Experimental investigations of particle sizes effects on exergy and entropy characteristics of AL2O3 - MWCNT hybrid nanofluid along the transitional flow regime

Experimental investigation on particle size effect on entropy and exergy characteristics of AL(2)O(3) - MWCNT hybrid nanofluid in transitional flow Regime was carried out with four different particle sizes (i.e., for Aluminum oxide (AL(2)O(3)), 20 nm, and 5 nm used while Multiwalled Carbon Nanotubes (MWCNT) <7 nm and 30-50 nm particles). 0.3 vol concentrations of three hybrid nanofluids with different particle size combinations (i.e., Al2O3(20 nm) - MWCNT(20-30 nm), Al2O3(20 nm) - MWCNT(<7 nm), and then Al2O3(5 nm) - MWCNT(<7 nm)) are prepared using a two-step method, at a percentage weight composition (PWC) of 60:40. Results shows that Nanofluid with Al2O3 (20 nm) and MWCNT (<7 nm) have shown the best performance. It has an exergy efficiency of 54.12% at turbulent Reynold number of 4500, while in the transitional flow regime, it records an exergy efficiency of 47.85%. Frictional entropy and thermal entropy in the transitional regime were reduced with hybrid nanofluid of Al2O3 (20 nm) and MWCNT (<7 nm) by 6.78% and 13.53%, respectively, as compared to Al2O3 (5)- MWCNT (<7) nanofluid. Both thermal and frictional entropy effects were better minimized in the turbulent regime than in the lamina and transitional regime, as they were reduced by 16.66 and 24.7%, respectively. The study also recommends that for further investigations, more samples need to be taken to reach a clearer conclusion the effect of particle size, and since this is a hybrid nanofluid the samples should be of different sizes from both nanoparticles.

Automated summary

The experimental investigation focused on the effects of particle size on the entropy and exergy characteristics of AL(2)O(3)-MWCNT hybrid nanofluid in transitional flow regime. The results showed that the nanofluid with Al2O3 (20 nm) and MWCNT (<7 nm) exhibited the best performance, with reduced frictional and thermal entropy.