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 6 of 33
- A. Heat flow rate
- B. Temperature difference
- C. Heat content in the system
- D. None of these
Explanation: In the thermal-electrical analogy, temperature difference corresponds to voltage and heat-flow rate corresponds to electrical current.
Correct answer: Heat flow rate- A. 1 BTU/ft2.hr.°F/ft = 1.488 kcal/m2. hr.°C/m
- B. 1 BTU/ft2.hr.°F/inch = 1.488 kcal/m2. hr.°C/m
- C. 1 kcal/m.hr.°C = 0.672 BTU/ft.hr.°F = 1.163 W/m. °K
- D. 1 W/cm.°C = 85.985 kcal/m.hr.°C = 57.779 BTU/ft.hr.°F
Explanation: The first conversion is for conductivity units equivalent to BTU/(ft·hr·°F), giving 1.488 kcal/(m·hr·°C).
Correct answer: 1 BTU/ft2.hr.°F/inch = 1.488 kcal/m2. hr.°C/m- A. 1 kcal/hr= 1.163 Watt
- B. 1 Watt = 1.163 kcal/hr
- C. 1 BTU/ft2.hr = 2.712 kcal/m2.hr
- D. 1 kcal/m2.hr = 0.3687 BTU/ft2.hr = 1.163 Watt/m2
Explanation: One watt equals approximately 0.8598 kcal/hr, so 1 kcal/hr equals 1.163 W, not the reverse.
Correct answer: 1 Watt = 1.163 kcal/hr- A. The minimum value of baffle spacing is 50 mm
- B. The maximum value of baffle spacing is equal to the I.D. of the shell
- C. The maximum unsupported tube span is generally about 75 times tube diameter, but is reduced to about 60 times for aluminium, copper & alloys of these
- D. Disk and doughnut baffle is the most commonly used baffle
Explanation: Segmental baffles are the usual choice in shell-and-tube exchangers, not disk-and-doughnut baffles.
Correct answer: Disk and doughnut baffle is the most commonly used baffle- A. jH = (St)(Pr)2/3 = f/2
- B. jH = (St)(Pr)1/3 = f/2
- C. jH = (St)2/3(Pr) = f/2
- D. jH = (St)1/3(Pr) = f/2
Explanation: The Colburn analogy defines jH = St Pr^(2/3), and for the usual analogy it equals f/2.
Correct answer: jH = (St)(Pr)2/3 = f/2- A. Nu = (Re) (Pr) (Gz)
- B. Nu = (Re) (Pr) (St)
- C. Nu = (Re) (Pr)
- D. Nu = (Pr) (St)
Explanation: The Stanton number is related to Nusselt number by St = Nu/(Re Pr), so rearranging gives Nu = Re Pr St.
Correct answer: Nu = (Re) (Pr) (St)- A. Lower economy
- B. Lower capacity
- C. Both A. & B.
- D. Higher economy
Explanation: In backward feeding, cold feed enters the last effect and is progressively heated as it moves toward the hotter effects, making better use…
Correct answer: Higher economy- A. Backward
- B. Forward
- C. Parallel
- D. None of these
Explanation: Backward feeding places the most concentrated and viscous solution in the hottest effect, where its viscosity is lower and heat transfer…
Correct answer: Backward- A. 15 min
- B. 22 min
- C. 44 min
- D. 51 min
Explanation: For batch heating with condensing steam at constant temperature, t = (mCp/UA) ln[(150−30)/(150−120)] = 3080 s, or about 51 minutes.
Correct answer: 51 min- A. Cannot pass through vacuum
- B. Travel in straight line
- C. Both B. and C.
- D. Can be reflected by a mirror
Explanation: Heat waves are electromagnetic radiation, so they can travel through a vacuum, propagate in straight lines, and undergo reflection from…
Correct answer: Both B. and C.- A. Increase
- B. Not affect
- C. Decrease
- D. Increase the condensing film co-efficient as well as
Explanation: Air adds a diffusion resistance between the condensing vapor and the cooling surface, reducing the effective condensation rate.
Correct answer: Decrease- A. > 10000
- B. 4000
Explanation: This correlation is the Dittus-Boelter equation, which applies to fully developed turbulent flow in a smooth pipe, normally for Reynolds…
Correct answer: > 10000- A. Peclet
- B. Prandtl
- C. Stanton
- D. Nusselt
Explanation: The ratio of momentum diffusivity to thermal diffusivity is the Prandtl number, Pr = ν/α.
Correct answer: Prandtl114. Vibrations in the tubes of a shell and tube heat exchanger is induced due to the _________________?
- A. Flow of fluid on the tube and shell sides
- B. Oscillations in the flow of shell/tube sides fluid
- C. All A., B. and C.
- D. Vibrations transmitted through piping and/or supports due to external reasons
Explanation: Tube vibration can arise from fluid-flow excitation on either side, oscillatory flow, or vibration transmitted from external piping and…
Correct answer: All A., B. and C.- A. 1
- B. > 1
- C. 0.1
- D. < 1
Explanation: In a single-effect evaporator, the steam economy is generally less than 1 because one kilogram of steam evaporates less than one kilogram…
Correct answer: < 1- A. 1
- B. 1.74
- C. 6.1
- D. 37
Explanation: With constant properties and doubled volumetric flow, halving the diameter makes velocity increase eightfold, so Reynolds number increases…
Correct answer: 6.1- A. Increase the cross-section of the shell side liquid
- B. Increase the shell side heat transfer co-efficient
- C. Force the liquid to flow parallel to the bank
- D. Decrease the shell side heat transfer co-efficient
Explanation: Baffles redirect shell-side fluid across the tube bundle rather than allowing mainly parallel flow, increasing turbulence and the…
Correct answer: Increase the shell side heat transfer co-efficient- A. No
- B. The least
- C. Lower
- D. The largest
Explanation: The overall resistance is dominated by the largest individual resistance because resistances act in series.
Correct answer: The largest- A. Lewis relationship
- B. Nusselt number
- C. Kutateladze number
- D. Froude number
Explanation: The Lewis relationship connects simultaneous heat and mass transfer, especially in gas-liquid contacting, by relating heat-transfer and…
Correct answer: Lewis relationship- A. Distillation
- B. Evaporation
- C. Crystallisation
- D. Humidification
Explanation: Dühring's rule states that the boiling point of a solution varies approximately linearly with the boiling point of the pure solvent at the…
Correct answer: Evaporation