Heat Transfer Coefficient Formula:
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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.
The calculator uses the formula:
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.
Details: Accurate calculation of h is crucial for designing heat exchangers, cooling systems, and thermal management solutions.
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).
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.