Liquid-vapor phase separation in a thermocapillary force field

¹ ESEME, Service des Basses Températures, DSM/DRFMC, CEA-Grenoble Grenoble, France (Mailing address: CEA-ESEME, Institut de Chimie de la Matière Condensée de Bordeaux - 87 Avenue du Dr. Schweitzer, 33608 Pessac Cedex, France.)
² CNRS-ESEME, Institut de Chimie de la Matière Condensée de Bordeaux 87, Avenue du Dr. Schweitzer, 33608 Pessac Cedex, France
³ Centre de Physique Moléculaire, Optique et Hertzienne, CNRS Université de Bordeaux I - Cours de la Libération, 33405 Talence Cedex, France
⁴ Department of Physics, University of New Orleans - New Orleans, LA 70148, USA

Corresponding author: dbeysens@cea.fr

Received: 15 January 2002
Accepted: 17 April 2002

Abstract

We study the growth of gas bubbles surrounded by liquid during the phase separation of a pure CO₂ sample quenched from one-phase to two-phase region of the phase diagram by rapid cooling in microgravity. The vicinity of the critical point ensures slowing-down of the growth process. The bubble growth by coalescence is modified by local laser heating. It induces a thermocapillary (Marangoni) effect that attracts the bubbles towards the center of the beam. At the beginning of the phase separation, a bubble is trapped there and “captures" the surrounding bubbles. The growth exponent for the central bubble radius is close to 0.5, while that for the other bubbles is 1/3. We present a theoretical model that explains the experimental data and justifies that the temperature can vary along the gas-liquid interface in a pure fluid during its phase separation.