Free Heat Transfer Operations MCQs with Answers
645 Heat Transfer Operations MCQs from Chemical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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645 questions · page 11 of 33
- A. Remains unchanged
- B. Decreases
- C. Increases or decreases depending on number of shell passes
- D. Increases
Explanation: Increasing baffle spacing enlarges the shell-side flow area, so shell-side mass velocity and fluid velocity fall.
Correct answer: Decreases- A. J/M2°K
- B. W/m°K
- C. W/m2°K
- D. J/m°K
Explanation: The heat-transfer coefficient relates heat flux to temperature difference, so its SI unit is power per area per temperature difference…
Correct answer: W/m2°K- A. Series and parallel set of shell and tube
- B. Plate fine
- C. Double pipe
- D. None of these
Explanation: Shell-and-tube exchangers can be arranged in series and parallel to provide a very large heat-transfer area and handle high heat duties.
Correct answer: Series and parallel set of shell and tube- A. Increases
- B. Decreases
- C. Remains unchanged
- D. May increase or decrease; depends on the solid
Explanation: Increasing porosity replaces more of the solid conducting path with gas-filled voids, and gases generally conduct heat much less…
Correct answer: Decreases- A. Capacity
- B. Rate of evaporation
- C. Economy
- D. Rate of vaporisation
Explanation: Economy is defined as the kilograms of solvent vapour produced per kilogram of steam consumed.
Correct answer: Economy- A. Laminar
- B. Transition
- C. Both A & B
- D. Highly turbulent
Explanation: In highly turbulent flow, mixing rapidly eliminates entrance-region effects, so the heat-transfer coefficient is essentially independent…
Correct answer: Highly turbulent- A. Reynolds number
- B. Prandtl number
- C. None of these
- D. Grashoff number
Explanation: Forced convection is governed mainly by Reynolds and Prandtl numbers, which represent flow regime and momentum-to-thermal diffusivity…
Correct answer: Grashoff number- A. C/E
- B. E/C
- C. CE
- D. 1/CE
Explanation: Economy equals evaporation rate divided by steam consumption, so rearranging gives steam consumption = capacity/economy.
Correct answer: C/E- 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