Piston effect in a supercritical fluid sample cell: A phenomenological approach of the mechanisms

Citation
Y. Garrabos et al., Piston effect in a supercritical fluid sample cell: A phenomenological approach of the mechanisms, J PHYS IV, 11(PR6), 2001, pp. 23-34
Citations number
21
Categorie Soggetti
Physics
Journal title
JOURNAL DE PHYSIQUE IV
ISSN journal
11554339 → ACNP
Volume
11
Issue
PR6
Year of publication
2001
Pages
23 - 34
Database
ISI
SICI code
1155-4339(200110)11:PR6<23:PEIASF>2.0.ZU;2-Z
Abstract
We report on the analysis of the response of a near-critical fluid sample c ell submitted to heating at different distances from the critical temperatu re T-c, in the Mir station microgravity environment. We recall the hydrodyn amic and thermodynamic bases of the mechanisms of fast adiabatic heating, a lso called "thermalization by Piston Effect" (PE). We give a phenomenologic al approach of these mechanisms in a highly compressible critical fluid sub mitted to heating until a steady state is reached, and present the main res ults of numerical experiments in a Van der Waals fluid. We then use this ph enomenological understanding to analyze an experimental case of heating in reduced gravity onboard Mir, using the Alice 2 facility between 1996 and 19 99 (Cassiopea to Perseus missions). We have measured the characteristic tim e of the PE as a function of the critical temperature distance, and investi gated the crossover behavior from the pure adiabatic regime for a surroundi ng wall of infinite conductivity, to the bottleneck conductivity regime ind uced by a real cell. Close to T-c, we have evidenced the key influence of t he geometry of the cell and of the thermal properties of the wall materials .