Thesis defence V. Valori: supercritical fluid
Rayleigh-Bénard convection of a Supercritical fluid: First PIV velocity fields and heat transfer study. Promotor 1: Prof.dr.ir. T.H.J.J. van der Hagen (TNW); Promotor 2: Prof.dr.ir. J. Westerweel (3mE).
Fluids above the critical point are widely used in industry. Supercritical (SC) fluids are characterized by strongly varying fluid properties, which are responsible for their particular heat transfer behavior and make them very difficult to model, simulate and experimentally investigate. The aim of the research described in this thesis is to investigate the possibility of performing non-intrusive local velocity measurements with the optical technique PIV and to acquire global heat transfer measurements, with strongly changing fluid properties at SC conditions. The experiments were performed in a pure buoyancy driven flow: a Rayleigh-Bénard (RB) flow.
It was observed that merely the Rayleigh and Prandtl numbers are not sufficient to determine the heat transfer through the cell. It was also seen that the measured Nusselt number was 16% larger with respect to the one predicted by the Grossmann-Lohse theory (2000) for the same Rayleigh and Prandtl numbers at OB conditions.
A feasibility study of particle image velocimetry (PIV) at SC conditions was done by using the background oriented schlieren technique (BOS). An estimation of the PIV experimental uncertainty at SC conditions was done with the statistical correlation method proposed by Wieneke et al. , (2015). PIV was successfully performed at SC conditions.
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