Numerical investigation of entropy generation of turbulent flow in twisted tri-lobed tubes

Abstract

Twisted tri-lobed tubes have garnered attention due to their exceptional heat transfer efficiency and straightforward fabrication. Existing literature lacks comprehensive assessments of the overall heat transfer performance of twisted tri-lobed tubes from the perspective of energy loss and irreversibility. This research aims to investigate entropy generation during turbulent water flow within twisted tri-lobed tubes, examining the influence of geometric parameters on local and average entropy production. Findings indicate that larger small circle radius (r) and straight lengths (l), coupled with smaller transition circle radius (R) and twist pitch lengths (p), result in diminished local and average heat transfer entropy production while enhancing local and average frictional entropy production, with heat transfer entropy generation dominating the overall entropy production. Additionally, with increasing Reynolds numbers, all twisted tubes demonstrate an increasing trend in average frictional entropy production, except for some cases (Case 1-Case 4) that exhibit an initial rise followed by a decline in average heat transfer entropy generation. Among the examined Reynolds range, Case 4 displays lower overall irreversibility compared to a plain tube. Following the second law of thermodynamics, Case 4 is preferred. The findings and methodology contribute to enhancing the thermodynamic evaluation of convective heat transfer in twisted tri-lobed tubes.