The performance of counter flow heat exchanger is analyzed with and without the insertion of sector cut twisted tape (TT) inserts in the presence of ZnO/MWCNT hybrid nanofluids (HNFs). The sector cut twisted tape inserts is positioned at the exit of tube heat exchanger (HEx). For the analysis, three different concentrations of hybrid nanofluids (0.01%, 0.03% and 0.05%) and three different sector cut twisted tape inserts (5 mm,
7 mm, and 9 mm) are employed. For numerical investigations, a standard two equations k-ɛ model is employed. The novelty of the study is to assess the influence of varying depth of sector cut twisted tape inserts and variations in concentrations of hybrid nanofluids. This study finds application in design and thermal management of engines. The results revealed that, 9 mm sector cut twisted tape inserts with 0.05% concentration of hybrid nanofluids, the augment in heat transfer rate (HTR) by 51.22% higher. Furthermore, performance evaluation criteria (PEC) at higher values of Re number reached to be 2.67, 3.66, 4.598 with the insertion of 5 mm, 7 mm & 9 mm depths of sector twisted tape inserts with 0.05% concentration of hybrid nanofluids.