A numerical study on thermo-hydraulic characteristics of turbulent flow in a circular tube fitted with conical strip inserts

In an attempt to enhance the heat transfer without significant increase of pressure drop, we developed a conical strip turbulator in the present work. Characteristics of heat transfer rate, flow resistance, and overall thermo-hydraulic performance of turbulent flow in a circular tube fitted with the conical strip inserts were investigated through numerical simulation. The computation results show that the maximal friction factor of the enhanced tube is increased by similar to 10 times (f = 0.062-0.36): while the Nusselt number is augmented by similar to 5 times (Nu = 98.35-400.41) as that of the smooth tube. The value of performance evaluation criterion (PEC) lies in the range of 1.67-2.06, which demonstrates that the conical strip insert has a very good thermo-hydraulic performance. Effects of the geometric parameters of the conical strip were also examined. The numerical results indicate that larger slant angle and small pitch can effectively enhance the heat transfer rate, but also increase the flow resistance. Moreover, it is shown that the Nusselt number and friction factor are more sensitive to the slant angle than the inserts pitch. Comparatively steady thermo-hydraulic performance can be obtained at a moderate slant angle together with a small pitch. In addition to those good performances, the conical strip is also easy to fabricate. Thus, it is a promising tube insert which would be widely used in heat transfer enhancement of turbulent flow. (C) 2011 Elsevier Ltd. All rights reserved.