Showing 21 results for Type of Study: Research
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Volume 2, Issue 2 (3-2017)
Abstract
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.
Sedigheh Janipour, Samad Nejatian, Mosayeb Bornapour,
Volume 2, Issue 2 (3-2017)
Abstract
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.
Asghar Lashanizadegan, Mahmoodreza Rahimi, Hadie Mazlumi,
Volume 3, Issue 1 (9-2017)
Abstract
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.
Amin Moosaie, Kourosh Goudarzi, Jalil Abbasi,
Volume 3, Issue 1 (9-2017)
Abstract
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.
Ali Hosseini, Ahmad Banakar,
Volume 3, Issue 1 (9-2017)
Abstract
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.
Afsaneh Ebrahimi, Sayyed Obaid Poordanesh,
Volume 3, Issue 1 (9-2017)
Abstract
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.
Gholamreza Karimi , Alireza Bidakhti Dehghan ,
Volume 3, Issue 1 (9-2017)
Abstract
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.
Vahab Kazerouni, Abedreza Farhadipor, Pourya Omidvar, Gholamreza Karimi,
Volume 3, Issue 1 (9-2017)
Abstract
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.
Burhan Azarm,
Volume 3, Issue 2 (12-2017)
Abstract
Solar energy is the most important type of modern and renewable energies. If it displace fossil fuels, can bring an end to concerns about finiteness of fuels, environmental pollution caused by the fossil fuels, price fluctuations and energy crisis. Among the energy sources, due to the high potential of solar energies in wide areas of the Iran, it has a great importance to researchers. The base of Photovoltaic technology is to converting sunlight into electricity and nowadays, most of the countries utilize it in the forms of grid-connected and off-grid. In recent years, few technologies are used for manufacturing of solar cells. The results of investigating show that the efficiency of the first generation in comparison to the other technologies are high due to the high quality raw materials which are used in the fabrication. It is expected that the differences between the efficiency of these for technologies will be decreased by the time and other technologies will be replaced by the first generation. In this paper, the structure of different technologies has been studied and the possible methods for improvement of the solar cells efficiency have been introduced.
Behrang Sajadi, Mohammad Yousefipour, Mohammad Ali Akhavan-Behabadi, Sadegh Khodaveisi,
Volume 3, Issue 2 (12-2017)
Abstract
In this study, the effect of using phase change materials on the air-conditioning system energy consumption of a typical room in a multi-floor building has been studied using EnergyPlus software. As the melting point of PCMs has an important impact on their effectiveness, as a part of this research, the effect of Iran climatic conditions on the appropriate melting point of the PCM has been investigated in 4 cities: Tabriz as a cold, Tehran as a moderate, Yazd a dry-hot and Bandar-e-Abbas a humid-hot climate. Based on the results, the proper temperature of PCM melting temperature is between 21 to 27°C and the saving varies from 1.6 to 13.2%. The results of this incestigation are useful in getting better understanding of the effect of PCMs on reducing the HVAC system energy consumption and in determining the PCM appropriate specifications.
, Afsaneh Rahimi, Touraj Dehghani,
Volume 4, Issue 1 (9-2023)
Abstract
According to the sources and methods of energy extraction and conversion and consumption in the world, in this article the types of fuel cells as an efficient system with the ability to convert different fuels into electricity with high efficiency compared to other energy conversion systems is studied. The advantages and disadvantages of each fuel cell is reviewed. Also, the research done in this field by the researcher during the last 20 years all over the world is collected and the presented results are compared. According to the results of this study the solid oxide fuel cells which have many advantages compared to other similar systems, are carefully studied and different methods of energy recovery from this system in combination with different systems and in different applications and different scales for production of heating, cooling and added power and as a result, efficiency and energy performance of the system is considered. In addition to these advantages, the investigated system faces several problems such as the lack of necessary infrastructures for its production and use and its high price compared to other methods of energy supply. In the future, these problems will be solved with the increase in the investments and supports of new technologies and it is expected that by using this system, every building will reach self-sufficiency in production and supply of energy consumption needs.
Aliasghar Tatari, Mohammadreza Dehghani Firouzabadi,
Volume 4, Issue 1 (9-2023)
Abstract
The gradual reduction of fossil resources has caused increasing concern about their supply and the emission of greenhouse gases and global warming, and in this context, biofuels can play an important role in solving these problems. Meanwhile, ethanol produced from corn starch, sugarcane molasses, lignocellulosic materials and biodiesel produced from rapeseed oil are the most important commercial uses in recent years. Ethanol production is a complex biochemical process in which yeasts, fungi, and certain bacteria are able to convert fermentable sugars into ethanol, carbon dioxide, and other metabolic byproducts. These byproducts contribute to the chemical composition and sensory properties of fermented foods. Ethanol production is important in a wide range of secondary products (such as health, medical and industrial). Controlling the fermentation process is usually a prerequisite for determining the quality of the final product. In this regard, monitoring the fermentation process is a basic need to ensure effective control of variable factors at all stages of the ethanol production process. Reducing the rate of fermentation in the process of ethanol production due to inhibitory compounds is considered a fundamental and significant problem in the economics of the process. In this review paper, the main aspects of ethanol fermentation and inhibitory compounds and their reduction methods in the ethanol production process from lignocellulosic materials have been discussed.
Mrs. Zahra Hassani, Dr. Abdolrasoul Pouranfard, Prof. Hajir Karimi,
Volume 4, Issue 1 (9-2023)
Abstract
In this study, the effect of adding polyisobutylene (PIB) as drag reducing agent (DRA) and nanoSiO2 particles as heat transfer enhancer to crude oil, separately and also the simultaneous addition of these materials to crude oil as poly-nanofluids (PNFs) in a vertical pipe and under constant heat flux conditions is investigated. The use of drag reducers is one of the most important and simplest methods to overcome some of the energy losses during fluid transpotation. The aim of this study is to investigate the effects of PIB solution and crude oil/silica nanofluid, separately and also the simultaneous effect of adding these two materials, called polyanofluid, on heat transfer and drag reduction in a vertical pipe. In order to make PNFs, polymer-based solutions with concentrations of 10-30 ppm are prepared. Then, nanoSiO2 with concentrations of 0.1-0.5wt% are added to the base fluid. The experiments were performed in the range of Reynolds 5800-8700 and temperature was 25°C. Experimental conclusions predicted that with increasing Reynolds number, temperature and concentration, Nusslet number and heat transfer rate in supplied nanofluids and PNFs enhanced with nanoparticle concentrations, while PIB concentration cause to reduce thermal propertied and improve the tribological properties of prepared PNFs. This occurrence can be attributed to the formation of the polymeric layer around the nanosilica particles.
Fatemeh Ghanbari, Amir Omidvar,
Volume 4, Issue 1 (9-2023)
Abstract
In this study, the effects of non-dimensional amplitude and frequency of pulsating flow are investigated on the heat transfer rate of a circular cylinder in the presence and absence of a splitter plate, for this purpose, at first the heat transfer rate of unpulsating flow is investigated and then compared with the results obtained from the pulsating flow. The pulsating flow over a circular cylinder is studied in the range of pulsating Strouhal number (0.1-2) and amplitude of pulsating flow A=0.75 in the Reynolds number of Re=100. Pulsating flow is one of the factors that can be effective on the heat transfer rate. But in general, the change in the heat transfer rate under pulsating flow depends on non-dimensional amplitude and frequency of pulsating flow. The best case for increasing the heat transfer rate is when the splitter plate is attached to the body. In all range of the pulsating Strouhal number, increase in the Nusselt number in the presence of a splitter plate is reported relative to the absence of splitter plate in pulsating flow.
Morteza Deilami, Pedram Pournaderi,
Volume 4, Issue 1 (9-2023)
Abstract
Heat transfer has an effective role in industrial and engineering applications. In this study, the effect of Al2O3 nanoparticles on laminar forced convection heat transfer flow in a tube is studied. Governing Equations are discretized using the finite difference method on a staggered grid. Nanofluid flow is simulated using single-phase and mixture models. Simulation results show that the average Nusselt Number increases with an increase in the Reynolds Number. Also, by increasing the volume fraction, the average Nusselt number and consequently the heat transfer rate increases. The results of the mixture model are in better agreement with experimental results than the single-phase model.
