Hydrogen has a heat transfer co-efficient __________ times that of air?

Related Mcqs:

1. The density of hydrogen is __________ times the density of air?

   A. 0.07 B. 1.5 C. 2.5 D. 3.5...

2. The thermal conductivity of hydrogen is _____________ times that of air?

   A. 2 B. 3 C. 5 D. 7...

3. The heated parts of an electrical machine dissipate heat into their surroundings by which of the following modes of heat dissipation ?

   A. Conduction B. Convection C. Radiation D. All of the above...

4. The mcrease in heat dissipation by air blasts is due to increase in______________?

   A. conduction B. convection E. radiation D. any ofthe above...

5. With conventional hydrogen cooling it is possible to increase the rating of a single unit to___________?

   A. 50 MW B. 100 MW C. 200 MW D. none of the above...

6. Which of the following is an advantage of hydrogen cooling ?

   A. Increase in efficiency B. Increase in ratings C. Increase in life D. Smaller size of coolers E. All of the above...

7. In direct cooled system using hydrogen both stator and rotor conductors are made____________?

   A. solid B. hollow C. perforated D. any ofthe above...

8. The length cf air gap to be provided in __________ is primarily determined by power factor consideration?

   A. d.c. series motor . B. d.c. shunt motor C. induction motor D. synchronous motor...

9. The heat dissipated by from a surface depends upon its temperature and its characteristics like colour, roughness etc?

   A. conduction B. convection C. radiation D. any of the above...

10. The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following ?

    A. Corrugations B. Fins C. Tubes D. Radiator tanks E. All of the above...