seyyed masoud seyyedi

A photovoltaic (PV) panel consists of several photovoltaic cells designed to convert solar radiation into electrical energy. Cooling of PV cells is an important task to increase PV panel efficiency, improve output power and optimize performance parameters. There are various methods for PV cooling. Phase change materials (PCMs) can be used to cool PV panels. The integrated system is called PV-PCM system. This paper provides an overview of the history, applications, mathematical modeling and economic evaluation for PV-PCM systems. The focus of this study is on the cooling of the PV cells using PCMs. Furthermore, the other types of PV systems (hybrid systems) are investigated. The effects of main parameters on the performance of PV or PV-PCM systems are investigated, too. Mathematical modeling including thermal and electrical models are presented. Finally, the advantages and disadvantages of PV-PCM system and its future overview are discussed. The results discover that the PV panel temperature up to 20 °C and electrical efficiency up to 5% can be reduced by PCM.The results discover that the PV panel temperature up to 20 °C and electrical efficiency up to 5% can be reduced by PCM.

In this study, the turbulent fluid flow and heat transfer performance of a concentric two-tube (air-nanofluid) heat exchanger with a helical turbulator is studied using STAR-CCM+. First, the computational code is validated according to the related experimental data and its simulation results for air and water. Then, the heat transfer performance and the effect of the different pitches of the helical turbulators are analyzed by replacing nanofluid instead of water for heat removal. The results show that the turbulator and nanoparticle has a high impact on heat transfer capability of the heat exchanger. The result shows that, the heat transfer is increased using turbulators in comparison with smooth tube for pitches of 15, 30 and 45 mm, respectively. In addition, the STAR-CCM+ is a proper tool for simulation of a complex geometries in three-dimensional. It is not only the CFD solver, STAR- CCM+ is an entire engineering process for solving problems involving flow (of fluids or solids), heat transfer and stress. It provides a suite of integrated components that combine to produce a powerful package that can address a wide variety of modeling needs. These components include: • 3D-CAD Modeler • CAD Embedding • Surface Preparation Tools • Automatic Meshing Technology • Physics Models • Post-processing

Biomass is considered as an effective energy carrier to meet the needs of clean energy for the whole world, which need to have sustainable renewable energy. Among the various methods of biomass, gasification is commendable. It is considered as one of the most important restoration and thermochemical methods for converting biomass energy into gaseous fuels, thermal and electrical energies, as well as its use for the production of biofuels. But there are some obstacles, which can be solve by more research in this area. In this article, various obstacles such as supply chain management include harvesting the waste, collection on the site, transportation to gasification site and storage are each a part of this chain. biomass pretreatment, generic low biomass resources and syngas conditioning from biomass energy conversion have been mentioned. Based on recent studies, the biggest challenges for biomass gasification is to produce heat and power. Also, different technologies of reactor design until reaching to the most efficient and high-efficiency reactor have been discussed in this paper. Ultimately, the most advanced gasification system with the most efficient gas conditioning technology can overcome all the mentioned obstacles.

Solar energy is a renewable source that can be used for a wide range of applications especially for power generation. In this paper, thermoeconomic analysis is performed for a steam Rankine cycle whereas solar energy is used for producing steam using parabolic trough solar collectors (PTSC). For this purpose, firstly the modeling of the solar collectors is performed. Then the mass and energy equations are solved to obtain the thermodynamic state of each point. The cost of each component is calculated using the purchase costs of the system components as a function of thermodynamic parameters. The effect of active parameters such as inlet temperature and pressure of steam turbine, solar irradiation intensity, pinch point, interest rate,  and lifetime are investigated on the number of solar collectors in rows, the total aperture area, the thermal efficiency and the average cost of electricity. The results shows that the average cost of electricity decreases with increasing the inlet temperature and pressure of steam turbine. The average cost of electricity is calculated to be less than 3 cent/kWh while it is normally more than 10 cent/kWh.

Todays, natural circulation loops (NCLs) are used in various industrial applications such as nuclear reactors, geothermal systems, electronic device cooling and so on. In a natural circulation loop, working fluid receives heat from a heat source (heater) and rejects it to a heat sink (cooler). The main objective of this paper is to investigate the effects of orientation of heater and cooler on the mass flow rate and temperature distribution in the natural circulation loop since the mass flow rate of the natural circulation loop is directly related to the heat transfer rate .The governing equations of the natural circulation loop are written as dimensionless form Cu-Water nanofluid considered as the working fluid and the effect of nanoparticles percentage on mass flow rate is investigated. Also, the effects of other parameters such as pipe diameter, height of the loop, loop inclination angle and the heater power on the mass flow rate of the loop and temperature distribution are investigated. The results show that increasing the diameter of the pipes, the percentage of nanoparticles, and the heater power increase the mass flow rate. However, the mass flow rate decreases with increasing loop inclination angle. The mass flow rate may be decreased or increased with increasing height depending on the orientation of the heater and cooler. In a constant heater power, the increase in the temperature of the nanofluid is much higher than other orientations when both the heater and the cooler are in the vertical position.

Residues are disposal remaining flows of matter or energy that are produced by energy systems. Residues cost allocation is a complex problem. One of the most important criteria for residues cost allocation is distributed entropy method. In this method, the fuel-product (FP) table (a mathematical representation of the thermoeconomic model) is used as input data. Average cost theory (ACT) method is one of the most important conventional exergoeconomic methods that can be applied to energy systems. In this paper, distributed entropy method and ACT method are applied to a combined cycle and a cogeneration system. Fuel and product costs for each component are obtained and compared with each other. Specific cost of product for each component is calculated, too.

In this work, free convection of Cu-water nanofluid in an enclosure by considering internally heat generated in the porous circular cavity and the impacts of viscous dissipation are numerically evaluated by control volume finite element method (CVFEM). The outer and inner sides of the circular porous enclosure are maintained at a fixed temperature while insulating the other two walls. The impacts of diverse effective parameters including the Rayleigh number, viscous dissipation, and nanofluid concentration on features of heat transfer and fluid flow are examined. Moreover, a new correlation for the average Nusselt number is developed according to the study’s active parameters. It can be deduced by the results that the maximum value of the temperature is proportional to the viscous dissipation parameter.

Exergoeconomic is the branch of engineering that combines exergy analysis with economic constraints to provide the system designer with information not available through conventional energy analysis and economic evaluation. In this study, exergy and exergoeconomic analysis has been performed for Qeshm cogeneration power plant. This cogeneration system can produce 26 MW electricity and 9000 m3 /day distilled water. Firstly, according to the mass and energy balance equations for cogeneration system’s component thermodynamic variables have been determined. Then, exergy analysis must be performed and exergy destruction of each component and its portion in the total exergy destruction can be determined. In order to determine cost of products, cost balance equation must be written for each component. The results of exergy analysis show that the maximum irreversibility is corresponding to the combustion chamber with the value of 11019.25 kW, and those of heat recovery steam generator (HRSG) and multi effect desalination with thermal vapor compression (MED-TVC) are 10305.43 kW and 9260.93 kW, respectively. The cost of producing electricity power is 10 $/MWh and the cost of producing distilled water is about 2 $/m3. Finally, the total cost of the understudy cogeneration cycle is in good agreement with the other cogeneration plant.

A natural circulation loop receives heat from a high-temperature source and rejects it to a low-temperature source without using a mechanical pump. Single phase natural circulation loop has been applied in many industrial systems for cooling. The heat transport capability of natural circulation loops (NCLs) is directly proportional to the flow rate that it can generate. To establish the heat transport capability of a natural circulation loop, it is essential to know the flow rate. Friction force and gravitational force are balanced with each other along the loop at steady state. In this paper, firstly the governing equations have been written for a natural circulation loop. Then the governing equations have been rewritten in the dimensionless form. Then, effects of heater length, cooler length, tube diameter, loop height, loops inclination angle, the distance of heater from the right side or left side, the distance of cooler from right or left sides and power of the heater on the loop mass flow rate and loop temperature distribution have been investigated. The results show that increasing of loop height, loop diameter and power of heater increase the mass flow rate. Also, increasing or decreasing of heater length, has no effect on the mass flow rate, whereas increasing of loop inclination angle decreases the mass flow rate. In this study, the friction coefficient is considered as continues for all regimes. In addition, the position of the heater and cooler has been unsymmetrically investigated.

The present paper investigates the relationship between the director's leadership styles and staff commitment of Fars Province police. The data were gathered by questionnaire. The management styles variables measured were based on Likeert leadership style and the variable of organizational commitment was assessed by Steers standardized questionnarie. Statistical population consisted of Fars Province police staff and 299 subjets were chosen. Based on the correlation coefficient, there was a meaning ful relationship between dictatorial and good-will styles of management and consultative and cooperational styles of management. The results showed that consultative and cooperational styles of management are more effective than the other styles of management.