chemical engineering Mcqs
3851. At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe ?
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A. 0.5

B. < 0.5

C. < 0.1

D. > 0.6
3852. Larger depth of liquid on the trays of a distillation column_________________?
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A. Leads to high tray efficiency

B. Results in higher pressure drop per tray

C. Both A. & B.

D. Neither A. or B.

3853. Optimum economic pipe diameter for fluid flow is determined by the____________________?
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A. Density of the fluid

B. Viscosity of the fluid

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

D. None of these

3854. Thermal diffusivity of a material __________________?
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A. Is defined as K/? . Cp

B. Is the ratio of thermal conductivity to thermal capacity

C. Has the unit m2 /sec

D. All A., B. and C.
3855. If a single tube pass heat exchanger is converted to two passes; for the same flow rate, the pressure drop per unit length in tube side will _____________ times?
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A. Increase by 1.8

B. Decrease by 22

C. None of these

D. Increase by 21.6
3856. Any shell opening greater than 5 cms for a storage tank must be reinforced for reason of ____________________?
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A. None of these

B. Preventing the local overstressing of the shell around the opening

C. Making the joint leak proof

D. Reduction of discontinuity in shape at the junction

3857. The ratio, (propeller agitator dia/tank dia) is normally taken as____________________?
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A. 0.15-030

B. 0.60-0.90

C. 0.75-0.85

D. 0.5-0.65

3858. In case of heat transfer by conduction in a hollow cylinder, ______________ mean area is used to calculate the heat transfer rate?
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A. Either A., B. or C.

B. Geometric

C. Arithmetic

D. Logarithmic
3859. Typical static submergence for bubble cap plate column operating at atmospheric pressure may be around _________________?
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A. 2.5?

B. 5?

C. 50% of the plate spacing

D. 0.5?
3860. In a cylindrical vessel subjected to internal pressure, the longitudinal stress ?L and the circumferential stress, ?n are related by___________________?
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A. No relation exists

B. ?h = ?L/2

C. ?h = 2 ?L

D. ?h = ?L

3861. The equation, Nst = f/2, is the _____________ analogy?
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A. Prandtl

B. Reynolds

C. Colburn

D. None of these

3862. In case of a super-cooled solution, which is on the verge of crystallisation, the free energy of the solution as compared to that of the solid is ________________?
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A. More

B. More or less; depends on the nature of solution

C. Less

D. Same

3863. The distance between the top of the slots and the liquid surface when the static liquid is just ready to flow over the overflow weir is called____________________?
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A. Skirt clearance

B. Downcomer liquid seal

C. Static submergence

D. None of these

3864. Heat flux, as defined in heat flow is analogous to _______________ in electricity flow?
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A. Resistance

B. Current

C. Voltage

D. None of these

3865. In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid___________________?
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A. Varies directly as the area and the LMTD

B. None of these

C. Varies as square of the area

D. Directly proportional to LMTD and inversely proportional to the area

3866. What is the minimum recommended ligament for square pitch arrangement in case of heat exchangers ?
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A. Equal to tube I.D

B. 6.5 cms

C. Equal to tube O.D

D. 6.5 mm
3867. Which one gives the monochromatic emissive power for black body radiation ?
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A. Stefan-Boltzmann law

B. Plancks law

C. Wiens law

D. Kirchhoffs law

3868. A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of__________________?
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A. 20.8

B. 20.5

C. 2

D. 20.2

3869. Needle valves are generally not used for___________________?
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A. Very accurate flow control

B. High pressure throttling service

C. Smaller sizes of pipe

D. Very large diameter pipes
3870. In a shell and tube heat exchanger, square pitch compared to triangular pitch__________________?
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A. None of these

B. Gives a higher shell side pressure drop

C. Can pack more surface area into a shell of given diameter

D. Gives a lower shell side pressure drop

3871. Theoretically calculated diameter of the stripping section of the continuous rectification column is ______________ that of the enriching section?
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A. Same as

B. Either more or less (depending upon relative volatility

C. More than

D. Less than

3872. Maximum heat transfer rate is obtained in ______________ flow?
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A. Turbulent

B. Transition region

C. Creeping

D. Laminar

3873. Maximum heat transfer rate is achieved in _____________ flow?
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A. Laminar

B. Co-current

C. Counter-current

D. Turbulent
3874. In pipe flow, heat is transferred from hot wall to the liquid by__________________?
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A. Free and forced convection

B. Conduction only

C. Forced convection and conduction

D. Forced convection only

3875. Stefan-Boltzmann law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in C T = absolute temperature in K) ?
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A. 1/T4

B. T4

C. t4

D. 1/t4

3876. Pick out the wrong statement pertaining to the design of the distillation column?
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A. None of these

B. idue build up

C. Generally, a skirt clearance of 0.5? to 1.5? is recommended to prevent plugging of the slots by

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

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

3877. Heat sensitive materials can be concentrated in an evaporator employing_______________?
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A. Vacuum

B. High pressure

C. High residence time

D. None of these

3878. Fruit juice (a heat sensitive material) can be concentrated in a ____________ evaporator?
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A. None of these

B. Long tube

C. Falling film

D. High pressure

3879. Maximum plate efficiency is achieved in case of ______________ flow?
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A. Cross

B. Split

C. Cascade

D. Reverse

3880. Brass valves are usually made for pipe sizes ______________ inches?
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A. ? 1

B. ? 2

C. > 3.5

D. > 2.5

3881. What is the unit of thermal conductivity ?
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A. Kcal/hr.m.C

B. Kcal/hr.m

C. Kcal/hr. C

D. Kcal/hr. m2 C

3882. The wall thickness of thin cylindrical shell with hemispherical ends is ______________ that of the spherical ends?
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A. Less than

B. Either B. or C.; depends on maximum permissible internal pressure

C. Equal to

D. More than
3883. Stefans block body radiation law can also be derived from ______________ law?
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A. None of these

B. Fouriers

C. Plancks

D. Kirchoffs

3884. Fqra cold viscous feed, backward feed gives _____________ than forward feed?
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A. None of these

B. Lower economy

C. A lower capacity

D. A higher capacity
3885. The inner wall of a furnace is at a temperature of 700C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.C- 1 respectively. The ambient air is at 30C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.C-1. The rate of heat loss from the outer surface in W.m-2is__________________?
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A. 175

B. 167.5

C. 172.5

D. 165.4
3886. The purpose of providing expansion bellows in the shell of tubular exchanger is to _____________________?
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A. Account for the uneven expansion of shell and tube bundles

B. Increase the heating load

C. Facilitate increase of shell length, if needed

D. Impart structural strength

3887. A sphere of radius R1 is enclosed in a sphere of radius R2. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is ________________?
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A. R2/(R1+R2)

B. (R1/R2)2

C. 0

D. 1

3888. Which has the lowest Prandtl number ?
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A. Lube oil

B. Water

C. Aqueous solution

D. Liquid metal
3889. In a shell and tube heat exchanger, the shell side fluid velocity can?t be changed by changing the_________________?
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A. Tube layout

B. Number of baffles

C. Tube diameter

D. Tube pitch

3890. In SI units, thermal conductivity is expressed in__________________?
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A. Watt/m2. K

B. Watt/m2. K

C. Watt/m4. K

D. Watt/m.K
3891. Movement of pipeline caused by thermal expansion is taken care by providing ___________________?
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A. Change in the shape of pipeline

B. Changes in its direction

C. Expansion joint

D. All A., B. and C.
3892. Rate of filtrate delivery is inversely proportional to the___________________?
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A. Filtering area & the pressure difference driving force

B. Viscosity of filtrate

C. Cake & filter medium resistance

D. Both A. and B.
3893. The heat transfer co-efficient in film type condensation is _______________ that for dropwise condensation?
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A. Lower than

B. Is same as

C. Half

D. Greater than

3894. In a forward feed multiple effect evaporator, the pressure is ____________________?
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A. Lowest in last effect

B. Dependent on the number of effects

C. Highest in last effect

D. Same in all effects

3895. Cylindrical storage tanks used for the storage of volatile liquids (e.g., naphtha) have ______________ roofs?
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A. Flat

B. Floating

C. Fixed

D. Conical

3896. A perfect black body is a perfect _____________ of radiation?
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A. Absorber

B. Emitter

C. Both A. & B.

D. Neither A. nor B.

3897. The equation, (NSt N2/3 Pr) = f/2, is the ____________ analogy ?
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A. Reynolds

B. Prandtl

C. None of these

D. Colburn
3898. It is not preferable to use superheated steam in evaporators, because of its very_________________?
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A. Low film co-efficient

B. High pressure

C. High temperature

D. None of these

3899. The force due to wind load acting on a tall vessel depends upon its___________________?
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A. Height

B. Shape

C. Outside diameter

D. All A, B. & C.
3900. The Stefan-Boltzmann constant depends on the_________________?
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A. Temperature

B. Surface

C. Medium

D. None of these