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tag Design and commissioning of a thermal stability test-rig for mixtures as working fluids for ORC applications
Luuc Keulen, Chiara Landolina, Andrea Spinelli, Paolo Iora, Costante Invernizzi, Luca Lietti, Alberto Guardone
Session: Poster session & Welcome drinks
Session starts: Wednesday 13 September, 17:30

Luuc Keulen (Politecnico di Milano)
Chiara Landolina (Politecnico di Milano)
Andrea Spinelli (Politecnico di Milano)
Paolo Iora (University of Brescia)
Costante Invernizzi (University of Brescia)
Luca Lietti (Politecnico di Milano)
Alberto Guardone (Politecnico di Milano)

A novel test-rig for studying the thermal stability of mixtures as working fluids for ORC applications was designed and commissioned at the Laboratory of Compressible-fluid dynamics for Renewable Energy Applications (CREA) of Politecnico di Milano, in collaboration with the University of Brescia. The set-up is a standard one, in which a vessel containing the fluid under scrutiny is placed in a vertical oven for ~ 100 hours at a constant temperature T=T^. During the test, the pressure P is monitored to detect thermal decomposition of the fluid. For P < 10 bar, pressure sensor T2 is used (Full Scale 10 bar, FS, expanded uncertainty 0.05% FS or +/-5 mbar), for P > 10 bar , pressure sensor T3 is used (FS 35 bar, expanded uncertainty 0.05% FS or +/- 17.5 mbar). After the test, the vessel is placed in a controlled thermal bath (with accuracy +/- 0.1°C), where the pressure is measured using transducer T1 (FS 1 bar, expanded uncertainty 0.05% FS or +/- 0.5 mbar) at different value of the temperature T, with T < T^ and T < Tc (Tc critical temperature). The resulting isochoric pressure-temperature dependence is compared to that obtained before the fluid underwent thermal stress. If departure from the initial fluid behaviour is observed, significant thermal decomposition occurred and a chemical analysis of the decomposition products is carried out using gas chromatography and mass spectroscopy. The novelty of the set-up is the possibility of taking samples of both liquid and vapour phases of the fluid, a capability that was introduced to study thermal decomposition of mixtures, whose composition depends on the pressure and temperature, as well as to capture the more volatile products of thermal decomposition of pure fluids and mixtures. Preliminary experimental results are reported for the pure siloxane fluids MM (Hexamethyldisiloxane, C6H18OSi2) and MDM (Octamethyltrisiloxane, C8H24O2Si3) and MM-MDM binary mixtures.