The aim of this study is to investigate the real behavior of the working fluids in the technical cycles. For the description of these effects, the group contribution – Peng-Robinson volume translated equation of state (VTPR-GCEOS) are used. Organic Rankine Cycle (ORC) can be used to generate power by using alternative heat sources at low temperatures. In order to develop and optimize the ORC process, the thermodynamic properties of the pure and mixture organic working fluids are needed. The present work deals with the analysis of pure substances (aromatics, linear siloxanes and cyclic siloxanes) and their mixtures for their use as working fluids in the ORC process. The vapor pressures, heat capacities, densities, melting temperatures and melting enthalpies, the thermal conductivities and viscosities were measured for five different siloxanes. These data were used on one hand to determine the pure component parameters of the equation of state (vapor pressures and heat capacities) and on the other hand they can be used for the optimization of the ORC-cycle (e.g. the thermal conductivity for the design of the heat exchanger). The binary group interaction parameters of the VTPR-GCEOS were fitted to the experimental the excess enthalpies and vapor-liquid data for selected binary mixtures. Using this model, the influence of mixing effects on the thermal efficiency can be calculated. The accurate modeling of the Joule-Thomson coefficient and the Joule-Thomson inversion curve is very important for the thermodynamic analysis of the refrigerate cycles. The analysis of the obtained results related to these properties allows the conclusion that the model can be successfully applied for the modeling of technical refrigerate cycles, if pure components or binary mixture as working fluids are used. The thermodynamic modeling of technical cycle processes requires to take into account the real behavior of the working fluid, because the efficiency of the process run through an extreme value as function of the mixture composition, where the kind of the extreme value depends on the sign of the mixing enthalpy.
|School:||Technische Universitaet Berlin (Germany)|
|Source:||DAI-C 81/1(E), Dissertation Abstracts International|
|Subjects:||Mechanical engineering, Fluid mechanics, Thermodynamics|
|Keywords:||Organic Rankine cycle|
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