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Mechanical Engineering :: Heat and Mass Transfer

  1. Which of the following is a case of steady state heat transfer?

  2. A.

     I.C. engine

    B.

     Air preheaters

    C.

     Heating of building in winter

    D.

     None of the above


  3. Radiation is the process of heat transfer in which heat flows from a ________, in a straight line, without affecting the intervening medium.

  4. A.

     Cold body to hot body

    B.

     Hot body to cold body

    C.

     Smaller body to larger body

    D.

     Larger body to smaller body


  5. Fourier's law of heat conduction gives the heat flow for

  6. A.

     Irregular surfaces

    B.

     Nonuniform temperature surfaces

    C.

     One dimensional cases only

    D.

     Two dimensional cases only


  7. In a shell and tube heat exchanger, baffles are provided on the shell side to

  8. A.

     Improve heat transfer

    B.

     Provide support for tubes

    C.

     Prevent stagnation of shell side fluid

    D.

     All of these


  9. A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100°C and leaves at 60°C. A cold fluid enters the heat exchanger at 40°C. The mean temperature difference between the two fluids is

  10. A.

     20°C

    B.

     40°C

    C.

     60°C

    D.

     66.7°C


  11. If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented by (eλ.dλ), then eλ is called

  12. A.

     Absorptive power

    B.

     Emissive power

    C.

     Emissivity

    D.

     None of these


  13. The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as

  14. A.

     Conduction

    B.

     Free convection

    C.

     Forced convection

    D.

     Radiation


  15. The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called

  16. A.

     Conduction

    B.

     Convection

    C.

     Radiation

    D.

     None of these


  17. Fourier's law of heat conduction is valid for

  18. A.

     One dimensional cases only

    B.

     Two dimensional cases only

    C.

     Three dimensional cases only

    D.

     Regular surfaces having non-uniform temperature gradients


  19. According to Newton's law of cooling, the heat transfer from a hot body to a cold body is

  20. 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)