Chemical Heat Transfer MCQs – Latest Competitive Chemical Engineering MCQs
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Latest Chemical Engineering MCQs
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Latest Chemical Heat Transfer Mcqs
The most occurred mcqs of Chemical Heat Transfer in past papers. Past papers of Chemical Heat Transfer Mcqs. Past papers of Chemical Heat Transfer Mcqs . Mcqs are the necessary part of any competitive / job related exams. The Mcqs having specific numbers in any written test. It is therefore everyone have to learn / remember the related Chemical Heat Transfer Mcqs. The Important series of Chemical Heat Transfer Mcqs are given below:
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__________________?
A. Decreases the outlet temperature of cooling medium
B. Decreases the pressure drop
C. Increases the overall heat transfer coefficient
D. None of these
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 100°C and the inside heat transfer coefficient is „3k/l’. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade ?
A. 43.75
B. 35.5
C. 81.25
D. 48.25
A graph between _____________ is called Wilson plot?
A. (1/U) Vs. (1/v0.8)
B. v0.8 Vs . U
C. (1/v0.8) Vs. U
D. (1/U) Vs. (1/V)
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________________?
A. 0.574 h1
B. 0.794 h1
C. 1.26 h1
D. 1.741 h1
Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface) ?
A. 1/U2 – 1/U1
B. 1/U1 – 1/U2
C. U1 – U2
D. U2 – U1
All analogy equations connecting friction factor and heat transfer co-efficient apply only to ___________________?
A. Wall or skin friction
B. Turbulent flow
C. Both A. and B.
D. Form friction
Reason for operating an evaporator in multiple effects is to secure ___________________?
A. Decreased steam consumption
B. Increased steam economy
C. Both A. and B.
D. Increased capacity
Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the_________________?
A. Buoyancy of the bubbles produced at active nucleation site
B. Temperature gradient produced due to density difference
C. Existence of thermal boundary layer
D. None of these
Critical value of the _____________ number governs the transition from laminar to turbulent flow in free convection heat transfer?
A. Reynolds
B. Grashoff
C. Both ‘a’ & ‘b’
D. Prandtl & Grashoff
In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is _____________ the outlet temperature of the cold fluid?
A. Equal to
B. Less than
C. More than
D. Either more or less than (depending upon the fluid)
Evaporator tubes are generally_____________________?
A. Inclined
B. Vertical
C. Horizontal
D. Random
Which of the following is the most widely used heat insulating material for pipelines carrying steam ?
A. Cotton followed by aluminium foil
B. Fireclay refractory followed by aluminium sheet
C. Tar dolomite bricks followed by asbestos
D. 85% magnesia cement and glass wool
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?
A. Parabolic
B. Linear
C. Hyperbolic
D. Logarithmic
Grashoff number is given by________________?
A. gD3.β.Δtρ2/μ2
B. gD2βΔtP2μ
C. gD2βΔtρ/μ2
D. gD3βΔtP2/μ
In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid___________________?
A. Varies directly as the area and the LMTD
B. Varies as square of the area
C. Directly proportional to LMTD and inversely proportional to the area
D. None of these
For what value of Prandtl number, St = f/2 ?
A. > 1
B. 1
C. 1.5
D. < 1
Heat sensitive materials can be concentrated in an evaporator employing_______________?
A. Vacuum
B. High residence time
C. High pressure
D. None of these
LMTD can’t be used as such without a correction factor for the_________________?
A. Baffled heat exchanger
B. Multipass heat exchanger
C. Condensation of mixed vapour in a condenser
D. All A. B. and C.
Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)?
A. K/Ax
B. KA/x
C. x/KA
D. A/Kx
Heat flux, as defined in heat flow is analogous to _______________ in electricity flow?
A. Current
B. Resistance
C. Voltage
D. None of these
The driving potential for the crystal growth during crystallisation is the _______________ of the solution?
A. Viscosity
B. Concentration
C. Super-saturation
D. Density
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 ?
A. Thrice
B. Twice
C. Once
D. Four times
With increase in temperature, the thermal conductivity of most liquids_________________?
A. Remain same
B. Decreases
C. Increases
D. First increases upto a certain temperature and then becomes constant
The film co-efficient between condensing vapour and metal wall increases with _____________________?
A. Increasing temperature of the vapour
B. Increasing temperature drop
C. Increasing viscosity of the film of condensate
D. Decreasing temperature of the vapour
The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ____________________?
A. Heat flux
B. Prandtl number
C. Nusselt number
D. Schmidt number
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______________?
A. Nu = (π/2) Gz
B. Nu = 0.023 Re0.8. Pr0.4
C. Nu = (2/π) Gz
D. Nu = 2Gz0.5
In a forward feed multiple effect evaporator, the pressure is ____________________?
A. Same in all effects
B. Lowest in last effect
C. Highest in last effect
D. Dependent on the number of effects
“The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium”. This is ______________ law?
A. Kirchoff’s
B. Wien’s displacement
C. Planck’s
D. Stefan-Boltzmann
Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ?
A. Diagonal square pitch
B. Triangular pitch
C. Square pitch
D. None of these
A multiple effect evaporator as compared to a single effect evaporator of the same capacity has _________________?
A. Lower steam economy
B. Lower heat transfer area
C. Higher steam economy
D. Higher solute concentration in the product
With increase in temperature, the total emissivity of conductors____________________?
A. Increases
B. Remain same
C. Decreases
D. Decreases linearly
Dittus-Boelter equation used for the determination of heat transfer co-efficient is valid ___________________?
A. For liquid metals
B. For fluids in turbulent flow
C. When Grashoff number is very important
D. For fluids in laminar flow
In a shell and tube heat exchanger, floating head is used for _________________?
A. Large temperature differentials
B. High heat transfer co-efficient
C. Less corrosion of tubes
D. Low pressure drop
Resistance to heat flow by conduction is proportional to (where, t & ρ are thickness & density of the material respectively and A = area normal to the direction of heat flow.) ?
A. 1/ρ
B. t
C. 1/A
D. All A., B. & C.
Maximum heat transfer rate is obtained in ______________ flow?
A. Creeping
B. Turbulent
C. Laminar
D. Transition region
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 ________________?
A. More
B. Same
C. Less
D. More or less; depends on the nature of solution
In a single evaporator system, the steam economy ________________ by creating vacuum in the evaporator?
A. Increases
B. Remain constant
C. Decreases
D. May increase or decrease, depends on the vacuum
Cpμ/K is termed as the ______________ number?
A. Nusselt
B. Grashoff
C. Prandtl
D. Stanton
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 _____________________?
A. 894 W/m2.K
B. 1200 W/m2.K
C. 333 W/m2.K
D. 287 W/m2.K
Chemical Engineering Basics Mcqs
At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe ?
A. < 0.5
B. 0.5
C. > 0.6
D. < 0.1
Nucleate boiling is promoted ___________________?
A. In the absence of agitation
B. On rough surfaces
C. On polished surfaces
D. None of these
The thermal boundary layer at NPr > 1 ?
A. Disappears
B. Is thinner than hydrodynamic boundary layer
C. And the hydrodynamic boundary layers are identical
D. Is thicker than hydrodynamic boundary layer
Which of the following is directly concerned with the heat transfer ?
A. Sherwood number
B. Strouhal number
C. Euler number
D. Grashoff number
The equation, Nst = f/2, is the _____________ analogy?
A. Prandtl
B. Reynolds
C. Colburn
D. None of these
Forced circulation evaporators are normally used for concentrating liquids having ___________________?
A. High viscosity
B. Scaling characteristics
C. Both A. & B.
D. Neither A. nor B.
View factor is important in heat transfer by_____________________?
A. Natural convection
B. Steady state conduction
C. Forced convection
D. Radiation
‘Duhring’s plot’ is of use in_________________?
A. Leaching
B. Evaporation
C. Extractive distillation
D. Absorption
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___________________?
A. Conduction becomes important
B. Convection becomes important
C. Radiation becomes important
D. Sub-cooled boiling occurs
In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is_________________?
A. Hyperbolic
B. Linear
C. Parabolic
D. None of these
Which has the lowest Prandtl number ?
A. Liquid metal
B. Water
C. Aqueous solution
D. Lube oil
The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is ________________?
A. 1/2
B. 2
C. 4
D. 1/4
What is the geometric mean of two heat transfer areas A1 and A2 ?
A. √(A1 . A2)
B. ½ √(A1 . A2)
C. √(A1 + A2)
D. 2 √(A1 . A2)
Stefan’s block body radiation law can also be derived from ______________ law?
A. Fourier’s
B. Planck’s
C. Kirchoff’s
D. None of these
Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212°F may be around ______________ BTU?
A. 180
B. 3.97
C. 970
D. Data insufficient, can’t be predicted
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__________________?
A. 0.5
B. 0.4
C. 0.6
D. 0.7
An equipment which converts the latent or sensible heat of one fluid into the latent heat of vaporisation of another, is called a_________________?
A. Recuperator
B. Heat exchanger
C. Boiler
D. Regenerator
A black body does not ____________ radiation?
A. Absorb or emit
B. Reflect
C. Refract
D. Both B. & C.
Multiple effect evaporation accounts for___________________?
A. Steam economy
B. Investment economy
C. Lower operating costs
D. None of these
Tube expansion allowances exist in _____________ heat exchanger?
A. Single pass fixed tube sheet
B. U-tube
C. Multipass fixed tube sheet
D. None of these
Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter)?
A. 0.2 D
B. 0.66 D
C. 0.5 D
D. 0.80 D
Corrosiveness of steam condensate is due to the presence of________________?
A. Dissolved O2
B. CO2
C. Both A. & B.
D. Neither A. nor B.
Solid angle subtended by the finite surface at the radiating element is_________________?
A. Expressed in terms of radians
B. Called the angle of vision
C. Proportional to the square of the distance between surfaces
D. Called the view factor
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 ________________?
A. 1
B. R2/(R1+R2)
C. 0
D. (R1/R2)2
One kilogram of water at 0°C is changed to superheated steam of one atm pressure and 300° C. The major heat consumption in the process will be to________________?
A. To superheat the steam
B. Evaporate the water
C. Heat the water from 0°C to 100°C
D. Data insufficient, can’t be predicted
The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are_______________?
A. Nu,Pr
B. Re.Gz
C. Nu,Pr,Re
D. Nu,Gz
In case of heat transfer by conduction in a hollow cylinder, ______________ mean area is used to calculate the heat transfer rate?
A. Arithmetic
B. Geometric
C. Logarithmic
D. Either A., B. or C.
The absorptivity of a grey body at a given temperature _____________ with increasing wavelength of radiation?
A. Decreases
B. Increases
C. Remain constant
D. May increase or decrease; depends on the material
Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator ?
A. Horizontal tube evaporator
B. Long vertical evaporator
C. Agitated film evaporator
D. Calandria vertical tube evaporator
Which of the following has the lowest overall heat transfer co-efficient ?
A. Dowtherm
B. Water
C. Molten sodium
D. Air
Indirect contact heat exchangers are preferred over direct contact heat exchangers, because_________________?
A. There is no mist formation
B. There is no risk of contamination
C. Heat transfer co-efficient are high
D. Cost of equipment is lower
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_______________?
A. 0.4
B. 0.2
C. 0.6
D. 0.8
The actual temperature drop across the heating surface of an evaporator depends on the_______________?
A. Solution being evaporated
B. Liquid depth over the heating surface
C. Pressure difference between the steam chest and the vapor space above the boiling liquid
D. All A., B. and C.
jH factor for heat transfer depends upon the ____________ number?
A. Nusselt
B. Biot
C. Reynolds
D. Prandtl
A perfect black body is a perfect _____________ of radiation?
A. Emitter
B. Absorber
C. Both A. & B.
D. Neither A. nor B.
The absorptivity of a body is equal to its emissivity _________________?
A. For circular bodies
B. At a particular temperature
C. Under thermal equilibrium
D. None of these
The inner wall of a furnace is at a temperature of 700°C. 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 30°C 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__________________?
A. 165.4
B. 172.5
C. 167.5
D. 175
If heat transfer rate varies with the time, it is termed as__________________?
A. Steady state conduction
B. Forced convection
C. Monochromatic radiation
D. None of these
_____________ heat exchanger is used for chilling oil to be dewaxed?
A. Fixed tube
B. Double pipe
C. U-tube
D. Floating head
It is not preferable to use superheated steam in evaporators, because of its very_________________?
A. High pressure
B. High temperature
C. Low film co-efficient
D. None of these
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__________________?
A. 20.2
B. 20.8
C. 2
D. 20.5
At constant temperature, the thermal conductivities of gases _____________ with rise in pressure?
A. Decrease
B. Remain unchanged
C. Increase
D. May increase or decrease; depends on the pressure
When warm and cold liquids are mixed, the heat transfer is mainly by_______________?
A. Radiation
B. Convection
C. Conduction
D. Both A. & C
Open pan evaporators are preferred to be used, when the solution to be concentrated is_________________?
A. Corrosive
B. Highly viscous
C. Scaling
D. Salty
The equation, Nst = (f/2)/[1 + 5 (Npr – 1) √(f/2)], corresponds to ______________ analogy?
A. Reynolds
B. Von-Karman
C. Colburn
D. Prandtl
The advantage of using a 1 – 2 shell and tube heat exchanger over a 1 – 1 shell and tube heat exchanger is_________________?
A. Lower shell side pressure drop
B. Lower tube side pressure drop
C. Higher tube side heat transfer co-efficient
D. Higher shell side heat transfer co-efficient
Vent pipes are provided in a condenser to ________________?
A. Remove non-condensable gases
B. Facilitate easy cleaning of tubes
C. Purge the condenser
D. None of these
LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________?
A. Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)
B. Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid
C. Outlet temperature of both the hot and cold fluid are same
D. None of these
Steam trap is used to_________________?
A. Stop the supply of steam
B. Remove water resulting from partial condensation of steam
C. Condense the steam flowing in the pipeline
D. None of these
Planck’s distribution law is valid for _____________ bodies?
A. White
B. Black
C. Coloured
D. All A., B. & C.
In a shell and tube heat exchanger, square pitch compared to triangular pitch__________________?
A. Gives a higher shell side pressure drop
B. Can pack more surface area into a shell of given diameter
C. Gives a lower shell side pressure drop
D. None of these
In a gas-liquid shell and tube heat exchanger, the_________________?
A. Gases under high pressure are routed through the tube side, because high pressure gases are corrosive in nature
B. Presence of a non-condensable gas decreases the condensing film co-efficient
C. Gases to be heated/cooled is normally routed through the shell side, because the corrosion
caused by the cooling water or steam condensate remain localised to the tubes
D. All A, B. & C.
Electro-magnetic spectrum range, which is important for radiation varies from _____________ microns?
A. 10 to 100
B. 0.5 to 50
C. 1 to 100
D. 100 to 1000
A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C in ______________ minutes?
A. < 10
B. > 10
C. 10
D. Either B. or C., depends on the mass of the body
For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it________________?
A. Is more economical
B. Occupies smaller space
C. Is easy to operate and maintain
D. All A., B. and C.
The Stefan-Boltzmann constant depends on the_________________?
A. Temperature
B. Medium
C. Surface
D. None of these
In a shell and tube type heat exchanger, the floating tube bundle heat arrangement is used________________?
A. Because of its low cost
B. In high range of temperature differences
C. In low range of temperature differences
D. To prevent corrosion of the tube bundles
In forced convection, the Nusselt number is a function of ____________________?
A. Re and Pr
B. Pr and Gr
C. Re and Gr
D. Re and Sc
Radiator of an automobile engine is a ______________ type of heat exchanger?
A. Cross-current
B. Co-current
C. Counter-current
D. Direct contact
Maximum heat transfer rate is achieved in _____________ flow?
A. Counter-current
B. Co-current
C. Turbulent
D. Laminar
Overall heat transfer co-efficient of a particular tube is U1. If the same tube with some dirt deposited on either side has coefficient U2, then_________________?
A. U1 = U2
B. U1 > U2
C. U2 > U1
D. U1 = dirt factor – U2