Question

For laminar flow over a hot flat plate, the local heat transfer coefficient decreases with distance because (select all that are correct):
A. The velocities near the plate are decreasing.
B. The thickness of the heated region near the plate is increasing.
C. The fluid temperatures near the plate are increasing.

Answer 1

Answer:

B. The thickness of the heated region near the plate is increasing.

Explanation:

First we know that, a boundary layer is the layer of fluid in the immediate vicinity of a bounding surface where the effects of viscosity are significant. The fluid is often slower due to the effects of viscosity. Advection i.e the transfer of heat by the flow of liquid becomes less since the flow is slower, thereby the local heat transfer coefficient decreases.

From law of conduction, we observe that heat transfer rate will decrease based on a smaller rate of temperature, the thickness therefore increases while the local heat transfer coefficient decreases with distance.