Influence of Nozzle-Type Inserts on the Heat Transfer Performance of EG/Water-Based Hybrid Nanofluid

The present investigation departs from conventional studies focusing on single-component nanofluids, instead analysing the thermophysical advantages of hybrid nanofluids, such as Al2O3/MWCNT, to enhance thermal conductivity and heat transfer efficiency in passive systems. This study aims to investigate the convective heat transfer properties of EG/water-based hybrid nanofluids within a circular tube, utilizing convergent and divergent nozzle-type inserts. The hybrid nanofluids are prepared from MWCNT and Al2O3 by varying weight concentrations as 0.004 vol%, 0.016 vol% and 0.028 vol%. Experiments were conducted in a plain tube employing passive techniques, including convergent and divergent nozzle inserts, with the hybrid nanofluid tested at various Reynolds numbers. A finite volume method is utilized to create a numerical model validated against the experimental results. In the case of convergent nozzle insert, it is found that the average Nusselt number over the given Reynolds number is enhanced by 16.9%, 36.7% and 49.9% for (hybrid nanofluid)HNF1, HNF2, and HNF3, respectively, compared to water. Similarly, the results are 17.5%, 36.9% and 51.2% for HNF1, HNF2, and HNF3, respectively, in the case of divergent nozzle insert. The study indicates that lower concentrations in hybrid nanofluid substantially improve the thermal performance factor (ThPF) through inserts. Higher ThPF is observed with the divergent nozzle insert in the plain tube at 0.028 wt% of MWCNT/Al2O3 at a Reynolds number of 3093.