Geometrical and coil revolution effects on the performance enhancement of a helical heat exchanger using nanofluids

Abstract

Nanofluids have been widely researched in recent years to improve the heat transfer rate in heat exchangers. However, no research is seen on improving heat transfer rate using nanofluids by incorporating multi-ribbed geometry with coil revolution into helical heat exchangers. This study thus numerically investigates the heat transfer performance of a helical heat exchanger using various water-based nanofluids, considering multiple head-ribbed geometries with different coil revolutions. The numerical results have been validated against experimental correlations and a published numerical study. A total of nine cases are initially modelled to compare and identify the most efficient heat exchanger design under various heating conditions. The helical heat exchanger with 2 head ribbed and 30 coil revolution is found to be the most effective among all the cases and is selected for the nanofluid study. The heat transfer rate could be enhanced by 20%–80% utilizing 2 rib head geometry and by 17%–66% using 30 coil revolutions. Four different water-based nanofluids, namely Al 2 O 3 , CuO, SiO 2 , and ZnO with 4% nanofluid concentration, are introduced in the most effective helical heat exchanger. It is revealed that Al 2 O 3 offers the highest heat transfer rate while SiO 2 provides the lowest. The heat transfer rate enhances when the number of the ribbed head reduces and the coil revolution increases.