Chemical Heat Transfer MCQs

Option A: Laminar flow

Option B: Co-current flow

Option C: Turbulent flow

Option D: Heat flow rate is independent of nature of flow

Correct Answer: Turbulent flow ✔

Option A: Remove dirt

Option B: Increase heat transfer rate

Option C: Reduce vibrations

Option D: Reduce heat transfer rate

Correct Answer: Increase heat transfer rate ✔

Option A: 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F

Option B: In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity

Option C: In unsteady state heat conduction, heat flows in the direction of temperature rise

Option D: In heat transfer by forced convection, Grashoff number is very important

Correct Answer: In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity ✔

Option A: Heat transfer from a hot body to cold body by the emission of heat waves is called radiation

Option B: Filmwise condensation takes place on non-wettable surfaces

Option C: The boiling point of a solution is affected by liquid head as well as boiling point elevation

Option D: None of these

Correct Answer: Filmwise condensation takes place on non-wettable surfaces ✔

Option A: Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection

Option B: The ratio NNu/NRe . Npr is called the Stanton number

Option C: The Peclet number is a measure of the ratio of energy transport by convection to that by conduction

Option D: The Colburn jH factor for heat transfer is given by Nst Npr

Correct Answer: The Colburn jH factor for heat transfer is given by Nst Npr ✔

Option A: Bubble size increases with the dynamic viscosity of the liquid in case of nucleate pool boiling

Option B: Thermal conductivity of a dry material is more than that of the damp material

Option C: Ratio of its capacity to economy equals the steam consumption in kg/hr in an evaporator

Option D: Vaporisation of organic substances in evaporator mostly causes foam formation

Correct Answer: Thermal conductivity of a dry material is more than that of the damp material ✔

Option A: In drying a solid containing moisture above the critical moisture content the number of degrees of freedom is 2

Option B: Sherwood number in mass transfer corresponds to Nusselt number in heat transfer and Schmidt number to Prandtl number

Option C: Forced convection is relatively more effective in increasing the rate of mass transfer, if Schmidt number is larger

Option D: Hot gases at moderate pressure are usually in the shell side of shell and tube heat exchangers. At higher pressure, however, it is customary to put gas in the tube side

Correct Answer: Forced convection is relatively more effective in increasing the rate of mass transfer, if Schmidt number is larger ✔

Option A: The emissivity of a surface decreases, if it gets corroded by atmospheric environment

Option B: The emissivity of a surface increases with increase in surface roughness

Option C: The emissivity of a polished surface is quite low

Option D: The emissivity of a non-metallic surface decreases with increase in the temperature

Correct Answer: The emissivity of a surface decreases, if it gets corroded by atmospheric environment ✔

Option A: In process heat exchangers, saturated steam is preferred over the superheated steam

Option B: The maximum is the emissive power of a surface at a temperature T1 occurs at a wavelength

Option C: When a vertical plate is heated in infinite air environmental under natural convection

Option D: A body at 925 K emits an energy of 1.42 x 1011ζW/m2 (ζ is the Stefan-Boltzmann constant) in

Correct Answer: B. The maximum is the emissive power of a surface at a temperature T1 occurs at a wavelength
of λ1. If the surface temperature is halved, the maximum in the emissive power would occur at
a wavelength of 0.5 λ1 ✔

Option A: jH = (St)(Pr)2/3 = f/2

Option B: jH = (St)(Pr)1/3 = f/2

Option C: jH = (St)2/3(Pr) = f/2

Option D: jH = (St)1/3(Pr) = f/2

Correct Answer: jH = (St)(Pr)2/3 = f/2 ✔

Option A: Economy of a multiple effect evaporator is not influenced by the boiling point elevation

Option B: Two identical cubes of iron and copper will have the same heat content under the same

Option C: Double pipe heat exchangers are mostly used in the field of refrigeration

Option D: Finned tube heat exchangers are suitable for heating air by steam

Correct Answer: B. Two identical cubes of iron and copper will have the same heat content under the same
conditions of temperature ✔

Option A: Higher is the temperature of the radiating body, higher is the wavelength of radiation

Option B: Logarithmic mean area is used for calculating the heat flow rate through a thick walled

Option C: The wavelength corresponding to maximum mono-chromatic emissive power increases with

Option D: Solid angle subtended by the finite surface at the radiating element is called the angle of

Correct Answer: B. Logarithmic mean area is used for calculating the heat flow rate through a thick walled
cylinder ✔

Option A: ‘Solvates’ are chemical compounds formed by solute with their solvents. When water is the

Option B: In heat exchanger calculations (Δt) weighted is used in place of Δt, when it involves more

Option C: Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted

Option D: In case of short tube vertical evaporators, area of central downtake is about 50 to 100% of the

Correct Answer: Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted ✔

Option A: Nu = (Re) (Pr) (Gz)

Option B: Nu = (Re) (Pr) (St)

Option C: Nu = (Re) (Pr)

Option D: Nu = (Pr) (St)

Correct Answer: Nu = (Re) (Pr) (St) ✔

Option A: With change in temperature, the radiant energy emitted by a black body remains unchanged

Option B: Absorptivity of a body approaches unity in case of diffuse reflection

Option C: Absorptivity of a perfectly black body is unity

Option D: Value of Stefan-Boltzmann constant is 4.876 × 10-8 KCal/m2.hr.°K4

Correct Answer: With change in temperature, the radiant energy emitted by a black body remains unchanged ✔

Option A: The condensing film co-efficient is about 3 times lower for vertical condenser as compared to the equivalent horizontal condenser for identical situation

Option B: Film co-efficient for vaporisation decreases as a result of vapor binding

Option C: In industrial practice, sub-cooling of condensate is required, when the condensate is a volatile

Option D: Overall heat transfer co-efficient in a heat exchanger is controlled by the value of the film coefficient,

Correct Answer: D. Overall heat transfer co-efficient in a heat exchanger is controlled by the value of the film coefficient,
which is higher ✔

Option A: The controlling resistance in case of heating of air by condensing steam is in the air fil

Option B: The log mean temperature difference (LMTD) for counter flow and parallel flow can be theoretically same when any one of the fluids (hot or cold fluid) passes through the heat exchanger at constant temperature

Option C: In case of a 1 – 2 shell and tube heat exchanger, the LMTD correction factor value increases

Option D: Phase change in case of a pure fluid at a given pressure from liquid to vapor or vice-versa occurs at saturation temperature

Correct Answer: C. In case of a 1 – 2 shell and tube heat exchanger, the LMTD correction factor value increases
sharply, when a temperature cross occurs ✔

Option A: Orifice baffles are never used in a shell and tube heat exchanger

Option B: Pressure drop on the shell side of a heat exchanger depends upon tube pitch also

Option C: In a horizontal tube evaporator, surface blanketing by air is avoided

Option D: Split ring type and pull through type floating heads are two commonly used floating heads is

Correct Answer: Orifice baffles are never used in a shell and tube heat exchanger ✔

Option A: Reciprocal of the resistance to heat flow is called thermal conductance

Option B: Unit of thermal conductance is W/°K

Option C: Thermal conductance of a wall of thickness ‘L’, thermal conductivity ‘k’ and heat flow area ‘A’ is kL/A

Option D: None of these

Correct Answer: C. Thermal conductance of a wall of thickness ‘L’, thermal conductivity ‘k’ and heat flow area ‘A’ is kL/A ✔

Option A: Swenson-Walker crystalliser is a batch crystalliser

Option B: Super saturation of the solution is the driving potential for a crystal growth

Option C: The liquor left after the removal of crystals from a solution is called mother liquor

Option D: The first stage of crystal formation is called nucleation

Correct Answer: Swenson-Walker crystalliser is a batch crystalliser ✔

Option A: Heat transfer by radiation cannot occur across an absolute volume

Option B: In case of a shell and tube heat exchanger, the pressure drop through the shell is proportional to the number of times the fluid crosses the bundle between baffles

Option C: Propagation velocity for travel of heat radiation through vacuum is equal to the velocity of the light

Option D: The amount of heat involved in the condensation or vaporisation of 1 kg of a fluid is the same

Correct Answer: Heat transfer by radiation cannot occur across an absolute volume ✔

Option A: Rate = Driving force × Resistance

Option B: Driving force = Rate × Resistance

Option C: Resistance = Driving force × Rate

Option D: Rate = Resistance/Driving force

Correct Answer: Driving force = Rate × Resistance ✔

Option A: Superheated steam is preferably not used for process heating because of its low heat transfer film co-efficient

Option B: In a shell and tube heat exchanger, the shell pressure drop is maximum for orifice baffles

Option C: S.I. unit of fouling factor is Watt/m2.°K

Option D: Longitudinal fins are used in extended surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube

Correct Answer: S.I. unit of fouling factor is Watt/m2.°K ✔

Option A: In case of heat transfer by purely forced convection, GR/Re 2 ≤ 1

Option B: The equivalent diameter of heat transfer for a duct of square cross-section (having each side as

Option C: Distillation process is not the same as evaporation

Option D: The effectiveness of nucleate boiling depends basically on the ease with which the bubbles are

Correct Answer: B. The equivalent diameter of heat transfer for a duct of square cross-section (having each side as
‘x’) is equal to 4x ✔

Option A: The capacity of an evaporator is reduced by the boiling point elevation

Option B: Corrosive liquid is normally passed through the tubes in a shell and tube heat exchanger

Option C: Steam jet ejector is used for vapor compression in a thermal recompression evaporator

Option D: Heat sensitive materials should be concentrated in high pressure evaporators

Correct Answer: Heat sensitive materials should be concentrated in high pressure evaporators ✔

Option A: Higher economy

Option B: Lower capacity

Option C: Both A. & B.

Option D: Lower economy

Correct Answer: Higher economy ✔

Option A: Forward

Option B: Backward

Option C: Parallel

Option D: None of these

Correct Answer: Backward ✔

Option A: 15 min

Option B: 22 min

Option C: 44 min

Option D: 51 min

Correct Answer: 51 min ✔

Option A: Cannot pass through vacuum

Option B: Travel in straight line

Option C: Can be reflected by a mirror

Option D: Both B. and C.

Correct Answer: D. Both B. and C. ✔

Option A: Increase

Option B: Decrease

Option C: Not affect

Option D: Increase the condensing film co-efficient as well as

Correct Answer: Decrease ✔

Option A: Absorptivity = 0

Option B: Transmissivity = 1

Option C: Reflectivity = 0

Option D: All A., B. & C.

Correct Answer: Transmissivity = 1 ✔

Option A: d0.8

Option B: d-0.2

Option C: d-1

Option D: d-1.8

Correct Answer: d-0.2 ✔

A. 4000
D. > 10000

Correct Answer: > 10000 ✔

Option A: Peclet

Option B: Prandtl

Option C: Stanton

Option D: Nusselt

Correct Answer: Prandtl ✔

Option A: Flow of fluid on the tube and shell sides

Option B: Oscillations in the flow of shell/tube sides fluid

Option C: Vibrations transmitted through piping and/or supports due to external reasons

Option D: All A., B. and C.

Correct Answer: D. All A., B. and C. ✔

Option A: 1

Option B: > 1

Option C: < 1

Option D: 0.1

Correct Answer: 1 ✔

Option A: 1

Option B: 1.74

Option C: 6.1

Option D: 37

Correct Answer: 1 ✔

Option A: Increase the cross-section of the shell side liquid

Option B: Force the liquid to flow parallel to the bank

Option C: Increase the shell side heat transfer co-efficient

Option D: Decrease the shell side heat transfer co-efficient

Correct Answer: Increase the shell side heat transfer co-efficient ✔

Option A: Dirhing’s

Option B: Heisler’s

Option C: Mollier’s

Option D: Cox

Correct Answer: A. Dirhing’s ✔

Option A: No

Option B: The least

Option C: The largest

Option D: Lower

Correct Answer: The largest ✔

Option A: Lewis relationship

Option B: Nusselt number

Option C: Kutateladze number

Option D: Froude number

Correct Answer: Lewis relationship ✔

Option A: Distillation

Option B: Crystallisation

Option C: Evaporation

Option D: Humidification

Correct Answer: Evaporation ✔

Option A: T1 – T2

Option B: T1 – Ta

Option C: T2 – Ta

Option D: None of these

Correct Answer: None of these ✔

Option A: Cumulatively increases

Option B: Cumulatively decreases

Option C: Remain constant

Option D: And the surface conductance increase

Correct Answer: Cumulatively increases ✔

Option A: Black

Option B: White lead

Option C: Grey

Option D: Light cream

Correct Answer: White lead ✔

Option A: Increases

Option B: Decreases

Option C: Remain constant

Option D: Passes through a maxima

Correct Answer: Passes through a maxima ✔

Option A: Radiation

Option B: Natural convection

Option C: Forced convection

Option D: Conduction

Correct Answer: Forced convection ✔

Option A: Condense steam

Option B: Release excess steam pressure by bleeding steam

Option C: Remove condensate and inert gases

Option D: None of these

Correct Answer: Remove condensate and inert gases ✔

Option A: Total

Option B: Monochromatic

Option C: Both A. & B.

Option D: Neither A. nor B.

Correct Answer: C. Both A. & B. ✔

Option A: Heat transfer co-efficient over the entire heat exchanger is not constant

Option B: There exists an unsteady state

Option C: The heat capacity is not constant and there is a phase change

Option D: None of these

Correct Answer: None of these ✔

Option A: Minimum

Option B: Maximum

Option C: Zero

Option D: Infinity

Correct Answer: Zero ✔

Option A: In the central core of the fluid

Option B: Uniformly distributed throughout the fluid

Option C: Mainly confined to a thin film of fluid near the surface

Option D: None of these

Correct Answer: Mainly confined to a thin film of fluid near the surface ✔

Option A: Thermal boundary layer lies inside the concentration boundary layer

Option B: Concentration boundary layer lies inside the thermal boundary layer

Option C: Thermal & concentration boundary layers are of equal thickness

Option D: Hydrodynamic (i.e., momentum) boundary layer is thicker than the other two

Correct Answer: Thermal boundary layer lies inside the concentration boundary layer ✔

Option A: Conduction

Option B: Radiation

Option C: Condensation

Option D: Natural convection

Correct Answer: Conduction ✔

Option A: 0

Option B: 1

Option C: > 1

Option D: < 1

Correct Answer: 1 ✔

Option A: Stefan-Boltzmann’s

Option B: Planck’s

Option C: Wien’s displacement

Option D: None of these

Correct Answer: C. Wien’s displacement ✔

Option A: Low density

Option B: High viscosity

Option C: Partial ionisation

Option D: Dense structure

Correct Answer: Partial ionisation ✔

Option A: Transient heat conduction

Option B: Natural convection

Option C: Forced convection

Option D: Radiation

Correct Answer: Transient heat conduction ✔

Option A: Absorbs

Option B: Reflects

Option C: Transmits

Option D: None of these

Correct Answer: Transmits ✔

Option A: Increases rapidly with temperature rise

Option B: Is almost independent of temperature

Option C: Is almost independent of pressure

Option D: Both B. and C

Correct Answer: D. Both B. and C ✔

Option A: √d

Option B: d

Option C: d2

Option D: d1.5

Correct Answer: d ✔

Option A: Maximum resistance in the series

Option B: Sum of all resistances

Option C: Average of all resistances

Option D: Minimum resistance presents in the series

Correct Answer: Sum of all resistances ✔

Option A: 0.5

Option B: 1

Option C: > 2

Option D: 1.5

Correct Answer: 1 ✔

Option A: Thin walled having the value of Ao Ai/< 2

Option B: Thick walled

Option C: Having the value of Ao/Ai > 2

Option D: Both B. and C.

Correct Answer: Thin walled having the value of Ao Ai/< 2 ✔

Option A: Reynolds

Option B: Nusselt

Option C: Grashoff

Option D: Both B. & C.

Correct Answer: D. Both B. & C. ✔

Option A: A section of the exchanger in which change in temperature of one stream equals the average

Option B: The size of the exchanger in which heat transfer rate is 1 kcal/hr

Option C: Both A. and B.

Option D: None of these

Correct Answer: A. A section of the exchanger in which change in temperature of one stream equals the average
driving force in the section ✔

Option A: Only counter-flow of fluids

Option B: Only parallel-flow of fluids

Option C: Both counter and parallel-flow of the fluids

Option D: Smaller pressure drop compared to 1-2 exchanger

Correct Answer: Both counter and parallel-flow of the fluids ✔

Option A: 0.25 D

Option B: 0.50 D

Option C: 0.75 D

Option D: None of these

Correct Answer: 0.75 D ✔

Option A: 180

Option B: 970

Option C: 3.97

Option D: None of these

Correct Answer: 180 ✔

Option A: Is not the same as baffle pitch

Option B: Should be less than one fifth the diameter of the shell

Option C: Should be less than the inside diameter of the shell

Option D: None of these

Correct Answer: Should be less than the inside diameter of the shell ✔

Option A: ∝ t

Option B: ∝ 1/t

Option C: ∝ √t

Option D: Independent of ‘t’

Correct Answer: ∝ 1/t ✔

Option A: Avoid buckling of tubes

Option B: Provide support for tubes

Option C: Decrease the pressure drop

Option D: Facilitate its lengthening, if needed

Correct Answer: Avoid buckling of tubes ✔

Option A: Alcohol

Option B: Distilled water

Option C: Salt

Option D: Fruits jam

Correct Answer: Distilled water ✔

Option A: Its evaporation loss

Option B: Excessive corrosion

Option C: Uneconomic LMTD

Option D: Decrease in heat exchanger efficiency

Correct Answer: Excessive corrosion ✔

Option A: Forced convection

Option B: Natural convection

Option C: Transient conduction

Option D: Steady state conduction

Correct Answer: Transient conduction ✔

Option A: Cube

Option B: Cylinder

Option C: Sphere

Option D: Equal for all the three

Correct Answer: Cube ✔

Option A: Dittus-Boelter equation

Option B: Sieder-Tate equation

Option C: Nusselt equation

Option D: None of these

Correct Answer: Sieder-Tate equation ✔

Option A: hf = hd

Option B: hf > hd

Option C: hf < hd

Option D: hf could be greater or smaller than hd

Correct Answer: hf < hd ✔

Option A: Eddies current

Option B: Conduction

Option C: Convection

Option D: None of these

Correct Answer: Conduction ✔

Option A: Single pass, fixed tube sheet

Option B: U-tube

Option C: Three pass, fixed tube sheet

Option D: None of these

Correct Answer: U-tube ✔

Option A: 0.4 – 0.6

Option B: 1-1.3

Option C: 1.8-2

Option D: 2 – 2.4

Correct Answer: 1-1.3 ✔

Option A: Increases

Option B: Decreases

Option C: Remains unchanged

Option D: May increase or decrease; depends on the liquid

Correct Answer: Decreases ✔

Option A: Create vacuum

Option B: Regulate the vapor flow

Option C: Vent the non-condensable gases

Option D: Arrest the entrained liquid

Correct Answer: Arrest the entrained liquid ✔

Option A: Super

Option B: Sensible

Option C: Latent

Option D: Both B. & C.

Correct Answer: Sensible ✔

Option A: Q ∝ T2

Option B: Q ∝ T4

Option C: Q ∝ T3

Option D: None of these

Correct Answer: Q ∝ T4 ✔

Option A: Aluminium foil

Option B: Refractory bricks

Option C: Iron plate

Option D: Coke breeze

Correct Answer: Coke breeze ✔

Option A: Exothermic

Option B: Mildly endothermic

Option C: Highly endothermic

Option D: None of these

Correct Answer: Exothermic ✔

Option A: Hardness

Option B: Dissolved solids content

Option C: Suspended solids content

Option D: All A., B. and C.

Correct Answer: D. All A., B. and C. ✔

Option A: Black

Option B: Yellow

Option C: White

Option D: Grey

Correct Answer: Black ✔

Option A: Fouling factor

Option B: Heat transfer area

Option C: Heat transfer co-efficient

Option D: Heat transfer rate

Correct Answer: Heat transfer co-efficient ✔

Option A: 0

Option B: 0.5

Option C: 1

Option D: 5

Correct Answer: 1 ✔

Option A: q = [2π k (Ti + T0)/2]/ln (ri/r0)

Option B: q = 2π ri k (Ti – T0)/(r0/ri)

Option C: q = 2π k (Ti – T0)/(r0/ri)

Option D: q = 2π k (Ti – T0)/[(r0 + ri)/2]

Correct Answer: D. q = 2π k (Ti – T0)/[(r0 + ri)/2] ✔

Option A: Increase by 1.8 times

Option B: Decrease by 22

Option C: Increase by 216

Option D: Remain unchanged

Correct Answer: Increase by 216 ✔

Option A: Condensation

Option B: Grashoff

Option C: Stanton

Option D: Brinkman

Correct Answer: Brinkman ✔

Option A: Keeping the heat transfer surface clean

Option B: Enhancing the fluid pumping rate

Option C: Increasing the tube length

Option D: None of these

Correct Answer: Keeping the heat transfer surface clean ✔

Option A: Open pan evaporation

Option B: Long tube vertical evaporator

Option C: Agitated film evaporator

Option D: None of these

Correct Answer: Open pan evaporation ✔

Option A: Ellipse

Option B: Straight line

Option C: Parabola

Option D: Circular arc

Correct Answer: Straight line ✔

Option A: White & rough

Option B: Black & rough

Option C: White & polished

Option D: Black & polished

Correct Answer: Black & rough ✔

Option A: Mass diffusivity to thermal diffusivity

Option B: Momentum diffusivity to thermal diffusivity

Option C: Thermal diffusivity to mass diffusivity

Option D: Thermal diffusivity to momentum diffusivity

Correct Answer: Momentum diffusivity to thermal diffusivity ✔

Option A: Nature of heating surface and distribution of bubbles

Option B: Surface tension of water

Option C: Viscosity of water

Option D: All A., B. and C.

Correct Answer: D. All A., B. and C. ✔