F or heat transfer across a solid-fluid interface, which one of the fo...
Explanation:
Biot number (Bi) is defined as the ratio of convective heat transfer resistance to conductive heat transfer resistance. Mathematically, Bi = hL/k, where h is the convective heat transfer coefficient, L is the characteristic length scale, and k is the thermal conductivity of the solid.
When the Biot number is very small compared to 1 (i.e., Bi < 1),="" the="" following="" statements="" are="" />
- Conduction resistance in the solid is very small compared to convection resistance in the fluid: Since Bi < 1,="" the="" convective="" heat="" transfer="" resistance="" is="" much="" larger="" than="" the="" conductive="" heat="" transfer="" resistance.="" therefore,="" convection="" dominates="" over="" conduction,="" and="" the="" heat="" transfer="" rate="" is="" mainly="" determined="" by="" the="" fluid="" flow="" />
- Temperature profile within the solid is nearly uniform: Since conduction resistance is very small, the temperature gradient within the solid is negligible. Therefore, the temperature distribution within the solid is nearly uniform.
- Temperature drop in the fluid is significant: Since convective heat transfer resistance is much larger than conductive heat transfer resistance, the temperature drop across the fluid is significant. This means that the fluid temperature decreases significantly as it flows over the solid surface.
- Temperature drop in the solid is significant: This statement is NOT true when Bi < 1.="" instead,="" the="" temperature="" drop="" in="" the="" solid="" is="" negligible="" because="" the="" temperature="" gradient="" within="" the="" solid="" is="" very="" />
Therefore, option D is the correct answer as it contradicts the statement that the temperature drop in the solid is significant.