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Heat Transfer Coefficient of Air Calculator

Heat Transfer Coefficient Formula:

\[ h = \frac{Nu \times k}{L} \]

dimensionless
W/mK
m

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1. What is Heat Transfer Coefficient of Air?

Definition: This calculator determines the convective heat transfer coefficient (h) for air using the Nusselt number, thermal conductivity, and characteristic length.

Purpose: It helps engineers and scientists calculate the heat transfer rate between a surface and the surrounding air.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ h = \frac{Nu \times k}{L} \]

Where:

Explanation: The Nusselt number represents the ratio of convective to conductive heat transfer, which when multiplied by thermal conductivity and divided by characteristic length gives the heat transfer coefficient.

3. Importance of Heat Transfer Coefficient

Details: Accurate calculation of h is crucial for designing heat exchangers, cooling systems, and thermal management solutions.

4. Using the Calculator

Tips: Enter the Nusselt number (typically from empirical correlations), thermal conductivity of air (default 0.0262 W/mK at 300K), and characteristic length (typically the length of the surface in flow direction).

5. Frequently Asked Questions (FAQ)

Q1: How do I determine the Nusselt number?
A: Nu is typically calculated from empirical correlations like Dittus-Boelter (for turbulent flow) or Churchill-Bernstein (for external flow).

Q2: What's the typical thermal conductivity of air?
A: At room temperature (300K), k ≈ 0.0262 W/mK, but it varies with temperature (higher at higher temperatures).

Q3: What is characteristic length?
A: It's the representative dimension of the system, such as diameter for pipes or length along flow for flat plates.

Q4: What's the range of typical h values for air?
A: Natural convection: 2-25 W/m²K, Forced convection: 25-250 W/m²K.

Q5: Does this work for other fluids besides air?
A: Yes, but you must use the appropriate thermal conductivity (k) for the specific fluid.

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