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Mechanical Engineering :: Heat and Mass Transfer

  1. The value of Prandtl number for air is about

  2. A.

     0.1

    B.

     0.3

    C.

     0.7

    D.

     1.7


  3. A steam pipe is to be insulated by two insulating materials put over each other. For best results

  4. A.

     Better insulation should be put over pipe and better one over it

    B.

     Inferior insulation should be put over pipe and better one over it

    C.

     Both may be put in any order

    D.

     Whether to put inferior OIL over pipe or the better one would depend on steam temperature


  5. Total heat is the heat required to

  6. A.

     Change vapour into liquid

    B.

     Change liquid into vapour

    C.

     Increase the temperature of a liquid or vapour

    D.

     Convert water into steam and superheat it


  7. Sensible heat is the heat required to

  8. A.

     Change vapour into liquid

    B.

     Change liquid into vapour

    C.

     Increase the temperature of a liquid of vapour

    D.

     Convert water into steam and superheat it


  9. When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by

  10. A.

     Conduction

    B.

     Convection

    C.

     Radiation

    D.

     Conduction and convection


  11. When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by

  12. A.

     Conduction

    B.

     Convection

    C.

     Radiation

    D.

     Conduction and convection


  13. The concept of overall coefficient of heat transfer is used in case of heat transfer by

  14. A.

     Conduction

    B.

     Convection

    C.

     Radiation

    D.

     Conduction and convection


  15. When heat is transferred by molecular collision, it is referred to as heat transfer by

  16. A.

     Conduction

    B.

     Convection

    C.

     Radiation

    D.

     Scattering


  17. Stefan Boltzmann law is applicable for heat transfer by

  18. A.

     Conduction

    B.

     Convection

    C.

     Radiation

    D.

     Conduction and radiation combined


  19. A non-dimensional number generally associated with natural convection heat transfer is

  20. A.

     Grashoff number

    B.

     Nusselt number

    C.

     Weber number

    D.

     Prandtl number