Majlesi Journal of Energy Management
Volume:1 Issue: 4, Dec 2012

Air management of the polymer fuel cell system is a key issue to increase the performance and the efficiency. The air compressor is used as an important lateral device for the fuel cell system. By using of this system, input parameters into the fuel cell collection are determined and used in other subsystems. The final goal of this paper is to design the dynamic model for an air compressor of the fuel cell collection in the Matlab\ Simulink software. This action is for obtaining an accurate and continuous control on the input air parameters. In this model, by using of the static feed forward function, requested electrical current of the fuel cell is related to the air compressor model. In addition, input thermodynamic parameters of the air compressor have been assumed to set in the determined value. With the designed model, changes in the compressor parameters are intercepted. Investigated parameters are angular velocity, temperature, compressor power, mass flow rate, outlet air pressure and the compressor efficiency. Finally, the results of the dynamic model as well as the compressor map are fully validated based on the available results in the open literature. Therefore, the centrifugal compressor model is produced that can be added to polymer fuel cell collection as a lateral system. In addition, the results show that the model can predict the dynamic behavior of the compressor accurately and it can be used directly for any control purposes.

Unit Commitment is the problem which finds the most economic production for power generation, when the power consumption and different constraints of the power plants are known. Also, economic dispatch as the operation of power plants to produce energy at the lowest cost to reliably serve consumers, and considering any operational limits related to generation and transmission is one of the most important calculations in power system. There are a lot of papers and researches to modeling the real constraints of these two problems. Economic dispatch considering prohibited operating zones and ramp-rate limits is one of the most important branches related to economic dispatch. This paper presents an effective algorithm for solving economic dispatch problem in power systems with units which have prohibited operating zones constraints and ramp-rate limits based on genetic algorithm. The proposed approach is a two stage algorithm which has two main advantages. First, it reduces the total costs of operation, and secondly, it increases the probability of convergences the solutions. The proposed algorithm has been tested successfully on 15 and 40 units and has been compared with other algorithm. The test results verify the advantages of the proposed method comparing to other works.

In the present paper, a second-law analysis is undertaken to study buoyancy-driven flow inside a rectangular porous enclosure with three adiabatic walls. To this aim, the conservation equations for mass, momentum, and energy are solved numerically using a control-volume based computational procedure. Thereafter, the generation of entropy is calculated in terms of heat transfer irreversibility and fluid friction irreversibility. All walls of the enclosure are thermally insulated except the bottom wall which is partially heated and cooled with a sinusoidal temperature profile. Results for a base case are presented in terms of streamlines, isothermal lines, iso-entropy generation lines, and iso-Bejan lines. Thereafter, effect of aspect ratio of the enclosure on the development of flow and thermal fields as well as entropy generation characteristics is examined. Finally, variations of average Nusselt number, global entropy generation rate, and global Bejan number are analyzed over a wide range of Darcy-modified Rayleigh number (), aspect ratio parameter (), and amplitude of the sinusoidal temperature function ().

This paper intends to present an effective analysis of the buckling phenomenon in wind loaded cylindrical storage tanks in the form of a program package based on general purpose finite element codes. This program, namely TK-INDUSTRIAL, written in ANSYS Parametric Design Language (APDL), aims to evaluate the buckling response of storage tanks under wind or hurricane. As a major result, the critical buckling wind speed and the influence of using ring stiffeners to increase this critical speed were assessed. The proposed program was shown to provide appropriate results and can be used as a strong tool to simulate the buckling of wind loaded cylindrical storage tanks.