Search

Energy storage systems with non-metallic charge carriers such as ammonium-ion (NH4 +) are inherently safe and enable large-scale storage. Unlike metal ions with spherical symmetry, the intercalation of ammonium ions with a tetrahedral structure is symmetry-specific, leading to high power density and long-term cycling stability. However, developing suitable electrode materials that can reversibly host NH4 + ions to improve electrochemical performance is challenging. To address these issues, here we synthesized a sandwichstructured ammonium vanadate (NH4V4O10) and MXene (Ti3C2Tx) composite for the first time and employed it as a high-performance electrode for ammonium ion storage. Benefiting from the unique nanoarchitecture, the developed NH4V4O10/MXene electrode delivered an areal capacitance of 229 mF cm2 at a specific current of 1 mA cm-2 with -98% retention after 5000 charge--discharge cycles. Electrochemical analyses, supplemented with Raman spectroscopy and X-ray diffractometry, reveal the superior charge kinetics and structural stability of the NH4V4O10/MXene electrode under harsh operation conditions. The cell-type ammonium ion asymmetric capacitor (AIC) assembled using NH4V4O8/MXene as the positive electrode and MXene as the negative electrode delivered an energy density of 17.3 W h kg1 with excellent capacitance retention after 10 000 charge--discharge cycles. These results provide new insights for the development of safe and reliable next-generation clean energy technologies based on unconventional, nonmetal- ion-based charge storage mechanisms. [ABSTRACT FROM AUTHOR]

In this study, the flow of Cu/oil nanofluids over an impermeable semi‐infinite plate was investigated. A complete single‐phase modeling of nanofluids flowing over a semi‐infinite plate was performed, bringing into account, real experimental data of oil‐based nanofluids. The empirical correlations revealed that the viscosity and thermal conductivity of the pure oil and oil‐based nanofluids strongly depend on temperature. The similarity transformation method was utilized to transform governing partial differential equations into coupled nonlinear ordinary differential equations solved by employing the standard Runge–Kutta. The results showed that even low volumetric fraction of copper/oil nanofluids noticeably enhanced the heat transfer; however, such behavior was not predicted accounting the classic modeling of nanofluids. Furthermore, both hydrodynamics and thermal characteristics were reliant on the thermal boundary conditions, which this seems to have received a marginal focus in the existing literature. [ABSTRACT FROM AUTHOR]

Thermal oils due to their high ability in cooling and lubricating have many applications in high-tech industries such as automotive industry. Dispersing nanoparticles in a thermal oil (which the resulted new liquid is called nanofluid) can modify further the cooling and lubrication efficiencies. This review paper aims to present the recent advances in the preparation methods and thermophysical properties measurements of oil-based nanofluids. Effects of various parameters such as nanoparticle concentration, size, and temperature on the values of properties including thermal conductivity, viscosity, density, and specific heat are reviewed. The correlations available for the properties of oil-based nanofluids are gathered from the literature that could be a worthy source for those who aim to work on oil-based nanofluids. Unlabelled Image [ABSTRACT FROM AUTHOR]

This study aims to first introduce a formulation which is quite simple for obtaining dielectric-barrier discharge plasma spatial body force. This new model comprises a combination of an empirical model and a numerical one. Although there are still some limitations in the new model (restriction to specific geometry, maximum voltage amplitude of 30 kV, maximum frequency of 30 kHz, dielectric coefficient of 2.8 and Debye length of 0.0001 m), it is straightforward compared to the existing ones. The model possesses a high accuracy for the abovementioned band. It is proposed an approximate integral solution for the wall jet problem which is associated with the induced jet produced by dielectric barrier discharge plasma actuator. The approximate integral solution for the wall jet is verified by similarity, and the details are extensively discussed. [ABSTRACT FROM AUTHOR]

The present work provides an empirical investigation on the thermal characteristics of Ag/oil nanofluids flow inside a sinusoidal tube under a constant heat flux boundary condition. Ag/oil nanofluids have been prepared in low-volume concentrations of 0.011%, 0.044%, and 0.171%. The average size of the nanoparticles was 20 nm. A heated coil was attached to the upper and lower surface of the tube that satisfied the constant thermal boundary condition of 204 W. The experiment has been pursued at low Reynolds numbers less than 160. A loop was designed to keep the flow hydrodynamically fully developed during the experiment. The test case was a sinusoidal tube. Upper and lower surfaces of the tube have been designed sinusoidally. Moreover, the width of the plates was long enough, so the problem was not considerably affected by the three-dimensional releasing effect. Convective heat transfer coefficient and Nusselt number were calculated. It has been observed that based on the acquired data of the present work, convective heat transfer coefficient increased up to 23% for the best case (nanofluid with a volume concentration of 0.171%) compared to the base fluid. This happened while the rise of the friction factor was very low. In addition, a comparison between the new results and the previous work by authors showed the positive performance of sinusoidal tubes in increasing the convective heat transfer coefficient (the average increase was calculated to be about 82%) compared to the annular tube. [ABSTRACT FROM AUTHOR]

The present study aims to experimentally investigate heat transfer performance of rectangular and semicircular tubes in the presence of Ag / water nanofluids. The nanoparticles of Ag (silver) were used in seven different volume concentrations of 0.03%, 0.07%, 0.1%, 0.2%, 0.4%, 1% and 2%. The experiment was conducted in relatively low Reynolds numbers of 301 to 740. A heater with the power of 200 W was used to keep the outer surface of the tubes under a constant heat flux condition. In addition, the rectangular tube has been designed within the same length as the semicircular one and also within the same hydraulic diameter. Moreover, the average nanoparticles size was 20 nm. The outcome results of the present empirical work indicate that, for all the examined Reynolds numbers, the semicircular tube has higher convective heat transfer coefficient for all the utilized volume concentrations of Ag nanoparticles. The possible reasons behind this advantage are discussed through the present work mainly by taking the boundary effect on Brownian motions into account. Coming to this point that the conventional design for cooling system of photovoltaic cells is a heat sink with the rectangular graves, it is discussed that using a semicircular design may have the advantage over the rectangular one in convective heat transfer coefficient enhancement and hence a better cooling performance for these solar cells. [ABSTRACT FROM AUTHOR]

The present study indicates the impact of different arrangements of dielectric barrier discharge (DBD) plasma actuators on temperature field in a channel flow. The modified lumped circuit element electro-static model was used to calculate induced Lorentz body force and plasma dissipation of the actuators. Different distributions of temperature in the modeled channel flow for each arrangement of actuators (one, two, and three attached actuators) are discussed. According to the numerical simulation, DBD plasma actuators are beneficial devices for increasing temperature in the channel flow, especially near the location of the actuators that can be considered for related applications. The actuators are modeled under an incompressible flow regime with low Reynolds number of 335, and the configurations of the actuators are set to be 3 KV for the peak voltage amplitude, 10,000 Hz for the voltage frequency, and Kapton as the dielectric. [ABSTRACT FROM AUTHOR]

In this study, thermo-physical properties including thermal conductivity, viscosity, density and specific heat capacity of an oil based nanofluid including silver as to be nanoparticles have been experimentally studied. The results indicate an enhancement in thermal conductivity which was depended on bulk temperature and volume fraction of utilized nanofluids. Viscosity data show a significant increment through volume fraction increasing. In addition, the specific heat capacity and density of nanofluids were studied experimentally and it was found that, all measured rheological properties of these nanofluids, were not in agreement to published correlations. [ABSTRACT FROM AUTHOR]

This study deals with an empirical investigation on the convective heat transfer of Cu/oil nanofluid flow inside a concentric annular tube with constant heat flux boundary condition and suggests a correlation to predict the Nusselt number. The average size of particles was 20 nm and the applied nanofluid was prepared by Electrical Explosion of Wire technique with no nanoparticle agglomeration during nanofluid preparation process and experiments. The nanofluid flowing between the tubes is heated by an electrical heating coil wrapped around it. The effects of different parameters such as the flow Reynolds number, tube diameter ratio, and nanofluid particle concentration on heat transfer coefficient are studied. Using the acquired experimental data, a correlation is developed for the estimation of the Nusselt number of nanofluid flow inside the annular tube. This correlation has been presented by using the exponential regression analysis and least-squares method. The correlation is valid for Cu/base oil nanofluid flow with weight concentrations of 0.12, 0.36, and 0.72 in the hydrodynamically full-developed laminar flow regime with Re <140, which is applicable in mini- and microchannel heat exchangers, and it is in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

An oil based nanofluid including silver as to be nanoparticles was created by EEW method as a one-step method in three different volume fractions have been experimentally studied. Assessing the stability and viscosity of the nanofluids was involved in this work. The results show that the nanofluids behave in both of Newtonian and non-Newtonian in different volume concentrations. Also, an enhancement in viscosity of nanofluids has been recognized. In addition, based on the experimental results of this study and the other previous published studies on the oil based nanofluids, a correlation for predicting viscosity of oil based nanofluids has been developed and a good agreement between the experimental viscosity of applied nanofluids in this study and the predicted one has been achieved. [ABSTRACT FROM AUTHOR]