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 19 of 33
- A. Lower economy
- B. A lower capacity
- C. A higher capacity
- D. None of these
Explanation: For a cold, viscous feed, backward feed sends the more concentrated liquid to the hotter effect, where its viscosity decreases and heat…
Correct answer: A higher capacity- A. Mass transfer between a gas and a liquid
- B. Absorption with chemical reaction
- C. Heat transfer in turbulent flow
- D. Heat transfer in laminar flow
Explanation: The Graetz number characterizes developing heat or mass transfer in internal flow, and in this context it is especially associated with…
Correct answer: Heat transfer in laminar flow- A. W/m
- B. W/°K
- C. W/m2
- D. W/m°K
Explanation: Thermal conductance is heat-transfer rate per unit temperature difference, so its SI unit is W/K, written here as W/°K.
Correct answer: W/°K- A. Transformer oil
- B. Water
- C. Molten sodium (a coolant used in fast breeder reactor)
- D. Dilute H2SO4
Explanation: The Prandtl number is the ratio of momentum diffusivity to thermal diffusivity.
Correct answer: Molten sodium (a coolant used in fast breeder reactor)- A. Is inversely proportional to the resistance across which the drop occurs
- B. None of these
- C. And the wall is not related
- D. And the wall are proportional to individual resistances
Explanation: For resistances in series, the heat rate is the same through each resistance and the temperature drop is ΔT = qR.
Correct answer: And the wall are proportional to individual resistances- A. Solution has an elevation of boiling point
- B. Evaporators operate under vacuum
- C. Evaporators operate at atmospheric pressure
- D. None of these
Explanation: A solution's boiling-point elevation reduces the effective temperature difference available in each effect, so the double-effect capacity…
Correct answer: Solution has an elevation of boiling point- A. Grashoff
- B. Biot
- C. Stanton
- D. Reynolds
Explanation: Natural-convection heat transfer depends mainly on buoyancy and fluid-property effects, represented by the Grashof and Prandtl numbers, so…
Correct answer: Grashoff- A. 0°C
- B. 0°K
- C. 100°C
- D. Room temperature
Explanation: Thermal radiation is emitted by matter at every temperature above absolute zero, although the intensity increases strongly with…
Correct answer: 0°K- A. Conduction
- B. Convection
- C. All A., B. & C.
- D. Radiation
Explanation: Heat travels through the pipe wall by conduction, leaves the outer surface by convection to the air, and is also emitted by radiation.
Correct answer: All A., B. & C.370. In Biot number, the characteristic length used is the ratio of the _______________ of the solid?
- A. Volume to surface area
- B. Perimeter to surface area
- C. Surface area to volume
- D. Surface area to perimeter
Explanation: For a solid of general shape, the characteristic length in the Biot number is V/A, the volume divided by the exposed heat-transfer surface…
Correct answer: Volume to surface area- A. Dynamic viscosity
- B. Boiling point
- C. Kinematic viscosity
- D. Density
Explanation: Duhring's rule states that, at a fixed pressure, the boiling temperature of a solution varies approximately linearly with the boiling…
Correct answer: Boiling point- A. t4
- B. 1/t4
- C. T4
- D. 1/T4
Explanation: The Stefan-Boltzmann law states that blackbody emissive power is proportional to the fourth power of absolute temperature, T⁴.
Correct answer: T4- A. None of these
- B. Reynolds
- C. Prandtl
- D. Colburn
Explanation: The relation St Pr^(2/3) = f/2 is the Colburn heat-and-momentum-transfer analogy.
Correct answer: Colburn- A. 0.5-50
- B. 0.38-0.78
- C. 100-1000
- D. 5-50
Explanation: Most thermal radiation of engineering interest lies roughly in the infrared range, extending approximately from 0.5 to 50 micrometres.
Correct answer: 0.5-50- A. Viscosity
- B. Boiling point (at the same pressure)
- C. Density
- D. Thermal conductivity
Explanation: Duhring's rule states that the boiling point of a solution varies linearly with the boiling point of pure water measured at the same…
Correct answer: Boiling point (at the same pressure)- A. 0.001
- B. 0.72
- C. 70
- D. 150
Explanation: For dry gases, the Prandtl number, Pr = Cpμ/k, is usually close to 0.7 because momentum and thermal diffusivities are of similar…
Correct answer: 0.72- A. Flexibility possible in the baffle arrangement
- B. Less corrosion problems
- C. Low pressure drop
- D. High heat transfer co-efficient
Explanation: The shell side can handle widely varying fluid volumes because baffle spacing and arrangement can be changed to adjust the flow area and…
Correct answer: Flexibility possible in the baffle arrangement- A. Increase the heating load
- B. Account for the uneven expansion of shell and tube bundles
- C. Impart structural strength
- D. Facilitate increase of shell length, if needed
Explanation: Shell and tubes may expand by different amounts when their temperatures differ, producing thermal stress.
Correct answer: Account for the uneven expansion of shell and tube bundles- A. Because of simplicity of fabrication
- B. For low heat load
- C. To obtain higher heat transfer co-efficient and shorter tube
- D. To reduce the pressure drop
Explanation: Multipass arrangements increase fluid velocity, which generally raises the convective heat-transfer coefficient, while allowing the…
Correct answer: To obtain higher heat transfer co-efficient and shorter tube- A. > 0.75
- B. < 0.25
- C. < 0.50
- D. < 0.75
Explanation: The LMTD correction factor accounts for departure from ideal countercurrent flow; a value below about 0.75 indicates an inefficient…
Correct answer: < 0.75