Experimental investigation into natural convective heat transfer enhancement by convective hybrid nanofluid in square cavity

Abstract

In the past decade, nanotechnology research has been increased rapidly. Reports reveal that nanofluids are beneficial heat transfer fluids for engineering applications as superior heat transfer fluids than traditional conventional heat transfer fluids such as water, ethylene glycol, engine oil, mixture EG/W, etc. The nanofluid have been good to occupied as operational fluids to transfer heat in numerous industrial equipment such as heat exchangers, cooling devices, and solar collectors. Researchers continuously have been doing research and investigations to attain the distinctive features of nanofluids and thermophysical properties; the first significant feature, thermal conductivity, has more influence on heat transfer. The idea of hybridization of different kinds of nanomaterial to prepare “hybrid” nanofluids have developed as progressive heat transfer fluids through better thermophysical properties and convective heat compared to single nanofluids. The investigation supports that the hybrid nanofluids have the capability to increase the effective thermal conductivity of traditional conventional base fluids and are beneficial for various engineering applications. The current study is interested in applying hybrid nanofluids synthesized by ZnO-MWCNT/DIW, ZnO-GPN/DIW, and ZnO-MWCNT/W: EG on natural convection heat transfer inside a square cavity. Hybrid nanofluids were synthesized by using the two-step process. Various techniques achieved NFs stability and surface characterization. The made HNFs were stable for a long period, and no sedimentation was detected. The effective thermal conductivity and viscosity experimentally were measured by standard devices under the influence of PWR, base fluids, temperature difference, and volume concentration. Base fluid κ and superior κ of nanopowder, rising temperature and 𝜑 were observed to augment κ of HNF. The κ augmentation by 23.11% for (ZnO: MWCNT_20:80/DIW) at (0.1 vol. % and 55oC), 34.72% for (40:60 – ZnO: MWCNT/W: EG (80:20)) at (0.2 vol. % and 55oC), 27.47% (ZnO: GPN_25:75/DIW) at (0.1 vol. % and 55oC). Temperature increase diminished μ and base fluids μ, higher density of nanopowder, 𝜑 improved it for AZM, BAZM, and AZG by an increase of 33.33%, 54.92%, and 12.28% respectively. Furthermore, models were established for calculating the κ and μ of AZM, BAZM, and AZG as a function of PWR, temperature, and 𝜑 at considered range from the found experimental data. Heat transfer performance of AZM, BAZM, and AZG was studied by occupying it into a square cavity by measuring natural convection parameters. The observation of natural convection parameters showed that nanocomposites are superior to those of the single nanofluids of ZnO, which showed the benefit of NP hybridization for industrial application. Furthermore, models were established for predicting the κ and μ, Nu of the formulated AZM, BAZM, and AZG from the achieved experimental data.