chemical engineering Mcqs
4001. A _____________ evaporator employs an annular downtake?
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A. Basket type

B. None of these

C. Long tube vertical

D. Horizontal

4002. If heat transfer rate varies with the time, it is termed as__________________?
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A. Monochromatic radiation

B. Steady state conduction

C. None of these

D. Forced convection

4003. An adequate clearance between the tray and the shell wall of a distillation column is provided to_____________________?
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A. Avoid back-trapping

B. None of these

C. Drain the liquid from the tray when the unit is not in operation

D. Allow for thermal expansion and facilitate installation
4004. In an extended surface heat exchanger, fluid having lower co-efficient________________?
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A. Should not be used as it gives very high pressure drop

B. Flows outside the tubes

C. Flows through the tube

D. Can flow either inside or outside the tubes

4005. Which of the following is not used as a medium for high temperature heating ?
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A. Mercury

B. Fused salts (e.g., an eutectic mixture of 53% KNO3, 40% NaNO2and 7% NaNO3)

C. Liquid metal (e.g. molten sodium)

D. Dowtherm

4006. The left face of a one dimensional slab of thickness 0.2 m is maintained at 80C and the right face is exposed to air at 30C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2.K. At steady state, the temperature of the right face in C is____________________?
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A. 77.2

B. 71.2

C. 63.8

D. 48.7
4007. 1000 kg of wet solids are to be dried from 60% to 20% moisture (by weight). The mass of moisture removed in kg is__________________?
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A. 400

B. 520

C. 500

D. 200

4008. Temperature profile in steady state heat transfer is________________?
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A. Asymptotic

B. Linear

C. Hyperbolic

D. Parabolic

4009. Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger ?
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A. Effective tube surface area for convective heat transfer

B. All A. B. and C.

C. Tube side pressure drop and the heat transfer rate

D. Convective heat transfer co-efficient

4010. Which type of heat exchanger is preferred for heavy heat loads ?
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A. Double pipe

B. None of these

C. Series and parallel set of shell and tube

D. Plate fine

4011. The unit of heat transfer co-efficient in SI unit is____________________?
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A. W/m2K

B. W/mK

C. J/mK

D. J/M2K

4012. Correction is applied to LMTD for __________ flow?
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A. Counter

B. Parallel

C. Cross

D. None of these

4013. In a forward feed multiple effect, the pressure build up will be____________________?
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A. Highest at the outlet of the last effect

B. Least at the inlet of the first effect

C. Least at the outlet of the last effect

D. Highest at the inlet of the last effect

4014. The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 10-8 W/m2.K4) ?
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A. 1000

B. 800

C. 727

D. 1200

4015. A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is__________________?
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A. 48000

B. 6000

C. 60000

D. 24000
4016. A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because__________________?
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A. Boiling point elevation in a single effect system is much higher than that in any effect in a

B. Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect

C. ti-effect system

D. Total amount of vapor produced per Kg of feed steam in a multiple effect system is much

E. her than in a single effect</strong>

F. Total heat transfer area of all the effects is -less than that in a single effect evaporator system

4017. Prandtl number is given by__________________?
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A. CP ?/a

B. ?/h CP

C. CP ?/k

D. hD/k

4018. Leidenfrost point is a term concerned with the____________________?
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A. Condensation of the saturated vapor on a cold surface

B. Heat transfer between two highly viscous liquids

C. Concentration of a corrosive solution by evaporation

D. Boiling of a liquid on a hot surface
4019. A process stream of dilute aqueous solution flowing at the rate of10 Kg.s-1 is to be heated. Steam condensate at 95C is available for heating purpose, also at a rate of 10 Kg.s-1. A 1 1 shell and tube heat exchanger is available. The best arrangement is_______________?
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A. Parallel flow with process stream on shell side

B. Counter flow with process stream on shell side

C. Parallel flow with process stream on tube side

D. Counter flow with process stream on tube side

4020. What is Nusselt number ?
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A. h. CP/?

B. CP. ?/k

C. hD/k

D. CP. ?/h

4021. Tube pitch is the _______________ of tube diameters and the clearances?
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A. Ratio

B. Difference

C. Sum

D. None of these

4022. The value of Stefan-Boltzmann constant in SI unit is_________________?
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A. 5.6697 10-8W/m2.K4

B. 0.1714 10-8W/m2.K4

C. 0.1714 10-8kcal/m2. K4

D. 5.6697 10-8kcal/m2. K4

4023. A long iron rod initially at a temperature of 20C has one end dipped in boiling water (100C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time ___________________?
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A. t = 400 s

B. t = 800 s

C. t = 283 s

D. t = 356 s

4024. With increase in porosity, the thermal conductivity of a solid substance__________________?
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A. May increase or decrease; depends on the solid

B. Increases

C. Remains unchanged

D. Decreases
4025. Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid ?
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A. Catchall

B. Baffle

C. Bleed point

D. Vent

4026. Dropwise condensation occurs on ______________ surfaces?
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A. Smooth clean

B. Contaminated cooling

C. Polished

D. Clean and dirt free

4027. Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is ________________ law?
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A. Kirchoffs

B. Wiens

C. Daltons

D. Stefans

4028. In counter flow compared to parallel flow, ?
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A. LMTD is greater

B. Less surface area is required for a given heat transfer rate

C. Both A. and B.

D. More surface area is required for a given heat transfer rate

4029. Air is best heated with steam in a heat exchanger of__________________?
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A. Shell and tube type

B. Plate type

C. Double pipe type with fin on steam side

D. Double pipe type with fin on air side
4030. The sum of reflectivity and absorptivity for an opaque body is equal to____________________?
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A. 0.5

B. 0

C. 1

D. 2

4031. Value of Prandtl number for water ranges from_________________?
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A. 1000 to 2000

B. 100 to 500

C. 1 to 2

D. 5 to 10
4032. Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is_____________?
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A. Horizontal heat exchanger with steam on shell side

B. Horizontal heat exchanger with steam on tube side

C. Vertical heat exchanger with steam on tube side

D. Vertical heat exchanger with steam on shell side
4033. The most conducive surface for dropwise condensation to occur is the _____________ surface?
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A. Smooth

B. Oily

C. Glazed & polished

D. Coated

4034. Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is________________?
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A. Finned tube heat exchanger with air inside and steam outside

B. Shell and tube heat exchanger with air inside tubes and steam on shell side

C. Finned tube heat exchanger with air outside and steam inside

D. Shell and tube heat exchanger with air on shell side and steam inside tubes

4035. Choose the most important factor on which the heat conducted through a wall in a unit time will depend on ?
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A. Area of the wall perpendicular to heat flow

B. Thickness of the wall

C. Material of the wall

D. Temperature difference between the two surfaces of the wall
4036. Out of the following four assumptions used in the derivation of the equation for LMTD [LMTD = (?t1 ?t2)/ln(?t1/?t2)], which one is subject to the largest deviation in practice ?
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A. No partial phase change in the system

B. Constant rate of fluid flow

C. Constant specific heat

D. Constant overall heat transfer co-efficient.

4037. Kg of liquid evaporated per hour in an evaporator is defined as its_________________?
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A. None of these

B. Economy

C. Steam load

D. Capacity
4038. A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun ?
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A. Yellow paint

B. White paint

C. Black paint

D. Grey paint

4039. A hot liquid is kept in a big room. The logarithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly a/an___________________?
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A. Ellipse

B. Parabola

C. Straight line

D. Circular arc

4040. Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is__________________?
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A. 2

B. 100

C. 0.5

D. 10

4041. Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around _____________ metres/second?
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A. 30

B. 1

C. 10

D. 20

4042. For what value of Prandtl number, the Col-burn analogy is valid ?
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A. 0.06 to 120

B. 1 to 103

C. 0.6 to 120

D. 1 to 50

4043. A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2.K. The Biot number is ______________?
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A. 3.5

B. 5.6

C. 0.025

D. 0.0035

4044. A metal ball of radius 0.1 m at a uniform temperature of 90C is left in air at 30C. The density and the specific heat of the metal are 3000 kg/m3 and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m2.K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60C is_________________?
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A. 0.55

B. 0.15

C. 555

D. 55.5

4045. A dephlegmator is a_____________________?
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A. Vacuum evaporator

B. Double pipe heat exchanger

C. Partial condenser

D. Total condenser

4046. The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re)0.8 (Pr)0.4] cannot be used for________________?
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A. Molten metals

B. All A., B. and C.

C. Low Reynolds number

D. Very low Grashoff number

4047. Steady state one dimensional heat flow by conduction as given by Fouriers low does not assume that_______________?
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A. Material is anisotropic

B. There is no internal heat generation

C. Constant temperature gradient exists

D. Boundary surfaces are isothermal

4048. Nusselt number is the ratio of the ____________________?
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A. Heat flux at the wall to that across the entire pipe

B. Temperature gradient of the wall to that across the entire pipe

C. None of these

D. Temperature difference to the temperature gradient at the wall

4049. Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube___________________?
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A. Exit fluid temperature < wall temperature

B. Exit fluid temperature = wall temperature

C. Exit-fluid temperature > wall temperature

D. Graetz number > 100

4050. Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is________________?
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A. > 1

B. < 1

C. 1

D. 0.1