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Heat Transfer - Engineering

Q1:

Pick out the wrong statement.

A Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection.

B The ratio NNu/NRe . Npr is called the Stanton number.

C The Peclet number is a measure of the ratio of energy transport by convection to that by conduction.

D The Colbum jH factor for heat transfer is given by Nst Npr.

ANS:D - The Colbum jH factor for heat transfer is given by Nst Npr.

The wrong statement is: "The Colburn jH factor for heat transfer is given by Nst Npr." Explanation:

  • The Colburn jH factor is not given by Nst * Npr. It is defined as the dimensionless heat transfer coefficient, which relates the convective heat transfer rate to the temperature difference and fluid properties.
  • The correct expression for the Colburn jH factor is typically given in terms of the Nusselt number (Nu) and the Reynolds number (Re). It represents the ratio of convective heat transfer to fluid frictional resistance.
  • Therefore, the statement as provided is incorrect.