Determination of Heat Transfer Coefficient for Internal Flow
- The Dittus-Boelter equation is a widely used empirical equation that relates the average heat transfer coefficient for forced convection to the fluid properties, the flow conditions, and the geometric properties of the system.
- The equation for heat transfer coefficients is given by:
h = Nu * k/d
where h is the average heat transfer coefficient, k is the thermal conductivity and D is the hydraulic diameter of the pipe or duct.
- The Reynolds number is defined as:
Re =ρ* V * D/ μ
where, ρ is the fluid density, V is the fluid velocity, D is the hydraulic diameter, and μ is the dynamic viscosity of the fluid.
- The Prandtl number is defined as:
Pr = μ*Cp / k
- where Cp is the specific heat at a constant pressure of the fluid.
The assumption for Equations Dittus -Boelter equation
- The Dittus – Boelter equation is valid for
- Fully developed for thermal and fluid flows
- Turbulent flow in a circular pipe, Reynolds numbers > 2300
- Constant Wall Temperature.
- However, it has been found to give reasonably accurate results for a wide range of geometries and flow conditions.
Calculator For Internal Heat Transfer
Validation with CFD Results
- The heat transfer from the experimntal correlations need to be comparedCFD Results for validation of any internal heat transfer problems as presented in the post.
- Difference up to 20% is acceptable depending on complexicity of case