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Heat Transfer - Engineering

Q1:

In forced convection, the heat transfer depends on

A Re, Pr

B Re, Gr

C mainly Gr

D Re only

ANS:A - Re, Pr

In forced convection, the heat transfer depends primarily on: a) Re, Pr Where:

  • Re is the Reynolds number, which characterizes the flow regime (whether laminar or turbulent) of the fluid.
  • Pr is the Prandtl number, which describes the relative importance of momentum diffusivity to thermal diffusivity in the fluid.
These two dimensionless numbers play crucial roles in forced convection heat transfer:
  • Reynolds number (Re) governs the flow regime, with laminar flow occurring at low Re and turbulent flow at high Re. The flow regime significantly affects the convective heat transfer coefficient.
  • Prandtl number (Pr) represents the ratio of momentum diffusivity to thermal diffusivity in the fluid. It influences the thickness of the thermal boundary layer and affects the rate of heat transfer in the fluid.
Therefore, the heat transfer in forced convection depends on both Reynolds number (Re) and Prandtl number (Pr).