Discussion
Home ‣ Mechanical Engineering ‣ Heat Transfer, Refrigeration and Air Conditioning Comments
- Question
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
- Correct Answer
- fourth power of the absolute temperature
- 1. The freezing point of carbon dioxide is equal to boiling point of R-12.
Options- A. Correct
- B. Incorrect Discuss
- 2. 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
- 3. The alignment circle is marked on the psychrometric chart at
Options- A. 20°C DBT and 50% RH
- B. 26°C DBT and 50% RH
- C. 20°C DBT and 60% RH
- D. 26°C DBT and 60% RH Discuss
- 4. The thermal diffusivity for gases is generally __________ those for liquids.
Options- A. equal to
- B. less than
- C. greater than Discuss
- 5. The capillary tube is not used in large capacity refrigeration systems because
Options- A. cost is too high
- B. capacity control is not possible
- C. it is made of copper
- D. required pressure drop can not be achieved Discuss
- 6. 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
- 7. 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
- 8. 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 Discuss
- 9. The thermostatic expansion valve is used in __________ type of evaporators.
Options- A. flooded
- B. DX coil
- C. dry Discuss
- 10. 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
Heat Transfer, Refrigeration and Air Conditioning problems
Search Results
Correct Answer: Incorrect
Correct Answer: 210 kJ/min
Correct Answer: 26°C DBT and 50% RH
Correct Answer: greater than
Correct Answer: capacity control is not possible
Correct Answer: two heat exchangers
Correct Answer:
Correct Answer: inertia force to viscous force
Correct Answer: dry
Correct Answer: three
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