We wish to express our thanks to Professor A. Sugawara for his measurement of the specific heat and density of the glass beads. The research was carried out partly with the grants-in-aid B-604~107 for scientific research and 61850035 for developmental scientific research of the Ministry of Education;
Science and Culture of Japan;
and by using a part of the experimental facilities for heat transfer of multiphase flow [19;
20] in the Institute;