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Heat Transfer Test - 5
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Heat Transfer Test - 5
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  • Question 1/10
    4 / -1

    What are the relevant boundary conditions in case of heat transfer from a bar connected to two heat sources at different temperatures?

    Solutions

    It should be at x = o and x = L.

     

  • Question 2/10
    4 / -1

    Radiation heat transfer is characterized by

    Solutions

    EM waves is characterized by radiant heat transfer.

     

  • Question 3/10
    4 / -1

    A thin metal plate of 4 cm diameter is suspended in atmospheric air whose temperature is 290 K. This plate attains a temperature of 295 K when one of its faces receives radiant energy from a heat source at the rate of 2 W. If heat transfer coefficient on both surfaces of the plate is stated to be 87.5 W/m 2 K, workout the reflectivity of the plate.

    Solutions

    Heat loss by convection from both sides of the plates = 2 h A d t = 1.1 W. Energy lost by reflection = 2.0 – 1.1 = 0.9 W.

     

  • Question 4/10
    4 / -1

    The radiant heat transfer from a plate of 2.5 cm2 area at 1250 K to a very cold enclosure is 5.0 W. Determine the emissivity of the plate at this temperature

    Solutions

    Emissivity = E/σ A T4 = 0.144.

     

  • Question 5/10
    4 / -1

    The calculation of heat transmission by convection is based on the determination of a Nusselt number or convective film coefficient. To that goal, which of the following strategies have been proposed

    (i) Non-dimensional analysis and experimental correlations

    (ii) Hydrodynamic concept of velocity boundary layer

    (iii) Reynolds similarity between the mechanism of fluid friction in the boundary layer and the transfer of heat by convection

    Identify the correct one

    Solutions

     It should be a dimensional analysis and experimental correlations.

     

  • Question 6/10
    4 / -1

    The non-dimensional parameter known as Stanton number is used in which of the following heat transfer?

    Solutions

    It’s the ratio of the heat transfer coefficient to the heat flow per unit temperature rise caused by fluid velocity. It can only be used for forced convection heat transfer.

     

  • Question 7/10
    4 / -1

    The convective heat transfer coefficient in the laminar flow over a flat plate __________

    Solutions

    It mostly increases if a denser fluid is used.

     

  • Question 8/10
    4 / -1

    Maximum heat transfer rate in a modern boiler is about

    Solutions

    Greater importance has recently been given to the boiling heat transfer.

     

  • Question 9/10
    4 / -1

    In spite of the large heat transfer coefficient in boiling liquids, fins are used advantageously when the entire surface is exposed to

    Solutions

    Here all modes of boiling i.e. film, transition and nucleate are of great importance.

     

  • Question 10/10
    4 / -1

    Which of the following is the unit of coefficient of radiant heat transfer?

    Solutions

    Its value can be calculated from the heat flux equation for any configuration.

     

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