Subtopic: Transient heat transfer in simple geometry
Question Statement:
For transient conduction in food materials modeled by Heisler charts, the lumped capacitance assumption is considered sufficiently accurate when the Biot number ($Bi$) satisfies:
Options:
(A) $Bi < 0.1$
(B) $Bi > 10$
(C) $0.1 < Bi < 1.0$
(D) $Bi = \infty$
Answer Key:
A
Step-by-Step Solution & Explanation
When $Bi = \frac{h L_c}{k} < 0.1$, the internal conductive resistance of the food body is less than 10% of the surface convective resistance. Consequently, internal temperature gradients are negligible (< 5% error) and the temperature may be treated as spatially uniform throughout.