CRITICAL SPEEDING UP IN PURE FLUIDS

We show how the extreme compressibility of a pure fluid near its critical point significantly affects its bulk dynamic response to temperature changes through adiabatic processes. We develop equations that describe the dynamics in the absence of gravity, and illustrate the magnitude of the effect with numerical solutions in one dimension. The results are remarkable: 5 mm of critical xenon, quenched from 20 to 10 mK above its critical temperature, cools by over 99% in less than 5 sec. Moreover, adiabatic cooling is faster when the fluid is closer to the critical point. © 1990 The American Physical Society.