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We developed a facile electroanalytical system for the rapid and sensitive detection of pyrimethanil through the modification of carbon paste electrode surface using the as-fabricated europium doped feather-type CuO nanoflowers (FT-Eu3+–CuO NF sensor). The peak current of pyrimethanil oxidation was elevated by the sensor due to the integration of appreciable electrochemical features of the modifier, which indicates the high ability of the modified electrode to enhance the sensitivity of pyrimethanil detection. The pyrimethanil sensor under the optimized setting had a broad linear dynamic range (0.001–800.0 μM) and a narrow limit of detection (0.18 nM). The practical applicability of the as-fabricated electrode was verified by sensing pyrimethanil in real samples; it also exhibited commendable specificity, stability and reproducibility.

Due to the short distance between the sources of production and consumption, microgrids (MGs) have received considerable attention because these systems involve fewer losses and waste less energy. And another advantage of MGs is that renewable energy sources can be widely used because these resources are not fully available and can provide a part of the required power. The purpose of this research is to model the MG considering the production sources of microturbines, gas turbines and internal combustion engines. Renewable energies such as wind turbines (WTs) and photovoltaic (PV) cells have been used to provide part of the required power and, because of the lack of access to renewable energy sources at all times, energy reserves such as batteries and fuel cells (FCs) have been considered. The power of the microturbine, gas turbine, internal combustion engine, FC and battery in this system is 162, 150, 90, 100 and 225 kW, respectively. After modelling the studied system, optimization was done using the imperialist competitive algorithm to minimize production costs and provide maximum thermal and electrical loads. The maximum production power for PVs is equal to 0.6860 MWh and at this time this value for WTs is equal to 0.3812 MWh, in which case the excess electricity produced will be sold to the grid.A microgrid, which produces energy from microturbines, fuel cells, wind turbines, PV arrays and internal combustion engines, is modelled. Optimization is carried out using the imperialist competitive algorithm to minimize production costs and provide maximum thermal and electrical loads.Graphical Abstract

Ionic liquids (ILs), defined as low-melting organic salts, are a novel class of compounds with unique properties and a combinatorially great chemical diversity. ILs are utilized as synthesis and dispersion media for nanoparticles as well as for surface functionalization. ILs are able to offer outstanding properties as media for the synthesis of nanoparticles. The low surface tension of many ILs leads to high nucleation rates and, in consequence, to small particles. The ILs themselves can act as an electronic as well as a steric stabilizer and depress particle growth. As highly structured liquids, ILs have a strong effect on the morphology of the particles formed. In this paper, the methods of modifying surfaces with ILs through covalent bonding, physical absorption, polymerization or sol–gel methods, metal nanoparticles in ionic liquids, and ionic liquids in catalysis, as well as the application of these modified surfaces in various fields of chemistry, have been investigated.

In this study, based on the energy balance for different components of a double-layered vacuum-tube solar collector with a U-tube, the thermal performance of the collector unit is investigated separately using an analytical and quasi-dynamic method. The model used in this study determines the temperature distribution in longitudinal and radial directions. In this research, the effects of physical parameters and heat transfer including the size of the collector, thermal-loss coefficient, absorption coefficient, mass flow and thermal resistance of the air layer under different climate conditions have been evaluated on the performance of the vacuum-tube collector. The results showed that by increasing the diameter of the tube with constant length, the annual thermal efficiency of the collector increased. Also, in a fixed-diameter tube, with increasing tube length, the annual efficiency increases, but this increase is meagre for lengths of >1.5 m. The optimal mass flow rate for maximum efficiency has been obtained for cities with different climates. According to the results, the optimal flow for different climates has different values that can be optimized as a relationship between the average solar radiation annually as a symbol of temperature and flow.The thermal performance of a vacuum-pipe solar collector is modeled with an analytical, quasi-dynamic method. The effects of physical parameters and heat transfer including the size of the collector, thermal-loss coefficient, absorption coefficient, mass flow and thermal resistance of the air layer are evaluated under different climate conditions.Graphical Abstract

Metal matrix composites have various structural and thermal applications in terms of their unique mechanical and thermal properties compared to their counterparts. These nanoparticle (NP)-reinforced composites have received much attention due to their relatively low production costs and excellent mechanical properties. In the present research, modeling and studying the effects of adding reinforcing NP on the hardness of aluminium-based composites is done using the molecular dynamics (MD) simulation. The expressed structures' equilibration, temperature, and potential energy are calculated and reported in the first simulation stage. In this regard, the parameters of Lennard-Jones potential function for the particles in the MD simulation of aluminium and oxygen. Finally, the results show that the hardness of pure nanocomposite (NC) was equal to 100, and by adding NP with a mass ratio of 6%, the hardness of NC increased from 100 to 190 HV. The radial distribution function (RDF) showed that the composition was in the solid phase at a temperature of 300 K, indicating the proper balance of simulated atomic systems. The results show that the maximum value of RDF decreased by increasing the amount of reinforcement. The results show that the yield stress decreased as the volume fraction of reinforcement increased in the crystal structure. Finally, it is expected that the results obtained from MD simulations will be considered in the practical use of aluminium NCs reinforced with alumina nanoparticles in various industrial, engineering and medical uses.

Using combined cooling, heat and power systems can be an appropriate substitute for preventing emissions of pollutants and excessive consumption of fossil fuels. Utilizing renewable energy in these systems as a source of power generation can be an appropriate substitute for fossil-fuel-based systems. Therefore, in this paper, cogeneration cooling, heat and power systems based on gas-fired internal combustion engines with a solar-thermal system with evacuated tube collectors have been modelled and thermo-economic analysis has been done to compare fossil-fuel-based systems. The required rate of heat to supply the hot water is 50 kW. In the studied system, the internal combustion engine produces electrical energy. Then, the solar-thermal system with evacuated tube collectors and the gas-burning generator provide the thermal energy required by the studied building and the primary stimulus of the absorption chiller for cooling. In this study, two different scenarios are conducted in states considering simultaneous production systems and regardless of this environmental and thermo-economic analysis system. The results showed that the efficiency of the studied system was 60% in summer and 56% in winter.Cogeneration cooling, heat and power (CCHP) systems based on gas-fired internal combustion engines with a solar-thermal system with evacuated tube collectors were modelled and thermo-economic analysis was used to compare to fossil-fuel-based systems. Summer and winter scenarios were evaluated considering the environmental and thermo-economic analysis of the system.Graphical Abstract

Liquid crystal materials are a suitable environment for the synthesis of nanostructures of uniform size and shape due to their order and yet mobility at the molecular level. Dense liquid crystal phases allow nanoparticles to self-assemble, resulting in larger organized nanostructures. Although both types of lyotropic liquid crystal and thermotropic liquid crystal have been used for the synthesis and self-assembly of nanoparticles, the use of lyotropic liquid crystal types is more in the synthesis of nanoparticles, while the use of thermotropic liquid crystal phases is mainly related to the self-assembly of nanoparticles.

Purpose: The present investigation is devoted to providing two/three-dimensional (2D/3D) models for estimating the amount of thermoelastic damping (TED) in circular cross-sectional micro/nanorings by capturing the effects of size on thermal domain via dual-phase-lag (DPL) heat conduction model. Methods: To achieve the goal of the article, first of all, the equation of heat conduction derived in the framework of DPL model is solved. In this way, for 2D and 3D models of heat propagation, the temperature field in the ring is obtained in the form of infinite series. Next, by exploiting the relation of quality factor in entropy generation (EG) approach, a formulation including the two phase lag parameters of DPL model is extracted to anticipate TED value in small-sized rings with circular cross section. Results: By comparing the results of this investigation with those of studies in the literature that are based on simpler heat conduction models, a validation study is accomplished. An intensive numerical study is also performed to discern the influence of some of the most significant factors such as phase lag parameters of DPL model, vibration mode, the dimensions and ring material on TED. Conclusion: The findings reveal the noticeable effect of phase lag parameters of DPL model on the magnitude of TED in miniaturized circular cross-sectional rings, especially in smaller dimensions and higher vibration modes.

The use of solar energy is highly welcomed due to its availability everywhere. Among the types of solar energy technologies, the use of this type of energy to produce heat from different aspects is much more common, so in this research we have tried to examine different aspects of producing thermal energy from solar energy to supply the heat required by the pool. For this purpose, numerical modelling of the solar pool has been done by considering the heat-transfer characteristics and validation has been done to ensure the obtained results. In this paper, according to the physical realities facing solar systems in two scenarios, an analysis with shadow and without shadow has been done. One of the important results is that as the surface of the pool increases, the amount of heat absorption by the pool fluid will increase, but the effect of the shadow will decrease.The solar pool is a low-cost collector with the ability to store thermal energy by means of a salt gradient. Modeling is validated on one year of experimental data for a salt-gradient solar pool. The model provides guidance on the optimum pool surface area and thickness of salt layers to maximize stored energy.Graphical Abstract

The graphene-based materials are promising for applications in supercapacitors and other energy storage devices due to the intriguing properties, i.e., highly tunable surface area, outstanding electrical conductivity, good chemical stability, and excellent mechanical behavior. This review summarizes recent development on graphene-based materials for supercapacitor electrodes, based on their macrostructural complexity, i.e., zero-dimensional (0D) (e.g., free-standing graphene dots and particles), one-dimensional (1D) (e.g., fiber-type and yarn-type structures), two-dimensional (2D) (e.g., graphenes and graphene-based nanocomposite films), and three-dimensional (3D) (e.g., graphene foam and hydrogel-based nanocomposites). There are extensive and on-going researches on the rationalization of their structures at varying scales and dimensions, development of effective and low-cost synthesis techniques, design and architecturing of graphene-based materials, as well as clarification of their electrochemical performance. There are several methods for producing graphene, each with its own advantages and disadvantages. Graphene-based materials have great potential to be employed in supercapacitors due to their unique two-dimensional structure and inherent physical properties like excellent electrical conductivity and large area. This text summarizes recent developments within the sector of supercapacitors, including double-layer capacitors and quasi-capacitors. The pros and cons of using them in supercapacitors are discussed. Compared to traditional electrodes, graphene-based materials show some new properties and mechanisms within the method of energy storage and release. During this paper, we briefly describe carbon structures, particularly graphene, and also the history of graphene discovery, and briefly describe the synthesis methods, properties, characterization methods, and applications of graphene.

The addition of nanoparticles (NPs) can change the thermophysical properties of materials. Hence, adding NPs to phase change materials (PCMs) can accelerate phase transition processes. Moreover, the NPs concentration changes can change the structures' dynamic and thermal properties. Thus, it is crucial to survey how the volume fraction (size and atomic ratio) of NPs affects the PCM's thermal behavior. In the current work, molecular dynamics (MD) simulation was used to examine the thermal behavior of PCM microcapsules containing gold NPs. These microcapsules were taken into consideration together with aminoacetaldehyde (C2H5NO) and bromohexadecane (BrC16) as PCM, and the effect of gold nanoparticle radius and atomic ratio on simulated structure's thermal behavior was investigated. The findings demonstrate that charging and discharging periods were shortened by increasing the radius and atomic ratio of gold NPs in the atomic microcapsule structure. The heat flux (HF), and thermal conductivity (TC), on the other hand, are increased by increasing the radius of NPs from 3 to 6 nm, reaching 299.43 W/m2and 1.42 W/mK, respectively. Moreover, by increasing the atomic ratio of NPs from 0.01 to 0.05, HF and TC values increased to 300.08 W/m2and 1.45 W/mK, respectively. Furthermore, increasing the radius and atomic ratio of gold NPs in the microcapsule structure increased viscosity and phase change time. The methods offered in this study might be used as a viable mechanism in application domains to improve the thermal efficiency of this structure.

Phase change material (PCM) is a material that has a specific melting point, and its latent heat of melting is large enough that it can be used to store thermal energy. This study investigated the effect of size (4–8 Å), and the number of layers (3–10 layers) of iron nanoparticles (NPs) channel on thermal behavior (TB) and phase change (PC) process of sodium sulfate/calcium chloride hexahydrate (Na2SO4/MgCl2·6H2O) PCM molecular dynamics (MD) simulation. By increasing the number of layers from 3 to 5, the maximum temperature and heat flux (HF) increased from 406 and 1471 W/m2to 451.51 K and 1496 W/m2. By increasing the number of layers from 3 to 7 layers, the charging time (CT) and discharge time (DT) of atomic samples decreased from 4.01 ns and 4.25 ns to 3.88 ns and 4.17 ns. By adding the iron NPs with a radius of 4, 5, 6, and 8 Å, the maximum temperature increased to 420, 429, 458, and 503 K, respectively. By adding the iron NPs with different radii from 4 to 8 Å, the HF increased from 1566 W/m2to 1657 W/m2. By adding the iron NPs into the Na2SO4/MgCl2·6H2O, the received HF increased, and the maximum temperature increased. By adding the iron NPs with different radii, the CT decreased from 3.95 ns to 3.73 ns. The DT increased from 4.33 ns to 4.36 ns by increasing the radius from 4 to 8 Å. According to the TB of this PCM, it should be used in refrigerants instead of toxic and dangerous refrigerants, such as ammonia and chlorofluorocarbon. Moreover, they were used for construction purposes for double-glazed windows.

Energy storage is among the factors that could reduce the use of fossil fuels. Having a large heat storage capacity, phase change materials found their wide applications in energy storage applications. The present study investigates the effect of using phase change materials on the performance of a double pipe heat storage system. The three-dimensional simulation was developed to model the transient flow and heat transfer via the finite volume method. To enhance the heat transfer, fins with the varying cross-sectional area are employed over the surface of the inner tube. Furthermore, to enhance the water side heat transfer, the vortex generator is employed there. The sensitivity analysis was performed to unveil the effect of inlet hot water temperature on the change and discharge processes. The results show that the fins inside the phase change material reduce the melting time up to 100 min and increase the outlet hot water temperature. Also, using the vortex generator in the water path had the reverse effect on the charging process and increases the charging time. For hot water temperature of 75 °C, the temperature of phase change material archives to its maximum value after 189 min. In the case of 70 °C hot water temperature, the phase change process begins 41 min later than in the case of temperature 75 °C and reaches its maximum temperature within 229 min.

Solar thermal collectors are devices that can be mounted on rooftops of buildings for domestic hot water or space heating applications. The higher the thermal performance of this instrument the lower the cost and size of that. Here, the three-dimensional numerical analysis of water flow inside the absorber of a solar thermal collector with a dual-twisted tape turbulator is investigated. The influences of Re number and twisted pitch distance (ξ; 100 mm, 150 mm, and 200 mm) on the water outlet temperature (T out), useful heat (Q u), and pressure drop (ΔP) are scrutinized. The results disclosed that the highest T out and tube wall temperature (T wall) are obtained at Re =800, which are respectively 2.97 % and 1.6 % higher than those at Re =2000. On the other hand, an insignificant influence for the escalation of ξ from 100 mm to 200 mm on T out was observed (e.g. 0.0395–0.001 % reduce). Meanwhile, the Re intensification from 800 to 2000 exhibited a ΔP of 68 % at different ξs, while the escalation in ξ at different Re numbers led to diminishing ΔP by almost 7.70 %. Besides, the lowest and highest Q u values at ξs of 100 mm, 150 mm, and 200 mm are respectively, associated with Re numbers of 1600 and 800, 1600 and 800, and 1200 and 800. Furthermore, a second-order polynomial with six coefficients was presented using the artificial neural network and group model for data handling model with a high coefficient of correlation (R 2=0.99824) and low root mean square error (RMSE=0.05109), which is capable of estimation T out using two input parameters of ξ and Re. [ABSTRACT FROM AUTHOR]

The solar thermal collectors are widely used for several applications nowadays. The improvement of their thermal performance helps to mitigate the initial costs and sizes of these components. In addition, the robust prediction of the solar thermal collectors' performance is a promising technique to eliminate the future numerical simulations of these devices. To this end, the present numerical research is performed to investigate how placing two similar twisted tape turbulators side by side inside the absorber tube of a solar water heater affects the second-law aspects of the device. The pattern of changes in outlet water temperature, useful thermal exergy (Q u,ex), and rate of entropy production due to heat transfer (S g , t h) and fluid flow (S g , f r) in different values of Reynolds number (Re) and twist pitch (H) were presented and analyzed. Validation of the numerical method was done with the experimental results available in the literature. The negative effect of boosting the Reynolds number and twist pitch on the entropy was reported. In addition, the downward (9.31–11.43 %) and upward (2.51–4.97 %) influence of Re and H on the S g , t h were reported. Moreover, it was found that the growth in Re and H is associated with the growth (654.97–661.27 %) and reduction (2.39–3.20 %) of S g , f r. Finally, the nonlinear calibration using the Chaos Control Method (CCM) was employed to determine a predictive model for the Q u,ex in terms of Re and H. The results demonstrated that two predictive models can estimate Q u,ex with high degree of accuracy with the correlation coefficient of R2=0.999 and RMSE of 0.089. [ABSTRACT FROM AUTHOR]

The application of V-cut twisted tape turbulator inserted in the absorber tube of a photovoltaic thermal (PVT) system was investigated through a 3-D numerical analysis. The objective was to determine the effect of turbulator pitch distance (50 mm, 77 mm, and 100 mm) and Re number (500, 1000, 1500, and 2000) on the PVT energy and exergy performances. The results were compared with those obtained for the absorber tube without turbulator. Our findings demonstrated that the pressure drop and PV temperature, respectively, escalates and diminishes by 78–84% and 5.69–6.68% for the case with turbulator (pitch of 100 mm) as Re increases from 500 to 2000. In consequence, the overall energy efficiency and overall exergy efficiency improve by 15.76–14.27% and 12.01–8.68%, respectively, for the increase in Re within the studied range. In addition, the application of turbulator with a pitch of 100 mm improves the overall energy and exergy efficiencies of the PVT system by 3.04–7.70% and 4.03–13.08% at the Re range of 500–2000 as compared to the without turbulator case. Moreover, the greatest useful thermal and electrical efficiencies were obtained for the PVT with turbulator pitch of 100 mm and at Re =2000, which yields the highest overall thermal and exergy efficiencies of 75.46% and 16.34%, respectively. Furthermore, RSM technique is utilized to obtain a model for the overall energy and exergy efficiencies versus Re and P. [ABSTRACT FROM AUTHOR]