Numerical prediction of laminar flow and forced convective heat transfer in a helical square duct with a finite pitch

Abstract

Fully developed laminar forced convective heat transfer in helical square ducts is studied numerically using a finite-volume method. The H1 thermal boundary condition is applied. Dean numbers up to 510 and Prandtl numbers between 0.005 and 500 are considered. Correlations for the mean Nusselt number are proposed. For a toroidally curved duct, two solution branches with a two-vortex secondary flow and one branch with a four-vortex flow are detected. The four-vortex solutions give, for high Pr, mean Nusselt numbers up to twice those of the two-vortex solutions. For ducts of small pitch or torsion, the flow and heat transfer characteristics are similar to those of a toroidally curved duct with the same dimensionless curvature