Uma avaliação das metodologias de desagregação da exergia física para a modelagem termoeconômica de sistemas

• Autor(a) principal: Faria, Pedro Rosseto de
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/1129
• topic: Engenharia Mecânica; Exergia; Termoeconomia; Modelagem termoeconômica; Desagregação da exergia física; 621

Most analysts agree that exergy, instead of enthalpy only, is the most appropriated thermodynamic property to associate with cost (originally an economic property) since it contains information from the Second Law of Thermodynamics and accounts for energy quality. However, many times during the Thermoeconomic Modeling, the exergy is disaggregated in their components (chemical, thermal and mechanical), or yet, it includes the negentropy, which is a fictitious flow, thus allowing the system disaggregation into its components (or subsystems) and also to improve modeling to local optimization, diagnosis and residues treatment. Although some authors believe that physical exergy disaggregation in their components (thermal and mechanical) improve the accuracy of the results, the increase in the complexity modeling is significant, and consequently increase the computational efforts. Recently some authors identified restrictions and possible limitations of using negentropy and this kind of physical exergy disaggregation, thus proposing alternatives for residues and dissipative equipment treatments targeting system disaggregation into its components. These alternatives consist of new proposals of physical exergy disaggregation. Thus, this work aims to evaluate the different approaches of physical exergy disaggregation for Thermoeconomic Modeling, taking into account some aspects: advantages, limitations, inconsistences, accuracy improvements, increase of complexity and computational efforts and the residues and dissipative equipment treatments for total system disaggregation. For this, the different approaches and levels of physical exergy disaggregation are applied for cost allocation of final products (net power and useful heat) in different cogeneration systems considering as working fluid both ideal gas and real fluid. These plants, with dissipative equipment (condenser and valve) and/or residues (exhaust gases from the recovery boiler). However, it was necessary to use one cogeneration plant without dissipative equipment neither residues in order to evaluate the effect of physical exergy disaggregation alone.