All Free Chemical Engineering MCQs with Answers
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6,983 questions · page 256 of 350
- A. Results in higher shell side pressure drop
- B. Can accomodate less number of tubes for a given shell diameter
- C. Facilitates easier shell side cleaning; hence is more suitable for handling high dirt factor shell
- D. side fluid
- E. Creates relatively lower turbulence on the shell side resulting in lower shell side heat transfer
- F. co-efficient
Explanation: Triangular pitch places tubes closer together and forces the shell-side fluid through more tortuous passages, giving higher turbulence and…
Correct answer: Results in higher shell side pressure drop- A. Regenerative
- B. Finned
- C. Plate type
- D. Double pipe
Explanation: A double-pipe exchanger consists of one pipe inside another, with the flow reversing through a return leg in the common hairpin…
Correct answer: Double pipe- A. 4
- B. 1/2
- C. 2
- D. 1/4
Explanation: A 1-4 exchanger divides the same total tube flow among four passes, so the number of tubes carrying flow in each pass is one-fourth that…
Correct answer: 45104. Ratio of tube length to shell diameter for a shell and tube heat exchanger is________________?
- A. 8 : 1 to 12 : 1 for both liquid-liquid and gas-gas heat exchangers
- B. Both B. & C.
- C. < 4 : 1 for gas-gas exchangers
- D. 4 : 1 to 8 : 1 for liquid-liquid exchanger
Explanation: Liquid-liquid exchangers commonly use a tube-length-to-shell-diameter ratio of about 4:1 to 8:1.
Correct answer: Both B. & C.- A. nth
- B. 0.5 nth
- C. (1/n)th
- D. 1.5 nth
Explanation: For a fixed total heating surface, adding effects divides the available surface among the effects, so evaporation per unit surface is…
Correct answer: (1/n)th- A. Equal to
- B. Three fourth
- C. Half
- D. 1.5 times
Explanation: The tube sheet is normally made about equal in thickness to the tube outside diameter, subject to the stated minimum thickness of 22 mm.
Correct answer: Equal to- A. 1
- B. ∞
- C. 20.8
- D. 2
Explanation: Since tube-side film coefficient varies approximately as flow rate^0.8, the overall coefficient follows the same dependence only when…
Correct answer: 15108. When one of the fluids is highly corrosive and has fouling tendency, it should_____________________?
- A. Flow at a very slow velocity
- B. Preferably flow outside the tube
- C. Preferably flow inside the tube for its easier internal cleaning
- D. Flow outside the tube, when the flow is counter-current and inside the tube when the flow is
- E. co-current
Explanation: A corrosive, fouling fluid is preferably passed through the tubes because the tube side can be mechanically or chemically cleaned more…
Correct answer: Preferably flow inside the tube for its easier internal cleaning- A. Are easier to clean
- B. Are less prone to fouling
- C. Can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less
- D. None of these
Explanation: For the same heat-transfer area, smaller tubes provide more area per unit shell diameter, so the required shell can be smaller and…
Correct answer: Can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less- A. Tube dia of 2.5-7.5 cms, tube length of 75-200 cms and cylindrical drum dia of 1-6 metres are
- B. normally used
- C. Area of central downtake is equal to 40 to 100% of total cross-sectional area of the
- D. All A., B. & C.
- E. Liquor is inside the tube while the steam is outside the tube
- F. surrounding tube
Explanation: A short-tube calandria uses relatively short tubes with liquor inside the tubes and heating steam outside; the central downtake provides…
Correct answer: All A., B. & C.- A. 1.25-1.50 times
- B. Less than
- C. 2.5 times
- D. one-fourth of
Explanation: Tube pitch is commonly about 1.25 to 1.5 times the tube outside diameter, providing space for shell-side flow, fabrication, and tube…
Correct answer: 1.25-1.50 times- A. To increase the residence time of shell side fluid
- B. To increase the tube side heat transfer co-efficient by inducing turbulence
- C. To reduce the induced vibration in the tubes
- D. To provide support to the tube bundle
Explanation: Baffles increase shell-side residence time, support the tubes, and limit vibration by directing cross-flow.
Correct answer: To increase the tube side heat transfer co-efficient by inducing turbulence5113. In case of 1.5″ heat exchanger tubes, the inside flow area _____________ with decrease in BWG?
- A. Increases
- B. None of these
- C. Remains same
- D. Decreases
Explanation: A decrease in BWG number means a thicker tube wall, so the inside diameter becomes smaller for the same outside diameter.
Correct answer: Decreases5114. What is the minimum recommended ligament for square pitch arrangement in case of heat exchangers ?
- A. 6.5 mm
- B. 6.5 cms
- C. Equal to tube I.D
- D. Equal to tube O.D
Explanation: The minimum ligament, or clear distance between adjacent tubes, in a square pitch layout is about 6.5 mm.
Correct answer: 6.5 mm- A. The corrosive and fouling fluid should be preferably routed through the tubes
- B. Higher pressure fluid stream should be routed through the shell side
- C. Lower flow rate fluid should be routed through the shell side
- D. The viscous fluid should be routed through the shell side
Explanation: The higher-pressure fluid should preferably pass through the tubes because tubes can be designed and tested more economically for high…
Correct answer: Higher pressure fluid stream should be routed through the shell side- A. Is economical in operation
- B. Employs high velocity, high heat transfer rate and less heating surface requirement
- C. Employs a centrifugal pump placed between external downtake from vapor drum and inlet to
- D. Both B. & C.
- E. tube bundle
Explanation: Forced circulation evaporators use a centrifugal pump to drive liquor through the tube bundle at high velocity, increasing heat-transfer…
Correct answer: Both B. & C.- A. Heat transfer between corrosive fluids
- B. Counter-current heat transfer systems
- C. Co-current heat transfer systems
- D. Cases where temperature difference between the shell and the tubes is more (>50°C)
Explanation: A floating head allows the shell and tubes to expand independently, so it is suitable when the shell-to-tube temperature difference is…
Correct answer: Cases where temperature difference between the shell and the tubes is more (>50°C)- A. Decreases very rapidly
- B. Increases very rapidly
- C. Remains constant
- D. Increases linearly
Explanation: As the temperature drop or approach becomes more severe, the exchanger temperature profile departs further from the ideal counter-current…
Correct answer: Decreases very rapidly- A. Containing suspended solids flows at high velocity
- B. Containing suspended solids flows at low velocity
- C. Is highly viscous
- D. Is of high specific gravity
Explanation: Suspended solids deposit more readily when liquid velocity is low, adding thermal resistance and requiring a fouling factor in design.
Correct answer: Containing suspended solids flows at low velocity- A. Hydrostatic head is required for refluxing the condensate
- B. Only the function of condensation is to be carried out
- C. Both the functions of condensation & sub cooling are carried out in a single unit
- D. Sub-cooling of condensate is desired
Explanation: A vertical condenser permits condensate to flow downward by gravity, allowing condensation and subsequent sub-cooling in the same unit.
Correct answer: Both the functions of condensation & sub cooling are carried out in a single unit