Chemical Heat Transfer MCQs – 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:
In forced convection, the heat transfer depends on _______________?
A. Re, Pr
B. Re, Gr
C. Mainly Gr
D. Re only
A composite flat wall of a furnace is made of two materials ‘A’ and ‘B’. The thermal conductivity of ‘A’ is twice of that of material ‘B’, while the thickness of layer of ‘A’ is half that of B. If the temperature at the two sides of the wall are 400 and 1200°K, then the temperature drop (in °K) across the layer of material ‘A’ is________________?
A. 125
B. 150
C. 133
D. 160
The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is_____________________?
A. 12.0 kW/m2
B. 11.2 kW/m2
C. 14.6 kW/m2
D. 16.5 kW/m2
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________________?
A. Very low Grashoff number
B. Low Reynold’s number
C. Molten metals
D. All A., B. and C.
Kirchoff’s law is applicable to________________?
A. Total radiation only
B. Monochromatic radiation only
C. Both A. and B.
D. Only volumes and not to surfaces
Agitated film evaporator is suitable for concentrating _____________ liquids?
A. Very thin
B. Viscous
C. Foaming
D. Corrosive
The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. 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____________________?
A. 71.2
B. 77.2
C. 63.8
D. 48.7
When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as ___________________ boiling?
A. Nucleate
B. Pool
C. Transition
D. Film
The main purpose of providing fins on heat transfer surface is to increase the_________________?
A. Mechanical strength of the equipment
B. Temperature gradient
C. Heat transfer area
D. Heat transfer co-efficient
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__________________?
A. 10
B. 2
C. 0.5
D. 100
Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger ?
A. Convective heat transfer co-efficient
B. Tube side pressure drop and the heat transfer rate
C. Effective tube surface area for convective heat transfer
D. All A. B. and C.
With increase in temperature, the thermal conductivity of non-metallic amorphous solids_________________?
A. Remain constant
B. Increases
C. Decreases
D. First decreases upto certain temperature and then increases
A black body when hot, emits heat radiation of _____________ wavelengths?
A. Large
B. Small
C. All
D. One fixed
Chemical Engineering Basics Mcqs
Tube pitch is the _______________ of tube diameters and the clearances?
A. Sum
B. Ratio
C. Difference
D. None of these
Heat transfer rate per unit area is called_________________?
A. Thermal diffusivity
B. Heat flux
C. Heat transfer co-efficient
D. Thermal conductivity
The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are _______________?
A. (COP)R = 2.5; (COP)HP = 1.5
B. (COP)R = (COP)HP = 0.6
C. (COP)R = 1.5; (COP)HP = 2.5
D. (COP)R = (COP)HP = 2.5
For what value of Prandtl number, the Col-burn analogy is valid ?
A. 1 to 103
B. 0.6 to 120
C. 0.06 to 120
D. 1 to 50
Colburn analogy is applicable for the value of Prandtl number from_________________?
A. 0.5 to 5
B. 0.6 to 120
C. 0.001 to 1
D. 120 to 400
The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at, where, K is the thermal conductivity and T is the temperature (in °K). The units of ‘a’ in SI system will be________________?
A. W/m
B. W/m.k
C. W/m.k2
D. None, ‘a’ is just a number
Heat exchanger tubes are never made of_________________?
A. Stainless steel
B. Plain carbon steel
C. Lead
D. Copper
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________________?
A. Shell and tube heat exchanger with air inside tubes and steam on shell side
B. Finned tube heat exchanger with air outside and steam inside
C. Finned tube heat exchanger with air inside and steam outside
D. Shell and tube heat exchanger with air on shell side and steam inside tubes
Multiple effect evaporators are commonly used in the manufacture of P. Paper Q. Superphosphate R. Sugar S. Fats ?
A. P and R
B. P and Q
C. P and S
D. R and S
In Joule’s experiment, an insulated container contains 20 kg of water initially at 25°C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms-2. Neglecting the heat capacity of agitator, the temperature of water (in °C) is________________?
A. 26.8
B. 34.4
C. 40.5
D. 25
The unit of heat transfer co-efficient is_________________?
A. BTU/hr. ft2°F
B. BTU/hr. °F
C. BTU/hr. °F. ft
D. BTU/hr. ft
Natural convection is characterised by__________________?
A. Grashoff number
B. Reynolds number
C. Peclet number
D. Prandtl number
A process stream of dilute aqueous solution flowing at the rate of10 Kg.s-1 is to be heated. Steam condensate at 95°C 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_______________?
A. Counter flow with process stream on shell side
B. Parallel flow with process stream on shell side
C. Counter flow with process stream on tube side
D. Parallel flow with process stream on tube side
The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe) ?
A. K/h0
B. hi/K
C. 2K/h0
D. 2hi/K
Presence of a non-condensing gas in a condensing vapour___________________?
A. Decreases thermal resistance
B. Increases the rate of condensation
C. Is desirable to increase the film co-efficient
D. None of these
A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions? Assume that the conductive heat transfer co-efficient is infinitely large ?
A. 5 minutes
B. 20 minutes
C. 10 minutes
D. 40 minutes
A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300°C and allowed to cool in natural air. Which one will cool the slowest ?
A. Plate
B. Cube
C. Sphere
D. All will cool at the same rate
Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2.°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the_________________?
A. Temperature of the incoming vapor is very high
B. Condensate is corrosive in nature
C. Lower pressure drop through the exchanger is desired
D. Higher condensing film co-efficient is desired
When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?
A. At high fluid velocity
B. When fluid flows past a smooth surface
C. At low velocity
D. None of these
During crystallisation, formation of crystal can occur in ______________ solution only?
A. Under-saturated
B. Supersaturated
C. Saturated
D. All A., B. and C.
Viscosity of gases ______________ with increase in temperature?
A. Decrease slowly
B. Increase slowly
C. Increase very rapidly
D. Remain unaffected
Chemical Reaction Mcqs
In case of surface condensers, a straight line is obtained on plotting 1/U vs. ____________ on an ordinary graph paper?
A. 1/V̅ -0.8
B. V̅ -2
C. V̅ -0.8
D. 1/ V̅ -2
Viscous & heat sensitive liquids are concentrated in _____________ evaporators?
A. Long tube
B. Open pan
C. Agitated film
D. None of these
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. Hyperbolic
C. Linear
D. Logarithmic
Grashoff number, which is defined as g . β (Ts – T∞) ρ2. L3/μ2, is proportional to the ratio of buoyancy force to ____________ force?
A. Viscous
B. Inertial
C. Elastic
D. None of these
In a 1-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is_________________?
A. Equal to the difference between hot and cold fluids inlet temperature
B. 0
C. ∞
D. Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature
A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because__________________?
A. Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect system
B. Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect
C. Boiling point elevation in a single effect system is much higher than that in any effect in a multi-effect system
D. Total heat transfer area of all the effects is -less than that in a single effect evaporator system
The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is ______________ compared to the same size pipes without fins?
A. Same
B. Less
C. More
D. Unpredictable
The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)?
A. α T4
B. α × 1/T
C. αT
D. Independent of T
According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor) ?
A. f
B. 2f
C. f/2
D. f/4
In forced circulation, the heating element is injected_________________?
A. Internally
B. Externally
C. Both of the above
D. Neither of the above
For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is_________________?
A. 0.33
B. 3
C. 1
D. 1.33
The separation of liquid droplets from the vapor is done by a/an _____________ in the evaporators?
A. Compressor
B. Entrainment separator
C. Steam ejector
D. Vacuum pump
Nusselt number (for forced convection heat transfer) is a function of the _____________ number?
A. Prandtl
B. Reynolds
C. Both of the above
D. Neither of the above
In case of _____________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid?
A. Low pressure
B. Pool
C. Nucleate
D. None of these
In a boiling curve, the peak heat flux is called the _____________ point?
A. Boiling
B. Leidenfrost
C. Nusselt
D. Burnout
Film condensation is promoted on a/an _______________________ surface?
A. Coated
B. Oily
C. Clean & smooth
D. Dirty
In a multiple effect evaporator, the effect of boiling point elevation is to______________________?
A. Reduce the capacity
B. Increase the economy
C. Reduce the economy
D. None of these
The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature) ?
A. (ΔT)4
B. (ΔT)2
C. (ΔT)3
D. √(ΔT)
In case of a vertical tube evaporator, with increase in the liquor level, the ____________ is increased?
A. Liquor-film co-efficient
B. Velocity of circulation
C. Both A. and B.
D. Neither A. and B.
Sensible heat of hot industrial flue gases cannot be recovered by a/an________________?
A. Regenerator
B. Economiser
C. Ceramic recuperator
D. None of these
A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________________?
A. Equal to that of the un-insulated steam pipe
B. Less than that of the un-insulated steam pipe
C. Greater than that for un-insulated steam pipe
D. Less than the steam pipe with 5 cms insulation
In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of___________________?
A. Concentrations
B. Activity co-efficients
C. Chemical potentials
D. Mass transfer co-efficients
The critical radius ‘r’ of insulation on a pipe is given by____________________?
A. r = k/2h
B. r = k/h
C. r = 2k/h
D. r = h/k
In an extended surface heat exchanger, fluid having lower co-efficient________________?
A. Can flow either inside or outside the tubes
B. Flows outside the tubes
C. Flows through the tube
D. Should not be used as it gives very high pressure drop
If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is________________?
A. Always higher than h2
B. Always between h1 and h2
C. Always less than h1
D. Dependent on metal resistance
Convective heat transfer, in which heat is transferred by movement of warmed matter is described by___________________?
A. Fick’s law
B. Newton’s law of cooling
C. Fourier’s law
D. None of these
Which of the following has the minimum absorptivity ?
A. Aluminium foil
B. Refractory bricks
C. Coal dust
D. Iron plates
In a forward feed multiple effect, the pressure build up will be____________________?
A. Highest at the inlet of the last effect
B. Least at the outlet of the last effect
C. Least at the inlet of the first effect
D. Highest at the outlet of the last effect
Thermal diffusivity is given by__________________?
A. k/ρCp
B. μCp/a
C. ρCp/k
D. μ/hCp
The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the___________________?
A. Nusselt number
B. Heat transfer area
C. Heating volume
D. None of these
In case of a vertical tube evaporator, with increase in the liquor level, the___________________?
A. Capacity of the evaporator is decreased
B. True temperature drop increases
C. Capacity of the evaporator is increased
D. Both B. and C.
Low thermal conductivity of heat insulating materials is due to its_______________?
A. High specific heat
B. High proportion of air space
C. Dense structure
D. None of these
Low thermal conductivity of heat insulating materials is due to its_________________?
A. High specific heat
B. High proportion of air space
C. Dense structure
D. None of these
In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always__________________?
A. < 1
B. 1
C. > 1
D. ∞
Small scale evaporation is done in a_________________?
A. Condenser
B. Heat exchanger
C. Multiple effect evaporator
D. Steam jacketed kettle
In a single effect evaporator, the economy is________________?
A. > 1
B. < 1
C. 1
D. None of these
Mode of heat transfer involved in the cooling of air cooled internal combustion engine is_________________?
A. Forced convection
B. Natural convection
C. Conduction
D. None of these
In counter flow compared to parallel flow, ?
A. Less surface area is required for a given heat transfer rate
B. LMTD is greater
C. Both A. and B.
D. More surface area is required for a given heat transfer rate
Heat exchangers operating, when the asymptotic range is reached, ?
A. Results in abruptly increased velocity
B. Results in making part of the heating surface inactive
C. Provide very large heat transfer co-efficient
D. None of these
In case of evaporators, liquid entrainment results primarily due to_________________?
A. High evaporation rate
B. High vacuum in the evaporator
C. Foaming of the solution
D. High heat transfer rate
Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube___________________?
A. Exit fluid temperature < wall temperature
B. Exit-fluid temperature > wall temperature
C. Exit fluid temperature = wall temperature
D. Graetz number > 100
Economy of a multiple effect evaporator is not influenced much by the_______________________?
A. Boiling point elevations
B. Rate of heat transfer
C. Temperature of the feed
D. Ratio of the weight of the thin liquor to thick liquor
What is the absorptivity of a black body?
A. 1
B. 0.78
C. 0
D. 0.95
Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger ?
A. Fouling characteristic
B. Corrosiveness
C. Viscosity
D. None of these
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is______________?
A. 88.66
B. 1.66
C. 3.66
D. Dependent on NRe only
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__________________?
A. 60000
B. 24000
C. 6000
D. 48000
In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred_________________?
A. By direct contact of hot flue gas with air
B. Through a metallic wall
C. By heating an intermediate material (like chequor bricks) and then heating the air from this hot material
D. None of these
The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by ______________ times, when the number of tube passes is increased to 8?
A. 40.4
B. 40.8
C. 20.8
D. 20.4
Which of the following is not used as a medium for high temperature heating ?
A. Liquid metal (e.g. molten sodium)
B. Mercury
C. Dowtherm
D. Fused salts (e.g., an eutectic mixture of 53% KNO3, 40% NaNO2and 7% NaNO3)
Leidenfrost point is a term concerned with the____________________?
A. Concentration of a corrosive solution by evaporation
B. Condensation of the saturated vapor on a cold surface
C. Heat transfer between two highly viscous liquids
D. Boiling of a liquid on a hot surface
Chemical Heat Transfer Mcqs
For concentrating an aqueous solution of a material like anhydrous Na2SO4, whose solubility decreases with rise in temperature, the most suitable evaporator is a _______________ evaporator?
A. Backward feed
B. Vacuum
C. High pressure
D. None of these
For an ideal black body______________________?
A. Absorptivity = 1
B. Emissivity = 0
C. Reflectivity = 1
D. Transmissivity = 1
Which of the following has the minimum thermal conductivity ?
A. Nitrogen
B. Carbon black
C. Steel
D. Tar
Reynold’s analogy states that_________________?
A. Nst α f
B. NNu α f
C. Nst α NRe
D. NRe α f
Graetz number is given by__________________?
A. mCp/kL
B. mCp/kμ
C. kL/mCp
D. kμ/mCp
Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately ?
A. 32
B. 45
C. 37
D. 50
For a cold dilute feed to produce thick viscous liquor, backward feeding as compared to forward feeding results in_____________________?
A. Increased economy
B. Lower capacity
C. Decreased economy
D. No effect on economy
In the equation Q = UAΔt; Δt is_________________________?
A. Arithmetic mean temperature difference
B. Geometric mean temperature difference
C. Logarithmic mean temperature difference
D. The difference of average bulk temperatures of hot and cold fluids
What is Nusselt number ?
A. h. CP/μ
B. hD/k
C. CP. μ/k
D. CP. μ/h
Black liquor generated during paper manufacture is concentrated in a___________________?
A. Single effect evaporator followed by a crystalliser
B. Single effect evaporator
C. Multiple effect evaporator
D. Multiple effect evaporators followed by a crystalliser
Boiling of milk in an open vessel is an example of ______________ boiling?
A. Film
B. Saturated nucleate
C. Sub-cooled
D. None of these
Crystal size in a continuous crystalliser depends upon the___________________?
A. Degree of turbulence
B. Rate of heat transfer
C. Degree of super-saturation
D. All A., B. and C
While the total emissivity of a perfect black body is unity, the same for a real body is__________________?
A. 1
B. 0
C. > 1
D. Between 0 and 1
A body is called grey if the monochromatic emissivity of the body is___________________?
A. Unity
B. Zero
C. Same for all wavelengths
D. Different for all wavelengths
Double pipe heat exchangers are used__________________?
A. When heat transfer area required is very high
B. When heat transfer area required is very low, i.e. (100-200 ft2).
C. Because it is less costly
D. Because it occupies less floor area
In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, D = inside diameter of the shell) ?
A. D/5 and D
B. D/4 and 2 D
C. D/2 and 2 D
D. D and 2 D