04 Ago Master Thesis Work on Thermal Stability
Experimental Characterization of the thermal stability of mixtures of linear siloxanes
Advisor: Spinelli Andrea
Co-Advisor: Simone Gallarini, Alberto Guardone
The work aims at evaluating the thermal stability limit (decomposition temperature) of organic fluids (siloxanes) for ORC applications, the fluids are pure and/or in binary mixtures. These fluids are largely employed in energy applications, since they can be favorably exploited in ORCs; indeed, their use leads to high efficiency cycles, they are non-toxic, environmentally friendly (zero ODP, almost zero GWP), relatively low-cost. Their use is limited at high temperature by the molecule cracking and the consequent formation of decomposition products featuring thermodynamic properties different from the original ones. Each fluid exhibits a thermal stability limit whose evaluation is crucial to realize cycles with the highest possible maximum temperature (thus with high efficiency) with no significant decomposition.
In this perspective the use of mixtures can possibly increase the thermal stability limit with respect to the pure counterparts (this aspect has to be investigated). Different fluids are characterized from the thermal stability perspective; on the contrary, a systematic investigation of pure/binary mixtures of linear siloxanes (MM, MDM, MD2M, MD3M) is still missing in open literature. The work will be carried out at the CREA Laboratory (crealab.polimi.it) and in collaboration with the Laboratory of Catalysis and Catalytic Processesof the Energy Department and with the University of Brescia.
The work consists in the completion of a test section of an existing experimental facility and in its use to perform thermal stability tests. Each test include thermal stress of the fluid at increasing temperatures and in the evaluation of the rate of decomposition by means of pressure and temperature measurements (in stress and in saturation conditions) and in the chemical analysis of the fluid samples (on both the liquid and vapor fraction) before and after the thermal stress, aiming at identifying the type and the amount of decomposition products.
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