Nanofluids are promising heat transfer fluids, which possess superior heat transfer properties compared with those of conventional fluids such as water, ethylene glycol, and engine oil. Nanofluids at volume concentrations of 0.5–5% were prepared by dispersing nanoparticles of silicon carbide (SiC) in ethylene glycol (EG) and distilled water (DW) using a two-step method. The stability of nanofluids was evaluated via zeta potential and also by analyzing the spectra obtained with a UV-vis spectrophotometer. The thermal and electrical conductivities of SiC/EG and SiC/DW nanofluids were determined. The results show that the SiC/DW possess better stability than SiC/EG nanofluids. Maximum thermal conductivity increases of 25% and 16% were observed for the SiC/EG and SiC/DW nanofluids at 5% volume concentration, respectively. In addition, it was observed that both nanofluids exhibited an increase in electrical conductivity with increase in the volume concentration of SiC nanoparticles. Specifically, an approximately 58 and 148 times increase in electrical conductivity, relative to the base fluid, was attained for the SiC/EG and SiC/DW nanofluids at 5% volume concentration, respectively.

Typical fuel-driven commercial dryers have excellent efficiency with homogeneous high-quality output, but they are beyond the access of farmers with limited agro land and financial resources. In this study, drying trials with potato slices were carried out utilizing a laboratory scale built drier coupled with an unique solar air heater. Assuming the set-up as mixed mode type solar dryer, performance of the dryer during the drying of potato slices was studied and the results were compared with that of open sun drying (OSD). The novel two pass solar air heater used in this project has aluminum turbulators arranged in staggered fashion. The absorber plate with aluminium turbulators present inside the double pass solar air heater reached a maximum temperature of 68°C. The average efficiency of the novel solar heater was about 72%. The moisture content of potato was reduced to 18.23% in 8 hours from 82.15%. The maximum thermal efficiency of the dryer was determined as 34%.The average specific energy requirement was estimated as 1.61 kWhkg⁻¹ and the shrinkage ratio was found to be 0.2 at the end of 7 hours.

The quest to have an effective and efficient heat transfer fluids has been a subject of great research interest for several decades. Nanofluids are preeminent fluids that have garnered increased attention recently due to their enhanced thermal properties. Moreover, viscosity is an essential characteristic of nanofluids and for this reason, many research works have been conducted on this subject over the last few decades. In this work, attempt is made to present the viscosity model of nanofluids. In addition, efforts are put forth to examine the existing empirical, semiempirical, and analytical correlations utilized for the evaluation of viscosity of nanofluids. Furthermore, there are a number of factors influencing the viscosity of nanofluids which has necessitated this review work. These factors not only feature the nanoparticle concentration, sizes, and types, they also include the temperature of the nanofluid as well as the base fluid surfactant and stability. This review also discuss several industrial applications of nanofluids such as those used for electronic cooling, solar applications, heat exchangers, and automotive industry. The available experimental results show that the above mentioned parameters have considerable effect over viscosity of nanofluid. However, there is no general trend to describe the influence of particle sizes on increase in viscosity. The lowest enhancement in viscosity with increase in nanoparticle concentration in literature was graphite/engine oil nanofluid with improvement of 6.25% with volume concentration increasing from 1 to 5.5%. It has also been observed that many empirical models have been formulated on viscosity of nanofluid; however, there is no universally accepted model. This review leads to some directions for future research in nanofluids.

The quest for effective and efficient heat exchange systems has been a subject of recent research. Nanofluids are high performance ultra-modern heat transfer fluids with superior properties compared to those of regular heat transfer fluids. Therefore, studies on the viscosity of nanofluids are essential owing to its effect on the pumping requirements of thermal systems. This article investigates the influence of concentration and temperature on the dynamic viscosity of AlN and SiC nanofluids. Nanofluids with a volume concentration of 0.5–5% were prepared by dispersing AlN nanoparticles in ethylene glycol (EG), SiC in ethylene glycol, and SiC in distilled water (DW) using the two-step method. The experimental investigation on the viscosity of these nanofluids was performed at the temperature range of 28–60 °C using an Ostwald viscometer. It was observed that the measured nanofluids exhibited an increase in the viscosity with an increase in the volume concentration of nanoparticles. Specifically, for SiC/DW nanofluids at 0.5 and 5% volume concentration, the viscosity ratio was 1.023 and 1.435 times that of the base fluid. Moreover, the viscosity of nanofluids is reduced by increasing the temperature relative to that of their base fluids. The experimental values were compared with existing theoretical model, and their predictions are below the experimental results; therefore, correlation was derived on the basis of the experimental data. The margin of deviation of these models in predicting the viscosity of the studied nanofluids varied between −15 and 23% for AlN/EG; −7 and 21% for SiC/EG, and −11 and 4% for SiC/DW nanofluid.