Comparative thermophysical and thermo-electrical performance of single, binary, and ternary (GNP–Al2O3–Fe2O3) hybrid nanofluids for heat transfer applications

Characterization of spark-discharge–synthesized multi-element oxide nanocomposites and thermophysical performance of their water-based nanofluids for solar collectors

Enhanced Thermophysical Properties of 40:60 % Ethylene Glycol and Water Mixture Based MgO + Fe3O4 Hybrid Nanofluids: An Experimental and ANN Predictions

Synthesis and Characterization of Enhanced Binary Carbonate Molten Salts Using Hybrid Nanoparticles (Al₂O₃–ZnO)

      Efficient thermal energy storage (TES) is necessary for the reliability of renewable energy systems, with molten salts recognized as effective high-temperature heat-transfer and storage media. This study examines the improvement of binary carbonate molten salts through the addition of Al₂O₃–ZnO hybrid nanoparticles produced via a one-step synthesis method. Two formulations have been created: a base mixture of Na₂CO₃ and K₂CO₃ (Sample 1) and a modified composition incorporating 0.5 wt% Al₂O₃–ZnO nanoparticles (Sample 2). The samples went through controlled stirring, evaporation, drying, and grinding, followed by comprehensive characterization utilizing Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Ultraviolet–Visible (UV–Vis) spectroscopy. The SEM analysis of Sample 2 demonstrated the presence of finer, needle-like structures characterized by an increased surface area and uniform dispersion of nanoparticles, which enhances heat conduction efficiency. FTIR confirms retention of the carbonate structure with strengthened metal–oxygen interactions, while Sample 2 shows up to 12–15% higher transmittance and an overall 6–8% increase relative to sample 1. UV–Vis results further reveal enhanced transmittance (up to 10–15%) accompanied by a marked 85–95% reduction in absorbance, indicating reduced agglomeration. The findings indicate that the addition of Al₂O₃–ZnO hybrid nanoparticles significantly improves the thermal stability, heat transfer properties, and energy-storage capacity of binary carbonate molten salts, highlighting their applicability in advanced solar-thermal thermal energy storage systems.

Enhanced Thermophysical Properties of a Quaternary Molten Salt NaNO3–KNO3–NaNO2–Ca(NO3)2 Doped with Al2O3 Nanoparticles

Thermophysical Properties And Heat Transfer Performance Of N-Doped Carbon-Metal Oxide Nanocomposite Nanofluids

Nanofluids, made by dispersing solid nanoparticles in a base fluid such as water or ethylene glycol, raise the thermal conductivity of ordinary coolants but come with two familiar penalties: the viscosity rises with loading, and the particles tend to settle or clump over time. Nitrogen-doped carbon combined with a transition metal oxide is one of the more promising particle chemistries for getting round these penalties. The carbon phase (graphene, graphene oxide or nanoplatelets) carries a high intrinsic thermal conductivity and, once nitrogen is doped into its lattice, improved wettability and dispersibility in polar base fluids; the metal oxide (Fe3O4, Al2O3, TiO2, CuO and related oxides) adds mass, magnetic or optical function, and anchoring sites that keep the carbon sheets from restacking. This review gathers what is known about these hybrid nanofluids. We first cover how they are prepared, the two-step and one-step routes, the choice of base fluid, and the surfactant or functionalization strategies that decide stability. We then treat the thermophysical properties one at a time: thermal conductivity and the mechanisms proposed for its enhancement (Brownian motion, the interfacial nanolayer and particle aggregation), dynamic viscosity, specific heat capacity, density and electrical conductivity, with reported enhancement figures drawn from the experimental literature. The heat-transfer section covers convective performance in laminar and turbulent flow, the Nusselt-number and heat-transfer-coefficient gains reported for nitrogen-doped graphene and carbon-metal oxide hybrids, entropy generation, and device-level results in heat exchangers and solar collectors. We close with the problems that still limit use: the trade-off between conductivity gain and pumping penalty, long-term stability, the gap between property measurements and full-system performance, and the shortage of data specific to nitrogen-doped carbon-metal oxide hybrids as opposed to their single-component parents.

An empirical investigation on the thermal conductivity of a hybrid nanofluid ( MgO ‐ ZnO /ethylene glycol) and proposal of a novel multivariate correlation

Recently, new research studies on nanofluids are increasingly focusing on hybrid nanofluids with enhanced thermophysical properties to overcome the limitations imposed by single‐component nanofluids. This work experimentally investigated the thermal conductivity of a novel hybrid nanofluid consisting of a mixture of MgO–ZnO and ethylene glycol (EG). Three significant variables were tested to investigate the performance of the new hybrid nanofluid: volume fraction (0.2%–1%, at a constant mixture of 50–50 ratio), temperature (set to 25–50°C with high accuracy), and nanoparticle diameter (set to 20, 55, and 90 nm). From the experimental study, it was identified that the maximum enhancement of the thermal conductivity was 11.48%, which was at the smallest nanoparticle diameter (20 nm), highest temperature (50°C), and highest solid concentration (1%). In addition, a new and accurate correlation function for this phenomenon was established. By using linear regression and MANOVA analysis, the correlation function achieved an R 2 of 0.99 with a difference of at most 1.15%, reflecting its high accuracy of prediction. It is clear that the values of all three variables—nanoparticle size, temperature, and volume fraction—played a highly important and interdependent role in the determination of the values of the thermal conductivity of the nanofluid. By performing a sensitivity analysis on the results of interest, the significant role of thermal conductivity in the variation of the variables at the extremes of the experimental range—20 nm, 50°C, and 1%—was established.