Spray Cooling Under Reduced Gravity Condition

The present paper reports on the results of a series of authors’ parabolic flight experiments on spray cooling in addition to ground-based experiments in which the influence of heater orientation and the behavior of rebounded droplets were especially studied in detail. Water and FC-72 (perfluorocarbon) were employed alternatively as a test liquid sprayed from a single full-cone nozzle onto a Cr-plated surface of an electrically heated copper block for transient cooling experiments or onto a transparent ITO (indium tin oxide) coated surface of a glass block for steady state experiments in a relatively low superheat region. Each experimental run was accomplished within some 15 sec through which a stable reduced gravity condition (0.01 times the terrestrial gravity) was maintained in the aircraft. Cooling curves were obtained over a wide range of each of the following parameters: the wall superheat, the spray volume flux and the Weber number for the spray droplets. It is demonstrated that the gravity dependency of the spray cooling characteristics varies with the spray volume flux and the droplet Weber number. Qualitative interpretations of the observed gravity dependency are provided.