This award will enable Prof. Chang-Lin Tien of the University of California, Irvine, to collaborate with Prof. Kunio Hijikata of the Tokyo Institute of Technology, Japan, and other Japanese researchers over a period of two years. They will investigate fundamental processes and mechanisms influencing the passive control of the performance of devices, such as heat pipes, which operate on the basis of counter-current, two-phase reflux condensation. Such passive control may be achieved by addition of a second component to the heat-pipe working fluid; this component might be a noncondensable gas or a binary mixture of working fluids to control the condensation. The heat and mass transfer mechanisms which control gas distribution, and hence overall performance of the heat-pipe system, will be investigated both analytically and experimentally. The purpose of this research is to enhance our basic understanding of the phenomena which control the performance of heat pipes and similar mechanisms. Adequate understanding of these phenomena could stimulate the use of heat pipes, which has been limited even though they offer considerable advantages over other heat-transfer methods in many applications. To achieve this objective the U.S. researcher will analyze the heat-trans- fer performance of heat pipes with noncondensable gases. Heat transfer with binary vapor mixtures will be investigated experimentally by the Japanese collaborator. By comparing the analytical and experimental results, the investigators will jointly determine the most effective combination of working fluids. This research thus utilizes the complementary analytical and experimental skills of the U.S. and Japanese investigators.
