Determination of Local Heat Transfer Coefficients and Friction Factors at Variable Temperature and Velocity Boundary Conditions for Complex Flows

• Published in: Fluids (Basel) Vol. 9; no. 9; p. 197
• Main Authors: Hartmann, Christopher, von Wolfersdorf, Jens
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.09.2024
• Subjects: adiabatic wall temperature; Aviation; Boundary conditions; Boundary layer flow; Boundary layers; Boundary value problems; conjugate heat transfer; equilibrium turbulent boundary layer; Flat plates; Fluid flow; Friction; Friction factor; Heat transfer; Heat transfer coefficients; Incompressible flow; Mathematical research; Parameters; pressure gradient effects; Pressure gradients; Reynolds analogy; Shear stress; Speed; Temperature; Tests, problems and exercises; Turbulent boundary layer; Velocity; Wall shear stresses; Germany
• ISSN: 2311-5521; 2311-5521
• DOI: 10.3390/fluids9090197

Transient conjugate heat transfer measurements under varying temperature and velocity inlet boundary conditions at incompressible flow conditions were performed for flat plate and ribbed channel geometries. Therefrom, local adiabatic wall temperatures and heat transfer coefficients were determined. The data were analyzed using typical heat transfer correlations, e.g., Nu=CRemPrn, determining the local distributions of C and m. It is shown that they are closely linked. A relationship lnC=A−mB is observed, with A and B as modeling parameters. They could be related to parameters in log-law or power-law representations for turbulent boundary layer flows. The parameter m is shown to have a close link to local pressure gradients and, therewith, near wall streamlines as well as friction factor distributions. A normalization of the C parameter allows one to derive a Reynolds analogy factor and, therefrom, local wall shear stresses.