is__________________?
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A. Dependent on NRe only

B. 4.36

C. 120.36

D. 2.36

3844. The safe height (h) to diameter D. ratio (i.e., h/d) for liquid/petro fuel storage tank of capacity more than 45 kilolitres is less than _________________?
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A. 3.5

B. 3

C. 1

D. 2

3845. What is the slope of the operating line in the rectifying section of a distillation column ?
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A. 0

B. ?

C.

D. > 1

3846. _____________ heat exchanger is also known as hair pin type exchanger?
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A. Finned

B. Plate type

C. Double pipe

D. Regenerative

3847. Weep holes provided in the plates of a distillation column ____________________?
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A. Must be large enough (usually 1/4? to 5/8? dia) to prevent plugging but should not deliver

B. lows approximately the same path as the overflow fluid

C. All A., B. and C.

D. Facilitate draining out liquid from a tray when the unit is not in operation

E. essive amount of fluid during operation

F. Are normally located near the overflow weir so that any delivery of liquid during operation

3848. In a shell and tube heat exchanger, floating head is used for _________________?
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A. High heat transfer co-efficient

B. Large temperature differentials

C. Low pressure drop

D. Less corrosion of tubes

3849. The overall resistance for heat transfer through a series of flat resistance, is the _____________ of the resistances?
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A. Sum

B. Average

C. Product

D. Geometric mean

3850. The advantage of using a 1 2 shell and tube heat exchanger over a 1 1 shell and tube heat exchanger is_________________?
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A. Higher tube side heat transfer co-efficient

B. Lower shell side pressure drop

C. Higher shell side heat transfer co-efficient

D. Lower tube side pressure drop