Thermosyphon Flooding in Reduced Gravity Environments Test Results

Abstract The condenser flooding phenomenon associated with gravity aided two-phase thermosyphons was studied using parabolic flights to obtain the desired reduced gravity environment (RGE). The experiment was designed and built to test a total of twelve titanium water thermosyphons in multiple gravity environments with the goal of developing a model that would accurately explain the correlation between gravitational forces and the maximum axial heat transfer limit associated with condenser flooding. Results from laboratory testing and parabolic flights are included in this report as part I of a two part series. The data analysis and correlations are included in a follow on paper. Nomenclature e A Density of the liquid e I Density of the vapor D Thermosyphon inner diameter g Acceleration of gravity e Surface tension $ â Bond number # e Vapor area D U U Heat of vaporization RGE Reduced Gravity Environment 1.0 Introduction Fission power systems have long been recognized as potential multikilowatt power solutions for lunar, Martian, and extended planetary surface missions. These power sources are especially attractive in places where solar intensity is limited by providing uninterrupted power, day or night, for extensive periods of time that can span one to two decades. Typically, 30 to 40 percent of the reactor heat gets converted to electricity and the remaining 60 to 70 percent gets rejected to space through large surface area heat rejection radiators. Current heat rejection technology for fission surface power systems has focused on titanium water thermosyphons embedded in carbon composite radiator panels with the working fluid temperature range of 300 to 450 K (Ref. 1). Figure 1 provides a graphical representation of