Numerical investigations on flow and heat transfer characteristics of a tube equipped with twisted tape inserts

Computational Fluid Dynamics (CFD) is gaining much popularity for analyzing and designing heat transfer enhancement techniques for complex systems. CFD gives an insight into flow patterns that are difficult, expensive or impossible to study using traditional experimental techniques. However, the application of CFD depends on its accuracy and reliability. This requires the CFD code be validated with laboratory measurements to ensure its predictive capacity. The present paper focuses on such a CFD validation study for flow and heat transfer characteristics of circular tube with twisted tape insert. Circular tube with twisted tape having twist ratios of 3 and 4 are considered for this study along with plain tube. Three Reynolds numbers of 8500, 11000 and 14000 are considered in this study. Simulations are performed with commercially available CFD tool, ANSYS FLUENT (v14.0). The variation of heat transfer and pressure drop in the form of Nusselt number (Nu) and friction factor (f) respectively is determined and the results are compared with those of plain tube. These results are also validated against the test data available in open literature. Results show that Nusselt number increases with increase in Reynolds number and decrease in twist ratio. While friction factor decreases with increase in Reynolds number and twist ratios. The enhancement of heat transfer with twisted tape inserts as compared to plain tube varied from 36-75%.