THE DEVELOPMENT OF NOVEL, HIGH-FLUX, HEAT TRANSFER CELLS FOR THERMAL CONTROL IN MICROGRAVITY

Abstract

In order to meet the future needs of thermal management and control in space applications such as the Space Lab, new heat-transfer technology capable of much larger heat fluxes must be developed. To this end, we describe complementary numerical and experimental investigations into the fundamental fluid mechanics and heat-transfer processes involved in a radically new, self- contained, heat transfer cell for microgravity applications (patent pending). In contrast to conventional heat pipes, the heat transfer in this cell is based on a forced droplet evaporation process using a fine spray. The spray is produced by a novel fluidic technology recently developed at Georgia Tech (patent pending). This technology is based on a vibration induced droplet atomization process. In this technique a liquid droplet is placed on a flexible membrane and is vibrated normal to itself. When the proper drop size is attained, the droplet resonates with the surface motion of the membrane and almost immediately bursts into a shower of very fine secondary droplets. The small droplets travel to the opposite end of the cell where they impact a heated surface and are evaporated. The vapor returns to the cold end of the cell and condenses to form the large droplets that are fragmented to form the spray. Preliminary estimates show that a heat transfer cell based on this technology would have a heat-flux capacity that is an order of magnitude higher than those of current heat pipes designs used in microgravity applications.