Free Heat Transfer Operations MCQs with Answers
645 Heat Transfer Operations MCQs from Chemical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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645 questions · page 15 of 33
- A. k/ρCp
- B. ρCp/k
- C. μCp/a
- D. μ/hCp
Explanation: Thermal diffusivity measures how quickly temperature disturbances spread through a material and is defined as α = k/(ρCp).
Correct answer: k/ρCp- A. Least at the inlet of the first effect
- B. Least at the outlet of the last effect
- C. Highest at the inlet of the last effect
- D. Highest at the outlet of the last effect
Explanation: In forward-feed operation, the feed and vapor move from the first effect toward the last, while pressure is progressively reduced to…
Correct answer: Least at the outlet of the last effect- A. Iron plates
- B. Coal dust
- C. Refractory bricks
- D. Aluminium foil
Explanation: A bright aluminium foil surface reflects most incident radiation and therefore has very low absorptivity.
Correct answer: Aluminium foil- A. Newton's law of cooling
- B. Fourier's law
- C. Fick's law
- D. None of these
Explanation: Convective heat transfer involves bulk movement of a fluid and is correlated by Newton’s law of cooling, Q = hAΔT.
Correct answer: Newton's law of cooling- A. Flows through the tube
- B. Flows outside the tubes
- C. Can flow either inside or outside the tubes
- D. Should not be used as it gives very high pressure drop
Explanation: The lower heat-transfer coefficient produces the greater thermal resistance, so that fluid is placed outside the tubes where extended fins…
Correct answer: Flows outside the tubes- A. r = 2k/h
- B. r = k/2h
- C. r = k/h
- D. r = h/k
Explanation: For a cylindrical pipe, the critical insulation radius is obtained by balancing the increase in outer convection area against the added…
Correct answer: r = k/h- A. Economiser
- B. Regenerator
- C. None of these
- D. Ceramic recuperator
Explanation: An economiser, regenerator, and ceramic recuperator can all recover sensible heat from hot flue gas by transferring it to incoming feed…
Correct answer: None of these- A. Velocity of circulation
- B. Liquor-film co-efficient
- C. Both A. and B.
- D. Neither A. and B.
Explanation: Raising the liquor level increases the static head over the heated tubes, which suppresses boiling and natural circulation.
Correct answer: Neither A. and B.289. The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature) ?
- A. (ΔT)3
- B. (ΔT)4
- C. (ΔT)2
- D. √(ΔT)
Explanation: In the nucleate-boiling region, empirical boiling correlations commonly give heat flux approximately proportional to the cube of excess…
Correct answer: (ΔT)3- A. Oily
- B. Coated
- C. Clean & smooth
- D. Dirty
Explanation: A clean, smooth surface is readily wetted by the condensate, allowing a continuous liquid film to form, which is film condensation.
Correct answer: Clean & smooth- A. Nucleate
- B. None of these
- C. Low pressure
- D. Pool
Explanation: Pool boiling occurs when a submerged heated surface boils a relatively stagnant liquid, allowing bubbles to rise and become absorbed into…
Correct answer: Pool292. The separation of liquid droplets from the vapor is done by a/an _____________ in the evaporators?
- A. Entrainment separator
- B. Steam ejector
- C. Compressor
- D. Vacuum pump
Explanation: An entrainment separator, also called a vapor-liquid separator or demister, removes liquid droplets carried along with evaporator vapor.
Correct answer: Entrainment separator- A. 3
- B. 0.33
- C. 1
- D. 1.33
Explanation: With the same total heat-transfer area and terminal temperature conditions, the total temperature driving force is distributed among the…
Correct answer: 1- A. αT
- B. α T4
- C. α × 1/T
- D. Independent of T
Explanation: Wien's displacement law states that the wavelength of maximum black-body emission is inversely proportional to absolute temperature: λmaxT…
Correct answer: α × 1/T- A. More
- B. Unpredictable
- C. Same
- D. Less
Explanation: Equivalent diameter is four times the flow area divided by the wetted perimeter.
Correct answer: Less- A. 0
- B. ∞
- C. Equal to the difference between hot and cold fluids inlet temperature
- D. Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature
Explanation: For concurrent flow, one terminal temperature difference is the difference between the two outlet temperatures.
Correct answer: 0- A. Elastic
- B. Viscous
- C. Inertial
- D. None of these
Explanation: The Grashof number compares buoyancy effects caused by density variation with viscous resistance in natural convection.
Correct answer: Viscous- A. Hyperbolic
- B. Parabolic
- C. Linear
- D. Logarithmic
Explanation: For one-dimensional steady conduction through a plane wall with constant thermal conductivity, the temperature gradient is constant, so…
Correct answer: Linear- A. Open pan
- B. Long tube
- C. None of these
- D. Agitated film
Explanation: Agitated-film evaporators provide rapid heat transfer with short residence time, making them suitable for viscous or heat-sensitive…
Correct answer: Agitated film- A. 1/V̅ -0.8
- B. V̅ -0.8
- C. V̅ -2
- D. 1/ V̅ -2
Explanation: For flow inside condenser tubes, the film coefficient commonly varies approximately as V̅^0.8.
Correct answer: 1/V̅ -0.8