chemical engineering Mcqs
3751. Column support for the roof of cylindrical storage tank must be provided for___________________?
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A. All tanks irrespective of their heights and diameters

B. Large diameter tanks

C. Small diameter tall tanks

D. Small diameter tanks

3752. Baffle spacing is generally _________________ the I.D. of the shell ?
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A. More than

B. Not greater than

C. Not less than one fifth of

D. Both B. and C.
3753. Tubes are fixed to the tube sheet (a thick circular metallic plate) by the method of tube rolling and brazing (non-removable) or ferrule connection (removable). Thickness of the tube, sheet is normally ____________ the outside diameter of the tube but in no case it should be less than 22 mm (7/8?)?
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A. Three fourth

B. Equal to

C. Half

D. 1.5 times

3754. In Biot number, the characteristic length used is the ratio of the _______________ of the solid?
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A. Surface area to volume

B. Surface area to perimeter

C. Volume to surface area

D. Perimeter to surface area

3755. Ratio of tube length to shell diameter for a shell and tube heat exchanger is________________?
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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.
3756. For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is______________?
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A. Nu = 0.023 Re0.8. Pr0.4

B. Nu = 2Gz0.5

C. Nu = (2/?) Gz

D. Nu = (?/2) Gz

3757. In a shell and tube heat exchanger for a given heat transfer surface area, smaller diameter tubes are favoured as compared to larger diameter ones; because the smaller diameter tubes ______________?
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A. None of these

B. Are less prone to fouling

C. Are easier to clean

D. Can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less
3758. The distance between the centres of a rivet hole to the nearest edge of the plate is called _________________?
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A. Pitch

B. None of these

C. Margin

D. Back pitch

3759. Safety valves are provided in chemical equipments to guard against excessive_________________?
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A. Noise

B. Pressure/pressure fluctuation

C. Turbulence

D. Temperature

3760. Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100C and the inside heat transfer coefficient is 3k/l. If the wall temperature on the outside is held at 25C, what is the inside wall temperature in degree centigrade ?
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A. 48.25

B. 35.5

C. 43.75

D. 81.25
3761. The thickness of condensate layer in filmwise condensation depends on the__________________?
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A. All A., B. and C.

B. Liquid flow rate from the surface

C. Condensation rate

D. Surface configuration

3762. In forced convection, the Nusselt number is a function of ____________________?
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A. Pr and Gr

B. Re and Pr

C. Re and Sc

D. Re and Gr

3763. In sub-cooled boiling ?
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A. Very large vapour space is necessary

B. Bubbles from heating surface are absorbed by the mass of the liquid

C. Temperature of the heating surface is more than the boiling point of the liquid

D. Temperature of the heating surface is less than the boiling point of the liquid

3764. When one of the fluids is highly corrosive and has fouling tendency, it should_____________________?
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A. current

B. Flow outside the tube, when the flow is counter-current and inside the tube when the flow is

C. Preferably flow outside the tube

D. Flow at a very slow velocity

E. Preferably flow inside the tube for its easier internal cleaning
3765. With increase in temperature drop (in a shell and tube heat exchanger), the LMTD correction factor, FT_________________?
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A. Remains constant

B. Decreases very rapidly

C. Increases very rapidly

D. Increases linearly

3766. Resistance to heat flow by conduction is proportional to (where, t & ? are thickness & density of the material respectively and A = area normal to the direction of heat flow.) ?
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A. 1/A

B. 1/?

C. t

D. All A., B. & C.
3767. In case of _______________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface?
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A. Nucleate

B. Pool

C. Saturated

D. Local
3768. What is the slope of the operating line in the stripping section of a distillation column ?
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A. ?

B. 0

C. < 1

D. > 1
3769. Vent pipes are provided in a condenser to ________________?
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A. None of these

B. Purge the condenser

C. Facilitate easy cleaning of tubes

D. Remove non-condensable gases
3770. In a shell and tube type heat exchanger, the floating tube bundle heat arrangement is used________________?
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A. In high range of temperature differences

B. Because of its low cost

C. In low range of temperature differences

D. To prevent corrosion of the tube bundles

3771. Grashoff number is given by________________?
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A. gD2??t?/?2

B. gD3??tP2/?

C. gD2??tP2?

D. gD3.?.?t?2/?2
3772. The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is_________________?
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A. Sherwood number

B. Stanton number

C. Nusselt number

D. Schmidt number
3773. In a vertical short tube evaporator (Calandria type), the ______________________?
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A. All A., B. & C.

B. Liquor is inside the tube while the steam is outside the tube

C. Tube dia of 2.5-7.5 cms, tube length of 75-200 cms and cylindrical drum dia of 1-6 metres are

D. mally used

E. rounding tube

F. Area of central downtake is equal to 40 to 100% of total cross-sectional area of the

3774. In a bag filter, the pressure drop increases directly as the___________________?
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A. Viscosity of the gas and inversely as density of the gas

B. None of these

C. Density of the gas and inversely as viscosity of the gas

D. Density of the gas, but is independent of the viscosity of the gas

3775. Nusselt number is the ratio of the temperature gradient at the wall to_________________?
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A. Heat flux

B. None of these

C. That across the entire pipe

D. Temperature difference

3776. Fresh orange juice contains 12% (by weight) solids and the rest water 90% of the fresh juice is sent to an evaporator to remove water and subsequently mixed with the remaining 10% of fresh juice. The resultant product contains 40% solids. The kg of water removed from 1 kg fresh juice is__________________?
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A. 0.5

B. 0.4

C. 0.6

D. 0.7
3777. The maximum heat transfer co-efficient from steam heating will be attained when the steam is_________________?
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A. Saturated

B. None of these

C. Wet

D. Supersaturated

3778. All analogy equations connecting friction factor and heat transfer co-efficient apply only to ___________________?
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A. Wall or skin friction

B. Form friction

C. Both A. and B.

D. Turbulent flow

3779. Heat transfer rate described by Fouriers law will decrease, if the _____________ increases?
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A. Temperature difference

B. Thermal conductivity

C. Heat transfer area

D. Thickness
3780. Open pan evaporators are preferred to be used, when the solution to be concentrated is_________________?
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A. Corrosive

B. Salty

C. Scaling

D. Highly viscous
3781. Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger ?
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A. Pressure

B. Viscosity

C. Corrosiveness & fouling characteristics

D. Density
3782. What is the geometric mean of two heat transfer areas A1 and A2 ?
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A. ?(A1 + A2)

B. ?(A1 . A2)

C. 2 ?(A1 . A2)

D. ?(A1 . A2)

3783. Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212F may be around ______________ BTU?
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A. 970

B. 3.97

C. Data insufficient, cant be predicted

D. 180
3784. Mc Cable Thiele method used for finding theoretical stages in a distillation column assumes that the_____________________?
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A. Sensible heat differences are small, because the temperature changes from tray to tray is small

B. Liquid/vapor loading across the column remains constant

C. All A., B. and C.

D. Troutons rule is applicable

3785. In a single evaporator system, the steam economy ________________ by creating vacuum in the evaporator?
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A. Decreases

B. May increase or decrease, depends on the vacuum

C. Increases

D. Remain constant

3786. Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the_________________?
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A. Buoyancy of the bubbles produced at active nucleation site

B. None of these

C. Existence of thermal boundary layer

D. Temperature gradient produced due to density difference

3787. Which of the following is the most widely used heat insulating material for pipelines carrying steam ?
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A. Tar dolomite bricks followed by asbestos

B. Cotton followed by aluminium foil

C. Fireclay refractory followed by aluminium sheet

D. 85% magnesia cement and glass wool
3788. Tube expansion allowances exist in _____________ heat exchanger?
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A. U-tube

B. Multipass fixed tube sheet

C. None of these

D. Single pass fixed tube sheet

3789. To reduce the tube side pressure drop for the same flow rate, the heat exchanger recommended is _______________?
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A. 1-1 heat exchanger

B. 2-4 heat exchanger

C. 3-2 heat exchanger

D. 1-2 heat exchanger

3790. The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co-efficient at this time is _____________________?
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A. 333 W/m2.K

B. 894 W/m2.K

C. 287 W/m2.K

D. 1200 W/m2.K

3791. In a gas-liquid shell and tube heat exchanger, the_________________?
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A. Gases to be heated/cooled is normally routed through the shell side, because the corrosion

B. Presence of a non-condensable gas decreases the condensing film co-efficient

C. rosive in nature

D. Gases under high pressure are routed through the tube side, because high pressure gases are

E. All A, B. & C.

F. sed by the cooling water or steam condensate remain localised to the tubes

3792. 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-Thieles method, this method_________________?
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A. is more accurate in finding the number of equilibrium stages

B. s method

C. All A, B. & C.

D. accounts for the enthalpy changes in the process

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

3793. The absorptivity of a body is equal to its emissivity _________________?
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A. At a particular temperature

B. None of these

C. Under thermal equilibrium

D. For circular bodies

3794. Absorptivity and reflectivity of a perfect black body are respectively _______________?
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A. 0 and 1

B. 1 and ?

C. 0 and 0.5

D. 1 and 0
3795. To avoid the tearing off the plate of an edge, the margin (i.e., the minimum distance from the centre of the rivet hole to the nearest edge of the plate) should be equal to ____________________?
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A. 0.5 d

B. d

C. 2.5 d

D. 1.5 d
3796. The equation, Nst = (f/2)/[1 + 5 (Npr 1) ?(f/2)], corresponds to ______________ analogy?
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A. Colburn

B. Prandtl

C. Von-Karman

D. Reynolds

3797. The units of resistance to heat transfer is _____________________?
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A. J.m-2.K-1

B. J.m-1.K-1

C. W.m-2.K-1

D. W-1m2K
3798. In common bubble cap distillation column design practice, riser area is approximately equal to (where, Aa = Annular passage area, and Sa = Slot area) ?
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A. Aa = Sa

B. 1.2 Aa = 1.2 Sa

C. Aa = 1.5 Sa

D. Sa = 1.5 Aa

3799. A black body does not ____________ radiation?
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A. Absorb or emit

B. Refract

C. Reflect

D. Both B. & C.
3800. The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is ________________?
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A. 2

B. 1/4

C. 2-Jan

D. 4