Competitive Chemical Engineering MCQs – Chemical Heat Transfer 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:
A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are kA and kB and the specific heat capacities are CPA and CPB for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when_________________?
A. CPA < CPB
B. CPA > CPB
C. kA < 0.5 kB
D. kA >2 kB
Terminal point temperature differences between fluids in case of a heat exchanger is termed as__________________?
A. Approach
B. Arithmetic mean temperature difference
C. Log mean temperature difference
D. Geometric mean temperature difference
For _______________ Prandtl number values, the heat conduction will be negligible in the buffer zone?
A. Low
B. Extremely low
C. High
D. No
In case of _______________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface?
A. Nucleate
B. Local
C. Saturated
D. Pool
To reduce the tube side pressure drop for the same flow rate, the heat exchanger recommended is _______________?
A. 3-2 heat exchanger
B. 1-1 heat exchanger
C. 1-2 heat exchanger
D. 2-4 heat exchanger
With increase in temperature, the thermal conductivity of fresh lubricating oil ___________________?
A. Remains unchanged
B. Decreases
C. Increases
D. May increase or decrease; depends on its composition
A _____________ evaporator employs an annular downtake?
A. Basket type
B. Long tube vertical
C. Horizontal
D. None of these
A BTU/hr.ft.2 °F is equal to_________________?
A. 1 kcal/hr. m2.°K
B. 4.88 kcal/hr. m.2°C
C. 1 kcal/hr. m2°C
D. None of these
Stefan-Boltzmann law applies to _____________ body?
A. Black
B. Grey
C. White
D. Any colour
Water is normally used as a coolant in the heat exchange equipments mainly because of its___________________?
A. Abundance & high heat capacity
B. Low viscosity
C. Low density
D. High fluidity
Absorptivity and reflectivity of a perfect black body are respectively _______________?
A. 1 and 0
B. 1 and ∞
C. 0 and 1
D. 0 and 0.5
Which one gives the monochromatic emissive power for black body radiation ?
A. Planck’s law
B. Wien’s law
C. Kirchhoff’s law
D. Stefan-Boltzmann law
In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will___________________?
A. Decrease
B. Increase
C. Remain unchanged
D. Either increase or decrease; depends on the coolant flow rate
Heat transfer rate described by Fourier’s law will decrease, if the _____________ increases?
A. Temperature difference
B. Thickness
C. Thermal conductivity
D. Heat transfer area
In pipe flow, heat is transferred from hot wall to the liquid by__________________?
A. Forced convection only
B. Conduction only
C. Forced convection and conduction
D. Free and forced convection
In SI units, thermal conductivity is expressed in__________________?
A. Watt/m.°K
B. Watt/m2. °K
C. Watt/m2. °K
D. Watt/m4. °K
What is the emissivity of a black body ?
A. 0.5
B. 1
C. 0
D. 0.90
Tubes are held between top and bottom tube sheets in Calandria type evaporator by keeping_________________?
A. Both the tube sheets fixed
B. The top tube sheet floating and bottom tube sheet fixed
C. Both the tube sheets floating
D. The top tube sheet fixed and the bottom tube-sheet floating
What is the unit of thermal conductivity ?
A. Kcal/hr.m
B. Kcal/hr.m.°C
C. Kcal/hr. m2 °C
D. Kcal/hr. °C
Nusselt number is the ratio of the temperature gradient at the wall to_________________?
A. Heat flux
B. Temperature difference
C. That across the entire pipe
D. None of these
Thermal diffusivity of a material __________________?
A. Has the unit m2 /sec
B. Is the ratio of thermal conductivity to thermal capacity
C. Is defined as K/ρ . Cp
D. All A., B. and C.
Which of the following has maximum thermal conductivity ?
A. Iron
B. Nitrogen
C. Coal
D. Tar
Chemical Heat Transfer Mcqs
The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is___________________?
A. Less
B. More
C. Some
D. Either more or less; depends on the nature of vapor
The maximum heat transfer co-efficient from steam heating will be attained when the steam is_________________?
A. Wet
B. Saturated
C. Supersaturated
D. None of these
LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counter-flow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the ______________ flow?
A. Mixed
B. Parallel
C. Counter flow
D. Same in either A , B. or C.
In a shell and tube heat exchanger, the shell side fluid velocity can‟t be changed by changing the_________________?
A. Tube pitch
B. Tube diameter
C. Tube layout
D. Number of baffles
For heat flow through very thick walled cylinder, use ___________mean radius?
A. Geometric
B. Logarithmic
C. Arithmetic
D. Either A. or C.
The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α 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 _________________?
A. D0.2
B. D-0.2
C. D-1.8
D. D1.8
Fruit juice (a heat sensitive material) can be concentrated in a ____________ evaporator?
A. High pressure
B. Falling film
C. Long tube
D. None of these
Finned tube heat exchangers__________________?
A. Give larger area per tube
B. Are used for smaller heat load
C. Facilitate very large temperature drop through tube wall
D. Use metal fins of low thermal conductivity
It is not recommended to use a 1-2 shell and tube heat exchanger for a particular heat duty, whenever the LMTD correction factor is___________________?
A. < 0.50
B. < 0.75
C. > 0.75
D. < 0.25
Multipass heat exchangers are used______________________?
A. For low heat load
B. Because of simplicity of fabrication
C. To obtain higher heat transfer co-efficient and shorter tube
D. To reduce the pressure drop
The purpose of providing expansion bellows in the shell of tubular exchanger is to _____________________?
A. Impart structural strength
B. Increase the heating load
C. Account for the uneven expansion of shell and tube bundles
D. Facilitate increase of shell length, if needed
Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the________________?
A. Low pressure drop
B. Flexibility possible in the baffle arrangement
C. Less corrosion problems
D. High heat transfer co-efficient
Prandtl number for most of dry gases is about________________?
A. 70
B. 0.72
C. 0.001
D. 150
Chemical Engineering Basics Mcqs
Boiling point of a solution according to Duhring’s rule is a linear function of the _____________ of water?
A. Boiling point (at the same pressure)
B. Density
C. Viscosity
D. Thermal conductivity
The range of electromagnetic spectrum important in heat transfer by radiation is ______________ microns?
A. 100-1000
B. 0.5-50
C. 0.38-0.78
D. 5-50
The equation, (NSt × N2/3 Pr) = f/2, is the ____________ analogy ?
A. Colburn
B. Prandtl
C. Reynolds
D. None of these
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) ?
A. 1/t4
B. T4
C. t4
D. 1/T4
Boiling point elevation for a strong and concentrated solution is found by Duhring’s rule, which states that at the same pressure, the boiling point of a solution is a linear function of the _______________ of pure water?
A. Boiling point
B. Kinematic viscosity
C. Dynamic viscosity
D. Density
In Biot number, the characteristic length used is the ratio of the _______________ of the solid?
A. Volume to surface area
B. Surface area to volume
C. Perimeter to surface area
D. Surface area to perimeter
Loss of heat from untagged steam pipe to the ambient air is by __________________?
A. Convection
B. Conduction
C. Radiation
D. All A., B. & C.
The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is_________________?
A. Sherwood number
B. Nusselt number
C. Schmidt number
D. Stanton number
Radiation energy is emitted by all the substances, which are above____________________?
A. 0°K
B. 100°C
C. 0°C
D. Room temperature
Nusselt number is a function of Prandtl number and ______________ number of fluid in natural convection heat transfer?
A. Grashoff
B. Stanton
C. Biot
D. Reynolds
The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the________________ ?
A. Solution has an elevation of boiling point
B. Evaporators operate at atmospheric pressure
C. Evaporators operate under vacuum
D. None of these
In case of a multipass shell and tube heat exchanger, the temperature drop in the fluid _______________?
A. And the wall is not related
B. And the wall are proportional to individual resistances
C. Is inversely proportional to the resistance across which the drop occurs
D. None of these
Which of the following has the lowest Prandtl number ?
A. Molten sodium (a coolant used in fast breeder reactor)
B. Transformer oil
C. Water
D. Dilute H2SO4
The unit of conductance in SI unit is_______________?
A. W/m2
B. W/m
C. W/°K
D. W/m°K
The Graetz number is concerned with the___________________
A. Absorption with chemical reaction
B. Mass transfer between a gas and a liquid
C. Heat transfer in turbulent flow
D. Heat transfer in laminar flow
Fqra cold viscous feed, backward feed gives _____________ than forward feed?
A. A higher capacity
B. Lower economy
C. A lower capacity
D. None of these
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 30°C. The boiling point of the solution is 110°C, 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____________________?
A. 3.06 × 105
B. 7.24 × 105
C. 6.12 × 105
D. 9.08 × 105
Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger ?
A. Corrosiveness & fouling characteristics
B. Viscosity
C. Pressure
D. Density
Dropwise condensation is promoted on a/an ______________ surface?
A. Coated
B. Oily
C. Glazed
D. Smooth
In a forward feed multiple effect evaporator unit__________________?
A. Transfer from effect to effect is done by pumps
B. Viscosity of liquid is highest in first effect
C. No pump is required to withdraw the product from the last effect
D. None of these
Steam economy in case of a triple effect evaporator will be _________________?
A. < 1
B. 1
C. > 1
D. Between 0 and 1
The heat transfer co-efficient in film type condensation is _______________ that for dropwise condensation?
A. Is same as
B. Lower than
C. Greater than
D. Half
The thickness of condensate layer in filmwise condensation depends on the__________________?
A. Surface configuration
B. Condensation rate
C. Liquid flow rate from the surface
D. All A., B. and C.
Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer cannot take place____________________?
A. From one part of a body to the another part of the same body
B. Between two bodies not in physical contact with each other
C. Between two bodies in physical contact with each other
D. Both B & C
In sub-cooled boiling ?
A. Temperature of the heating surface is less than the boiling point of the liquid
B. Temperature of the heating surface is more than the boiling point of the liquid
C. Very large vapour space is necessary
D. Bubbles from heating surface are absorbed by the mass of the liquid
For hot feed, forward feeding as compared to backward feeding results in ______________ economy?
A. Increased
B. No effect on
C. Decreased
D. None of these
The units of resistance to heat transfer is _____________________?
A. J.m-1.K-1
B. J.m-2.K-1
C. W.m-2.K-1
D. W-1m2K
When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is _______________?
A. Forced convection
B. Entry length problem in laminar forced conduction (developing thermal boundary layer)
C. Mixed convection (both free and forced)
D. Free convection
In Fourier’s law, the proportionality constant is called the______________________?
A. Thermal diffusivity
B. Heat transfer co-efficient
C. Thermal conductivity
D. Stefan-Boltzmann constant
Peclet number (Pe) is given by____________________?
A. Pe = Re.Pr
B. Pe = Pr/Re
C. Pe = Re/Pr
D. Pe = Nu.Re
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______________________?
A. 4000
B. 2000
C. 5000
D. 6000
An ejector is used to__________________?
A. Increase temperature
B. Increase pressure
C. Remove condensate
D. None of these
Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8. Pr n, is not valid, if the value of __________________?
A. n = 0.3 is used for cooling
B. n = 0.4 is used for heating
C. Reynolds number for the flow involved is > 10000
D. Reynolds number for the flow involved is < 2100
The overall resistance for heat transfer through a series of flat resistance, is the _____________ of the resistances?
A. Geometric mean
B. Average
C. Product
D. Sum
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is__________________?
A. 120.36
B. 4.36
C. 2.36
D. Dependent on NRe only
What is the logarithmic mean of r1 and r2 ?
A. (r1 – r2)/ln(r1/r2)
B. (r2 – r1)/ln(r1/r2)
C. (r1 – r2)/ln(r2/r1)
D. (r1 – r2)/-ln(r1/r2)
Out of the following four assumptions used in the derivation of the equation for LMTD [LMTD = (Δt1 – Δt2)/ln(Δt1/Δt2)], which one is subject to the largest deviation in practice ?
A. Constant specific heat
B. Constant rate of fluid flow
C. Constant overall heat transfer co-efficient.
D. No partial phase change in the system
In a cooling tower, water becomes cool by________________?
A. Loosing sensible heat
B. Loosing latent heat
C. Vaporisation due to heat loss to air
D. Heat transfer to surroundings
The rate of emission of radiation by a body does not depend upon the__________________?
A. Nature of the surface
B. Surface temperature of the body
C. Wavelength of radiation
D. Shape and porosity of the body
Which area is used in case of heat flow by conduction through a cylinder ?
A. Logarithmic mean area
B. Geometric mean area
C. Arithmetic mean area
D. None of these
With increase in temperature, the thermal conductivity of a gas ___________________?
A. Increases
B. Remain same
C. Decreases
D. May increase or decrease depending on the type of gas
The interchange factor for radiation heat transfer from surface ‘x’ to surface ‘y’ in case of an infinite parallel planes with emissivities εx & εy is given by_______________?
A. εx . εy
B. εx + εy
C. 1/εx + 1/εy
D. (εx + εy)/( εx + εy – εx . εy)
Thermal conductivity of a gas at low density, ___________ with increase in temperature ?
A. Remains unchanged
B. Increases
C. Decreases
D. May increase or decrease; depends on the gas
For a multipass shell and tube heat exchanger, the LMTD correction factor is always________________?
A. > 1
B. 1
C. < 1
D. Between 1 & 2
Prandtl number is the reciprocal of____________________?
A. Thermal diffusivity/Momentum diffusivity
B. Thermal diffusivity × Mass diffusivity
C. Thermal diffusivity × Momentum
D. Mass diffusivity × Momentum diffusivity
Nusselt number is the ratio of the ____________________?
A. Temperature difference to the temperature gradient at the wall
B. Temperature gradient of the wall to that across the entire pipe
C. Heat flux at the wall to that across the entire pipe
D. None of these
Chemical Reaction Mcqs
Heat transfer by ____________ may not necessarily require the presence of a medium?
A. Natural convection
B. Conduction
C. Forced convection
D. Radiation
Which of the following situations can be approximated to a steady state heat transfer system ?
A. Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C
B. 10 kg of dry saturated steam at 8 kgf/cm2 flowing through a short length of stainless steel pipe exposed to atmospheric air at 35°C
C. A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmospheric air at 35°C
D. A sub-cooled refrigerant liquid at 8°C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C
Use of transverse baffles in a shell and tube heat exchanger is done to increase the___________________?
A. Flow velocity
B. Rate of heat transfer
C. Turbulence of shell side fluid
D. All A., B. and C.
Evaporation by thermo compression results in the _________________________?
A. Realisation of multiple effect economy in a single effect
B. Saving of steam
C. Both A. and B.
D. None of these
The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of ‘n’ is exactly 4 for__________________?
A. Polished bodies only
B. All bodies
C. Black painted bodies only
D. A black body
Three materials A, B and C of equal thickness and of thermal conductivity of 20, 40 & 60 kcal/hr. m. °C respectively are joined together. The temperature outside of A and C are 30°C and 100°C respectively. The interface between B and C will be at a temperature of ____________ °C?
A. 95
B. 40
C. 70
D. 50
A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun ?
A. White paint
B. Yellow paint
C. Black paint
D. Grey paint
Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around _____________ metres/second?
A. 1
B. 20
C. 10
D. 30
Temperature profile in steady state heat transfer is________________?
A. Hyperbolic
B. Asymptotic
C. Parabolic
D. Linear
A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature difference across the wall is 36°C. The temperature difference across the layer A is ______________ °C?
A. 18
B. 12
C. 6
D. 24
Economy of a multiple effect evaporator depends upon the _____________________?
A. Heat balance consideration
B. Rate of heat transfer
C. Both of the above
D. Neither of the above
Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is ________________ law?
A. Dalton’s
B. Stefan’s
C. Wien’s
D. Kirchoff’s
Trap is used to remove ________________ from steam pipe lines?
A. Non-condensable
B. Condensate
C. Steam
D. None of these
Prandtl number is given by__________________?
A. hD/k
B. CP μ/a
C. CP μ/k
D. μ/h CP
Prandtl number is the ratio of________________?
A. Thermal diffusivity to mass diffusivity
B. Momentum diffusivity to thermal diffusivity
C. Momentum diffusivity to mass diffusivity
D. Thermal diffusivity to momentum diffusivity
In the free convection regime of pool boiling, the heat flux is proportional to__________________?
A. Δt1/2
B. Δt
C. Δt5/4
D. Δt2
Radiation heat losses from satisfactorily insulated high pressure boiler may be about _____________ percent?
A. 18
B. 7
C. 1
D. 26
In SI units, fouling factor is expressed in __________________?
A. m2°K/W
B. m2°K
C. W/m2°K
D. m°K/W
Kg of liquid evaporated per hour in an evaporator is defined as its_________________?
A. Capacity
B. Economy
C. Steam load
D. None of these