Discussion
Home ‣ Mechanical Engineering ‣ Heat Transfer, Refrigeration and Air Conditioning Comments
- Question
Reynolds number is the ratio of
Options- A. energy transferred by convection to that by conduction
- B. kinematic viscosity to thermal diffusivity
- C. inertia force to viscous force
- D. none of the above
- Correct Answer
- inertia force to viscous force
- 1. The logarithmic mean temperature difference (tm) is given by (where ?t1 and ?t2 are temperature differences between the hot and cold fluids at entrance and exit)
Options- A.
- B.
- C. tm = (?t1 - ?t1) loge(?t1/?t1)
- D.
Discuss
- 2. A boot-strap air cooling system has
Options- A. one heat exchanger
- B. two heat exchangers
- C. three heat exchangers
- D. four heat exchangers Discuss
- 3. According to Stefan-Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the
Options- A. absolute temperature
- B. square of the absolute temperature
- C. cube of the absolute temperature
- D. fourth power of the absolute temperature Discuss
- 4. The freezing point of carbon dioxide is equal to boiling point of R-12.
Options- A. Correct
- B. Incorrect Discuss
- 5. One tonne of refrigeration (1TR) means that the heat removing capacity is
Options- A. 21 kJ/min
- B. 210 kJ/min
- C. 420 kJ/min
- D. 620 kJ/min Discuss
- 6. The thermostatic expansion valve is used in __________ type of evaporators.
Options- A. flooded
- B. DX coil
- C. dry Discuss
- 7. Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The number of shields should be
Options- A. one
- B. two
- C. three
- D. four Discuss
- 8. According to Newton's law of cooling, the heat transfer from a hot body to a cold body is
Options- A. directly proportional to the surface area
- B. directly proportional to the difference of temperatures between the two bodies
- C. either (a) or (b)
- D. both (a) and (b) Discuss
- 9. The ratio of emissive power of a body to the emissive power of a perfectly black body is called emissivity.
Options- A. Agree
- B. Disagree Discuss
- 10. The index which corelates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as
Options- A. mean radiant temperature
- B. effective temperature
- C. dew point temperature
- D. none of these Discuss
Heat Transfer, Refrigeration and Air Conditioning problems
Search Results
Correct Answer:
Correct Answer: two heat exchangers
Correct Answer: fourth power of the absolute temperature
Correct Answer: Incorrect
Correct Answer: 210 kJ/min
Correct Answer: dry
Correct Answer: three
Correct Answer: both (a) and (b)
Correct Answer: Agree
Correct Answer: effective temperature
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