per
University of Kashan
Energy Engineering & Management
2345-2951
2251-8061
2014-12
4
3
2
11
article
Load Sharing in Parallel Microgrid Inverters Using One-Cycle Control
Abbas Ketabi
aketabi@kashanu.ac.ir
1
Mahdi Zeraati
zeraatimahdi@gmail.com
2
Kashan University
Kashan University
This paper investigate the properties of the circulating current and load sharing in parallel microgrid inverters. The existing methods cannot minimize efficient circulating current for the case of nonlinear load. The one-cycle control (OCC) technique and virtual complex impedance loop are included in the proposed controller in order to proper load sharing and reduce the circulating current due to impedance mismatch. Simulation results are presented to prove the improvement achieved by the new controller. Compared to the pulse width modulation (PWM), the proposed method, under different system impedances, reduces more effectively the voltage total harmonic distortion (THD) and offers advantages such as: constant switching frequency, simple circuitry, improved dynamic behavior of the control system during load change and start up.
http://energy.kashanu.ac.ir/article-1-183-en.html
Load sharing
One-Cycle control
Droop method
Parallel inverters
Virtual impedance.
per
University of Kashan
Energy Engineering & Management
2345-2951
2251-8061
2014-12
4
3
12
19
article
Heat Transfer in Dual Continuous Flow of Two Immiscible Liquids
hajir karimi
Hakar@yu.ac.ir
1
milad boostani
Milad.boostani@std.yu.ac.ir
2
mahnood reza rahimi
Mrrahimi@yu.ac.ir
3
In this study, heat transfer coefficients are measured for diesel-water two-phase flow in a horizontal pipe for dual continuous, dispersion of oil in water and dispersion of water in oil flow patterns. Flow patterns are observed using high speed photography for diesel-water mixture and two phase heat transfer data are obtained under a uniform heat flux boundary condition. The test section is a 1.1 mm ID pipe with a 1.8 m length. The Reynolds number is distributed from about 350 to 3,700 for diesel and from about 1,300 to 13,700 for water. The results show that the heat transfer coefficient of dual continuous pattern is higher than that of dispersion of water in oil pattern.
http://energy.kashanu.ac.ir/article-1-378-en.html
Two phase
Liquid-Liquid
Heat transfer
Flow pattern
Dual continuous.
per
University of Kashan
Energy Engineering & Management
2345-2951
2251-8061
2014-12
4
3
20
29
article
Numerical Study on Performance of Refrigeration Cycle with Double Stage Ejector
Ebrahim Afshari
e.afshari@eng.ui.ac.ir
1
Nabi Jahantigh
njahantigh@uoz.ac.ir
2
Reyhane laly
em_afshari@yahoo.com
3
Maryam Jafari
ebrahimafshari@yahoo.com
4
Isfahan University
Zabl university
Isfahan University
Isfahan University
In this paper, the performance of arefrigeration cycle with double stage ejector is studied. Also the effect of some working fluids, the ejector geometry including the diameter change in the part of constant diameter at the first and second stages and operating parameters on the entrainment ratio of the first and second stages in the ejector and coeﬃcient of performance cycle (COP) are studied. A 2D model of the ejector is considered andthe continuity, momentum, energy, and state equations are numerically solved. The thermodynamic analysis is carried out to study the performance of the double stage ejector. The results show that using R245faand water as the working fluids in the cycle leads to the lowest and highest coefficients of performance (0.799 and 1.808 at TG=120oC and TC=12oC) respectively in comparison with other refrigerants. Increasing diameter of the mixing chamber in the second stage causes decrement in the COP at a constant diameter in the mixing chamber of the first stage. Also, increasing the diameter in the mixing chamber of the first stage causesincrease in the COP at a constant diameter in the mixing chamber of the second stage.
http://energy.kashanu.ac.ir/article-1-401-en.html
Ejector refrigeration cycle
Doublestage ejector
Coeﬃcient of performance
Geometry
Working fluid.
per
University of Kashan
Energy Engineering & Management
2345-2951
2251-8061
2014-12
4
3
30
37
article
Analysis of Effective Parameters on Hydrogen Desorption From an Industrial Metal Hydride Tank
A.Ali Rabinataj
a.rabinataj@gmail.com
1
Hamid Hasanzade Afrozi
hamidhasanzade@yahoo.com
2
Kourosh Sedighi
ksedighi@nit.ac.ir
3
Musa Farhadi
mfarhadi@nit.ac.ir
4
Mazandaran University
Babol Noshirvani University of Technology
Babol Noshirvani University of Technology
Babol Noshirvani University of Technology
In present study, the desorption process of hydrogen from an industrial scale metal hydride tank with the thermal jacket system has been simulated. Commercial Fluent 6.3 code is used to solve the set of differential equations. The thermal equilibrium condition is considered between hydrogen gas and metal solid bed. In addition the hydrogen flow obeys the ideal gas condition. The effects of hot water temperature and convective heat transfer coefficient on the desorption process from the porous bed have been investigated. The results show that increasing the two parameters has great effect on desorption time. Specifically, augmentation of convective heat transfer coefficient from 1000 w/m2.k-1 to 4000 w/m2.k-1 yields to 7 percent decrement of discharge time. Desorption time becomes 8 percent shorter when the hot water temperature increases by 10k.
http://energy.kashanu.ac.ir/article-1-309-en.html
Metal hydride
Hydrogen desorption
Heat and mass transfer
Jacket heating
fuel cell
CFD.
per
University of Kashan
Energy Engineering & Management
2345-2951
2251-8061
2014-12
4
3
38
47
article
Evaluation of Artificial Neural Network Performance to Predict Daily Solar Radiation in Iran
Mehran Ameri
ameri_mm@uk.ac.ir
1
Mohamad Hadipoor
mmhadipoor@gmail.com
2
Shahid Bahonar University
Shahid Bahonar University
Iran has an average of 5.5 KWh per square meter solar radiation and 300 sunny days per year on 90% of the land. Regarding this amount of solar radiation and the necessity for solar potential zoning for better efficiencies, drawing solar potential maps is essential. In this study, the monthly data of 39 synoptic of Iran meteorological stations over years (1991-2000) has been used as the input data to the MATLAB software and artificial neural network (ANN). In the ANN, a multi-layer feed forward model is used. After applying the input data to the network with desired architecture, in output layer the solar radiation is predicted. The solar radiation anticipated by ANN is highly in accordance with meteorological data so that the final correlation coefficient is 0.96, depicting the great accuracy of the data derived from the software. By selecting the predicted data of ANN as input to ArcGIS software, the annual solar potential map of Iran is obtained.
http://energy.kashanu.ac.ir/article-1-219-en.html
Solar energy
Artificial neural networks (ANN)
Multi layer feed forward model
Solar potential map.
per
University of Kashan
Energy Engineering & Management
2345-2951
2251-8061
2014-12
4
3
48
59
article
Numerical Simulation of Heat Transfer and Pressure Drop inShell and Tube Heat Exchanger with Elliptic Tube Bundle
Elham Molaye
Elham.Molaye@gmail.com
1
Ahmad Fakhar
A.fakhar@iaukashan.ac.ir
2
Hosin Nori Bidgoli
HNouriB@iaukashan.ac.ir
3
Islamic Azad University of Kashan
Islamic Azad University of Kashan
Islamic Azad University of Kashan
Shell and tube heat exchanger, singular baffles have been stimulated by means of the computational fluid dynamic technique and Fluent software. Several elliptical cross sections for the tubes are examined. So each model drawn by using Gambit software. In stimulating, 3D meshes is used for irregular Couper and tetrahedral networks. Also the performance of each of two shell and tube exchanger is compared with, one of the optimized set of elliptical tubes, and the other with circular tubes according to heat transfer coefficient and pressure drop. The results accuracy is compared with Bell’s theory plus using an engineering equation solver software. The main objective at this stage is finding the best geometry for elliptical tubes used in the shell and tube exchangers as a new idea among the heat exchangers for future use. The results indicate the increase in the heat transfer rate to 59.9 percent, and the rise in pressure to 9.5 percent which is negligible in comparison with a boost in heat transfer.
http://energy.kashanu.ac.ir/article-1-272-en.html
Computational fluid dynamics
Heat transfer
Pressure drop
Tube with an elliptical cross section.