All Free Chemical Engineering MCQs with Answers
Every Chemical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
6,983 questions · page 239 of 350
- 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: Decreases4765. 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 liquid4766. 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 ∝ T44767. 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- A. Increasing the tube length
- B. Enhancing the fluid pumping rate
- C. Keeping the heat transfer surface clean
- D. None of these
Explanation: Deposits and dirt add thermal resistance between the fluid and the wall, lowering the overall heat-transfer coefficient.
Correct answer: Keeping the heat transfer surface clean- A. Ellipse
- B. Circular arc
- C. Parabola
- D. Straight line
Explanation: For a body cooling in a large surroundings at nearly constant temperature, Newton's law gives dT/dt proportional to the temperature…
Correct answer: Straight line- A. White & rough
- B. Black & rough
- C. White & polished
- D. Black & polished
Explanation: Radiation is greatest from a surface with high emissivity, and black, rough surfaces have much higher emissivity than white or polished…
Correct answer: Black & rough- A. Mass diffusivity to thermal diffusivity
- B. Thermal diffusivity to mass diffusivity
- C. Momentum diffusivity to thermal diffusivity
- D. Thermal diffusivity to momentum diffusivity
Explanation: Prandtl number is defined as the ratio of momentum diffusivity, represented by kinematic viscosity, to thermal diffusivity.
Correct answer: Momentum diffusivity to thermal diffusivity4777. Rate of heat transfer by vaporisation from pools of water is affected by the ____________________?
- A. Nature of heating surface and distribution of bubbles
- B. Surface tension of water
- C. Viscosity of water
- D. All A., B. and C.
Explanation: Pool-boiling heat transfer depends on bubble formation and departure, which are influenced by surface condition, surface tension and…
Correct answer: All A., B. and C.- A. Facilitate removal of non-condensable gases
- B. Remove the product
- C. Admit the feed
- D. Create vacuum
Explanation: Bleed points allow trapped air and other non-condensable gases to escape from the evaporator.
Correct answer: Facilitate removal of non-condensable gases- A. Increases
- B. Decreases
- C. Remains unchanged
- D. Increases exponentially
Explanation: For steel, increasing temperature generally increases lattice scattering of conducting electrons, so thermal conductivity decreases over…
Correct answer: Decreases- A. Same as average heat transfer co-efficient for tube side
- B. Zero
- C. Infinity
- D. None of these
Explanation: At the tube entrance, the thermal boundary layer starts with essentially zero thickness, so the local temperature gradient and hence the…
Correct answer: Infinity