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 17 of 33
- A. Mainly Gr
- B. Re, Gr
- C. Re, Pr
- D. Re only
Explanation: Forced-convection correlations commonly express Nusselt number as a function of Reynolds and Prandtl numbers, such as Nu = f(Re, Pr).
Correct answer: Re, Pr- A. m°K/W
- B. W/m2°K
- C. m2°K
- D. m2°K/W
Explanation: Fouling factor is a thermal resistance per unit area, since it is added to heat-transfer resistance on an area basis.
Correct answer: m2°K/W323. In the free convection regime of pool boiling, the heat flux is proportional to__________________?
- A. Δt1/2
- B. Δt5/4
- C. Δt2
- D. Δt
Explanation: In the free-convection region before vigorous nucleate boiling, the pool-boiling heat flux varies approximately as the temperature excess…
Correct answer: Δt5/4- A. CP μ/a
- B. hD/k
- C. CP μ/k
- D. μ/h CP
Explanation: Using thermal diffusivity α = k/(ρCp) and momentum diffusivity ν = μ/ρ gives Pr = ν/α = μCp/k.
Correct answer: CP μ/k- A. Steam
- B. None of these
- C. Non-condensable
- D. Condensate
Explanation: A steam trap automatically discharges condensate and sometimes non-condensable gases while retaining live steam in the line.
Correct answer: Condensate- A. Wien's
- B. Dalton's
- C. Stefan's
- D. Kirchoff's
Explanation: Wien's displacement law states that the wavelength at maximum blackbody emission is inversely proportional to absolute temperature, λmaxT…
Correct answer: Wien's- A. Rate of heat transfer
- B. Heat balance consideration
- C. Both A. and B.
- D. Neither A. nor B.
Explanation: Evaporator economy is determined primarily from the heat and mass balance, especially how the vapour generated in one effect supplies heat…
Correct answer: Heat balance consideration- A. 6
- B. 12
- C. 18
- D. 24
Explanation: For layers in series, temperature drop is proportional to thermal resistance L/k.
Correct answer: 12- A. Asymptotic
- B. Hyperbolic
- C. Parabolic
- D. Linear
Explanation: For steady one-dimensional conduction through a plane wall with constant thermal conductivity and no heat generation, the heat flux is…
Correct answer: Linear- A. 1
- B. 10
- C. 20
- D. 30
Explanation: Tube-side water velocity is commonly kept near 1 m/s as an upper practical value in heat exchangers to limit erosion, vibration, and…
Correct answer: 1- A. Yellow paint
- B. White paint
- C. Black paint
- D. Grey paint
Explanation: Black surfaces absorb the greatest fraction of incident solar radiation because they have high absorptivity.
Correct answer: Black paint- A. Saving of steam
- B. Realisation of multiple effect economy in a single effect
- C. None of these
- D. Both A. and B.
Explanation: Thermo-compression recompresses the vapour so it can serve again as the heating medium, reducing fresh-steam consumption.
Correct answer: Both A. and B.- A. All A., B. and C.
- B. Flow velocity
- C. Turbulence of shell side fluid
- D. Rate of heat transfer
Explanation: Transverse baffles force the shell-side fluid across the tubes, increasing its velocity and turbulence.
Correct answer: All A., B. and C.- A. Conduction
- B. Radiation
- C. Forced convection
- D. Natural convection
Explanation: Radiation transfers energy through electromagnetic waves and can occur through a vacuum, unlike conduction and convection, which require…
Correct answer: Radiation- A. Temperature gradient of the wall to that across the entire pipe
- B. Heat flux at the wall to that across the entire pipe
- C. Temperature difference to the temperature gradient at the wall
- D. None of these
Explanation: The Nusselt number, Nu = hL/k, compares convective heat flux at a wall with the conductive heat flux through the fluid over the…
Correct answer: Heat flux at the wall to that across the entire pipe- A. Mass diffusivity × Momentum diffusivity
- B. Thermal diffusivity × Momentum
- C. Thermal diffusivity × Mass diffusivity
- D. Thermal diffusivity/Momentum diffusivity
Explanation: Prandtl number is the ratio of momentum diffusivity to thermal diffusivity, Pr = ν/α.
Correct answer: Thermal diffusivity/Momentum diffusivity337. For a multipass shell and tube heat exchanger, the LMTD correction factor is always________________?
- A. < 1
- B. > 1
- C. 1
- D. Between 1 & 2
Explanation: The LMTD correction factor accounts for the departure of a multipass exchanger from ideal countercurrent flow and is normally less than…
Correct answer: < 1- A. Decreases
- B. Increases
- C. Remains unchanged
- D. May increase or decrease; depends on the gas
Explanation: At low gas density, gas molecules travel relatively freely between collisions, and their thermal conductivity generally increases as…
Correct answer: Increases- A. Remain same
- B. Decreases
- C. Increases
- D. May increase or decrease depending on the type of gas
Explanation: Gas molecules move faster at higher temperature, increasing the transport of molecular energy and hence thermal conductivity.
Correct answer: Increases- A. None of these
- B. Arithmetic mean area
- C. Geometric mean area
- D. Logarithmic mean area
Explanation: Radial heat flow through a cylinder occurs over an area that changes with radius, so the appropriate equivalent area is the logarithmic…
Correct answer: Logarithmic mean area