جستجوی مقالات مرتبط با کلیدواژه "energy" در نشریات گروه "شیمی"

This study investigated the potential of retrofitting rainwater collection tanks (RWH) into the facades of student residential colleges to improve internal temperature control. Carbon nanomaterials, including carbon nanotubes (CNTs) and graphene, were incorporated into the RWH facades to enhance thermal conductivity and mechanical strength. The aim was to address urbanization and climate change challenges through passive cooling strategies. The study analyzed ambient temperature, relative humidity, and wall surface temperature based on heat transfer principles. Statistical attributes, such as maximum, minimum, and average values, as well as daily fluctuations were examined. Heat transmission from external to internal walls was also quantified.   Materials analysis in this study involved the utilization of X-ray diffraction (XRD) for phase analysis, scanning electron microscopy (SEM) for investigating the morphology of CNTs, and transmission electron microscopy (TEM) for further characterization. The results demonstrated the cooling effectiveness and thermal efficiency of the proposed RWH technology. The west-facing walls with RWH facades showed a remarkable cooling effect of up to 14.41°C compared to non-RWH counterparts. Similarly, east-facing walls equipped with RWH facades exhibited a maximum temperature reduction of 3.41°C. Carbon nanomaterials enhanced the structural integrity of the RWH facades, ensuring long-lasting reliability under challenging conditions. This study highlighted the effectiveness of RWH facades as passive cooling strategies for student residential colleges. The utilization of carbon nanomaterials further enhanced their thermal and mechanical properties. The results indicated valuable insights for improving internal temperature control and addressing climate change challenges in urban environments.

Solar thermal (ST) collectors could only generate thermal power, while photovoltaic thermal (PVT) systems could provide both electricity and thermal power. However, the PVTs outlet temperature is usually not high enough for use in many applications such as space heating. Therefore, a new system called PVT system and ST collector in series (PVT-ST) is inducted to generate thermal power with higher outlet temperature and electricity. This paper explores the potential and feasibility of using PVT-ST under relatively hot and dry weather conditions in four cities of Tehran, Abadan, Baghdad, and Basra. To this end, the yearly performance of the system in terms of the first and second laws of thermodynamics is numerically evaluated. Moreover, the effects of the working fluid mass flow rate, in both laminar and turbulent regimes, on the module performance are investigated. Additionally, a comparative study is made between the PVT-ST, single PVT, and single ST systems. The working fluid regime analysis reveals that optimal thermal and electrical efficiency can be obtained in a turbulent regime. While the turbulent regime reflects better electrical exergy, the thermal exergy is dramatically decreased by raising the mass flow rate. Considering the mass flow rate of 0.0304 kg/s (turbulent regime) in July, the thermal efficiencies of the single ST, PVT-ST, and single PVT systems are 85.7%, 78%, and 72.9%, respectively. However, regardless of the mass flow rate, the PVT-ST system has the highest thermal exergy, peaking at 14.56 W/m2 at the lowest mass flow rate (laminar regime), which is double the thermal exergy of the single PVT. Finally, the annual study of the system performance in different cities illustrates that the maximum thermal power and exergy can be produced in Basra, averaging 375.72 and 1.46 W/m2. However, the maximum electricity production, with  an average of 77 W/m2 belongs to Baghdad.

The research presents the synthesis and fabrication of dye-sensitized solar cells (DSSCs) on the influence of sodium arsenic on the enhancement of TiO2/dye as photosensitizers, where Hibiscus sabdariffa (roselle) and Vernonia amygdalina (bitter leaf) were used as a source of the chlorophyll, sodium arsenic (NaAs) material of different concentration (0.1-0.4 mol), was synthesized as a layer on top of TiO2. The surface morphology study of TiO2/NaAs0.1, TiO2/NaAs0.2/ bitter leaf dye, TiO2/NaAs0.3/ roselle dye, and TiO2/NaAs0.4/the mixture of bitter leaf dye and roselle dye revealed that the micrograph is usually defined with the granular shape of nanotubes. The grain size of TiO2/NaAs0.1 is not too large and delineated by an immense sum of aggregated nanoparticles. The cells structure is polycrystalline with a most outstanding peak at 2 theta angles of 26.73° and 51.84o corresponding to hkl index numbers (111) and (202). The films have a very high absorbance from the plot, and the absorbance of the films increases as the dye molecules vary. The high absorbance of the films shows that the DSSCs will be a good material for photovoltaic applications. The fill factor of the films is 0.54, 1.24, 1.23, and 0.99 respectively while the conversion efficiency of 0.86%, 4.48%, 3.44%, and 1.81% was recorded.

Natural gas holds significant importance as a prospective energy source for meeting growing energy demands in the future. Gas hydrates offer a solution for the transportation and storage of natural gas. Within the sphere of gas hydrate formation, both the kinetics and thermodynamics play crucial roles and directly impact the economic feasibility of the process. In our current study, we focus on examining one specific kinetic parameter related to hydrate formation: the methane hydrate volume fraction (HVF) produced within a stirred batch reactor operating at a speed of 10 rpm. Our experiments were done out in a double-walled reactor with a capacity of 169 cm3, maintaining a temperature of 275.15 K and a pressure of 7.5 MPa, utilizing a constant volume-constant temperature methodology. The experimental findings indicated that the utilization of SDS, noticeably, increases the amount of water to hydrate conversion, and the amount of combined volume of unreacted water and formed hydrate during hydrate growth. The addition of 350 ppm and 700 ppm SDS resulted in an increase in HVF by 491.2% and 495.7%, respectively, after 1 hour of hydrate growth.

Gas hydrates could provide a clean and sustainable option to meet global energy demands. Accelerating gas hydrate formation is crucial to exploiting its positive applications, as these ice-like structures can serve as a vast and clean source of energy. In this research, we delve into the influence of sodium dodecyl sulfate (SDS) on the growth rate of double tetra n-butylammonium chloride (TBAC) + methane semiclathrate hydrate. To investigate this, we conducted experiments utilizing a stirred batch cell with a total volume of 169 cm3. The cell's temperature was maintained at 278.15 K, while the initial pressures were set at 6 and 8 MPa. Comparing the results with pure water, SDS showed a significant positive effect on the growth rate of methane hydrate formation. However, when 400 ppm of SDS was introduced, it had a detrimental impact on the average growth rate of the double (TBAC + methane) semiclathrate hydrate within just 50 minutes of the process.

The kinetics of methane hydrate formation in the presence of tetra n-butylammonium chloride (TBAC) and sodium dodecyl sulfate (SDS) is investigated in this research. The hydrate formation reactions are carried out in the isothermal condition of 278.15 K in a 169 cm3 stirred batch reactor. The amount of gas uptake and the storage capacity of methane hydrate formation are calculated. Results indicate that utilization of TBAC with a concentration of (3 and 5) wt% and SDS with a concentration of 400 ppm increases the amount of gas consumption and the storage capacity of methane hydrate formation. Utilization of TBAC along with SDS decreases the amount of gas consumption and storage capacity, compared to aqueous the solution of SDS. Investigation of the impact of pressure on the gas hydrate formation indicates that by increasing the initial pressure of the cell from 6 MPa to 8 MPa, the amount of gas consumption and the storage capacity of methane hydrate formation increases, considerably.

Due to the landfill leachate and the lack of drainage beds for collecting and directing leachate, especially in developing countries, the need to study Municipal Solid Waste (MSW) dryers is of particular importance. According to the technical literature, so far no comprehensive study has been performed on MSW dryers considering the actual components of the waste and the moisture content above 40%. Here a comprehensive study of wet MSW dryers consisting of three different parts is performed.  In the first part, a semi-theoretical mathematical model is developed to calculate the drying rate (internal) of wet MSW. For this purpose, with the laboratory results in the technical literature and Statistica software, a suitable mathematical model for drying MSW is validated and determined. Then, the external drying rate is determined according to the type of dryer selected and after its validation; it is compared with the internal drying rate. In the second and third parts, after validation of EES developed code, energy and exergy analysis are reviewed and finally, a parametric study is performed to investigate the effects of different parameters on energy and exergy efficiencies of the unsorted wet MSW drying process. The results show that the best model for drying the unsorted MSW is the logarithmic model with a corresponding  of 0.999. The internal and external evaporation rates are 0.157 and 0.165 kg/s and it is seen these two rates are well-matched together and differ by only 5%. The energy efficiency and exergy efficiency of the dryer are 13.92% and 2.91%, respectively. According to the parametric study, the inlet air temperature and the temperature of inlet MSW have the greatest effect on energy efficiency, respectively. Inlet air conditions such as absolute humidity of inlet air and atmospheric pressure have the greatest effect on the exergy efficiency of MSW drying.

There are no literature data on the effects of air velocity and relative humidity on moisture diffusivity, mass transfer coefficient, and energy-exergy analysis of chili pepper during cabinet-tray hot-air drying. This study tends to address this gap by presenting comprehensive drying kinetic, energy, and exergy analyses of a cabinet-tray hot-air drying for red chili pepper. Drying was conducted at varying levels of air temperature (40-70 oC), air velocity (0.5-2.0 m/s), and relative humidity (60-75%). The effect of drying conditions on drying time, drying coefficient, lag factor, drying efficiency, moisture ratio, effective moisture diffusivity, mass transfer coefficient, total energy consumption (TEC), specific energy consumption (SEC), energy utilization ratio (EUR), heat loss, energy efficiency, exergy loss, exergy efficiency, exergetic improvement potential (EIP), and exergy sustainability index (ESI)) was evaluated. Five different mass transfer models (Dincer-Dost, Bi-Di, Bi-S, Bi-G, and Bi-Re) were applied to determine the mass transfer parameters. A new drying mathematical model was developed for the prediction of drying kinetic, energy, and exergy parameters. Effective moisture diffusivity values of 1.58×10–8 - 5.10×10–8 m2/s and mass transfer coefficient values of 0.053×10–6 - 8.79×10–6 m/s over the drying conditions range were respectively obtained. The TEC, SEC, and EUR achieved over the range of drying conditions in the course of drying were in the range of 43.56-77.36 MJ, 49.0-87.02 MJ/kg, and 0.035-0.325, respectively. Heat loss and exergy loss varied from 0.16 to 2.39 MJ and from 0.026 to 0.622 kW, respectively. Drying, energy, and exergetic efficiency values obtained varied in the range of 2.80-8.25%, 2.69-7.91%, and 73-94.5%, respectively. EIP and the ESI values varied from 0.0068-0.114 kW and 3.70-18.18, respectively. The developed multivariate linear regression model provided an innovative model to predict drying kinetic, energy, and exergy parameters.

The Kirchhoff energy and Kirchhoff Laplacian energy for Kirchhoff matrix are examined in this paper‎. ‎The Kirchhoff index with Kirchhoff Laplacian eigenvalues is defined and different inequalities including the distances‎, ‎the vertices and the edges are obtained‎. ‎Indeed‎, ‎some bounds for the degree Kirchhoff index associated with its eigenvalues are found.‎

These days, the increased global warming due to the adverse effects of greenhouse gases is one of the most significant issues. One of the most common energy efficiency structures is the combination of wind turbines and photovoltaic systems. Increasing the use of renewable energy may results in economic growth, job creation, increased national security, protection of consumers against rising prices, a shortfall in the global fuel market, and a significant reduction in pollutants that cause global warming and greenhouse effects. Therefore, the problem facing electricity market policymakers is how to bring renewable energy into the electricity market to play its role well in the future market. The mentioned properties of renewable energies have caused them to be used on a large scale today. Wind energy, and solar energy are the most available energies among renewable energies. However, one of their problems is their dependence on environmental and climatic conditions. Combining two energy sources can overcome the weakness of each of them. Today, the combined power generation system has become one of the most promising solutions to meet the electricity needs of different regions. One of the most basic needs in a hybrid system is to ensure the continuity of nutrition by storing additional energy from renewable energy sources. A combined energy system based on alternative technologies that work in parallel with renewable sources can be a suitable solution for small productions.

The eigenvalues of a digraph are the eigenvalues of its adjacency matrix. Let $z_1,ldots,z_n$ be the eigenvalues of an $n$-vertex digraph $D$. Then we give a new notion of energy of digraphs defined by $E_p(D)=sum_{k=1}^{n}|{Re}(z_k) {Im}(z_k)|$, where ${Re}(z_k)$ (respectively, ${Im}(z_k)$) is real (respectively, imaginary) part of $z_k$. We call it $p$-energy of the digraph $D$. We compute $p$-energy formulas for directed cycles. For $ngeq 12$, we show that $p$-energy of directed cycles increases monotonically with respect to their order. We find unicyclic digraphs with smallest and largest $p$-energy. We give counter examples to show that the $p$-energy of digraph does not possess increasing--property with respect to quasi-order relation over the set $mathcal{D}_{n,h}$, where $mathcal{D}_{n,h}$ is the set of $n$-vertex digraphs with cycles of length $h$. We find the upper bound for $p$-energy and give all those digraphs which attain this bound. Moreover, we construct few families of $p$-equienergetic digraphs.

The present study is a combined research because it uses qualitative and quantitative methods in order to collect and analyze data by identifying indices and indigenous components of professional competence of hotel, oil and gas industry hotel managers. The qualitative and meta-analysis approach has been used. In a quantitative approach, he has used the fuzzy structural equation modeling method. Finally, based on the data, a new model of sustainable development in the oil, gas and energy industry has been reached. These components are: general professional performance, analytical skills, specific professional skills, general professional skills, job information and awareness, psychological abilities, innovative personality, basic specialized knowledge, job commitment, professional attitude, desire to Job development, intrinsic personal characteristics, and increasing factors that psychological abilities and increasing factors of competence are placed in the fourth level and were identified as the main and most effective dimensions in the development of sustainable development of oil, gas and energy industry. And the element of general professional performance is the least important among the studied dimensions.

The increasing attention of researchers to reduce the thickness of two-dimensional nanostructures, is due to their unique physical, chemical, mechanical, and optical properties, which is based on their two-dimensional morphology and ultrathin thickness. In this research, the aim is introduce and express the applications of ultrathin two-dimensional nanomaterial. Ultrathin two-dimensional nanomaterial are more important than other nanomaterial due to a number of their unique properties. In fact, these characteristics have attracted interest in using them in the fields of the electronics/optoelectronics, catalysis, energy storage and conversion, water remediation, sensors and biomedicine. Recently, using them are increasing in extraction and removal of materials from aqueous media and complex matrices.

A spongy hypercube is a Cartesian product of a d-connected polyhedral graph and a k-dimensional hypercube‎. ‎The aim of this paper is to compute the energies of signed spongy hypercubes T□□(Q_k ) and O□□(Q_k )‎, ‎where T and O are tetrahedron and octahedron‎, ‎respectively‎.

Combined heat and power systems are becoming more and more important, regarding their enhanced efficiency, energy saving, and environmental aspects. In the peresent study, three configurations of combined heat and power systems are intended as an alternative to separate production plant by considering environmental aspects. First and second laws of thermodynamics are adapted to the operating data. The energy and exergy indicators, their distribution and exergy loss are evaluated. The economic analysis was done by determining the Rate of Return on Investment, Payback Period and Net Present Worth. The optimal configuration of system equipment has been determined based on economic feasibility and emission saving in view of power and steam demand. The method employed here may be applied to making a decision on the adoption of the combined plant to any separate heat and power systems.

The Laplacian-energy-like of a simple connected graph G is defined as
LEL:=LEL(G)=∑_(i=1)^n√(μ_i ),
Where μ_1 (G)≥μ_2 (G)≥⋯≥μ_n (G)=0 are the Laplacian eigenvalues of the graph G. Some upper and lower bounds for LEL are presented in this note. Moreover, throughout this work, some results related to lower bound of spectral radius of graph are obtained using the term of ΔG as the number of triangles in graph.