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 8 of 33
- A. Is not the same as baffle pitch
- B. Should be less than the inside diameter of the shell
- C. Should be less than one fifth the diameter of the shell
- D. None of these
Explanation: Baffle spacing is the distance between adjacent baffles, whereas baffle pitch is normally the centre-to-centre distance.
Correct answer: Should be less than the inside diameter of the shell- A. ∝ t
- B. ∝ √t
- C. ∝ 1/t
- D. Independent of 't'
Explanation: For laminar film condensation, heat passes through the condensate film mainly by conduction, giving h approximately equal to k/t.
Correct answer: ∝ 1/t- A. Alcohol
- B. Fruits jam
- C. Salt
- D. Distilled water
Explanation: Mechanical vapour recompression reuses the compressed vapour as the heating medium, making it especially useful in evaporative production…
Correct answer: Distilled water- A. Excessive corrosion
- B. Its evaporation loss
- C. Uneconomic LMTD
- D. Decrease in heat exchanger efficiency
Explanation: Keeping cooling-water outlet temperature below about 50°C limits corrosion, especially because higher temperatures accelerate corrosion…
Correct answer: Excessive corrosion- A. Forced convection
- B. Transient conduction
- C. Natural convection
- D. Steady state conduction
Explanation: The Fourier number, Fo = αt/L², compares heat diffusion through a body with the time available for diffusion.
Correct answer: Transient conduction- A. Sphere
- B. Cylinder
- C. Cube
- D. Equal for all the three
Explanation: For equal masses and the same material, the object with the largest surface-area-to-volume ratio cools fastest under comparable…
Correct answer: Cube- A. Dittus-Boelter equation
- B. None of these
- C. Nusselt equation
- D. Sieder-Tate equation
Explanation: The Sieder-Tate correlation includes a viscosity correction, commonly written as a ratio of bulk to wall viscosity, so it is suitable for…
Correct answer: Sieder-Tate equation- A. hf < hd
- B. hf > hd
- C. hf = hd
- D. hf could be greater or smaller than hd
Explanation: Dropwise condensation exposes much more of the cold surface directly to fresh condensate and avoids the insulating liquid film.
Correct answer: hf < hd- A. Eddies current
- B. Conduction
- C. Convection
- D. None of these
Explanation: The laminar sub-layer is a very thin region near the pipe wall where turbulent mixing is strongly suppressed.
Correct answer: Conduction- A. Single pass, fixed tube sheet
- B. None of these
- C. Three pass, fixed tube sheet
- D. U-tube
Explanation: A U-tube exchanger permits the tubes to expand freely when the shell-side fluid is much hotter, avoiding large thermal stresses between…
Correct answer: U-tube- A. 1-1.3
- B. 0.4 - 0.6
- C. 1.8-2
- D. 2 - 2.4
Explanation: In a single-effect evaporator, roughly 1 kg of steam supplies the latent heat needed to evaporate 1 kg of water, with the practical…
Correct answer: 1-1.3- A. Increases
- B. Decreases
- C. Remains unchanged
- D. May increase or decrease; depends on the liquid
Explanation: For most liquids, increasing temperature weakens intermolecular interactions and reduces thermal conductivity.
Correct answer: Decreases153. The purpose of providing a 'catchall' in the vapor line of an evaporator is to__________________?
- A. Create vacuum
- B. Regulate the vapor flow
- C. Arrest the entrained liquid
- D. Vent the non-condensable gases
Explanation: A catchall is placed in the vapor line to remove liquid droplets carried with the vapor, preventing entrainment into downstream equipment.
Correct answer: Arrest the entrained liquid154. The energy radiated from a surface Q at absolute temperature T is related as__________________?
- A. Q ∝ T2
- B. None of these
- C. Q ∝ T3
- D. Q ∝ T4
Explanation: The Stefan-Boltzmann law states that radiation from an ideal surface varies with the fourth power of absolute temperature, Q proportional…
Correct answer: Q ∝ T4155. Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity ?
- A. Coke breeze
- B. Refractory bricks
- C. Iron plate
- D. Aluminium foil
Explanation: Coke breeze is a dark, carbonaceous material and absorbs radiation more strongly than reflective aluminium foil or lighter refractory and…
Correct answer: Coke breeze- A. Hardness
- B. Dissolved solids content
- C. All A., B. and C.
- D. Suspended solids content
Explanation: Condensate has been formed from relatively pure steam, so it normally contains very little hardness, dissolved material, or suspended…
Correct answer: All A., B. and C.- A. Grey
- B. Yellow
- C. White
- D. Black
Explanation: Black paint absorbs most wavelengths of incident radiation and therefore has the greatest absorption coefficient among these colours.
Correct answer: Black- A. Heat transfer co-efficient
- B. Heat transfer area
- C. Fouling factor
- D. Heat transfer rate
Explanation: Baffles redirect the shell-side fluid and increase turbulence, reducing the thermal boundary layer and raising the heat-transfer…
Correct answer: Heat transfer co-efficient- A. 0
- B. 0.5
- C. 1
- D. 5
Explanation: Prandtl's and Reynolds' heat-transfer analogies coincide when the Prandtl number is unity, because momentum and thermal diffusivities are…
Correct answer: 1- A. Condensation
- B. Brinkman
- C. Stanton
- D. Grashoff
Explanation: The Brinkman number compares heat generated by viscous dissipation with heat conducted because of the imposed temperature difference.
Correct answer: Brinkman