부산대학교 도서관

This research aims to assess the in detail thermal performance and entropy generation of a helical heat exchanger with multiple rib profiles and coil revolutions using water-based Al2O3 nanofluid with 5% concentration. A steady-state computational fluid dynamic model was used in determining the thermal and hydraulic parameters. The numerical model was validated with a numerical study and an experimental study. Three multiple rib profiles (2 rib, 3 rib and 4 rib) and three different coil revolutions (10, 20 and 30) were considered to design nine cases of heat helical exchangers. The geometrical effect was assessed and further represented as the streamlines, isotherms, overall Nusselt number, friction factor, thermal enhancement factor, and entropy generation. It is found that with the growth of coil revolutions the overall heat transfer rate and friction factor rise. The most efficient heat exchanger found in terms of thermal enhancement factor is 3 rib 10 revolutions with the value of 1.34. The entropy generation increases with the rise of the coil revolution. The maximum entropy generation increased by 19.5% for varying the coil revolution with a constant rib profile. Finally, this study is a guide of choosing an efficient heat transfer in terms of thermo-hydraulic performance.