Home / Mechanical Engineering / Heat and Mass Transfer :: section-1

Mechanical Engineering :: Heat and Mass Transfer

  1. Heat conducted through per unit area and unit thick face per unit time when temperature difference between opposite faces is unity, is called

  2. A.

     Thermal resistance

    B.

     Thermal coefficient

    C.

     Temperature gradient

    D.

     Thermal conductivity


  3. The rate of heat flow through a body is Q = [kA (T₁ - T₂)]/x. The term x/kA is known as

  4. A.

     Thermal coefficient

    B.

     Thermal resistance

    C.

     Thermal conductivity

    D.

     None of these


  5. Depending on the radiating properties, a body will be white when
    (Where a = absorptivity, p = reflectivity, x = transmissivity)

  6. A.

     P = 0, x = 0 and a = 1

    B.

     P=1, T = 0 and a = 0

    C.

     P = 0, x = 1 and a = 0

    D.

     X = 0, a + p = 1


  7. Depending on the radiating properties, body will be transparent when
    (Where a = absorptivity, p = reflectivity, x = transmissivity)

  8. A.

     P = 0, x = 0 and a = 1

    B.

     P=1, x = 0, and a = 0

    C.

     P = 0, x= 1, and a = 0

    D.

     X = 0, a + p = 1


  9. The expression Q = ρ AT4 is called

  10. A.

     Fourier equation

    B.

     Stefan-Boltzmann equation

    C.

     Newton Reichmann equation

    D.

     Joseph-Stefan equation


  11. In heat transfer, conductance equals conductivity (kcal/hr/sq.m/°C/cm) divided by

  12. A.

     Hr (time)

    B.

     Sq. m (area)

    C.

     °C (temperature)

    D.

     K.cal (heat)


  13. The time constant of a thermocouple is

  14. A.

     The time taken to attain the final temperature to be measured

    B.

     The time taken to attain 50% of the value of initial temperature difference

    C.

     The time taken to attain 63.2% of the value of initial temperature difference

    D.

     Determined by the time taken to reach 100°C from 0°C


  15. The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit

  16. A.

     Temperature

    B.

     Thickness

    C.

     Area

    D.

     Time


  17. Heat transfer takes place as per

  18. A.

     Zeroth law of thermodynamics

    B.

     First law of thermodynamic

    C.

     Second law of the thermodynamics

    D.

     Kirchoff's law


  19. Thermal diffusivity is

  20. A.

     A dimensionless parameter

    B.

     Function of temperature

    C.

     Used as mathematical model

    D.

     A physical property of the material