Nusselt Number For Gases And Liquids Calculator

Nusselt Number Formula:

\[ Nu = 2 + (0.4 \times Re^{0.5} + 0.06 \times Re^{0.67}) \times Pr^{0.4} \times \left( \frac{\mu_{\infty}}{\mu_w} \right)^{0.25} \]

Reynolds Number (Re):

Prandtl Number (Pr):

Dynamic Viscosity at Free Stream Temperature (μ∞):

Pa·s

Dynamic Viscosity at Wall Temperature (μw):

Pa·s

Nusselt Number (Nu):

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1. What is the Nusselt Number?

The Nusselt Number is the ratio of convective to conductive heat transfer at a boundary in a fluid. Convection includes both advection and diffusion. It is a dimensionless number used in heat transfer calculations.

2. How Does the Calculator Work?

The calculator uses the Nusselt Number formula:

\[ Nu = 2 + (0.4 \times Re^{0.5} + 0.06 \times Re^{0.67}) \times Pr^{0.4} \times \left( \frac{\mu_{\infty}}{\mu_w} \right)^{0.25} \]

Where:

\( Nu \) — Nusselt Number
\( Re \) — Reynolds Number (ratio of inertial forces to viscous forces)
\( Pr \) — Prandtl Number (ratio of momentum diffusivity to thermal diffusivity)
\( \mu_{\infty} \) — Dynamic Viscosity at Free Stream Temperature
\( \mu_w \) — Dynamic Viscosity at Wall Temperature

Explanation: This formula calculates the Nusselt number for gases and liquids, accounting for fluid properties and flow conditions.

3. Importance of Nusselt Number Calculation

Details: The Nusselt number is crucial for designing heat exchangers, predicting heat transfer rates, and analyzing thermal systems in various engineering applications.

4. Using the Calculator

Tips: Enter Reynolds Number, Prandtl Number, and both dynamic viscosity values. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the physical significance of Nusselt Number?
A: The Nusselt number represents the enhancement of heat transfer through a fluid layer due to convection compared to conduction alone.

Q2: What are typical Nusselt Number values?
A: For laminar flow, Nu is typically 3.66 for constant wall temperature in circular tubes. For turbulent flow, values range from 50 to 1000 or higher.

Q3: When is this specific formula applicable?
A: This formula is particularly useful for calculating Nusselt number for both gases and liquids in various flow conditions.

Q4: Are there limitations to this equation?
A: This equation works well for a wide range of Reynolds and Prandtl numbers, but may have limitations in extreme conditions or for non-Newtonian fluids.

Q5: How does viscosity ratio affect the Nusselt number?
A: The viscosity ratio accounts for the variation in fluid properties with temperature, which affects the heat transfer characteristics.