Question

How does heat transfer enhance due to turbulence?
A. Decrease in thermal resistance.
B. Increase in convective coefficient.
C. Mixing is induced by velocity change.
D. Thinning of boundary layer.
Choose the correct answer from the options given below:

• A. A, C, B, D
• B. B, C, D, A
• C. A, D, C, B
• D. C, D, A, B

Hint:

Turbulence acts like a "scrubber" for the boundary layer. By physically mixing the fluid, it eliminates the "insulating" effect of stagnant fluid, letting heat move much faster.

Answer 1

The Correct Option is D

Concept: Heat transfer in fluids is often limited by the stagnant boundary layer near a surface. Turbulence introduces chaotic fluctuations that enhance energy transport.

Step 1: Determine the causal chain.
The physical progression of enhancement is:
• C (Mixing is induced by velocity change): Rapid fluctuations in velocity cause intense bulk mixing of hot and cold fluid parcels.
• D (Thinning of boundary layer): This intense mixing disrupts the stable laminar layer near the wall, significantly reducing its thickness.
• A (Decrease in thermal resistance): Since the stagnant layer is thinner, heat can flow through it more easily (less resistance).
• B (Increase in convective coefficient): The reduction in resistance directly results in a much higher convective heat transfer coefficient ($h$).

Step 2: Sequence Selection.
The most accurate physical order is C $\rightarrow$ D $\rightarrow$ A $\rightarrow$ B.