Download Aptitude Crack
img not found img not found

Mass Transfer - Engineering

Q1:

Pick out the wrong statement pertaining to the analogy between equations of heat and mass transfer operations.

A Sherwood number in mass transfer is analogous to Nusselt number in heat transfer.

B Prandtl number in heat transfer is analogous to Schmidt number in mass transfer.

C Reynolds number in mass transfer is analogous to Grashoff number in heat transfer.

D Reynolds number remains the same in both heat and mass transfer.

ANS:C - Reynolds number in mass transfer is analogous to Grashoff number in heat transfer.

The wrong statement pertaining to the analogy between equations of heat and mass transfer operations is: Reynolds number remains the same in both heat and mass transfer. In heat transfer, the Reynolds number (𝑅𝑒Re) is defined as the ratio of inertial forces to viscous forces and is given by: 𝑅𝑒=πœŒπ‘’πΏπœ‡Re=μρuL​ Where:

  • 𝜌ρ is the fluid density,
  • 𝑒u is the characteristic velocity,
  • 𝐿L is the characteristic length, and
  • πœ‡μ is the dynamic viscosity of the fluid.
In mass transfer, the Reynolds number is similarly defined as the ratio of inertial forces to viscous forces, but it involves properties relevant to mass transfer, such as the density of the fluid, the velocity of the fluid, and the diffusivity of the solute. It is given by: 𝑅𝑒=πœŒπ‘’πΏπ·Re=DρuL​ Where:
  • 𝐷D is the diffusivity of the solute.
So, the Reynolds number is not the same in both heat and mass transfer operations, making the statement incorrect.