1. What is the Nusselt Number?

The Nusselt number (Nu) is a dimensionless number that represents the ratio of convective to conductive heat transfer across a boundary. For a flat plate, it's calculated using the Reynolds number (Re) and Prandtl number (Pr).

2. How Does the Calculator Work?

The calculator uses the Nusselt number equation for laminar flow over a flat plate:

Where:

• \( Nu \) — Nusselt number (dimensionless)
• \( Re \) — Reynolds number (dimensionless)
• \( Pr \) — Prandtl number (dimensionless)

Explanation: This equation is valid for laminar flow (Re < 5×10⁵) over an isothermal flat plate.

3. Importance of Nusselt Number

Details: The Nusselt number is crucial in heat transfer calculations as it helps determine the convective heat transfer coefficient, which is essential in designing heat exchangers and cooling systems.

4. Using the Calculator

Tips: Enter Reynolds number and Prandtl number as positive dimensionless values. The calculator is valid for laminar flow conditions.

5. Frequently Asked Questions (FAQ)

Q1: What is the range of validity for this equation?
A: This equation is valid for laminar flow with Reynolds number below 500,000 (Re < 5×10⁵).

Q2: How does the Nusselt number relate to heat transfer coefficient?
A: The heat transfer coefficient h can be calculated as h = Nu × k/L, where k is thermal conductivity and L is characteristic length.

Q3: What's the difference between local and average Nusselt number?
A: This calculator provides the average Nusselt number for the entire plate. Local Nusselt number varies along the plate length.

Q4: Can this be used for turbulent flow?
A: No, for turbulent flow (Re > 5×10⁵), a different correlation should be used (typically Nu = 0.037 Re^0.8 Pr^1/3).

Q5: What are typical values for Prandtl number?
A: Pr ≈ 0.7 for gases, 1-10 for water, and up to 1000 for oils, depending on temperature.