This award will support a long-term visit by Professor Per Peterson, Department of Nuclear Engineering, University of California, Berkeley to Japan for a cooperative research project with Professor Kunio Hijikata, Department of Mechanical Engineering Sciences, Tokyo Institute of Technology. The researchers plan to undertake a study of instability and bifurcation in vertical condensing systems. The study will focus on instabilities which occur when lower molecular weight vapor condenses beneath higher molecular weight noncondensable gas, and also on the inverse condition of high molecular weight vapor above low molecular weight noncondensable gas. The research is of fundamental importance because as higher Rayleigh numbers are encountered in industrial applications, no experimental, numerical or theoretical information is available even though the unstable gas vapor interface is known to cause large temperature and pressure fluctuations in condensing systems. The research should result in significant advances in our understanding of heat transfer mechanisms in the heat pipe or other high efficiency thermal energy transport systems. Additional areas that will be impacted by this research include electronics, cooling, satellite thermal control, and surface condenser efficiency. The Department of Mechanical Engineering Sciences at Tokyo Institute of Technology has excellent facilities for laser holographic and shadow-graph investigations of condensation. Professor Hijikata has extensive research experience in condensation problems and in numerical investigation of condensation in stable systems with noncondensable gases. This complements Professor Peterson's work in stable systems which should insure a fruitful collaboration resulting in benefits to both countries. It is expected that this collaboration will continue after the formal agreement has terminated.
