Laminar flow and heat transfer through square duct with twisted tape insert

Numerically predicted characteristics of laminar flow and heat transfer through square duct with twisted tape insert are presented in this paper. The transport equations are solved on a non-staggered non-orthogonal grid using the curvilinear version of the "Complete Pressure Correction" algorithm. Both the flow and heat transfer are in a state of periodic development in the axial direction. The heat transfer characteristics are predicted under axially and peripherally constant wall heat flux conditions. Correlations for friction factor and Nusselt number are developed from the predicted data. The agreement between the correlation and experimental data for friction factor is found to be excellent. Relative thermo-hydraulic performance of square and circular ducts, both fitted with twisted tapes of same twist ratio is also presented in this paper. The study shows significant improvements can be achieved,vith the square duct, particularly at higher Prandtl numbers and lower twist ratios. Improvement is observed even for air, over certain ranges of Reynolds number. (C) 2001 Published by Elsevier Science Inc.