chemical engineering Mcqs
3901. The range of electromagnetic spectrum important in heat transfer by radiation is ______________ microns?
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A. 0.5-50

B. 100-1000

C. 0.38-0.78

D. May-50

3902. The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ____________________?
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A. Prandtl number

B. Heat flux

C. Schmidt number

D. Nusselt number

3903. With increase in temperature, the thermal conductivity of fresh lubricating oil ___________________?
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A. Decreases

B. Remains unchanged

C. May increase or decrease; depends on its composition

D. Increases

3904. Stefan-Boltzmann law applies to _____________ body?
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A. Black

B. Any colour

C. Grey

D. White

3905. Terminal point temperature differences between fluids in case of a heat exchanger is termed as__________________?
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A. Log mean temperature difference

B. Approach

C. Geometric mean temperature difference

D. Arithmetic mean temperature difference

3906. Angled baffles are preferred in the agitation tank to control the swirling action; if the viscosity of the liquid to be mixed is about 200 poise. However, the baffle may be completely eliminated for mixing liquids having viscosity above ____________________ poise?
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A. 1000

B. 300

C. 1500

D. 600
3907. The actual temperature drop across the heating surface of an evaporator depends on the_______________?
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A. Liquid depth over the heating surface

B. Solution being evaporated

C. All A., B. and C.

D. Pressure difference between the steam chest and the vapor space above the boiling liquid

3908. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows _____________ law?
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A. Linear

B. Parabolic

C. Hyperbolic

D. Logarithmic

3909. The driving potential for the crystal growth during crystallisation is the _______________ of the solution?
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A. Density

B. Super-saturation

C. Concentration

D. Viscosity

3910. Loss of heat from untagged steam pipe to the ambient air is by __________________?
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A. Conduction

B. All A., B. & C.

C. Radiation

D. Convection

3911. The film co-efficient between condensing vapour and metal wall increases with _____________________?
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A. Decreasing temperature of the vapour

B. Increasing temperature of the vapour

C. Increasing viscosity of the film of condensate

D. Increasing temperature drop

3912. In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m2.s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m2/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is______________________?
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A. 4000

B. 5000

C. 6000

D. 2000

3913. Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter) ?
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A. 0.5 D

B. 0.66 D

C. 0.80 D

D. 0.2 D
3914. (Le/D) for couplings and unions would be_______________?
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A. 60

B. Negligible

C. 200

D. 350

3915. The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu ? Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter D. as _________________?
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A. D1.8

B. D0.2

C. D-0.2

D. D-1.8

3916. Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator ?
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A. Long vertical evaporator

B. Calandria vertical tube evaporator

C. Horizontal tube evaporator

D. Agitated film evaporator
3917. In a shell and tube heat exchanger, the overall heat transfer co-efficient is proportional to the tube side (volumetric flow rate)0.8. This is valid, only when the ratio of the tube side film resistance to the total resistance is almost equal to____________________?
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A. 2

B. 20.8

C. ?

D. 1
3918. Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter)?
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A. 0.2 D

B. 0.80 D

C. 0.66 D

D. 0.5 D

3919. Boiling point elevation for a strong and concentrated solution is found by Duhrings rule, which states that at the same pressure, the boiling point of a solution is a linear function of the _______________ of pure water?
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A. Density

B. Kinematic viscosity

C. Boiling point

D. Dynamic viscosity

3920. Solid angle subtended by the finite surface at the radiating element is_________________?
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A. Expressed in terms of radians

B. Called the view factor

C. Called the angle of vision

D. Proportional to the square of the distance between surfaces

3921. A shell may by termed as thin if its thickness to diameter ratio is less than 0.1. The factor which can be neglected in the calculation of membrane stresses is________________?
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A. Bending

B. Deformation

C. Shear

D. Elongation

3922. In case of 1.5? heat exchanger tubes, the inside flow area _____________ with decrease in BWG?
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A. Remains same

B. Decreases

C. None of these

D. Increases

3923. View factor is important in heat transfer by_____________________?
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A. Steady state conduction

B. Forced convection

C. Natural convection

D. Radiation
3924. In case of a multipass shell and tube heat exchanger, the temperature drop in the fluid _______________?
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A. None of these

B. And the wall is not related

C. And the wall are proportional to individual resistances

D. Is inversely proportional to the resistance across which the drop occurs

3925. It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30C. The boiling point of the solution is 110C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/kg.K. The rate at which the heat has to be supplied in (kJ/min) to the evaporator is____________________?
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A. 6.12 105

B. 9.08 105

C. 7.24 105

D. 3.06 105
3926. For a laminar flow of fluid in a circular tube, h1 is the convective heat transfer co-efficient at velocity V1. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is________________?
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A. 0.574 h1

B. 0.794 h1

C. 1.26 h1

D. 1.741 h1

3927. Nucleate boiling is promoted ___________________?
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A. On polished surfaces

B. None of these

C. In the absence of agitation

D. On rough surfaces
3928. Dropwise condensation is promoted on a/an ______________ surface?
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A. Glazed

B. Coated

C. Oily

D. Smooth

3929. What is the emissivity of a black body ?
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A. 1

B. 0.5

C. 0

D. 0.9

3930. Water is normally used as a coolant in the heat exchange equipments mainly because of its___________________?
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A. High fluidity

B. Abundance & high heat capacity

C. Low density

D. Low viscosity

3931. Tubes are held between top and bottom tube sheets in Calandria type evaporator by keeping_________________?
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A. Both the tube sheets fixed

B. Both the tube sheets floating

C. The top tube sheet floating and bottom tube sheet fixed

D. The top tube sheet fixed and the bottom tube-sheet floating

3932. Which of the following has the lowest Prandtl number ?
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A. Water

B. Molten sodium (a coolant used in fast breeder reactor)

C. Transformer oil

D. Dilute H2SO4

3933. Pick out the wrong statement about routing of fluids in a shell and tube heat exchanger ?
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A. The corrosive and fouling fluid should be preferably routed through the tubes

B. Higher pressure fluid stream should be routed through the shell side

C. The viscous fluid should be routed through the shell side

D. Lower flow rate fluid should be routed through the shell side

3934. Welded joint efficiency in the design of chemical process equipment is taken as_________________?
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A. 0.55

B. 0.95

C. 0.85

D. 0.75

3935. Souders Brown equation given by, U = Kv ?(?l ?v)/?v, is used for the calculation of the ______________ in a continuous distillation column?
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A. Tray pressure drop

B. Residence time in the downcomer for the disengagement of entrained vapour

C. Diameter of the bubble cap column

D. Diameter of the sieve plate column

3936. Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)?
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A. K/Ax

B. x/KA

C. KA/x

D. A/Kx

3937. Prandtl number for most of dry gases is about________________?
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A. 0.72

B. 150

C. 70

D. 0.001

3938. Radiator of an automobile engine is a ______________ type of heat exchanger?
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A. Co-current

B. Direct contact

C. Counter-current

D. Cross-current

3939. Cp?/K is termed as the ______________ number?
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A. Stanton

B. Grashoff

C. Nusselt

D. Prandtl
3940. For a given fluid, as the pipe diameter increases, the pumping cost ____________________?
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A. Increases

B. May increase or decrease depending upon whether the fluid is Newtonian or non-Newtonian

C. Remain unaffected

D. Decreases
3941. Finned tube heat exchangers__________________?
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A. Facilitate very large temperature drop through tube wall

B. Give larger area per tube

C. Use metal fins of low thermal conductivity

D. Are used for smaller heat load

3942. For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it________________?
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A. All A., B. and C.

B. Is easy to operate and maintain

C. Is more economical

D. Occupies smaller space

3943. Minimum tube pitch recommended for shell and tube heat exchangers is about _______________ times the outside diameter of the tube?
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A. 2.5

B. 1.25

C. 3.5

D. 1.75

3944. Which of the following is directly concerned with the heat transfer ?
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A. Grashoff number

B. Strouhal number

C. Euler number

D. Sherwood number

3945. A body cools down from 75C to 70C in 10 minutes. It will cool down from 70 C to 65 C in ______________ minutes?
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A. 10

B. Either B. or C., depends on the mass of the body

C. < 10

D. > 10
3946. Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is_______________?
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A. 0.4

B. 0.6

C. 0.8

D. 0.2

3947. Le/D) for 90 elbow (medium radius) and 90square elbow would be respectively around___________________?
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A. 3 and 5

B. 25 and 60

C. 250 and 600

D. 100 and 250

3948. Steam economy in case of a triple effect evaporator will be _________________?
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A. > 1

B. < 1

C. 1

D. Between 0 and 1

3949. Pressure differential maintained across a continuous rotary vacuum filter is in the range of _______________ mm Hg column?
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A. 250 to 500

B. 600 to 700

C. 100 to 150

D. 50 to 100

3950. A BTU/hr.ft.2 F is equal to_________________?
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A. 1 kcal/hr. m2C

B. 4.88 kcal/hr. m.2C

C. 1 kcal/hr. m2.K

D. None of these