In this paper we report initial results from space experiments in which heat transport in near-critical SF6 was studied. The experiment utilized the Critical Point Facility (CPF) which was flown aboard ESA's Spacelab in the cargo bay of the Space Shuttle Columbia during the 1994 IML-2 mission. We report temperature and density measurements made during a number of transient heating runs in which energy was supplied by a plane heater immersed in the sample. Temperature measurements were made with a resolution of 10 micro deg K by means of a set of five thermistors while density changes in the sample were monitored interferometrically. The results of these measurements show clearly that diffusive heat transfer slows dramatically as one approaches the critical point and that only a thin boundary layer adjacent to the heater is influenced directly by thermal conduction. We also observe clear evidence of the so-called adiabatic or piston-effect which results in a spatially-uniform temperature and density rise in the bulk of the fluid. The adiabatic temperature rise is shown to be essentially linear in time, synchronous with the heating and proportional to the heater power. The magnitude of the temperature rise is found to be consistent with theory, only when heat losses are taken into account.
Adiabatic compressive heating of critical fluids under microgravity conditions
Adiabatische Verdichtungserwärmung kritischer Fluide unter Mikrogravitationsbedingungen
1995
9 Seiten, 6 Bilder, 13 Quellen
Aufsatz (Konferenz)
Englisch
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