Experimental study of thermo-convection performance of hybrid nanofluids of Al_2O_3-MWCNT/water in a differentially heated square cavity

摘要

Hybrid nanofluids as a new class of nanofluids known for their improved thermal and flow properties over single-particle nanofluids. However, experimental studies on the natural convection of hybrid nanofluids in enclosures are very scarce in the public domain. This paper investigates the natural convection of Al_2O_3-MWCNT/water nanofluids at various bi-nanoparticles' percent weights (Al_2O_3:MWCNT; 80:20, 60:40, 40:60, and 20:80) for 0.1 vol% in a square cavity. The Nu_(av), h_(av), Ra and Q_(av) at varying temperature gradients (20 °C-50 °C) were considered. The viscosity and thetmal conductivity of the stable nanofluids and base fluid were experimentally measured at a temperature range of 20 °C-50 °C. The obtained experimental data rot these properties were engaged in the study. The range of Ra considered in this work was 1.65 × 10~8-3.80 × 10~8. A direct relationship was noticed between Ra and Nu_(av). Temperature gradient and percent weight of bi-nanoparticles in the nanofluids were observed to augment Nu_(av). h_(av). and Q_(av) The hybrid nanofluid with 60:40 wt% of Al_2O_3 and MWCNT nanoparticles was identified to have the highest value for Ra, Nu_(av), h_(av), and Q_(av) at various temperature gradients. Furthermore, maximum enhancements of 16.2%, 20.5%, and 19.4% were recorded for Nu_(av), h_(av), and Q_(av), respectively, at AT = 50 °C, in relation to the base fluid. The engagement of Al_2O_3-MWCNT/water nanofluids in a square cavity has shown improved natural convection performance. A new correlation as related to Ra and bi-nanoparticles ratio has been developed for predicting Nu_(av). Results from this study further corroborate the advantage afforded by hybrid nanofluids over single-particle nanofluids.