this study compares the tribological and thermophysical features of the lubricating oil using MoS 2 and Zno nano-additives. the average size of MoS 2 and ZnO nanoparticles were 90 nm and 30 nm, respectively. The nanoparticles were suspended using Triton X-100 in three different concentrations (0.1, 0.4 and 0.7 wt.%) in a commercial diesel oil. Tribological properties such as mass loss of the pins, friction coefficient, and worn surface morphologies and thermophysical properties such as viscosity, viscosity index, flash point and pour point of resulting nano lubricant were evaluated and compared with those of pure diesel oil. the tribological behavior of nano lubricants was evaluated using a pin-ondisc tribometer. the worn surface morphologies were observed by scanning electron microscopy. the overall results of this experiment reveal that the addition of nano-MoS 2 reduces the mass loss values of the pins in 93% due to the nano-MoS 2 lubricant effect. With 0.7 wt.% in nanoparticles content, the viscosity of MoS 2 and ZnO nano lubricants at 100 °C increased by about 9.58% and 10.14%, respectively. Pure oil containing 0.7 wt.% of each nanoparticle increased the flash point because of its small size and surface modifying behavior compared to the pure oil. Moreover, the addition of Zno nanoparticles with pure oil lubricant is more suitable than MoS 2 nanoparticles for improving the thermophysical properties of pure oil.

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In this research, two different diesel oil-based nanofluids were prepared and the influence of temperature and nanoparticle content were examined on viscosity, tribological, and physicochemical features of diesel oil. The kinematic viscosity of samples was experimentally evaluated based on standard ASTM D445. The greatest viscosity increment was diagnosed at 0.7 wt.% and 100°C for both of the prepared nanofluids. The anti-friction behavior of the nanofluids was studied utilizing a pin-on-disc tribometer. The acquired outcomes revealed that ZnO and MoS 2 nanoparticles (NPs) could promote the tribological characteristics of pure diesel oil. By analyzing the friction coefficient values and line roughness of the wear surface (Ra), an optimal concentration of ZnO and MoS 2 nanoparticles (NPs) were found to be around 0.4 wt.% and 0.7 wt.%, respectively. The friction factor and pumping power were also measured at diverse content of nanoparticles and flow rates showing that the pumping power was enhanced by the incorporation of nanoparticles.

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This study aimed to investigate the effect of titanium dioxide (TiO2) nano additives on the thermal performance of a pilot-scale cross-flow cooling tower. Moreover, it is a continuation of our previous study on the effect of using multi-walled carbon nanotubes (MWCNTs) nanofluid, and the results were compared with the results of TiO2 and previous work. An experimental design by response surface methodology (RSM) based on central composite design (CCD) with two factors (concentration and flow rate) was used to study the effectiveness of the setup, Merkel number, and the cooling range. The nanofluids were prepared by the two-step method. The stability tests were performed considering different surfactants such as Gum Arabic, Triton X-100, and sodium dodecyl sulfate, and Gum Arabic was determined as the optimal surfactant. The visual method, dynamic light scattering (DLS), and Zeta potential analyses were used to ensure the stability of the nanofluids and determine the size distribution of the nanoparticles in the nanofluids. The findings revealed that the heat transfer characteristics of the working fluid were improved with the addition of nanoparticles. Moreover, by comparing the effect of nanoparticles, it was found that MWCNTs could enhance the thermal features better than TiO2. The nanofluid containing 0.085 wt% of the MWCNTs improves the Merkel number, effectiveness, and cooling range by 28, 10.2, and 15.8%, respectively, whereas these values for TiO2 containing nanofluids are 5, 4.1, and 7.4%, respectively. MWCNTs nanofluid with a concentration of 0.069 wt% and a flow rate of 2.092 kg/min was proposed for optimal system setup. Under these conditions, the cooling range, effectiveness, and Merkel number were about 23.5, 55.75%, and 0.64, respectively.