Heat Transfer - Mechanical Engineering (MCQ) questions and answers

1)   For the same heat transfer Q and same overall heat transfer coefficient Uo, surface area required for cross flow operation is always
- Published on 12 Aug 15

a. less than LMTD for parallel flow
b. more than LMTD for parallel flow
c. same as LMTD for parallel flow
d. unpredictable
Answer  Explanation  Related Ques

ANSWER: less than LMTD for parallel flow

Explanation:
No explanation is available for this question!


2)   In parallel flow heat exchangers,
- Published on 12 Aug 15

a. the exit temperature of hot fluid is always equal to the exit temperature of cold fluid
b. the exit temperature of hot fluid is always less than the exit temperature of cold fluid
c. the exit temperature of hot fluid is always more than the exit temperature of cold fluid
d. we cannot predict comparison between exit temperatures of hot fluid and cold fluid
Answer  Explanation  Related Ques

ANSWER: the exit temperature of hot fluid is always more than the exit temperature of cold fluid

Explanation:
No explanation is available for this question!


3)   For the same heat transfer Q and same overall heat transfer coefficient Uo, surface area required for parallel flow operation is always
- Published on 12 Aug 15

a. less than LMTD for counter flow
b. more than LMTD for counter flow
c. same as LMTD for counter flow
d. unpredictable
Answer  Explanation  Related Ques

ANSWER: more than LMTD for counter flow

Explanation:
No explanation is available for this question!


4)   For the same inlet and exit temperatures of two fluids, the LMTD for counterflow is always
- Published on 12 Aug 15

a. smaller than LMTD for parallel flow
b. greater than LMTD for parallel flow
c. same as LMTD for parallel flow
d. unpredictable
Answer  Explanation  Related Ques

ANSWER: greater than LMTD for parallel flow

Explanation:
No explanation is available for this question!


5)   Which of the following temperature difference is safer than other to consider in designing of heat exchangers?
- Published on 12 Aug 15

a. Arithmetic Mean Temperature Difference (ΔTam)
b. Logarithmic Mean Temperature Difference (LMTD)
c. Both have nothing to do with safety
d. Other
Answer  Explanation  Related Ques

ANSWER: Logarithmic Mean Temperature Difference (LMTD)

Explanation:
No explanation is available for this question!


6)   How can the arithmetic mean temperature difference and LMTD of a same heat exchanger be compared?
- Published on 12 Aug 15

a. the arithmetic mean temperature difference is less than LMTD of a same heat exchanger
b. the arithmetic mean temperature difference is more than LMTD of a same heat exchanger
c. the arithmetic mean temperature difference and LMTD of a same heat exchanger are equal
d. none of the above
Answer  Explanation  Related Ques

ANSWER: the arithmetic mean temperature difference is more than LMTD of a same heat exchanger

Explanation:
No explanation is available for this question!


7)   When is the arithmetic mean temperature difference of heat exchanger used instead of LMTD?
- Published on 12 Aug 15

a. when the temperature profiles of two fluids of heat exchanger are sloping downward with curve
b. when the temperature profiles of two fluids of heat exchanger are sloping upward with curve
c. when the temperature profiles of two fluids of heat exchanger are straight
d. none of the above
Answer  Explanation  Related Ques

ANSWER: when the temperature profiles of two fluids of heat exchanger are straight

Explanation:
No explanation is available for this question!


8)   The Grashof number in natural convection plays same role as
- Published on 12 Aug 15

a. Prandtl number (Pr) in forced convection
b. Reynolds number (Re) in forced convection
c. Nusselt number (Nu) in forced convection
d. none of the above
Answer  Explanation  Related Ques

ANSWER: Reynolds number (Re) in forced convection

Explanation:
No explanation is available for this question!


9)   If there are no externally induced flow velocities, then the Nusselt number (Nu) does not depend upon
- Published on 12 Aug 15

a. Prandtl number (Pr)
b. Reynolds number (Re)
c. Grashof number (Gr)
d. none of the above
Answer  Explanation  Related Ques

ANSWER: Reynolds number (Re)

Explanation:
No explanation is available for this question!


10)   Which of the following condition is correct for natural convection?
- Published on 12 Aug 15

a. (Gr / Re2) = 1
b. (Gr / Re2) << 1
c. (Gr / Re2) >> 1
d. none of the above
Answer  Explanation  Related Ques

ANSWER: (Gr / Re2) >> 1

Explanation:
No explanation is available for this question!


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