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Heat Transfer
Convection & Radiation
GATE 2023
Medium

Consider incompressible laminar flow of a constant property Newtonian fluid in an isothermal circular tube. The flow is steady with fully-developed temperature and velocity profiles. The Nusselt number for this flow depends on

  • neither the Reynolds number nor the Prandtl number
  • Bboth the Reynolds and Prandtl numbers
  • Cthe Reynolds number but not the Prandtl number
  • Dthe Prandtl number but not the Reynolds number

Explanation

For fully-developed laminar internal flow with a fixed thermal boundary condition, the Nusselt number is a constant (e.g. Nu=3.66 for constant wall temperature, Nu=4.36 for constant heat flux) that depends only on the duct geometry and thermal boundary condition — not on Re or Pr.

Source: GATE ME 2023 Official Paper (2023)

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