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GATE 2019 ME (ME1) – Question 19

Heat Transfer · Convection: boundary layer, dimensionless parameters and correlations · 1 mark · Multiple choice

For hydrodynamically and thermally fully developed laminar flow through a constant-section circular pipe, compare Nusselt numbers at constant wall heat flux $Nu_q$ and constant wall temperature $Nu_T$.

  1. $Nu_q>Nu_T$
  2. $Nu_q<Nu_T$
  3. $Nu_q=Nu_T$
  4. $Nu_q=(Nu_T)^2$

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Show answer and explanation

Correct answer: (A) $Nu_q>Nu_T$

Explanation

Fully developed laminar circular-pipe flow gives $Nu_q=4.36$ for uniform wall flux and $Nu_T=3.66$ for uniform wall temperature. Thus **$Nu_q>Nu_T$, A**.