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 254 of 350
- A. Linear
- B. Hyperbolic
- C. Parabolic
- D. None of these
Explanation: With uniform internal heat generation in a cylinder, the radial conduction equation gives temperature varying with the square of radius.
Correct answer: Parabolic- A. Convection becomes important
- B. Conduction becomes important
- C. Sub-cooled boiling occurs
- D. Radiation becomes important
Explanation: Beyond the Leidenfrost point, a stable vapour film separates the liquid from the hot surface, reducing direct conduction and convection.
Correct answer: Radiation becomes important- A. Evaporation
- B. Extractive distillation
- C. Leaching
- D. Absorption
Explanation: A Duhring plot compares the boiling point of a solution with that of the pure solvent at the same pressure.
Correct answer: Evaporation- A. Steady state conduction
- B. Radiation
- C. Forced convection
- D. Natural convection
Explanation: View factor, also called configuration factor, specifies how much radiation leaving one surface reaches another.
Correct answer: Radiation- A. Scaling characteristics
- B. High viscosity
- C. Both A. & B.
- D. Neither A. nor B.
Explanation: Forced circulation keeps liquid moving rapidly through the heating tubes, reducing deposition and handling viscous liquids better.
Correct answer: Both A. & B.- A. Colburn
- B. None of these
- C. Prandtl
- D. Reynolds
Explanation: The Reynolds analogy equates the heat-transfer and momentum-transfer relationships, giving the approximate relation Stanton number, Nst…
Correct answer: Reynolds- A. Grashoff number
- B. Sherwood number
- C. Euler number
- D. Strouhal number
Explanation: The Grashof number measures the relative importance of buoyancy to viscous forces and is central to natural-convection heat transfer.
Correct answer: Grashoff number- A. Is thicker than hydrodynamic boundary layer
- B. And the hydrodynamic boundary layers are identical
- C. Is thinner than hydrodynamic boundary layer
- D. Disappears
Explanation: When Prandtl number exceeds one, momentum diffuses more rapidly than heat, so the velocity or hydrodynamic boundary layer is thicker.
Correct answer: Is thinner than hydrodynamic boundary layer- A. On polished surfaces
- B. None of these
- C. In the absence of agitation
- D. On rough surfaces
Explanation: Rough surfaces contain cavities that trap vapour and act as sites for bubble formation, so they promote nucleate boiling.
Correct answer: On rough surfaces- A. > 0.6
- B. < 0.5
- C. 0.5
- D. < 0.1
Explanation: For turbulent heat transfer, molecular conduction in the turbulent core is usually negligible when the Prandtl number is greater than…
Correct answer: > 0.6- A. 1200 W/m2.K
- B. 333 W/m2.K
- C. 894 W/m2.K
- D. 287 W/m2.K
Explanation: Add the fouling resistance to the clean exchanger resistance: 1/U = 1/400 + 1/2000 = 0.003 m²·K/W.
Correct answer: 333 W/m2.K- A. Grashoff
- B. Nusselt
- C. Prandtl
- D. Stanton
Explanation: The dimensionless group Cpμ/k compares momentum diffusivity with thermal diffusivity and is the Prandtl number.
Correct answer: Prandtl- A. May increase or decrease, depends on the vacuum
- B. Decreases
- C. Remain constant
- D. Increases
Explanation: Creating a vacuum lowers the boiling temperature, usually reducing the sensible heat needed to bring the feed to its boiling point…
Correct answer: Increases- A. Laminar
- B. Turbulent
- C. Creeping
- D. Transition region
Explanation: Turbulent flow produces strong mixing and a thinner thermal boundary layer, which raises the convective heat-transfer coefficient.
Correct answer: Turbulent- A. High heat transfer co-efficient
- B. Large temperature differentials
- C. Low pressure drop
- D. Less corrosion of tubes
Explanation: A floating head allows one tube sheet to move relative to the shell, accommodating differential thermal expansion.
Correct answer: Large temperature differentials- A. For fluids in laminar flow
- B. When Grashoff number is very important
- C. For fluids in turbulent flow
- D. For liquid metals
Explanation: The Dittus-Boelter correlation is an empirical relation for forced convection in fully developed turbulent flow, commonly for smooth…
Correct answer: For fluids in turbulent flow- A. Decreases linearly
- B. Decreases
- C. Remain same
- D. Increases
Explanation: For metallic conductors, increasing temperature generally increases the total emissivity because electrical resistivity and the associated…
Correct answer: Increases- A. Higher steam economy
- B. Lower steam economy
- C. Lower heat transfer area
- D. Higher solute concentration in the product
Explanation: In a multiple-effect evaporator, vapour from one effect supplies heat to the next, allowing the same steam to evaporate more solvent.
Correct answer: Higher steam economy- A. Square pitch
- B. Triangular pitch
- C. Diagonal square pitch
- D. None of these
Explanation: A triangular pitch fits more tubes into a given shell area and gives a higher shell-side heat-transfer coefficient.
Correct answer: Triangular pitch- A. Wien's displacement
- B. Planck's
- C. Kirchoff's
- D. Stefan-Boltzmann
Explanation: Kirchhoff's law states that at thermal equilibrium, emissive power divided by absorptivity is the same for bodies at the same temperature.
Correct answer: Kirchoff's