Film Coefficient Calculator
Calculate the Convective Heat Transfer Coefficient (h)
Understanding the Film Coefficient
The film coefficient, also known as the convective heat transfer coefficient ($h$), is a quantitative measure of how effectively heat is transferred between a solid surface and a fluid (liquid or gas) in motion. Unlike thermal conductivity, which is a property of the material itself, the film coefficient depends on the fluid properties, the flow geometry, and the flow regime (laminar or turbulent).
In engineering, accurately determining $h$ is critical for the design of heat exchangers, radiators, HVAC systems, and electronic cooling solutions. A higher film coefficient indicates more efficient heat transfer.
Formulas Used
The fundamental relationship relating the film coefficient to the fluid properties and flow conditions is derived from the dimensionless Nusselt Number ($Nu$):
h = (Nu × k) / L
- h: Film Coefficient $[W/(m^2 \cdot K)]$
- Nu: Nusselt Number (dimensionless)
- k: Thermal Conductivity of the fluid $[W/(m \cdot K)]$
- L: Characteristic Length (or Diameter $D$ for pipes) $[m]$
Dittus-Boelter Correlation
When the Nusselt number is not directly known, it is often estimated using empirical correlations. This calculator includes the Dittus-Boelter equation for fully developed turbulent flow in smooth circular tubes:
Nu = 0.023 × Re0.8 × Prn
- Re: Reynolds Number (Inertial forces / Viscous forces)
- Pr: Prandtl Number (Momentum diffusivity / Thermal diffusivity)
- n: 0.4 for heating the fluid, 0.3 for cooling the fluid.
Note: This correlation is generally valid for $Re > 10,000$ and $0.7 \le Pr \le 160$.