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 28 of 33
- A. Heat transfer co-efficient is proportional to 0.8th power
- B. Pressure drop is proportional to the square
- C. Neither A. nor B.
- D. Both A. & B.
Explanation: For turbulent flow in the tube side, the heat-transfer coefficient commonly varies approximately as mass velocity to the 0.8 power, while…
Correct answer: Both A. & B.- A. 4 to 8
- B. 3 to 5
- C. 2 to 3
- D. 6 to 12
Explanation: For liquid shell-and-tube heat exchangers, a tube length several times the shell diameter is preferred for economical design and…
Correct answer: 4 to 8- A. hG = 1.004G0.37
- B. 1.004G0.8
- C. hG = 0.0176G0.37
- D. 0.0176G1.37
Explanation: For air flowing perpendicular to the drying surface, the empirical correlation changes to hG = 1.004G^0.37.
Correct answer: hG = 1.004G0.37- A. 25 cms
- B. 40% of the I.D. of the shell
- C. 5 cms
- D. I.D. of the shell
Explanation: Baffle spacing should not be reduced below about 5 cm, because closer spacing increases shell-side pressure drop and makes fabrication and…
Correct answer: 5 cms- A. 0.3 to 0.8
- B. 8 to12
- C. 3.5 to 7.0
- D. 1.25 to 3.125
Explanation: Corrugated plates for conventional plate heat exchangers are commonly specified in the approximate 1.25 to 3.125 mm range in this…
Correct answer: 1.25 to 3.125- A. 0.5 to 1
- B. 1 to 1.5
- C. 1.5 to 2
- D. 2 to 2.5
Explanation: In a calandria evaporator, the downcomer or downtake cross-sectional area is typically about 0.5 to 1 times the total tube-flow area.
Correct answer: 0.5 to 1- A. 75% cut segmental baffle
- B. 25% cut segmental baffle
- C. Orifice baffle
- D. Disk and doughnut baffle
Explanation: The 25% cut segmental baffle is the usual industrial choice because it provides effective cross-flow over the tubes without imposing…
Correct answer: 25% cut segmental baffle- A. Equal to
- B. Half
- C. One fourth
- D. Three fourth
Explanation: The ligament is the clear distance between adjacent tubes, and standard exchanger practice takes its minimum as about one-fourth of the…
Correct answer: One fourth- A. 250
- B. 450
- C. 650
- D. 750
Explanation: A vacuum of 650 mm Hg corresponds to an absolute pressure of about 110 mm Hg when atmospheric pressure is 760 mm Hg.
Correct answer: 650- A. Same as that for fluid flow
- B. More than that for fluid flow
- C. Less than that for fluid flow
- D. D2 - D1 (D1 and D2 are I.D. of inner and outer pipes respectively)
Explanation: For annular flow, the heat-transfer hydraulic radius is based on the heat-transfer surface, whereas the flow hydraulic radius uses the…
Correct answer: More than that for fluid flow- A. Equal to the tube diameter
- B. More than the tube diameter
- C. Not less than one-fourth of the tube diameter or 3/16″
- D. More in case of triangular pitch as compared to the square pitch tube layout
Explanation: Tube layout requires sufficient clearance for fabrication, cleaning, and fluid flow, generally at least one-fourth of the tube diameter or…
Correct answer: Not less than one-fourth of the tube diameter or 3/16″- A. Less than arithmetic mean value
- B. More than arithmetic mean value
- C. More than geometric mean value
- D. Both B. & C.
Explanation: The logarithmic mean temperature difference lies between the geometric and arithmetic means, and the multipass correction factor further…
Correct answer: Less than arithmetic mean value- A. Both B. and C.
- B. Not greater than
- C. Not less than one fifth of
- D. More than
Explanation: Shell-side baffle spacing is normally kept between about one-fifth of the shell inside diameter and the shell diameter.
Correct answer: Both B. and C.- A. 4(P2 - πd2/4)/πd
- B. (P2 - rd2/4)/rd
- C. 4P2/πd
- D. πd/4P2
Explanation: Equivalent diameter is four times the flow area divided by the wetted perimeter.
Correct answer: 4(P2 - πd2/4)/πd- A. Same
- B. Less
- C. About 3 times
- D. About 0.33 times
Explanation: For similar condensing conditions, condensate drains more effectively and the film resistance is lower on a horizontal condenser, giving a…
Correct answer: About 3 times- A. 15-20
- B. 5-10
- C. 30-35
- D. 35-40
Explanation: Heat-transfer equipment is commonly given an overdesign allowance of about 15–20% to cover fouling, uncertainty in coefficients, and…
Correct answer: 15-20- A. Higher
- B. Lower
- C. Same
- D. Unpredictable
Explanation: At equal mass velocity, gases generally have much lower film coefficients because their thermal conductivity and density are far lower…
Correct answer: Lower- A. Always less than the diameter of the tube
- B. Called tube clearance
- C. Called tube pitch
- D. None of these
Explanation: Tube pitch is the centre-to-centre distance between adjacent tubes in a tube bundle.
Correct answer: Called tube pitch559. Which of the following is the best tube material from thermal conductivity point of view alone ?
- A. Aluminium
- B. Stainless steel
- C. Copper
- D. Carbon steel
Explanation: Copper has a higher thermal conductivity than aluminium, carbon steel, and stainless steel, so it gives the lowest tube-wall resistance…
Correct answer: Copper- A. Geometric mean of the true temperature difference and the LMTD
- B. Ratio of LMTD to the true temperature difference
- C. Differenced of true temperature difference and the LMTD
- D. Ratio of true temperature difference to the LMTD
Explanation: For multipass or cross-flow exchangers, the actual mean temperature driving force is lower than the ideal countercurrent LMTD.
Correct answer: Ratio of true temperature difference to the LMTD