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 242 of 350
- A. Grashoff number
- B. Prandtl number
- C. Thermal conductivity
- D. Viscosity
Explanation: The Dittus-Boelter correlation is unreliable for molten metals because their Prandtl numbers are extremely low, indicating very high…
Correct answer: Prandtl number- A. 25°C
- B. 30°C
- C. 35°C
- D. 40°C
Explanation: From Fourier’s law, q = KΔT/L, so the temperature difference is 10 × 0.16/0.04 = 40°C.
Correct answer: 35°C- A. Four times
- B. Twice
- C. Square root of
- D. Square of
Explanation: In a multipass exchanger, the return bends cause a pressure loss commonly taken as four velocity heads.
Correct answer: Four times- A. IR
- B. I2R
- C. IR2
- D. I2R2
Explanation: The electrical heating rate is given by Joule’s law, P = I²R, where current squared multiplied by resistance gives heat produced per unit…
Correct answer: I2R- A. Convection
- B. Radiation
- C. Conduction
- D. All A., B. & C.
Explanation: Fourier’s law relates conductive heat flux to the temperature gradient, q = −k(dT/dx).
Correct answer: Conduction- A. Nature of material of body
- B. Wavelength of monochromatic radiation
- C. Both A. and B.
- D. Temperature of the body only
Explanation: Kirchhoff’s law for total radiation gives E/α = Eᵦ, the emissive power of a blackbody at the same temperature.
Correct answer: Temperature of the body only- A. Nucleate boiling
- B. Film boiling
- C. Vapour binding
- D. None of these
Explanation: In nucleate boiling, vapour bubbles form directly at the heated surface and detach into the liquid.
Correct answer: Nucleate boiling- A. Temperature
- B. Both A. & B.
- C. Porosity
- D. Neither A. nor B.
Explanation: Thermal conductivity varies with temperature and is strongly affected by porosity because pores usually contain poorly conducting gas.
Correct answer: Both A. & B.- A. Surrounding temperature
- B. Average temperature of the fin
- C. Temperature of the fin end
- D. Constant temperature equal to that of the base
Explanation: Fin efficiency compares actual heat transfer with the maximum possible transfer if the entire fin were maintained at the base temperature.
Correct answer: Constant temperature equal to that of the base- A. All A., B. and C.
- B. Depth of liquid over heating surface
- C. Pressure difference between steam chest and vapour space
- D. Feed
Explanation: The effective temperature drop is influenced by the steam-to-vapour-space pressure difference, liquid depth and its boiling-point effect…
Correct answer: All A., B. and C.- A. Length
- B. Area
- C. Volume
- D. None of these
Explanation: Heat flux is heat-transfer rate divided by the area normal to heat flow, so its units are W/m².
Correct answer: Area- A. Remove condensate from the steam pipelines
- B. Superheat the steam
- C. Create vacuum
- D. None of these
Explanation: A steam ejector converts the pressure energy of motive steam into a high-velocity jet, which entrains air or vapour and produces a vacuum.
Correct answer: Create vacuum- A. Vertical heat exchanger with steam on tube side
- B. Vertical heat exchanger with steam on shell side
- C. Horizontal heat exchanger with steam on tube side
- D. Horizontal heat exchanger with steam on shell side
Explanation: Placing steam on the shell side allows condensation over the outside of the tubes, while cooling water flows inside them.
Correct answer: Vertical heat exchanger with steam on shell side- A. Both B. and C.
- B. Solids
- C. Liquids
- D. Gases
Explanation: Solids and most liquids absorb or reflect thermal radiation rather than transmitting it, so they are generally treated as opaque.
Correct answer: Both B. and C.- A. Both A. and B.
- B. Non-isothermal
- C. Isothermal
- D. Neither A. and B.
Explanation: Fourier’s law relates conductive heat flux to the temperature gradient, and it can be applied with respect to isothermal surfaces as well…
Correct answer: Both A. and B.- A. √(ΔT1 . ΔT2)
- B. 2 (ΔT1 . ΔT2)/(ΔT1 - ΔT2)
- C. 2 (ΔT1 . ΔT2)/(ΔT1 + ΔT2)
- D. (ΔT1 - ΔT2)/(ΔT1 . ΔT2)
Explanation: The harmonic mean of two temperature differences is twice their product divided by their sum. Therefore, ΔT_h = 2ΔT1ΔT2/(ΔT1+ΔT2).
Correct answer: 2 (ΔT1 . ΔT2)/(ΔT1 + ΔT2)- A. ha = hl
- B. ha = 0.75 hl
- C. ha = 0.5 hl
- D. ha = 2hl
Explanation: For laminar flow over a flat plate, the local coefficient varies approximately as x⁻¹ᐟ².
Correct answer: ha = 2hl- A. Density
- B. Viscosity
- C. Thermal conductivity
- D. Heat capacity
Explanation: Heating changes fluid density, causing the warmer and cooler regions to rise or sink differently under gravity.
Correct answer: Density- A. 555
- B. 55.5
- C. 0.55
- D. 0.15
Explanation: For a lumped sphere, the time constant is ρc_pr/(3h) = 800 s. Since (60−30)/(90−30) = 0.5, t = 800 ln 2 = 554 s ≈ 0.15 h, so the very…
Correct answer: 0.15- A. Stanton
- B. Nusselt
- C. Prandtl
- D. Grashoff
Explanation: The Prandtl number is the ratio of momentum diffusivity, ν, to thermal diffusivity, α: Pr = ν/α.
Correct answer: Prandtl