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This study challenges the capabilities of artificial neural network (ANN) as well as response surface methodology (RSM) in estimating the viscosity (μ) and thermal conductivity (k) of β − SiC/EG and β − SiC/PG nanofluids. The implementation of these methods is performed by defining statistical criteria with a great obsession to forecast viscosity ratio as well as thermal conductivity ratio with the least error. The nanoparticle of β − SiC has a bigger effect on μEG and μPG so that they increase up to 78.71% and 56%, while kEG and kPG improve under the best conditions up to 14.64% and 4.85%, respectively. Statistical calculations show that for RSM, R-square is 0.987 for μ β − SiC / EG μ EG , 0.975 μ β − SiC / PG μ PG , 0.99 k β − SiC / EG k EG and 0.987 k β − SiC / PG k PG . This figure for ANN is 0.994, 0.992, 0.994 and 0.991. This implies that ANN ability is superior. Although β − SiC nanoparticles increase the viscosity by 78.7% (for EG) and 56% (for PG) which is not desirable, fortunately, fluid mechanics-based calculations reveal that in turbulent regime, the pumping power increases by only 17.2% and 13.5% under worst conditions.

The quiddity of ethylene glycol (EG) surface tension is attributed to the cohesive forces between EG molecules. The presence of tungsten oxide (WO3) nanoparticles certainly affects the cohesive forces and the surface tension will be affected. In this study, SITA dynotester was utilized for measuring surface tension at 20–50°C and 0.005–5 wt%. Loading nanoparticles intensified the adhesive force between EG and WO3 molecules and simultaneously attenuated cohesive forces between EG molecules. According to the results, the positive effect of the adhesive force was overcome by the negative effect of reducing the adhesion force and therefore the surface tension was weakened. At 20 ° C the EG surface tension was attenuated up to 15.57% by adding WO3 nanoparticles (5 wt%). Performing response surface methodology and artificial neural network for navigating the surface tension was successful. The acceptable R-squared for RSM (0.982) and ANN (0.99) led to maximum error of 1.43% and 0.95%.

In this paper, the exergy rate analysis at a pin–fin micro-heat sink (MH/S) is investigated numerically. The critical part of a MH/S contains several square-shaped pin–fins. A turbulent flow of water/boehmite alumina nanofluid (N-F) moves on the pin–fins and cools the MH/S. Constant heat flux is entered into the lower part of the pin–fin MH/S. The governing equations are solved based on the control volume method and simple algorithm. The K-epsilon model is applied to model the N-F flow over pin–fins. The first-law, second-law efficiencies, gains exergy rate, loss exergy rate, and output exergy rate are studied in analysis. Variables considered in the problem consist of the inlet flow rate of N-F, N-Ps shape, and volume fraction of N-Ps in water. The main purpose of this paper is to investigate the exergy rate of various N-P shapes in a MH/S. The results of this study showed that increasing the flow rate reduces the temperature of the MH/S. Increasing the velocity and volume percentage reduces the amount of out exergy rate. In fact, by increasing the velocity from 1 to 3 m s−1 for water, the amount of out exergy rate output decreases by 7.36 W. The greatest reduction in loss exergy rate is for platelets N-Ps with a reduction of 441 W. Also, increasing the velocity and decreasing the volume percentage reduce the efficiency of the first law of thermodynamics, which is 8.5% for platelets N-Ps. The addition of these N-Ps reduces the efficiency of the second law by 5.7%.

In this article, a numerical method was employed to perform an exergy analysis on water/boehmite alumina nanofluid in a pin-fin micro heat sink. The heat sink is a micro-sized component, which is in charge of cooling an electronic unit. Nanoparticles possess various shapes such as brick, blade, platelet, and cylinder. Hence, the effect of their shape was studied on exergy analysis, and the control volume approach was used for the simulation. The analysis revealed that the simultaneous increase in the velocity and volume fraction of all nanoparticle shapes decreases the output and gain exergy values, where the decrease in gain exergy is more significant. Brick-shaped nanoparticles exhibited the greatest reduction in out exergy. The reduction of out and loss exergies for brick-shaped nanoparticles is about 0.2W and 23W, respectively, when 5% of these nanoparticles are added to the base fluid. Furthermore, decreasing the inlet fluid velocity and increasing the volume fraction of nanoparticles reduce the amount of exergy loss. The study of the first and second laws of thermodynamics showed that increasing the velocity slightly increases the efficiency of the first law for both water and nanofluids, but reduces the efficiency of the second law of thermodynamics. In the case of water, the reduction in the efficiency of the second law is 5.9% for increasing the velocity from 0.2 to 0.8 m s−1. Adding nanoparticles to water reduces both the efficiency of the first and second laws of thermodynamics.

The present investigation aims to experimentally examine the effects of shear rate, temperature, and solid concentration of nanoparticles on the rheological properties of TiO2-MWCNT (80%–20%)/oil (5 W50) nanofluid. The rheological behavior of the nanofluid, whether it is a Newtonian or non-Newtonian fluid, has been studied in different temperatures, shear rates, and solid concentrations. It is found that the nanofluid behaves as a Newtonian fluid under the conditions of the present study. In addition, the increasing trend in the dynamic viscosity of the nanofluid has been observed as the solid concentration increases. The maximum increase has been observed at the solid concentration and temperature of 2% and 50 °C, respectively, by 42%. Moreover, employing the experimental results, a new correlation for estimating the dynamic viscosity of the nanofluid in terms of temperature and solid concentrations has been proposed with the accuracy of 4%.

There are many debates on the preparation methods and the role of ultrasonication on the stability, thermophysical properties, and heat transfer performance of nanofluids. The present study, which is the continuation of the authors previous study, the effects of ultrasonication on the thermal and fluid dynamic performance of MWCNT-water nanofluid, over a different range of temperatures and solid concentrations, based on the thermophysical properties of the nanofluid, has been investigated. The effects of ultrasonication time on the stability and thermophysical properties of the nanofluid were studied over 30 days of the samples preparation. The thermophysical properties of the nanofluid have been experimentally measured at the optimum ultrasonication time. Using the experimental data, and employing different figures-of-merit, the effects that the addition of MWCNTs had on the heat transfer effectiveness and pumping power have been studied. It was confirmed that the nanofluid is a good heat transfer fluid, with a negligible penalty in pumping power. The thermal and fluid dynamic performance of the nanofluid in a microchannel heat sink has also been studied, by comparing the enhancement ratio of the convective heat transfer coefficient and the increase in pumping power.

The primary objective of the present study is to investigate the possible effects of ultrasonication time on stability and thermal conductivity of MWCNT-water nanofluid. The samples have been prepared in three different solid concentrations of 0.1, 0.3, and 0.5 vol.% applying different ultrasonication times, ranging from 10 to 80 min. The stability of the samples has been investigated over 30 days after preparation by conducting zeta potential analysis and visual observation. It is found that increasing the ultrasonication time until 60 min results in enhancing the stability of the samples in all the solid concentrations while prolonging the ultrasonication time leads to deteriorating the stability. The thermal conductivity of the samples has been experimentally measured over different temperatures ranging from 25 to 60 °C, and it is found that increasing the solid concentration and temperature results in enhancing the thermal conductivity. Moreover, the effects of ultrasonication time on thermal conductivity have also been studied, and it is found that increasing the ultrasonication time leads to a gentle enhancement in thermal conductivity. The maximum conductivity was achieved by applying 60 min ultrasonication. Thus, it is concluded that 60 min ultrasonication is the optimum time in which the thermal conductivity and stability reached their highest point.

In the present study, the natural frequency of finite element modeled geometrically imperfect shear deformable functionally gradient (FG) sandwich arches in the thermal environment has been studied. The formulation is based on the higher-order shear deformation theory. The upper layer of the sandwich arch is considered to be ceramics, whereas the lower layer is made of metal. The core of the sandwich arch is made of gradient materials. The material properties of the sandwich arches are varying continuously in the thickness direction only by a simple power-law distribution in terms of volume fractions of the constituents. Comparison and convergence studies have been performed to validate the present formulation with the limited available literature. Parametric studies have been performed to study the effect of various influencing parameters on the frequency of the FG sandwich arches, i.e., volume fraction index, thickness-to-length ratio, imperfection amplitude, and opening angle. New results are presented which can be treated as benchmark solutions for future researches.