Sharif Digital Repository

Load management and cost optimization are among the important factors in trigeneration systems and combined cooling, heating and power (CCHP) systems. In this study, an innovative CCHP system uses a gas turbine as the prime mover and has a heat recovery steam generator (HRSG) in addition to an auxiliary boiler, electric and absorption chillers. The system is tied with the bulk electric grid; to export and sell excess power or import power when necessary. This study analyzes load management and cost optimization of CCHP systems. A heuristic strategy to optimize the total energy cost is then presented. The optimal size of CCHP is determined from the study results. This paper proposes a model... 

This paper presents the mathematical modeling of single-phase natural circulation of the University of Genoa's rectangular loop (LOOP#1) by a computer program and using RELAP5 system code. The mass, momentum and energy conservation equations in transient form were solved numerically using the finite difference method. One-dimensional linear stability analysis was performed for the single-phase natural circulation loop and the numerical perturbation technique was used in this analysis. The Nyquist criterion was employed to find the stability map of the LOOP#1. The obtained transient results using the first order upwind scheme of the fluid temperatures in various sectors of the LOOP#1 are... 

In this paper, a finite volume scheme is used to discretize flow in porous media. A numerical method for treating advection-dominated contaminant transport for flow of groundwater is described. This system combines the advantages of numerical discretization and the finite volume method (like local mass conservation). The equations are dicretized using a finite volume approach. The resulting nonlinear differential system is integrated in time using a solver. The conservation of energy (convection-diffusion) equation is solved using a special method for reducing the oscillation induced by the standard finite volume method. Consequently, a mathematical model for multi-component flow transport... 

Energy-Aware routing is a promising technique for reducing energy consumption in future networks. Under this scheme, traffic loads are aggregated over a subset of the network links, allowing other links to be turned off to save energy. Since the capacity of links is the main limiting constraint in this problem, to further improve energy saving, the idea of using redundancy elimination (RE) in energy-Aware routing has been proposed. As performing RE in routers consumes some energy, it should be specified, which routers should perform RE and which links should be deactivated so that the total energy consumption of the network is minimized. As a result, the problem of energy-Aware routing with... 

A two-dimensional non-isothermal mathematical model has been developed for the ethane dehydrogenation reaction in a fixed-bed catalytic membrane reactor. Since ethane dehydrogenation is an equilibrium reaction, removal of produced hydrogen by the membrane shifts the thermodynamic equilibrium to ethylene production. For further displacement of the dehydrogenation reaction, oxidative dehydrogenation method has been used. Since ethane dehydrogenation is an endothermic reaction, the energy produced by the oxidative dehydrogenation method is consumed by the dehydrogenation reaction. The results show that the oxidative dehydrogenation method generated a substantial improvement in the reactor... 

In this paper we present a general formalism for the establishment and mean-square performance analysis of the family of selective partial update affine projection (SPU-AP), selective regressor affine projection (SR-AP), and selective partial update subband adaptive filter (SPU-SAF) algorithms. This analysis is based on energy conservation arguments and does not need to assume a Gaussian or white distribution for the regressors. We demonstrate through simulations that the results are useful in predicting the performance of these adaptive filter algorithms  

This article discusses a hexagonal prism rolling down an inclined plane, which is easy to realize experimentally and yields results that are consistent with a simple theory. This investigation would make an excellent undergraduate project. © 2009 American Association of Physics Teachers  

An effective approach for energy conservation in wireless sensor networks is scheduling sleep intervals for extraneous nodes while the remaining nodes stay active to provide continuous service. For the sensor network to operate successfully the active nodes must maintain both sensing coverage and network connectivity, It proved before if the communication range of nodes is at least twice the sensing range, complete coverage of a convex area implies connectivity among the working set of nodes. In this paper we consider a rectangular region A =a *b , such that Rs ≤ a, Rs ≤ b where Rs is the sensing range of nodes. and put a constraint on minimum allowed distance between nodes( Rs ). according... 

Specific fuel consumption of vehicles has been improved through technical changes in the last three decades. There has been little study of the impact of behavioral aspects on the specific fuel consumption of vehicles. Analytical tools developed recently have included options for quantifying the specific fuel consumption in certain predefined driving cycles. Empirical studies have shown that real driving cycles are different from predefined ones. It has also been observed that optimal coordination of both speed of vehicle and gear ratio are detrimental to the improved performance of a vehicle. Previous studies have only considered the vehicle speed as the explanatory parameter, and gear... 

In this paper a fuzzy power controller for a parallel hybrid passenger car is developed in order to minimize its fuel consumption and optimize its components efficiencies. This is done by controlling the engine operating points in its optimal region and maintaining the SoC of batteries and electric motor operating point at the highest possible efficiency. Of course the designed control strategy must be able to obey the driver's commands and achieve the PNGV regulations. The controller implemented in this paper is a Mamdani fuzzy logic controller which takes the batteries SoC, electric motor's speed, ICE speed and the total demanded torque as its input variables and gives the ICE torque as... 

One of the most prominent hybrid solar devices is the photovoltaic thermal system (PVTS), which is able to provide simultaneous electricity and thermal energy. The thermal energy is the heat absorbed by the photovoltaic (PV) module and transferred to the attached thermal collector and finally to the heat transfer fluid. Utilizing a proper heat transfer fluid is an effective means to increase in obtained thermal and electrical powers and enhance PV thermal management. Over the past decade, employing nanofluids thanks to their superior thermophysical properties became a proved strategy to improve the efficiency of the PVTS. This paper covers cutting-edge researches on nanofluid-based PVTS via... 

A smeared crack approach has been proposed to model the static and dynamic behavior of mass concrete in three-dimensional space. The proposed model simulates the tensile fracture on the mass concrete and contains pre-softening behavior, softening initiation, fracture energy conservation and strain rate effects under dynamic loads. The validity of the proposed model has been checked using the available experimental results under static and dynamic loads. The direct and indirect displacement control algorithms have been employed under incremental increasing static loads. It was found that the proposed model gives excellent results and crack profiles when compared with the available data under... 

The necessity for flexible electric systems, energy saving, loss reducing and environmental impact are providing Impetus to the development of Distributed Generation (DG). DG Includes the application of small generators, scattered throughout a power system, to provide the electric power needed by electrical customer. Such locally distributed generation, has several merits from the viewpoint of environmental restriction and location limitations, as well as transient and voltage stability In the power system. The exact solution of the DG allocation can be obtained by a complete enumeration of all feasible combinations of sites and sizes of DGs In the network. The number of alternatives could... 

In the natural gas transmission network, from supply points to demand nods there are various technological options that include processing, transportation, conversion and gas distribution. Comprehensive analysis of natural gas network requires evaluation of different chains of gas flow through various levels based on economical and environmental criteria subject to technical and operational constraints such as feasibility, operability and reliability of different alternatives. To aid decision-making process in the sector of natural gas, a generic optimization-based model has been developed for assessing long term energy issues related to planning and design of natural gas supply systems. The... 

The current study aims at introducing a 2D and fast-running code for the issues pertinent to design, analysis and safety in modular high temperature reactors. While the porous media approach is only applied to pebble bed type, the analysis in this paper covers both pebble bed and prismatic reactor. A time-dependent mass equation along with energy conservation equation for the cooling gas and a time-dependent energy conservation equation for the solid was solved. Appropriate series of constitutive equations (e.g. heat transfer coefficient, effective heat conductivity of solid, heat transfer coefficient, pressure drop etc.) has been recruited as well. In addition a finite-volume method is...