Mohammad Hassan Shojaei Fard , Mojtaba Tahani , Ali Mahtab , Javad Zare ,
Volume 3, Issue 2 (12-2017)
Abstract
In this work thermal performance of a cylindrical heat pipe at steady state has been investigated empirically. The used heat pipe, made of copper, has been designed and manufactured by considering effective parameters on heat pipe thermal performance. Then heat pipe has been charged by water as the working fluid. By installing sensors and the other equipment, the test set up has been prepared. After preparing the test set up by changing voltage, various input powers have been inserted into evaporator and the heat pipe surface temperature distribution has been obtained for each case. Then by using the obtained temperature distributions, thermal resistance variations and equivalent thermal conductivity coefficient have been computed. and variation of them versus input power have been plotted. The results show that the thermal resistance has its minimum value at maximum operating limit (maximum passing power) and equivalent thermal conductivity has its maximum value at this point.
Shahram Derakhshan, Ehsan Abdolahnejad, Javad Zare,
Volume 3, Issue 2 (12-2017)
Abstract
Nowadays, according to increasing energy consumption especially in industry, the need for optimizing energy consumption and determining energy efficiency class of different devices is essential. The main challenge of the present study is developing an energy label instruction for centrifugal pumps. Since the used standard in Iran (ISIRI 7817-2, 1st.edition) only considers the effect of efficiency in energy labeling, a new method is presented to modify this standard. In the proposed method the effect of specific speed on efficiency is considered by choosing one of the constant specific speed curves in η- Q diagram and modifying efficiency for each specific speed. Then, different pumps are tested and labeled by different standards. While the used standard in Iran labels all the pumps in one class, but the new proposed method can label pumps properly as European standards that show the benefit of using the proposed method in centrifugal pumps energy labeling.
Rasoul Rajabpour , Bahram Sami Kashkoli , Tahereh Faraji , Abolghasem Mohamadzadeh , Seyfollah Amin,
Volume 3, Issue 2 (12-2017)
Abstract
In this paper, the optimal operation of pumping stations was determined using a genetic algorithm so that the minimum energy cost. The schedule for the operation of the water pump system can be a significant savings in the cost of energy to be achieved. Determine the optimum pump operation schedule an optimization model - simulation-based genetic algorithm was developed. The model integrates GA optimizer and EPANET hydraulic network solver in MATLAB. The proposed model is applied to find the optimal pump operation schedule of Dogonbadan water conveyance system from Kowsar Dam in an ordinary day of the year. The comparison of optimal schedule with ordinary operation strategy shows 26.8 percent reduction in total energy cost. This indicates the high capability of the proposed model.
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.
Seyyed Hossein Hashemi , Ehsan Fathalinia, Mohsen Fathalinia,
Volume 3, Issue 2 (12-2017)
Abstract
The Trombe wall heating system known as one of the most important consumption reduction technology that utilizes solar energy is the energy efficiency. In this paper, the effects of temperature on system performance Trembath glass wall temperature of wall heating Trembath according to the intensity of solar radiation is investigated numerically. The results confirmed the increase in efficiency heating system with regard to solar radiation intensity emitted in the study area. With such intensity 466.281 w / m
2 close to the glass surface temperature (in air duct) up to 14.422 ° C arrives while lower-intensity radiation (394.91 w / m
2) in the final heat to about 12.71 ° C goes. Considering the solar radiation, can be expected to increase the flow of thermal energy in the air duct. The effect of improving the efficiency of the underlying performance heating technology Trembath wall. The results of this study, changes in temperature glass, to the the amount of solar radiation intensity in the relationship. When the radiation intensity maximum the amount of 466.81 w / m
2 is concerned, more secondary radiation is emitted. As a result, the glass has a temperature range between 11.32 to the 12.73 ° C.
, 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.
Iman Akbarpour,
Volume 4, Issue 1 (9-2023)
Abstract
On a global scale, the pulp and paper industry lead to produce significant amounts of effluents, solid wastes and gaseous wastes, and these wastes originate mainly from the pulping process, deinking and wastewater treatment. Solid biomass in wood waste as well as black liquor of pulping process can be converted to synthetic gas, mainly CO and H2 by thermal processes, with small amounts of methane, Co2 and H2o, and this can be a good opportunity to revive the pulp and paper industry. The main raw materials of biomass in the biorefinery process include hemicellulose, cellulose, lignin and skin, and with mechanical-thermal methods including biomass gasification, black liquor gasification, pyrolysis or liquefaction and carbonization of biomass, synthetic gas can be converted into electricity as well as liquid fuels and chemicals. The results obtained by comparing different hemicellulose pre-extraction technologies of lignocellulosic materials indicate that the steam explosion method is much more environmentally friendly than other alternative methods requiring less investment cost. At present, the use of steam explosion method has increased at the commercial level due to its cost-effectiveness and this method is very efficient for hardwood residues as well as crops leftovers. Also, the organosolve fractionation technology for the separation of hardwoods is well operational and leads to the production of high purity cellulose and the selective dissolution of lignin and hemicellulose. Nanofiltration is a desirable separation method for the recovery of hemicellulose from hydrolysates, and in this regard, the combination of a twin-screw extruder system can be the best way to extract hemicelluloses from hardwood chips. Nanofiltration is much better than ultrafiltration to separate hemicelluloses from hydrolysates by alkaline methods.
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.
Dr Mohammad Sajjadnejad,
Volume 4, Issue 2 (11-2023)
Abstract
Nowadays, lithium-ion batteries have been commercialized and extensive research is done on improving their properties. The things that are currently the major part of the research are reducing the price of the battery, increasing the energy density of the battery, increasing the lifespan and improving the safety of the battery. In military applications and aviation industries, special attention is paid to battery reliability and safety. The gradual degradation of the materials used in lithium-ion batteries over a long period of time has a negative effect on the electrical performance, lifespan and safety of the battery. This is through increasing the electrical resistance of the battery and even cutting the internal connection of the battery, producing corrosion products and creating passive films on the surface of the material, creating pollutants inside the battery that may react with active materials and leading to loss of uniformity in the material enters the battery and the electrolyte is destroyed. Most of the materials used in lithium-ion batteries were modified after identifying these problems in the battery structure. This article mainly deals with the phenomenon of corrosion in positive and negative current collectors in lithium-ion batteries.
