Question

In forced convection inside a pipe, the Nusselt number for fully developed laminar flow with constant wall temperature is:

• A. 3.66
• B. 4.36
• C. 5.66
• D. 6.36

Hint:

Remember:
- Constant Wall Temperature $\to$ $Nu = 3.66$ (lower value)
- Constant Heat Flux $\to$ $Nu = 4.36$ (higher value)

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
This question asks for the standard value of the Nusselt number in fully developed laminar flow inside a pipe with a constant wall temperature boundary condition.

Step 2: Key Formula or Approach:
For fully developed laminar flow in a circular tube, the Nusselt number ($Nu_D = \frac{hD}{k}$) is a constant value that depends only on the thermal boundary condition at the tube wall.

Step 3: Detailed Explanation:

• In a circular pipe with fully developed laminar flow:
- For a constant surface temperature ($T_s = \text{constant}$) boundary condition, the Nusselt number is:
\[ Nu_D = 3.66 \]
- For a constant surface heat flux ($q_s'' = \text{constant}$) boundary condition, the Nusselt number is:
\[ Nu_D = 4.36 \]

• Since the question specifies constant wall temperature, the correct value is $3.66$.

Step 4: Final Answer:
The Nusselt number for fully developed laminar flow with constant wall temperature is $3.66$.