All Free Chemical Engineering MCQs with Answers

• A. Condensation
• B. Radiation
• C. Conduction
• D. Natural convection

Explanation: Thermal diffusivity, α = k/(ρCp), governs the penetration of temperature changes into a material and is central to heat conduction…

• A. 0
• B. 1
• C. > 1
• D. < 1

Explanation: A cross-flow exchanger does not achieve the ideal countercurrent temperature distribution, so its LMTD correction factor is below unity.

• A. Stefan-Boltzmann's
• B. Wien's displacement
• C. Planck's
• D. None of these

Explanation: Wien's displacement law states that the wavelength of maximum emission varies inversely with absolute temperature: λmaxT = constant.

• A. Low density
• B. High viscosity
• C. Partial ionisation
• D. Dense structure

Explanation: Water conducts heat relatively well among liquids because its polar molecules form a strongly connected, hydrogen-bonded structure…

• A. Transient heat conduction
• B. Natural convection
• C. Forced convection
• D. Radiation

Explanation: The Biot number, Bi = hLc/k, compares internal conduction resistance with surface convection resistance and is especially important in…

• A. Absorbs
• B. Transmits
• C. Reflects
• D. None of these

Explanation: A diathermanous material allows thermal radiation to pass through it, so it transmits radiation.

• A. Increases rapidly with temperature rise
• B. Is almost independent of temperature
• C. Both B. and C
• D. Is almost independent of pressure

Explanation: For a fixed concentration, boiling-point elevation is approximately ΔTb = Kb m, and its dependence on temperature and pressure is weak…

• A. Maximum resistance in the series
• B. Minimum resistance presents in the series
• C. Average of all resistances
• D. Sum of all resistances

Explanation: For conductive resistances arranged in series, the same heat rate passes through each resistance and the temperature drops add.

• A. 0.5
• B. 1
• C. > 2
• D. 1.5

Explanation: Prandtl and Reynolds analogies coincide when Pr = 1, because the momentum and thermal diffusivities are then equal.

• A. Having the value of Ao/Ai > 2
• B. Thick walled
• C. Thin walled having the value of Ao Ai/< 2
• D. Both B. and C.

Explanation: For a thin-walled cylinder, the inner and outer areas are close enough that their arithmetic mean can represent the heat-transfer area.

• A. Only counter-flow of fluids
• B. Only parallel-flow of fluids
• C. Smaller pressure drop compared to 1-2 exchanger
• D. Both counter and parallel-flow of the fluids

Explanation: In a 2-4 exchanger, the multiple tube passes and shell-side flow arrangement produce both parallel-flow and counter-flow sections.

• A. 0.75 D
• B. 0.50 D
• C. 0.25 D
• D. None of these

Explanation: A 25% baffle cut means that 25% of the shell diameter is removed from the baffle, leaving a baffle height of 75% of the shell inside…

• 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.

• 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.

• 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…

• 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…

• 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.

• 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…

• 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…

• 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.