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Mechanical Engineering QUESTION #2423
Question 1
The Biot number (Bi) in transient heat conduction is defined as \(Bi = hL_c/k\). It represents:
  • Convective resistance at surface divided by conductive resistance inside body
  • Internal conductive resistance to external convective resistance: \(Bi = hL_c/k = \frac{L_c/(kA)}{1/(hA)}\)✔️
  • Thermal diffusivity to kinematic viscosity
  • Inertial forces to viscous forces
Correct Answer Explanation
Biot number: \(Bi=hL_c/k\), the ratio of internal conductive resistance \(L_c/(kA)\) to external convective resistance \(1/(hA)\). When \(Bi\ll 0.1\), the lumped capacitance method is valid.