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Session: Poster session & Sponsor Exhibition
Session starts: Monday 07 October, 14:00

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Eiichi Sakaue (Toshiba Corporation)
Katsuya Yamashita (Toshiba Corporation)

Abstract:
In response to growing interest in the global environment, many low-GWP hydro-fluorocarbon fluids have been developed. Some of their accurate physical properties are disclosed to public from their suppliers or from public organizations, such as National Institute of Standards and Technology (NIST). To evaluate the performance of the ORC system, process simulators are often used. In case a new fluid is used as the ORC’s working fluid, its physical properties need to be input to the simulators. Equation of State (EOS), which models the relationship of pressure P, volume V and temperature T, is commonly used to express the thermodynamic properties of the fluid. Many simulators accommodate an option to select the type of EOS and require us to input the parameters for the selected EOS. Cubic EOSs, such as Peng-Robinson, are most popular type and only critical pressure Pc, critical temperature Tc and the eccentric factor ω are required to be input. However they do not perform well near the critical points and do not show accurate ORC performance even if we obtain accurate thermodynamic data of the working fluid. On the other hand, virial types of EOS, which have large degree of freedom, are so complicated formula that they require large computational resources to conduct their parameters while they have the risk to fall into local minimum. To solve above problems, simplified BWR (Benedict–Webb–Rubin) EOS is proposed here. BWR [1] is a virial type EOS. Taylor expansion is applied here to achieve its simplified formula. Accordingly this enables us to use least-square method for curve-fitting from accurate thermodynamic data. Hence the EOS parameters can be solved analytically with small computational power. The proposed method expresses the PVT relationship well near the critical point with providing plenty of neighborhood data to curve fitting. The deviation from the original data decreases to 1/6 compared to the estimation from Peng-Robinson EOS. This will help to evaluate the ORC system which comprises a new fluid as its working fluid. REFERENCES [1]　K.E. Starling, Fluid Properties for Light Petroleum Systems, Gulf Publishing,1973