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 244 of 350
- A. Parallel
- B. Counter
- C. Cross
- D. None of these
Explanation: The simple LMTD applies directly to parallel- and counter-flow exchangers, but cross-flow and multipass arrangements require a correction…
Correct answer: Cross- A. Increased true temperature drop
- B. Increase in liquor film co-efficient
- C. Decreased effect of hydrostatic head
- D. Decreased capacity
Explanation: A higher liquid level increases the hydrostatic pressure and therefore the local boiling point, reducing the effective temperature driving…
Correct answer: Decreased capacity- A. D/5 and D
- B. D/2 and 2 D
- C. D/4 and 2 D
- D. D and 2 D
Explanation: For conventional shell-and-tube exchangers, baffle spacing is normally limited to about D/5 minimum and D maximum to maintain adequate…
Correct answer: D/5 and D- A. When heat transfer area required is very high
- B. When heat transfer area required is very low, i.e. (100-200 ft2).
- C. Because it occupies less floor area
- D. Because it is less costly
Explanation: Double-pipe exchangers are simple and economical for relatively small heat-transfer areas, commonly around 100–200 ft².
Correct answer: When heat transfer area required is very low, i.e. (100-200 ft2).- A. Zero
- B. Unity
- C. Same for all wavelengths
- D. Different for all wavelengths
Explanation: A grey body has constant monochromatic emissivity over all wavelengths, although its emissivity is less than unity.
Correct answer: Same for all wavelengths- A. 0
- B. 1
- C. > 1
- D. Between 0 and 1
Explanation: A black body absorbs and emits perfectly, so its emissivity is 1. A real surface emits less than a black body under the same conditions…
Correct answer: Between 0 and 1- A. None of these
- B. Sub-cooled
- C. Saturated nucleate
- D. Film
Explanation: Milk develops a protein- and fat-rich surface film during heating, which inhibits heat transfer and produces the characteristic…
Correct answer: Film4868. What is Nusselt number ?
- A. CP. μ/k
- B. hD/k
- C. h. CP/μ
- D. CP. μ/h
Explanation: The Nusselt number compares convective heat transfer with conduction across a fluid layer and is defined as Nu = hD/k, using the…
Correct answer: hD/k- A. Geometric mean temperature difference
- B. Arithmetic mean temperature difference
- C. Logarithmic mean temperature difference
- D. The difference of average bulk temperatures of hot and cold fluids
Explanation: For a heat exchanger, the temperature-driving force is represented by the logarithmic mean temperature difference, which accounts for the…
Correct answer: Logarithmic mean temperature difference- A. mCp/kL
- B. kL/mCp
- C. mCp/kμ
- D. kμ/mCp
Explanation: The Graetz number compares convective heat transport by the flowing stream with axial conduction, and is written as mCp/(kL), where m is…
Correct answer: mCp/kL- A. Nst α f
- B. Nst α NRe
- C. NNu α f
- D. NRe α f
Explanation: Reynolds analogy relates momentum and heat transfer, giving the Stanton number as proportional to the friction factor, commonly written…
Correct answer: Nst α f- A. Steel
- B. Nitrogen
- C. Carbon black
- D. Tar
Explanation: Gases generally conduct heat much less effectively than solids or liquids.
Correct answer: Nitrogen- A. Emissivity = 0
- B. Reflectivity = 1
- C. Absorptivity = 1
- D. Transmissivity = 1
Explanation: A black body absorbs all incident radiation, so its absorptivity is 1; correspondingly, its reflectivity and transmissivity are zero and…
Correct answer: Absorptivity = 1- A. High pressure
- B. None of these
- C. Backward feed
- D. Vacuum
Explanation: Vacuum evaporation lowers the boiling temperature, which is suitable for materials whose solubility decreases as temperature rises.
Correct answer: Vacuum- A. Condensation of the saturated vapor on a cold surface
- B. Boiling of a liquid on a hot surface
- C. Heat transfer between two highly viscous liquids
- D. Concentration of a corrosive solution by evaporation
Explanation: The Leidenfrost point is the surface temperature above which a stable vapour film forms between a hot surface and a boiling liquid.
Correct answer: Boiling of a liquid on a hot surface- A. Dowtherm
- B. Liquid metal (e.g. molten sodium)
- C. Mercury
- D. Fused salts (e.g., an eutectic mixture of 53% KNO3, 40% NaNO2and 7% NaNO3)
Explanation: Dowtherm, molten metals such as sodium, and fused salts are used as high-temperature heating media.
Correct answer: Mercury- A. 20.8
- B. 40.8
- C. 40.4
- D. 20.4
Explanation: For turbulent flow in a tube, the inside heat-transfer coefficient varies approximately as velocity^0.8.
Correct answer: 40.8- A. Through a metallic wall
- B. By direct contact of hot flue gas with air
- C. None of these
- D. hot material
- E. By heating an intermediate material (like chequor bricks) and then heating the air from this
Explanation: A regenerative air preheater first stores heat in a solid intermediate material such as chequer bricks.
Correct answer: By heating an intermediate material (like chequor bricks) and then heating the air from this- A. 6000
- B. 24000
- C. 60000
- D. 48000
Explanation: The 4000 kg of caustic soda represents 25% of the final solution, so the final solution is 4000/0.25 = 16000 kg.
Correct answer: 24000- A. 1.66
- B. 88.66
- C. 3.66
- D. Dependent on NRe only
Explanation: For fully developed laminar flow in a circular tube with constant wall temperature, the Nusselt number reaches the standard limiting value…
Correct answer: 3.66