Which factor does NOT influence the convective heat transfer coefficient h?

Which factor does NOT influence the convective heat transfer coefficient h?

• A. Fluid velocity
• B. Turbulence
• C. Surface condition
• D. Insulation thickness

Answer: (D)

The main idea is that the convective heat transfer coefficient h depends on how the fluid moves and how it interacts with the surface at the boundary. Fluid velocity and turbulence change the boundary layer: higher speed thins the boundary layer and turbulence mixes the fluid more effectively, both of which raise h. The surface condition also matters because rough or textured surfaces disturb the near-wall flow, often increasing heat transfer and thus increasing h. Insulation thickness, however, sits in the solid insulation layer and controls the conduction resistance through that material. It does not alter the boundary-layer behavior or the fluid–surface interaction where h is defined. So changing insulation thickness changes the overall heat transfer rate through the system, but not the convective coefficient at the fluid–surface interface.

The main idea is that the convective heat transfer coefficient h depends on how the fluid moves and how it interacts with the surface at the boundary.

Fluid velocity and turbulence change the boundary layer: higher speed thins the boundary layer and turbulence mixes the fluid more effectively, both of which raise h. The surface condition also matters because rough or textured surfaces disturb the near-wall flow, often increasing heat transfer and thus increasing h.

Insulation thickness, however, sits in the solid insulation layer and controls the conduction resistance through that material. It does not alter the boundary-layer behavior or the fluid–surface interaction where h is defined. So changing insulation thickness changes the overall heat transfer rate through the system, but not the convective coefficient at the fluid–surface interface.