The process of heat and mass transport at the critical point of pure fluids

The effects of fast isentropic temperature propagation, called the piston effect, or critical speeding up, and slow mass diffusion, called critical slowing down, are investigated. A temperature propagation experiment in a spherical cell filled with pure SF₆ at critical density was performed during the Second German Spacelab Mission D2 in 1993. The results evidently confirm the presence of the piston effect both in the one-phase region and in the two-phase region. The numerical simulations are in remarkable good quantitative agreement with the experimental results.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.