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GATE 2021 ME (ME1) – Question 23

Heat Transfer · Unsteady conduction and lumped parameter systems · 1 mark · Multiple choice

A hot steel spherical ball is suddenly dipped into a low temperature oil bath. Which of the following dimensionless parameters are required to determine instantaneous center temperature of the ball using a Heisler chart?

  1. Biot and Fourier
  2. Reynolds and Prandtl
  3. Biot and Froude
  4. Nusselt and Grashof

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Show answer and explanation

Correct answer: (A) Biot and Fourier

Explanation

Biot number $Bi=hR/k$ compares surface convection resistance with internal conduction resistance. Fourier number $Fo=\alpha t/R^2$ measures elapsed diffusion time.

Heisler transient-conduction charts use these two parameters. **Answer: A**.