Thermohydraulic investigation of graphene quantum dots nanofluids in a novel microchannel heat sink with a combination of elliptical ribs, secondary channels, and sinusoidal cavity

Microchannel heat sink units are designed with cavities and ribs, and their combination may provide the best effectiveness. The combination techniques for them affect the unit’s effectiveness and performance. Consequently, the aim of this study is numerically evaluated the microchannel (MC) with rectangular channel (RC) and MC with sinusoidal cavities and rectangular ribs (SCRR) to enhance heat transfer and reduce pressure drop. Additionally, a novel modification has been done MC with sinusoidal cavities by introducing a secondary channel with elliptical ribs (SCSCER). In this work, the graphene quantum dots (GQDs)/water nanofluids are used as working fluids with different concentrations from 0.1 to 0.5% and with Reynolds numbers (Re) range from 100 to 500. The results in this study demonstrated that the novel design provided a significant improvement in the thermohydraulic performance using water compared to other MC configurations. At Re = 100, the maximum temperature of the heated wall is reduced by 9.6 K and 10.7 K with the MC-SCRR and MC-SCSCER configurations, respectively, compared with the MC-RC. At Re = 500, these reductions are 8.6 K and 8.9 K, respectively. The pressure drop of the SCSCER was reduced by 12.8% and 23.4% compared to the SCRR at Re = 100 and Re = 500, respectively. Regarding impact of GQDs nanofluids with SCSCER, the results of cooling uniformity and thermal resistance at 100 of Re decreased by 14.8% and 16.3%, respectively, when GQDs concentration changed from 0 to 0.5%. The findings in this study showed that the enhancement percentages of convective heat transfer coefficient compared to the water were 12.7%, 15.2%, and 23.3%, respectively, for 0.1%, 0.3%, and 0.5% of ϕ values at Re = 100. These percentages are reduced and became 8.6%, 11.1%, and 16.4%, respectively, at Re = 500. Concluding, the highest performance evaluation criteria value was 9.2% at Re = 100 and 0.5% of GQD nanoparticles concentration, making these conditions may be recommend with the proposed SCSCER for feasible applications.