Experimental observation and thermodynamic modeling of non-ideal expanding flows of siloxane MDM vapor for ORC applications

This paper reports extensive experimental results characterizing the supersonic expansion of an organic vapor in non-ideal thermodynamic conditions typical of organic Rankine cycle (ORC) turbines. Data are also employed to assess the accuracy of different thermodynamic models used to describe non-id...

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Bibliographic Details
Published in:Energy (Oxford) 2019-02, Vol.168, p.285-294
Main Authors: Spinelli, Andrea, Cammi, Giorgia, Conti, Camilla Cecilia, Gallarini, Simone, Zocca, Marta, Cozzi, Fabio, Gaetani, Paolo, Dossena, Vincenzo, Guardone, Alberto
Format: Article
Language:English
Subjects:
Equations of state
Expanders
Experiments in non-ideal compressible flows
Heat recovery
Mach number
Model accuracy
Non-ideal supersonic expanding flows
Nozzle flow
ORC power systems
Pressure
Rankine cycle
Siloxane MDM
Siloxanes
State of the art
Static pressure
Test rig for organic vapors
Thermodynamic models
TROVA
Turbines
Vapors
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Summary:This paper reports extensive experimental results characterizing the supersonic expansion of an organic vapor in non-ideal thermodynamic conditions typical of organic Rankine cycle (ORC) turbines. Data are also employed to assess the accuracy of different thermodynamic models used to describe non-ideal expansions. Experiments were carried out on a converging-diverging nozzle test section, where siloxane vapor MDM expanded in the proximity of the saturation curve, the typical operating region of ORC expanders, thus proving the importance of the present investigation for ORC technology. Indeed, detailed experimental data representative of ORC expansions, useful for design tool assessment, were lacking in the open literature up to date. Two nozzles, featuring exit Mach number of 2.0 and 1.5, were tested from highly non-ideal states to dilute gas conditions. The nozzle flow was characterized by measuring total pressure, total temperature and static pressure along the axis. The Mach number was measured at the centerline through schlieren imaging. Vapor expansion was found to be dependent on inlet conditions, thus proving the flow non-ideality. State-of-the-art thermodynamic models proved their capability of fully describing the flow non-ideality, while simpler and easier to implement equations of state, such as van der Waals, can be acceptable for preliminary expander calculations.
ISSN:0360-5442
1873-6785
DOI:10.1016/j.energy.2018.11.071