An experimental investigation of heat transfer on the annular side of helically coiled double pipe heat exchangers

Abstract

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.

Despite its industrial importance, data on single phase heat transfer in helically coiled annular ducts are lacking. The present work present experimental data on average heat transfer coefficients for four annular-coil geometries, covering the laminar, transition and turbulent flow regimes, spanning the range 700 < Re < 2,5·104 and 4 < Pr < 13. The effect of the centrifugal forces due to the coil curvature was evident, enhancing the heat transfer significantly in the laminar and transition regions. In the turbulent flow regime, the effects of curvature on heat transfer were small. Laminar flow was stabilized by secondary flow motion, shifting the transition to turbulence to higher Re. Heat transfer correlations were developed, taking into consideration the asymptotic behavior at high and low Re. The correlation reproduced 80% of the data to within ±15%.