Abstract

This chapter presents the features of the Enhanced-Predictive-PR78 equation of state (E-PPR78), a model highly suitable to perform “physical fluid screening” in power and refrigeration cycles. It enables, in fact, the accurate and predictive (i.e., without the need for its preliminary optimization by the user) determination of the thermodynamic properties of pure and multicomponent fluids usable in power and refrigeration cycles: hydrocarbons (alkanes, alkenes, alkynes, cycloalkane, naphthenic compounds, and so on), permanent gases (such as CO2 , N2 , H2 , He, Ar, O2 , NH3 , NO2/N2O4, and so on), mercaptans, fluorocompounds, and water. The EPPR78 equation of state is a developed form of the Peng-Robinson equation of state, which enables both the predictive determination of binary interaction parameters and the accurate calculation of pure fluid and mixture thermodynamic properties (saturation properties, enthalpies, heat capacities, volumes, and so on)

Highlights

  • Performance and design of closed power and refrigeration cycles are basically driven by the thermodynamic properties of their working fluids

  • This is the reason why, since the early 1900s, many researchers have been stressing over the importance of optimizing the working fluid of these cycles and of selecting a proper thermodynamic model to accurately calculate their properties

  • The aims of this chapter are to present this model, to outline the proper way to apply it according to the latest advancements over pure fluid modeling [42–46], and to perform the screening of pure and/or multicomponent working fluids for power and refrigeration cycles

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Summary

Introduction

Performance and design of closed power and refrigeration cycles are basically driven by the thermodynamic properties of their working fluids. An interesting chapter [10] has been recently published by Bell and Lemmon to spread the use of multiparameter equations of state in the ORC community At their current state of development, these models are not sufficiently flexible to be used in a screening approach extended to a population of hundreds of existing pure fluids and mixtures. If we focus on studies about closed power cycles, the equations of state, which have mainly been applied, are as follows: PC-SAFT-based model [12, 13] (which requires three molecule-specific parameters) in [14–16], BACKONE equation of state [17] (with four molecule-specific parameters) in [18], and the standard Peng-Robinson equations of state [19, 20] (with three parameters for each pure fluid) in [21–23] These authors considered a different number of fluids. The aims of this chapter are to present this model, to outline the proper way to apply it according to the latest advancements over pure fluid modeling [42–46], and to perform the screening of pure and/or multicomponent working fluids for power and refrigeration cycles

From Peng-Robinson to E-PPR78 equation of state
PR78: the application to pure fluids
From PR78 to E-PPR78: the application to mixtures
Bkl À1
Volume correction
Findings
Conclusion
Full Text
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