Parabolic Flight Experiments of Spray Cooling With Water and FC-72 Under Reduced and Elevated Gravity

This paper reports on the authors’ latest parabolic-flight experiments (November 1996) of spray cooling. Water and FC-72 (perfluorocarbon) were employed alternately as a test liquid sprayed from a single full-cone nozzle onto a Cr-plated surface of an electrically heated copper block (transient cooling experiments) or onto a transparent In₂O₃-coated surface of a glass block (steady state experiments in a relatively low superheat region). Each experimental run was accomplished during some 15 seconds through which a reduced gravity condition (∼0.01 times the terrestrial gravity) or an elevated gravity condition (∼2 times the terrestrial gravity) was maintained in the laboratory used — the cabin of an MU-300 aircraft. Cooling curves over a wide range of wall-superheat were obtained with water sprayed at significantly different volume fluxes and with FC-72 sprayed at rather low volume fluxes. It is demonstrated that the gravity dependency of the spray cooling characteristics varies with the spray volume flux and the impinging droplet velocity. Qualitative interpretations of the observed gravity dependency are provided.