Question Bank • QB_DFE_EXP_101 MCQ • 1 Mark

Section 7: Dairy and Food Engineering

Heat and Mass Transfer

Subtopic: Transient heat transfer in simple geometry

Question Statement:

The lumped heat capacity method for transient heat conduction analysis of a solid food object is considered valid only when the Biot number ($Bi = h L_c / k$) satisfies:

Options:

  • (A) $Bi < 0.1$
  • (B) $Bi > 1.0$
  • (C) $Bi = 10$
  • (D) $Bi > 100$

Answer Key:

A

Step-by-Step Solution & Explanation

When $Bi < 0.1$, the internal conductive resistance is negligible compared to the external surface convective resistance, allowing the entire body temperature to be treated as spatially uniform (lumped parameter approximation).
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