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:
Increasing the liquor level in the evaporator results in the_______________?
A. Decreased capacity
B. Decreased effect of hydrostatic head
C. Increase in liquor film co-efficient
D. Increased true temperature drop
Correction is applied to LMTD for __________ flow?
A. Counter
B. Parallel
C. Cross
D. None of these
In natural convection heat transfer, the correlating parameter is the_______________________?
A. Eckert number
B. Graetz number
C. Grashoff number
D. Bond number
Multiple effect evaporators ar used to___________________?
A. Decrease the steam economy & the capacity
B. Increase the steam economy & the capacity
C. Increase the steam economy & decrease the capacity
D. Decrease the steam economy & increase the capacity
Heat transfer co-efficient (h1) for liquids increases with__________________?
A. Increasing temperature
B. Decreasing Reynolds number
C. Decreasing temperature
D. None of these
Steady state one dimensional heat flow by conduction as given by Fourier’s low does not assume that_______________?
A. Boundary surfaces are isothermal
B. There is no internal heat generation
C. Material is anisotropic
D. Constant temperature gradient exists
An evaporator while concentrating an aqueous solution from 10 to 40% solids evaporates 30000 kg of water. The amount of solids handled by the system in kg is___________________?
A. 4000
B. 4600
C. 9000
D. 3000
Analogy between mass and heat transfer is not applicable in case of____________________?
A. Same velocity profile or equal eddy diffusivities
B. Viscous heating or chemical reaction
C. Thermal or pressure mass diffusion
D. Both B. and C.
The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) ?
A. h0/K
B. 2K/h0
C. K/h0
D. h0/2K
Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be_________________?
A. 0.55
B. 0.45
C. 0.35
D. 0.85
The most conducive surface for dropwise condensation to occur is the _____________ surface?
A. Glazed & polished
B. Oily
C. Coated
D. Smooth
Shell side pressure drop in a shell and tube heat exchanger does not depend upon the_________________?
A. Tube diameter & pitch
B. Baffle spacing & shell diameter
C. Viscosity, density & mass velocity of shell side fluid
D. None of these
In evaporators, lowering the feed temperature_______________?
A. Reduces the economy
B. Increases the heating area required
C. Both A. and B.
D. Decreases the heating area required
In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient______________?
A. Is not affected
B. Decreases
C. Increases
D. May increase or decrease; depends on the feed
Intermittent tube cleaning is possible to be done in case of a _____________ evaporator?
A. Basket type
B. Calandria
C. Horizontal tube
D. None of these
Overall heat transfer co-efficient for cooling of hydrocarbons by water is about_________________?
A. 50 -100 W/m2.°K
B. 50 -100 Kcal/hr.m2.°C
C. 50 -100 BTU/hr. ft.2°F
D. 1000 – 1500 BTU/hr. ft.2°F
For small temperature difference, the heat transfer rate as per Newton’s law of cooling is proportional to (where, Δt = excess temperature) ?
A. Δt
B. Δt3
C. Δt2
D. √(Δt)
Chemical Reaction Mcqs
The ratio of total radiating power to the absorptivity of the body depends upon the _____________ as per Kirchoff‟s law?
A. Nature of the body
B. Wavelength of radiation
C. Temperature of the body
D. None of these
Steam side heat transfer co-efficient in an evaporator is in the range of ______________ kcal/hr.m2°C?
A. 100-500
B. 10-50
C. 1000-1500
D. 5000-15000
The main function of baffles provided in a shell and tube heat exchanger is to______________?
A. Hold the tubes in position
B. Enhance turbulence
C. Facilitate the cleaning of outer tube surface
D. All A , B & C
Boiling point elevation of an ideal solution_______________?
A. Increases rapidly with temperature rise
B. In independent of pressure
C. Decreases rapidly with temperature rise
D. Both B. and C.
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) ?
A. 1000
B. 800
C. 727
D. 1200
Which is the most suitable for the concentration of foamy & frothy liquors ?
A. Open pan evaporator
B. Long tube vertical evaporator
C. Agitated film evaporator
D. None of these
Air is best heated with steam in a heat exchanger of__________________?
A. Double pipe type with fin on steam side
B. Plate type
C. Double pipe type with fin on air side
D. Shell and tube type
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 ______________?
A. 3.5
B. 0.025
C. 5.6
D. 0.0035
The value of Stefan-Boltzmann constant in SI unit is_________________?
A. 5.6697 × 10-8W/m2.°K4
B. 5.6697 × 10-8kcal/m2. °K4
C. 0.1714 × 10-8W/m2.°K4
D. 0.1714 × 10-8kcal/m2. °K4
What is the thermal conductivity of a perfect heat insulator ?
A. Zero
B. ∞
C. One
D. Between 0 and ∞
The ratio of momentum diffusivity to thermal diffusivity is the ______________ number?
A. Prandtl
B. Stanton
C. Nusselt
D. Grashoff
A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. 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 60°C is_________________?
A. 555
B. 0.55
C. 55.5
D. 0.15
Heat transfer occurs by natural convection because change in temperature causes difference in__________________?
A. Thermal conductivity
B. Density
C. Viscosity
D. Heat capacity
The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as______________?
A. (ΔT)1/2
B. (ΔT)1/4
C. (ΔT)5/4
D. (ΔT)3/4
If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length________________?
A. ha = 0.5 hl
B. ha = 2hl
C. ha = hl
D. ha = 0.75 hl
Harmonic mean temperature difference is given by_________________?
A. 2 (ΔT1 . ΔT2)/(ΔT1 – ΔT2)
B. 2 (ΔT1 . ΔT2)/(ΔT1 + ΔT2)
C. √(ΔT1 . ΔT2)
D. (ΔT1 – ΔT2)/(ΔT1 . ΔT2)
200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, Nc = 0.5 × 10-3 kg/m2.s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m2/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid)?
A. 0.05
B. 0.5
C. 0.1
D. 0.15
Fourier’s law of heat conduction applies to _____________ surfaces?
A. Non-isothermal
B. Isothermal
C. Both A. and B.
D. Neither A. and B.
Which of the following is generally considered as opaque surface towards radiations ?
A. Gases
B. Liquids
C. Solids
D. Both B. and C.
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_____________?
A. Horizontal heat exchanger with steam on tube side
B. Vertical heat exchanger with steam on shell side
C. Vertical heat exchanger with steam on tube side
D. Horizontal heat exchanger with steam on shell side
The steam ejector is used to__________________?
A. Superheat the steam
B. Create vacuum
C. Remove condensate from the steam pipelines
D. None of these
Heat flux is the time rate of heat transfer per unit_______________?
A. Volume
B. Area
C. Length
D. None of these
The actual temperature drop across the heating surface in an evaporator depends on the_________________?
A. Depth of liquid over heating surface
B. Feed
C. Pressure difference between steam chest and vapour space
D. All A., B. and C.
Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the________________?
A. Average temperature of the fin
B. Surrounding temperature
C. Temperature of the fin end
D. Constant temperature equal to that of the base
Thermal conductivity of a conducting solid material depends upon its_______________?
A. Porosity
B. Temperature
C. Both A. & B.
D. Neither A. nor B.
When vaporisation takes place directly at the heating surface, it is called________________?
A. Vapour binding
B. Nucleate boiling
C. Film boiling
D. None of these
As per Kirchoff‟s law, the ratio of the total radiating power to the absorptivity of a body depends on the_______________?
A. Temperature of the body only
B. Nature of material of body
C. Both A. and B.
D. Wavelength of monochromatic radiation
Fourier’s law applies to the heat transfer by__________________?
A. Radiation
B. Convection
C. Conduction
D. All A., B. & C.
The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by__________________?
A. Giving the surface a mirror finish
B. Painting the surface white (with aluminium paint)
C. Painting the surface black
D. Roughening the surface
Heat produced when a steady state current, I passes through an electrical conductor having resistance, ‘R’ is___________________?
A. IR2
B. I2R
C. IR
D. I2R2
In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to _____________ the velocity head?
A. Square root of
B. Four times
C. Twice
D. Square of
The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is – 5°C. The outside wall temperature is___________________?
A. 30°C
B. 25°C
C. 35°C
D. 40°C
Dittus-Boelter equation cannot be used for molten metals mainly due to its very low_____________________?
A. Prandtl number
B. Thermal conductivity
C. Grashoff number
D. Viscosity
Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively) ?
A. C/E
B. CE
C. E/C
D. 1/CE
Which of the following is unimportant in forced convection ?
A. Prandtl number
B. Reynolds number
C. Grashoff number
D. None of these
Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the _____________ zone?
A. Transition
B. Laminar
C. Both A & B
D. Highly turbulent
The number of kg vaporised per kg of steam fed to the evaporator is defined as____________?
A. Rate of evaporation
B. Capacity
C. Economy
D. Rate of vaporisation
Chemical Engineering Basics Mcqs
Vacuum is generally maintained in the vapour space of an evaporator mainly to__________________?
A. Get economical temperature difference by using moderate pressure steam
B. Concentrate heat sensitive materials
C. Facilitate forward feeding in multiple effect evaporation
D. Achieve very high concentration of the final product
With increase in porosity, the thermal conductivity of a solid substance__________________?
A. Remains unchanged
B. Decreases
C. Increases
D. May increase or decrease; depends on the solid
Which type of heat exchanger is preferred for heavy heat loads ?
A. Plate fine
B. Double pipe
C. Series and parallel set of shell and tube
D. None of these
The unit of heat transfer co-efficient in SI unit is____________________?
A. W/m°K
B. W/m2°K
C. J/M2°K
D. J/m°K
If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid_________________?
A. Remains unchanged
B. Increases or decreases depending on number of shell passes
C. Increases
D. Decreases
Fouling factor_____________________?
A. Does not provide a safety factor for design
B. Is a dimensionless quantity
C. Accounts for additional resistances to heat flow
D. None of these
As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient ?
A. Continues to decrease
B. Continues to increase
C. Goes through a minimum
D. Goes through a maximum
The equivalent diameter for pressure drop is ________________ that for heat transfer?
A. Smaller than
B. Equal to
C. Greater than
D. Not related with
Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid ?
A. Vent
B. Bleed point
C. Catchall
D. Baffle
In a heat exchanger, floating head is provided to____________________?
A. Increase the heat transfer area
B. Facilitate cleaning of the exchanger
C. Relieve stresses caused by thermal expansion
D. Increase log mean temperature gradient
Electromagnetic radiations propagate in vacuum with a velocity of _______________ metre/second?
A. 3 × 1010
B. 3 × 108
C. 3 × 105
D. 3 × 1012
With the increase of temperature, the Col-burn jH factor_____________________?
A. Increases
B. Remains unchanged
C. Decreases
D. May increase or decrease; depending on temperature
In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side ______________ the heat transfer rate?
A. Increases
B. Does not affect
C. Decreases
D. May increase or decrease, depends on the type of baffle
The advantage of backward feed multiple effect evaporators over forward feed units is that___________________?
A. There is no additional cost of pumping
B. Heat sensitive material can be handled
C. Most concentrated liquid is at highest temperature
D. Equal heat transfer co-efficients exist in various effects
Film boiling is usually not desired in commercial equipments, because____________________?
A. The heat transfer rate is low in view of the large temperature drop
B. It is not economic
C. It is difficult to maintain
D. None of these
A dephlegmator is a_____________________?
A. Vacuum evaporator
B. Total condenser
C. Partial condenser
D. Double pipe heat exchanger
Reynold’s analogy states that (where, St = Stanton number f = friction factor) ?
A. St = f/2
B. St = 4f
C. St = f/4
D. St = f1/2
Heat transfer by natural convection is enhanced in system with__________________?
A. Low temperature gradients
B. High co-efficient of thermal expansion
C. High viscosity
D. Low density change with temperature
At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical ?
A. 1
B. 1
D. None of the above
Heat flux through several resistances in series in analogous to the current flowing through several_____________________?
A. Capacitors in series
B. Resistances in parallel
C. Resistances in series
D. None of these
For a counter current heat exchanger with Ti h = 80°C, T°c = 60°C, T°h = 50°C and Ti c = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy___________________?
A. d2T/dZ2 < 0
B. d2T/dZ2 = 0
C. d2T/dZ2 > 0
D. dT/dZ = 0
For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally ?
A. Decreases
B. Remains unchanged
C. Increases
D. Increases exponentially
With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer ?
A. Decreases
B. Increases exponentially
C. Increases
D. Remain unaffected
Double pipe heat exchangers are preferably useful, when____________________?
A. Overall heat transfer co-efficient is very high
B. Requirement of heat transfer area is low
C. High viscosity liquid is to be cooled
D. A corrosive liquid is to be heated
Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is_________________?
A. > 1
B. < 1
C. 1
D. > 5
Choose the most important factor on which the heat conducted through a wall in a unit time will depend on ?
A. Material of the wall
B. Area of the wall perpendicular to heat flow
C. Thickness of the wall
D. Temperature difference between the two surfaces of the wall
Film boiling occurs at ________________ pressure?
A. Sub-atmospheric
B. Atmospheric
C. Negative
D. Very high
At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the___________________?
A. Turbulent core
B. Buffer zone
C. Both A. and B.
D. Viscous sub-layer
‘Fouling factor’ used in the design of a multipass shell and tube heat exchanger is a_____________________?
A. Conversion factor for individual film heat transfer co-efficient to overall heat transfer coefficient
B. Factor of safety
C. Non-dimensional factor
D. None of these
Chemical Heat Transfer Mcqs
Economy of an evaporator is influenced by the_____________________?
A. Steam pressure
B. Number of effect
C. Feed temperature
D. Both B. & C.
Circulation pump is located below the evaporator to___________________?
A. Avoid frequent priming
B. Avoid cavitation
C. Create more suction head
D. None of these
Which of the following has the highest thermal conductivity ?
A. Air
B. Brick
C. Water
D. Silver
A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case ?
A. The cooling rate will be the same for the two spheres and hence the two spheres will have equal temperatures at any instant
B. Both will absorb equal amount of radiation from the surrounding in the beginning
C. Both the spheres will emit equal amount of radiation per unit time in the beginning
D. Both B. & C.
A _____________ surface has the maximum thermal emissivity out of the following ?
A. White & smooth
B. Black & rough
C. Black & smooth
D. White & rough
1 BTU/hr.ft.°F is equal to _____________ kcal/hr. m.°C?
A. 1.49
B. 4.88
C. 1
D. None of these
Multiple effect evaporation is generally recommended, when the______________________?
A. Large scale evaporation of liquor is needed
B. Fuel is cheaply available
C. Corrosive liquids are to be concentrated
D. Evaporation on small scale is to be done
Steam is routed through the tube in case of a ______________ evaporator?
A. Short tube vertical
B. Horizontal tube
C. Basket type
D. Long tube vertical
The sum of reflectivity and absorptivity for an opaque body is equal to____________________?
A. 0
B. 1
C. 0.5
D. 2
In a backward feed multiple effect evaporator ___________________ ?
A. No pumps are required between successive effects
B. Feed flows from low pressure to high pressure
C. Feed is introduced in the first effect
D. None of these
For a given ambient air temperature with increase in the thickness of insulation of a hot cylindrical pipe, the rate of heat loss from the surface would ?
A. Increase
B. Decrease
C. First decrease and then increase
D. First increase and then decrease
The type of liquor circulation system to be ‘ employed in evaporators (viz. natural or forced circulation) is determined mainly by the ______________ of the liquid?
A. Viscosity
B. Thermal conductivity
C. Density
D. Corrosive nature
Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is________________?
A. 0.1
B. < 1
C. > 1
D. 1
Dropwise condensation occurs on ______________ surfaces?
A. Smooth clean
B. Clean and dirt free
C. Contaminated cooling
D. Polished
1000 kg of wet solids are to be dried from 60% to 20% moisture (by weight). The mass of moisture removed in kg is__________________?
A. 200
B. 520
C. 400
D. 500
For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are__________________?
A. Never different
B. Different
C. Same
D. Linearly related
Value of Prandtl number for water ranges from_________________?
A. 100 to 500
B. 5 to 10
C. 1 to 2
D. 1000 to 2000