Stability Of Hybrid Nanofluids Research Articles

A critical review of specific heat capacity of hybrid nanofluids for thermal energy applications

Nanofluids have gained tremendous research interests in diverse fields of study due to their improved properties, especially as heat transfer fluids. Numerous studies have revealed the characteristics, limitations, and applicability of single type nanoparticles and the attributes of their colloidal mixtures. The discovery of the synergistic effect of nanoparticles, as relating to their improved thermophysical properties have been further explored in experimental and numerical studies of hybrid nanofluids. While the major focus has been on thermal conductivity, and viscosity, another extremely important property that gets little study attention is the specific heat capacity, which is a key thermal property in energy systems. Proper understanding of the specific heat capacity (SHC) of hybrid nanofluids is a sine qua non for proper decisions for heat transfer and heat storage applications. The crux of this review study is to give a detailed and comprehensive review of the specific heat capacity of hybrid nanofluids. The synthesis, characterization, and stability of hybrid nanofluids are presented. Furthermore, the different effects like temperature, volume concentration, mixture ratio, and particle size that influence the SHC behaviour of hybrid nanofluids are analyzed in this study. A compilation and discussion on correlation and machine learning models developed for hybrid nanofluids are also presented. Results suggest that volume concentration have an inverse relationship with the SHC of hybrid nanofluids, an increase in temperature improves the SHC of hybrid nanofluids, and this is more significant at temperatures above 50 ℃. Finally, although scarcely researched, the SHC is also affected by the size of the nanoparticles.

Stability of Graphene Oxide-Al2O3 Hybrid Nanofluids

In recent years, more and more researches and reports on nanofluids have been made, and hybrid nanofluids as new fluids have gradually entered the field of vision. Hybrid nanofluids have many excellent properties at the same time. Because the stability of hybrid nanofluids has an important influence on the thermal properties and flow heat transfer properties of the solution, the stability of nanoparticles suspended in the base liquid has become an important direction of research. The stability of graphene oxide-Al2O3 hybrid nanofluids was studied with ultrasonic time, dispersant and ultrasonic power as variables. The experimental results show that when the ratio of graphene oxide: Nano-Al2O3: dispersant is 1:1:1, ultrasonic time is 2 h and ultrasonic power is 300 w, the stability of graphene oxide- Al2O3 hybrid nanofluid solution is the best.

A review on the properties, preparation, models and stability of hybrid nanofluids to optimize energy consumption

These days, the importance of energy consumption has led scientists to optimize thermal devices. One of the solutions proposed for this purpose is using solid nanoparticles to amend the thermal properties of conventional fluids. Adding the nanoparticles into the foundation fluids results in an improvement in the fluid properties (thermal conductivity, viscosity, etc.). Nanofluid (NF) has been drawing attention in various engineering applications in the past decade due to its superior heat transfer characteristics than the conventional working fluid. In recent years, the researchers have focused on adding two or more nanoparticles into foundation fluids, known as hybrid nanoparticles. Hybrid nanofluids (HNFs) suggest a more appropriate heat transfer performance and thermophysical features than the conventional heat transfer fluids (ethylene glycol, water and oil) and even NFs with single nanoparticles. It was proven that HNF can be an alternative to the single NF, since it can provide more heat transfer enhancement, particularly in the context of the solar energy, electromechanical, HVAC, electromechanical and automobile. In the current research, the properties, preparation and stability of HNFs are investigated. Also, some models and correlations for predicting HNFs properties are presented.

The stability, optical properties and solar-thermal conversion performance of SiC-MWCNTs hybrid nanofluids for the direct absorption solar collector (DASC) application

Hybrid nanofluids have an advanced application prospect in the community of heat transfer fluids and particularly for the direct absorption solar collectors (DASCs). Therefore, stable ethylene glycol-based SiC-MWCNTs nanofluids with mass fractions ranging from 0.01% to 1% were prepared in this study. Combined with the unique properties of these two nanomaterials, the studied hybrid nanofluids displayed excellent stability, optical properties and photothermal conversion properties. The purpose of this paper is to simultaneously achieve the enhanced stability and high solar-thermal conversion efficiency of hybrid nanofluids used for DASC applications. The stability of hybrid nanofluids was confirmed. In addition, the hybrid nanofluids displayed an excellent solar irradiation absorption capacity in both visible and near-infrared regions (200–1100 nm). The fact proved that the hybrid nanofluid was effective working fluid in DASCs, where 0.5 wt% SiC-MWCNTs nanofluids could absorb 99.9% solar energy at only 1 cm path length. In addition, the solar-thermal conversion efficiency of hybrid nanofluids increased with the mass concentration. The maximum value of solar-thermal conversion efficiency was found to be 97.3% on 1 wt% SiC-MWCNTs nanofluid at 10 min, which was 48.6% higher than that of pure EG. The application potentials of SiC-MWCNTs hybrid nanofluids in low-temperature DASCs system were presented.

Stability and rheological properties of hybrid γ-Al2O3 nanofluids with cationic polyelectrolyte additives

In the present work, the stability and rheological properties of a water-based hybridaluminum oxide (γ-Al2O3) nanofluid containing polyethylenimine (PEI), a cationic polyelectrolyte additive, were investigated. The γ-Al2O3 nanoparticles used in the suspension was characterized using X-ray diffraction, TEM and FTIR analysis. Rheological results confirmed a non-Newtonian behavior in the shear range 0.01 s−1–1000 s−1 for hybrid γ-Al2O3 nanofluid with PEI as an additive. Interestingly, these nanofluids form gel or paste above 0.5 wt.% of PEI due to strong interaction among alumina nanoparticles as a result of surface charge screening brought about by protonation of PEI. Nearly temperature independent rheological behavior was observed in the temperature range 20–60 °C. The oscillatory rheological measurements indicate the elastic nature of the hybrid nanofluids at low strains due to the extended network structure formed by alumina nanoparticles. The preferred mode of interaction between PEI and alumina, different conformations and orientations were studied using DFT calculation, which shows that one NH bond from each NH2 groups interact with AlO bond. The AlO bond length of alumina was found to diminish upon interaction with PEI (i.e. AlO bond length of bare alumina is 1.746 Å and is reduced to 1.654 Å in the PEI-alumina complex) and the NH bonds of PEI is stretched to a bond length of 1.040 Å from 1.018 Å, indicating the interaction of NH bonds with AlO bond. The calculated interaction energy of PEI and alumina, is found to be −8.08 kJ/mol. These results offer possibilities of strongly altering the rheological behavior and stability of hybrid nanofluids with a very small amount of appropriate polyelectrolyte.

Experimental investigation on properties of hybrid nanofluids (TiO2 and ZnO) in water–ethylene glycol mixture

This paper presents an experimental investigation on properties and stability of hybrid nanofluids (TiO2 and ZnO) in water-ethylene glycol mixture. The nanofluids are important in heat enhanced due to its inherent operative performance. The performance of hybrid nanofluids in mixture based fluids is not explored vigorously yet. The properties of TiO2 and ZnO nanoparticle dispersed in mixture of water and ethyelene glycol (EG) were considered in this study. The outcome of base fluid proportion (water: EG) to hybrid nanofluids was investigated. Hybrid nanofluids with different volume concentration up to 0.1-1.5% were prepared with 21nm particle size of TiO2 and 10-30nm ZnO nanoparticle. The nanoparticle were suspended in various ratio of TiO2 : ZnO including 70:30, 80:20 and 90:10 by volume percent. The measurements of viscosity were performed using Brookfield LVDV III Ultra Rheometer for hybrid nanofluid temperature of 50 to 70 oC, while the measurements of thermal conductivity were performed using KD2 PRO thermal conductivity. Viscosity and thermal conductivity of hybrid nanofluids were perceived to impact by hybrid nanofluids concentration, temperature and waterethelene glycol as base fluid strongly.