Journal of Selected Topics in Energy

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In this study, the performance and emission characteristics of a direct injection diesel engine using coconut oil biodiesel were investigated. For this aim, coconut oil was converted to its biodiesel via transesterification approach. Then, the effects of the biodiesel percentage in blend, engine load, and speed on brake power, brake specific fuel consumption (BSFC), nitrogen oxides (NOx), carbon dioxide (CO₂), carbon monoxide (CO), and particle matter (PM) have been considered. Fuel blends with various percentages of biodiesel (0%0 - %3%) at various engine speeds and loads were tested. The results indicated that blends of cocunut with diesel fuel provide admissible engine performance on the other side, emissions decreased so much.

 

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Effect of open windows on car drag and consequently on the required power and fuel consumption has been investigated in this study. To do this, a simulated model as possible as similar to the actual model has been considered. For example round angles and side slopes have been considered. The drag caused by aerodynamic forces has been calculated, for different cases. Results show, as the percentage of windows opening increased, the car drag first decreased and then increased such that, the car drag with open windows for a certain percentage is equal to that of the closed windows car. This certain percentage depends on the car velocity.

 

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The limited available energy resources and it basic role in industrial development, employing the renewable sources of energy including wind, sun, water and etcetera as appropriate choice described. Renewable energies are not only economically advisable, but even can contribute to provide a cleaner approach of energy production and healthier environment. Hence, assessment of some old structures such as Middle East wind catcher that are established on the ground of clean energies and adapting them to the modern age demands with optimizing models is noteworthy. This work, by keeping focus on calculus of variation and analysis of the wind load on the wind catcher structures and present an optimal more resistant model. Optimization of the design parameters of wind catcher structures led to a hyperbolic model with least wind catcher surface and a higher stability and strength compared with the older structures of this category.

 

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Copper oxide nanofluid that is obtained by dispersion of copper oxide nanoparticles in water base fluid is used as heat pipe working fluid. Nanofluids because of having better thermophysical properties in comparison with conventional heat transfer fluids, cause heat pipe performance improvement as an effective heat transfer equipment. In this work, a computational fluid dynamic method (CFD) is used to study the effect of using nanofluid and varying volume fraction, size and shape of suspended nanoparticles in nanofluid on heat pipe thermal performance. The results show thermal resistance reduction and heat pipe performance improvement by using nanofluid in comparison with pure water. Also volume fraction enhancement, nanoparticle’s diameter reduction and using cylindrical nanoparticles cause the evaporator and condenser temperature gradient reduction that in low volume fractions the effect of using nanoparticles with small diameter on heat transfer is more than using non spherical nanoparticles

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 Supersonic wind tunnels are strong and useful tools for the detection of the flow physics around flying vehicles. In this work, a blowdown type supersonic wind tunnel with a Mach number of 3 was studied. The required air for the tunnel was supplied by a storage tank containing compressed air. The intended velocity in the test section of the wind tunnel is provided by the high pressure discharge of the air from the storage tank into the atomosphere. The nozzle's geometry has been designed based on the "characteristics" method. Embedding the injector in the wind tunnel provides the opportunity to launch the wind tunnel at lower compression ratios. Since the duration of the experimental data collection is limited in blowdown supersonic wind tunnel, proper design and exploitation of the injector in a way to allow tunnel launching at decreased compression ratios, provides significant influence on the saving the compressed air of the storage tank and increasing the experiment duration. It has been attempted in this work to study the effect of installation of the injector in wind tunnel through assessing the boundary layer and the flow physics inside the wind tunnel. The results show that the injected flow increases the energy level of the low energy boundary layer, so as the energy of the boundary layer in a placed ahead of the injector location is higher than a place before the injector location. This fact results in a decreased required compression ratio for tunnel launching. The physics of the formed flow was studied and physical phenomena such as boundary layer separations, bow shock, barrel shock and mach disk were reported around the injection site 

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In this paper, the impact of micro bubbles as the second phase in the turbulent flow inside the channel flow has been investigated. The developed turbulent flow inside channel containing micro bubbles has been solved using large eddy simulation. Numerical analysis has been done to survey the impact of micro bubbles on turbulent characteristics derived from carrier flow. Finally, the mechanism of reducing frictional drag force was illustrated. According to the results, increasing the volume fraction of bubbles in the constant diameter will decrease the frictional drag force. Also studying the energy spectrum showed that the energy in the small scales has increased and in the large scales decreased.

 

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The study aimed at investigating radiation properties of multi-layers constructions including underneath layer of silicon, slightly covered by non-metal coating of silicon nitrate and silicon dioxide, and metal coating of gold, silver and cooper in temperature of 25 degrees Celsius and polarized incident radiation. Ray Transfer Matrix model was used to calculate radiation properties of multi-layers constructions as well as experimental expressions of optical constants of slightly covered silicon. The transmission coefficient of metallic coatings in polarization types of P and S and non-polarized status was zero due to low penetration power and high radiation coefficient. In non-metallic coatings, on the other hand, the transmission coefficient increased contributing to the larger penetration depth of electromagnetic waves. The overall results indicated that polarization coefficient of transmission of type P was significantly larger than Type S in non-metallic coatings. Radiation coefficient of metallic coatings was significantly larger in comparison to non-metallic coatings. As the result, they can be used in industries requiring high radiation. The results indicated that in underneath silicon layers, in room temperature and wave length of.4 to.84 micrometer, the absorption and consequently radiation coefficients were insignificant. However, silver coating indicated significantly higher absorption and radiation. In addition, the fluctuation in polarization of the incident ray of P and S type resulted in an increase in emissivity and transmission factors. The findings showed that silver in comparison to gold and cooper revealed significantly higher radiation coefficient. In radiation angle of zero (normal), radiation properties were equal for both types of S and P.

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This paper presents a new hybrid method for optimal multi-objective reconfiguration simultaneous determining the optimal size and location of Distributed Generation (DG) in a distribution feeder. The purposes of this research are reducing the losses, improving the voltage profile and equalizing the feeder load balancing in a distribution system. Ant Colony Optimization (ACO) approach as a Swarm Intelligence (SI) based algorithm is used to simultaneously reconfigure and identify the optimal capacity and location for installation of DG units in the distribution network. In order to facilitate the algorithm for multi-objective search ability, the optimization problem is formulated for minimizing fuzzy performance indices. The multi-objective optimization problem is transformed into a fuzzy inference system (FIS), where each objective function is quantified into a set of fuzzy objectives selected by fuzzy membership functions. The proposed method is validated using the IEEE 33 bus test system at nominal load. The obtained results prove this combined technique is more accurate and has an efficient convergence property compared to other intelligent search algorithms. Also, the obtained results lead to the conclusion that multi-objective reconfiguration along with placement of DGs can be more beneficial than separate single-objective optimization.

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In this paper, coal combustion process in a bubbling fluidized bed furnace were investigated experimentally. Analysis of experimental data shows that the coal size particles inlet to bed and rate of air injected into the furnace, are determinant parameter in bed temperature and proper combustion in the fluidized bed furnace. The highest temperature of 1050°C was obtained with air flow rate of 12 for the combustion of coal mixture with 75 wt% particles in group 2 and 25 wt% in group 3.

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This study aims at investigating aerodynamic coefficients changes by applying a two-dimensional heat flux on the wing in transonic regime. The numerical and experimental researches have shown that heat transfer on the fuselage has a significant impact on reducing drag (force). The current study aims also at investigating the effects of the heat transfer on aerodynamic coefficients of wing section. Accordingly, the turbulent transonic flow was numerically simulated around RAE2822 transonic airfoil with two different methods of modeling turbulent flow, namely, k–ε two-equation method and Reynolds stress five-equation model (RSM) and the obtained results were compared with experimental results. After choosing RSM as an appropriate method, subsequent investigations have been carried out with it. By applying heat flux in certain parts of upper and lower airfoil, the flow around it, is modeled and aerodynamic coefficients are extracted for airfoil and investigated. Studies showed that heating below the airfoil surface leads to change of aerodynamic coefficients with increasing the lift to drag ratio which can reduce fuel consumption and increase endurance of aircraft.

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In this paper, effect of a horizontalisothermal wall on the natural convection heat transfer from a horizontal cylinder is numerically studied.For this purpose, effect of wall when it is located above the cylinder at various Rayleigh numbers and wall vertical positions are studiedand compared with the situation that wall is adiabatic. Fluent software is used to simulate the problem.Comparison of simulation results with available numerical results,confirms the accuracy of simulation. Simulation results show that in low wall distance from the cylinder,the isothermal wall causes an increase in meanNusselt number. By increasing this distance, mean Nusselt number decreases until reaching a minimum value. By more increase of this distance mean Nusselt number increases. Also, it is considered that in the case of isothermal wall Nusseltnumber is higher rather than adiabatic wall.

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In this study, heat transfer coefficient and the bubble diameter during pool boiling of pure water, pure ethanol and water-ethanol solutions on a horizontal tube in an atmospheric pressure is examined. Experiments are accomplished for different mole fraction of ethanol in water and in heat flux of 5-103   .The results reveal that heat transfer coefficient increases by increasing heat flux for pure water and pure ethanol and the combination of these two liquids. The heat transfer coefficient in the solution except for ethanol molar concentration of 0.04 is less than those in single component substances at the same heat flux. Also the heat transfer coefficient for azeotrope molar concentration y an error about 6% is almost equal to ideal heat transfer coefficient. Finally, the results are analyzed by Genetic Algorithm and a new model is presented to calculate the heat transfer coefficient of the water-ethanol solution.

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Due to pollution and limited fossil fuels, renewable sources can be considered the main alternative of these resources. Generally, the organic Rankine Cycle(ORC) uses renewable Low Grade Heat Source(LGHS) such as solar, geothermal and etc. In this study a novel configuration of ORC has been proposed to improve the efficiency and power generation using both of an ejector and a regenerator. In this cycle an ejector with a regenerator have been integrated in ORC. Also a dual-stage evaporator has been used. Steam from the second stage evaporator is entered to ejector as the primary fluid and after the pressure decrement tends to increase of the suction of the secondary fluid from the steam turbine outlet. This modification tends to the higher power generation. Also steam enters to the regenerator prior to the ejector and in this way a part of energy of needed for the first stage evaporator is supplied and the efficiency is increased. For thermodynamic modeling a code was developed in the Engineering Equation Solver(EES) software. In addition different working fluids were examined to evaluate of the thermodynamic performance of the proposed cycle. The results show that the efficiency of the cycle increased 17.5% compared to the ORC in the best case(depending on the working fluid). To evaluate of the thermodynamic parameters on the efficiency and output power, parametric study was done. The fluid with the highest efficiency was R245fa.

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Distribution feeder reconfiguration for loss reduction is a very important way to save the electrical energy. This paper proposes a new hybrid evolutionary algorithm to solve the Distribution Feeder Reconfiguration problem (DFR) .The algorithm is based on combination of a New Fuzzy Adaptive Particle Swarm Optimization (NFAPSO) and differential evolution algorithm (DE) called NFAPSO-DE. To exploit the advantages of the exploration ability of DE and the high speed search system and the ability to control and adjust the parameters of PSO algorithm, a hybrid PSO-DE method is proposed. The hybrid method uses the PSO to find the region of optimal solution, and then a combination of PSO and DE to find the optimal solution. In other hand, due to the results of PSO algorithm highly depends on the values of their parameters such as the inertia weight and learning factors, a fuzzy system is employed to adaptively adjust the parameters during the search process. Finally, the proposed algorithm is tested on 33 bus and 69 bus distribution test systems. The results of simulation shows that the proposed method is very powerful and effective to obtain the global optimization.

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Furnaces in refinery and petrochemical processes are major consumers of energy. The most important factors for the controlling the energy consumption of the furnace can be divided into three main groups The first group includes the potential savings without cost or low cost, such as adjusting air – fuel ratio in the burner and pressure control into the furnace, The second group includes the potential savings with medium cost such as insulating body, and the third group includes the potential savings with high investment such as heat recovery from the exhaust flue. In this paper, the thermal energy savings potential on the 4 fixed- furnaces in the Loabiran companies are investigated and calculated that savings potential of adjusting air – fuel ratio in the burner is 165,973,500 Rials in the year, controlling pressure inside the furnace 95,822,300 Rials in the year, body insulation 622,167,700 Rials and recycled flue gases 929,762,400 Rials in the year. Also Loabiran companies uses regenerator that is a periodic heat recovery system to preheat the incoming air. This will result in annual savings for the daily production of 20 tons of frit, are 3,577,000,000 Rials.

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Drag reduction in turbulent flows allows achieving of higher speeds and reducing energy consumption in the motion of submerged objects. An efficient technique for drag reduction uses dilute solutions of microfibers. In this paper, a review of available methods for the simulation of turbulent drag reduction by microfiber additives is presented. To compute the turbulent flow, the direct numerical simulation (DNS) technique is employed. The effect of the fibers on the flow is described by a non-Newtonian stress tensor, involving the distribution of fiber position and orientation. The fiber dynamics is governed by a Fokker-Planck equation. The computation involves a numerical solution of three-dimensional, time-dependent Navier-Stokes equations for the incompressible flow of a non-Newtonian fluid. In this article, various methods for solving the Fokker-Planck equation are reviewed.

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Water shortage and energy crisis are two major challenges for human societies. Solar distillation devices the best solution for converting salt water to fresh water and saline domestic scale using free energy from the sun. This paper presents an overview of a variety of active and passive solar distillation devices for desalination of saline waters in remote rural areas with high solar radiation potential is done.

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The reduction of energy consumption on sensor nodes using cognitive radio network routing algorithm to help Dayjkstra, Can help a lot in increasing the life of nodes and improve the whole problem of the exchange of information without slowing down. Holes containing channel energy threshold is detected and checked by applying a range of secondary users assigned. From the simulation results of cognitive radio-based network routing algorithm can be seen Dayjkstra sensor nodes send data from the source node to the final node of their shortest and best route. Energy consumption by as much as 80 percent less sensor nodes with Dayjkstra algorithm of algorithms such as LEACH, DASC, EEUC that this factor is an increase in the lifetime of nodes in the network.

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Because of increasing demand on new reliable power source for hybrid electric vehicles, lithium-ion (Li-ion) batteries have received much attention in the last decade. Problem free Li-ion batteries are already in use for low power demand applications such as cell phone and laptop battery packs, however; for high power applications such as in automotive propulsion drives, there are serious issues which need to be addressed. Among various issues that high power application lithium-ion (Li-ion) batteries are encountered, thermal issues have received more attention because of their potential to degrade battery performance. In this work, a lumped capacitance heat transfer model is developed in conjunction with a flow network approach to study performance of a commercial-size Lithium-ion battery pack, under various design and operating conditions of a thermal management system. Air, silicon oil and water are chosen as cooling media in the battery pack. Different flow configurations are considered and temperature dispersion, cell-averaged voltage and resistance distributions, and parasitic losses due to the fan/pump power demand are calculated. It is found that application of a coolant with an appropriate viscosity and heat capacity, such as water, in conjunction with a Y-type flow configuration will result in uniform temperature and voltage distributions in the battery pack while keeping the power requirement at low, acceptable levels.

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Considering the significant waste of gas in the oil and gas industry flares, it is highly desired to recover the gas in the industrial processes. Gas recovery reduces the energy consumption as well as the negative environmental impacts. In this study, different flare gas recovery methods are presented from exergy perspectives. Exergy analysis based on the second law overcomes the limitations of the energy-based analysis and offers a much more meaningful evaluation by indicating the association of irreversibilities. Analytical results indicate that simultaneous generation of power and heat by flare gases is the most effective method and can decrease the exergy destruction and fuel gas consumption of the cycle by 77.58 MW and 5793 kg/hr, respectively. When there is no demand for power, recycling the flare gases to process units and steam generating by the turbine exhaust gases can decrease fuel gas consumption of the cycle by 5605 kg/hr. It is also observed that pressurizing and recycling the gas for utility consumption can decrease the exergy destruction and fuel gas consumption of the cycle by 28 MW and 2100 kg/hr, respectively.