ABSTRACT
This article discusses a focused study on visualizing the flow patterns in a two-phase pulsating heat pipe (PHP) using Fe3O4/water as the working fluid at 3 V/V% concentration. The research also aims to meticulously examine phase change phenomena in the heating section, particularly focusing on bubble formation and expansion processes. A high-speed video camera was utilized to capture dynamic insights into the behavior of the Fe3O4/water mixture. Based on the findings, a straightforward model was developed to explain bubble generation and growth in the mixture, serving as a useful reference for future PHP designs and optimizations. Visual observations also noted the stable nature of the Fe3O4/water nanofluid over a 4-day period, confirming its consistency throughout the experiments. Moreover, the impact of heat load variation on the evaporator section was assessed using controlled heat inputs ranging from 10 to 80 W. Observations on the arrangement of slugs and plugs at a 50% filling ratio revealed interesting self-adjusting flow patterns in response to increasing heat inputs, providing valuable insights into PHP operational dynamics. Notably, the oscillatory flow behavior of Fe3O4/water, the chosen working fluid, exhibited greater activity in comparison to water. This distinctive flow behavior contributed to achieving heightened thermal performance efficiency for the Fe3O4/water system, attributed to its faster attainment of the annular flow condition.
ABSTRACT
Natural gas stands as the most ecologically sustainable fossil fuel, constituting nearly 25% of worldwide primary energy utilization and experiencing rapid expansion. This article offers an extensive comparative analysis of nano filter elements, focusing on pressure drop and pollutant removal efficiency. The primary goal was to assess the superior performance of nano filter elements and their suitability as an alternative for Town Border Station (TBS). The research encompassed a six-month examination period, involving routine pressure assessments, structural examinations, and particle characterization of the filter elements. The results revealed that nano filters showed better performance in adsorbing aluminum than conventional filters, possibly due to their cartridge composition. Nano filters contained phosphorus, sulfur, and copper, while conventional filters lacked these elements. The disparity can be attributed to the finer mesh of the nano filter, capturing smaller pollutants. Although the nano filter had minimal silicon, the conventional filter showed some, posing concerns. Despite having 19 extra pleats, the nano filter maintained gas flow pressure while capturing more particles than the conventional filter.
ABSTRACT
This study aimed to assess the UV-shielding features of the PMMA-based thin film coatings with the addition of TiO2 and ZnO nanoparticles as nanofillers considering different contents. Furthermore, the effect of TiO2/ZnO nanohybrids at different ratios and concentrations was examined. The XRD, FTIR, SEM, and EDX analyses characterized the prepared films' functional groups, structure, and morphology. Meanwhile, the coatings' optical properties and UV-protecting capability were investigated by ultraviolet-visible (UV-Vis) spectroscopy. The UV-Vis spectroscopic study revealed that as the concentration of nanoparticles increased in the hybrid-coated PMMA, the absorption in the UVA region increased. Overall, it can be concluded that the optimal coatings for PMMA were 0.1 wt% TiO2, 0.1 wt% ZnO, and 0.025:0.025 wt% TiO2: ZnO nanohybrid. Considering the acquired FT-IR of PMMA with different content of nanoparticles before and after exposure to the UV irradiation, for some films, it was confirmed that the polymer-based thin films degraded after 720 h, with either decreasing or increasing intensity of the degraded polymer, peak shifting, and band broadening. Notably, the FTIR results were in good agreement with UV-Vis outcomes. In addition, XRD diffraction peaks demonstrated that the pure PMMA matrix and PMMA coating films did not show any characteristic peaks indicating the presence of nanoparticles. All diffraction patterns were similar with and without any nanoparticles. Therefore, it depicted the amorphous nature of polymer thin film.
ABSTRACT
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.
ABSTRACT
This study compares the tribological and thermophysical features of the lubricating oil using MoS2 and ZnO nano-additives. The average size of MoS2 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-on-disc tribometer. The worn surface morphologies were observed by scanning electron microscopy. The overall results of this experiment reveal that the addition of nano-MoS2 reduces the mass loss values of the pins in 93% due to the nano-MoS2 lubricant effect. With 0.7 wt.% in nanoparticles content, the viscosity of MoS2 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 MoS2 nanoparticles for improving the thermophysical properties of pure oil.
ABSTRACT
Imidaclopride is an insecticide widely used for pest control in agriculture around the world. It acts on the central nervous system of insects, while posing lower toxicity to mammals. This is an organic material made of Pyridinium, Dihydroimidazol and Nitramide. This structure poses a threat to the environment and humans. Until now, different types of methods have been used for elimination of this organic pollution. Recently, advanced oxidation processes (AOPs) are presented as a proposed method to remove this organic pollution. Photocatalytic degradation is also used as an efficient method for destruction of organic structures. In this study, the effect of titanium dioxide (TiO2) nanoparticle as a photocatalyst activated by UV irradiation is investigated. The new design of the reactor was prepared with coaxial cylinders in which the inner cylinder is rotated at a constant speed. The reactor worked in two batch and continuous modes. The results show that the UV irradiation is more effective than activated TiO2 nanoparticle, as the designed reactor with UV irradiation eliminated Imidaclopride in less than 2 hours.
