A combined approach to predict friction coefficients and convective heat transfer characteristics in A tube with twisted tape inserts for a wide range of Re and Pr

Generalized correlations are evolved to predict friction factors and convective heat transfer coefficients with twisted tapes in a tube for a wide range of Reynolds numbers and Prandtl numbers. Satisfactory agreement between the present correlations and the data of others validate the proposed correlations. The observations purports the fact that the physical presence of the tape in the flow might lead to monotonic transition from the laminar to turbulent regime. This phenomenon enabled to have a unique correlation for a wide range of Reynolds numbers and Prandtl numbers. Further, a theoretical approach yielded a combined solution for the range of 200 < Re < 10(5) and 2 < H/D < 10. The combined friction coefficient correlation valid for a wide range of Reynolds number is further extended to predict theoretically the convective heat transfer coefficients for the overall range of Reynolds number on the basis of the concept that transition might not be present distinctly separating the flow as laminar and turbulent regimes. The theoretical predictions are compared with earlier correlations revealing good agreement between them. (c) 2005 Elsevier SAS. All rights reserved.