Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Manuel E. Cruz is active.

Publication


Featured researches published by Manuel E. Cruz.


Numerical Heat Transfer Part A-applications | 2007

Effective Thermal Conductivity of Composite Materials with 3-D Microstructures and Interfacial Thermal Resistance

Carlos F. Matt; Manuel E. Cruz

This article presents a numerical scheme, based on an isoparametric second-order finite-element discretization of the unit cell heat conduction problem, to calculate the effective thermal conductivity of composite materials with general 3-D microstructures and interfacial thermal resistance. Representative numerical results for the effective conductivity of ordered arrays of spheres, prolate ellipsoids of revolution, and finite-length circular cylinders are presented and, when possible, validated against previous analytical predictions. Furthermore, the effective conductivity of a disordered multiparticle cell is calculated, showing that the present computational approach is a valuable tool for understanding the macroscopic thermal behavior of composite materials.


Journal of Engineering for Gas Turbines and Power-transactions of The Asme | 2010

Maximization of the Profit of a Complex Combined-Cycle Cogeneration Plant Using a Professional Process Simulator

Leonardo S. Vieira; Carlos F. Matt; Vanessa G. Guedes; Manuel E. Cruz; Fernando V. Castellões

The high cost of energy resources has driven a strong and continued quest for their optimal utilization. In this context, modern thermoeconomic optimization techniques have been developed to analyze and design improved energy systems, leading to a better compromise between energetic efficiency and cost. Thermoeconomic optimization can be parametric (plant configuration is fixed), applicable both at the design phase or operation phase of a system, or structural (plant configuration may vary). In practice, mathematical thermoeconomic optimization may be accomplished in two ways: (i) the conventional way, which manipulates all pertinent equations simultaneously or (ii) integrated with a professional process simulator, such that the equations are manipulated separately. In the latter case, the simulator deals with the thermodynamic property and balance equations, while an external optimization routine, linked to the simulator, deals with the economic equations and objective function. In this work, a previous implementation of an integrated approach for parametric mathematical thermoeconomic optimization of complex thermal systems is applied to an actual combined-cycle cogeneration plant located in the outskirts of the city of Rio de Janeiro in Brazil. The plant contains more than 60 thermal components, including two gas turbines, one steam turbine, and two heat recovery steam generators. Several hundred variables are required to simulate the plant at one operational steady-state. The plant produces 380 MW of power nominally, and exports a mass flow rate between 200 tons/h and 400 tons/h of superheated process steam, at 45 bars and 404°C, to a neighboring refinery. The simulator is the THERMOFLEX software, which interfaces with the Microsoft Excel program. The optimization routine is written in the Visual Basic for Applications language and is based on Powell’s method. The cogeneration plant operates subjected to time-changing economic scenarios, because of varying fuel, electricity, and steam prices. Thus, to manage the plant, it is necessary to vary the operational state appropriately as the economic parameters change. For a prescribed economic scenario, previous work determined the minimum operational cost, when a fixed contracted hourly-rate of process steam was to be exported, while a variable amount of electrical power was produced. In this paper, a broader optimization problem is formulated and solved, for which the objective is to maximize the plant profit under different economic scenarios. It is shown that the optimal operating conditions depend on the economic parameters, and do not necessarily imply maximum efficiency. The integrated optimization approach proves effective, robust, and helpful for optimal plant management.


International Journal for Numerical Methods in Fluids | 1998

Variational bound finite element methods for three-dimensional creeping porous media and sedimentation flows

Matteo Pedercini; Anthony T. Patera; Manuel E. Cruz

SUMMARY We present an analytico-computational methodology for the prediction of the effective properties of two types of three-dimensional particulate Stokes flows: porous media and sedimentation flows. In particular, we determine the permeability and average settling rate of media that consist of non-colloidal monodisperse solid spherical particles immersed in a highly viscous Newtonian fluid. Our methodology recasts the original problem into three scale-decoupled subproblems: the macro-, meso- and microscale subproblems. In the macroscale analysis the appropriate effective property is used to calculate the bulk quantity of interest. The mesoscale problem provides this effective property through the finite element solution of the transport equations in a periodic cell containing many particles distributed according to a prescribed joint probability density function. Finally, the microscale analysis allows us to accommodate mesoscale realizations in which two or more inclusions are in very close proximity; this geometrical stiffness is alleviated by introducing simple domain modifications that relax the mesh generation requirements while simultaneously yielding rigorous bounds for the effective property. Our methodology can treat random particle distributions as well as regular arrays; in the current paper we analyse only the latter. # 1998 John Wiley & Sons, Ltd. Int. J. Numer. Meth. Fluids, 26: 145‐175 (1998)


Journal of The Brazilian Society of Mechanical Sciences and Engineering | 2011

Maximum profit cogeneration plant - MPCP: system modeling, optimization problem formulation, and solution

Alessandro N. da Costa; Marcus Vinicius Da Silva Neves; Manuel E. Cruz; Leonardo S. Vieira

The well-known CGAM optimization problem was formulated to serve as a benchmark for comparison of different thermoeconomic methodologies. The CGAM cogeneration plant produced 30 MW of power and 14 kg/s of saturated vapor at 20 bar. The objective function was the total cost rate of the system, related to thermodynamic variables and installation costs. Because the CGAM problem originates from an academic viewpoint, its models do not reflect the industrial reality of energy systems, and do not conform to important operational and technological restrictions. The objective of this work is to propose an alternative cogeneration-system optimization problem, denoted the MPCP problem – Maximum Profit Cogeneration Plant, which incorporates functional economic concepts and modern technologies. The objective function is the net present value (NPV) of the monetary gain for the period of plant operation. The optimum (i.e., maximum) NPV value is obtained using two different professional optimization toolboxes appropriate for multivariable nonlinear constrained functions. The optimal operational conditions indicate that the MPCP plant reaches the allowed physical limits of the main equipment, namely, maximum efficiency of the gas turbine generator set and minimum temperature difference inside the heat recovery steam generator. Formal findings like these help to direct efforts to improve current technologies.


Heat Transfer Engineering | 2009

Single and Multi-Objective Optimization of a Cogeneration System Using Hybrid Algorithms

Ricardo S. Padilha; Hugo F. L. Santos; Marcelo J. Colaço; Manuel E. Cruz

Current design and operation of energy systems must consider the efficient utilization of energy resources, reduced environmental harms, and sustainable development. Many techniques for energy systems analysis and optimization have thus been developed worldwide. To evaluate different methodologies, the benchmark CGAM problem was proposed, which consisted of the optimization of a cogeneration system with explicit physical, thermodynamic, and economic models. The original CGAM problem was formulated as a single objective optimization problem, where the objective function was the sum of the purchased equipment, maintenance and operation, and fuel consumption costs. However, in real-life applications, costs must be analyzed individually: for example, one might increase equipment costs but save in fuel consumption for the entire system life. In this paper, single- and multi-objective hybrid optimizations of the CGAM system are performed. A hybrid optimization algorithm combines the strengths of deterministic and heuristic methods. Usually, it employs a heuristic method to locate a region where the global extreme point lies, and then switches to a deterministic method to get to the exact point faster. The objective functions are the fuel consumption cost rate and the total capital investment. Thus, a Pareto front is obtained for all non-dominated solutions, from which the final decision can be made considering appropriate scenarios.


Heat Transfer Engineering | 2013

Exergetic Analysis of Cogeneration Plants Through Integration of Internal Combustion Engine and Process Simulators

Leonardo de Oliveira Carvalho; Albino J. K. Leiroz; Manuel E. Cruz

Internal combustion engines (ICEs) have been used in power generation even before they were massively employed for transportation. Their high reliability, excellent power-to-weight ratio, and thermal efficiency have made them a competitive choice as main energy converters in small to medium-sized power plants. Process simulators can model ICE-powered energy plants with limited depth due to the highly simplified engine models used, which require the description of individual energy and mass flows entering or leaving the engine. ICE models available in process simulators are therefore not predictive but merely descriptive representations of the engines. Because the combustion process within the ICE is typically the main cause of exergy destruction in ICE-powered energy plants, a better understanding of the global effects of different engine parameters is desirable. This article presents and exploits the integration of an internal combustion engine simulator with a process simulator, so as to obtain a novel, fully coupled simulation platform to analyze the performance of ICE-based power plants. A simulation model of an actual cogeneration plant is used as an example for the application of the proposed computational methodology. The results show that by manipulating engine mapping parameters the plant overall efficiency can be improved.


Archive | 2010

Heat Conduction in Two-Phase Composite Materials with Three-Dimensional Microstructures and Interfacial Thermal Resistance

Carlos F. Matt; Manuel E. Cruz

The goals envisioned for the current chapter are threefold. First, it gives a general overview of heat conduction in two-phase composite materials with three dimensional microstructures and interfacial thermal resistance. Second, it describes the application of homogenization theory to the multiscale heat conduction problem in the composite medium in order to derive the boundary-value problem defined on a representative volume element of the composite microstructure (the cell problem) and an expression for the composite effective thermal conductivity. Third, it describes a finite-element-based computational scheme to calculate the effective thermal conductivity of composite materials with general 3-D microstructures and interfacial thermal resistance. Numerical results for the effective conductivity are presented and, when possible, compared with available analytical predictions. The numerical results reported here confirm that computational approaches are a helpful tool for understanding the complex macroscopic thermal behavior of composite materials.


Volume 8: Energy Systems: Analysis, Thermodynamics and Sustainability; Sustainable Products and Processes | 2008

Optimization of the Operation of a Complex Combined-Cycle Cogeneration Plant Using a Professional Process Simulator

Leonardo S. Vieira; Carlos F. Matt; Vanessa G. Guedes; Manuel E. Cruz; Fernando V. Castellões

Thermoeconomic optimization is a relatively modern technique to analyze and design more efficient energy systems, leading to a better compromise between energetic efficiency and cost. Thermoeconomic optimization can be parametric (plant configuration is fixed), applicable both at the design phase or the operation phase of an energy system, or structural (plant configuration may vary). In practice, mathematical thermoeconomic optimization may be accomplished in two ways: (i) the conventional way, which manipulates all pertinent equations simultaneously, or (ii) integrated with a professional process simulator, such that the equations are manipulated separately. In the latter case, the simulator deals with the thermodynamic property and balance equations, while an external optimization routine, linked to the simulator, deals with the economic equations and objective function. In this work a previous implementation of an integrated approach for parametric mathematical thermoeconomic optimization of complex thermal systems is applied to an actual combined-cycle cogeneration plant located in the outskirts of the city of Rio de Janeiro, in Brazil. The simulator is the Thermoflex software, which interfaces with the MS-Excel program. Thus, the Powell’s method for optimization integrated with Thermoflex is written in the VBA language. The plant contains more than 60 thermal components, including two gas turbines, one steam turbine, and two heat recovery steam generators. Simulation of one operational condition of the plant requires several hundred variables. The plant produces nominally 380 MW of power, and exports a mass flow rate between 200 and 400 ton/h of superheated process steam, at 45 bar and 404°C, to a neighboring refinery. The cogeneration plant operates subjected to an economic scenario, which changes with time, because of varying fuel, electricity, and steam prices. Therefore, to manage the plant, it is important to know the minimum operational cost, when a fixed contracted hourly-rate of process steam has to be exported, while a variable amount of electrical power is produced. An optimization problem can thus be formulated, for which the objective is to minimize the cost of consumed resources per unit electrical power generated. Results of optimization exercises to determine the optimal operational conditions of the plant for various exported mass flow rates of process steam are presented and discussed.Copyright


ASME 2012 International Mechanical Engineering Congress and Exposition | 2012

Effective Thermal Conductivity of Ordered Short-Fiber Composites With Single-Fiber Uniform Hexagonal Prism Cell

Marcelo B. Martinez; Manuel E. Cruz; Carlos F. Matt

The bulk behavior of short-fiber composite materials in mechanical, thermal, and electrical applications is of great engineering interest. The reliability of analytical and numerical studies dedicated to these topics depends to a large extent on the postulated, or prescribed, microstructure configurations. Of course, different spatial distributions of fibers lead to different configurations, which in turn influence the effective properties. There are no established (or benchmarked) microstructure configurations (or models) to be used in investigations aimed at calculating the macroscopic behavior of classes of real composite material bodies. In the present numerical study of heat conduction in composites, accurate results for the longitudinal and transverse effective thermal conductivities of short-fiber composites with single-fiber uniform hexagonal prism cell are calculated and validated. The three-dimensional periodic cell microstructure consists of one short circular cylindrical fiber placed at the center, and perpendicular to the two parallel regular hexagons, of the prism. Previous continuous formulation and computational implementation are employed, based on the method of homogenization and finite element discretization. A procedure for generating the domain of the uniform hexagonal prism cell, and the respective tetrahedral finite-element mesh, has been realized using a third-party software. The numerical effective conductivity results obtained in the 3-D calculations are validated against analytical results for the 2-D hexagonal array of circular cylinders.Copyright


2010 14th International Heat Transfer Conference, Volume 3 | 2010

Influence of Fiber Orientation and Aspect Ratio on the Effective Conductivity of Parallelepipedonal-Cell Short-Fiber Composites

Juliana S. Bezerra; Manuel E. Cruz; Carlos F. Matt

Modern applications of short-fiber composite materials demand accurate characterization of their macroscopic thermal properties. Many physical and microstructural factors influence the effective thermal conductivity of a composite material body. The objective of the current work is to investigate the influence of the microstructure configuration on the effective conductivity of a parallelepipedonal-cell composite containing equal-sized short fibers; the orientation and aspect ratio of the fibers are varied. The possible presence of voids in the matrix or of an interfacial thermal resistance between the constituent phases are not considered. A previous continuous formulation and computational implementation of heat conduction in a statistically homogeneous and periodic composite material are employed. The approach is based on the application of homogenization theory to the variational form of the original heat conduction boundary value problem for the multiscale composite medium. The variational form is well suited for subsequent numerical solution by the finite element method. The expression for the composite effective conductivity is here computed for several parallelepipedonal-cell microstructures. The numerical results are critically compared with available experimental data for short-fiber composites, and indications for important future research efforts are drawn.Copyright

Collaboration


Dive into the Manuel E. Cruz's collaboration.

Top Co-Authors

Avatar

Carlos F. Matt

Federal University of Rio de Janeiro

View shared research outputs
Top Co-Authors

Avatar

Albino J. K. Leiroz

Federal University of Rio de Janeiro

View shared research outputs
Top Co-Authors

Avatar

Julián Bravo-Castillero

National Autonomous University of Mexico

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Julián Bravo-Castillero

National Autonomous University of Mexico

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Marcelo J. Colaço

Federal University of Rio de Janeiro

View shared research outputs
Top Co-Authors

Avatar

João L M Donatelli

Universidade Federal do Espírito Santo

View shared research outputs
Top Co-Authors

Avatar

Thiago S. Pires

Federal University of Rio de Janeiro

View shared research outputs
Researchain Logo
Decentralizing Knowledge