Variable-Gravity Effects on a Single-Phase Partially-Confined Spray Cooling System

Abstract

This paper discusses the testing of a single-phase spray cooling system that was flown on the NASA KC-135 Reduced-Gravity Research Aircraft. An experimental package, consisting of a spray chamber coupled to a fluid delivery loop system, was fabricated for variable gravity flight tests. The spray chamber contains two opposing nozzles spraying on Indium Tin Oxide (ITO) heaters. These heaters are mounted on glass posts, which are part of a sump system to remove unconstrained liquid from the test chamber. Thermocouples mounted in and around the posts were used to determine both the heat loss through the underside of the ITO heater and the heat extracted by the spray. During flight tests, for Weber numbers of We = 771 ± 19 and 757 ± 15, the non-dimensional heat input was varied from G∆ = 30 to 110 for the non-dimensional grouping (Fr 1/2 Ga) 1/2 = 20 to 66. Flight test data and terrestrial data were compared to analytical and numerical solutions in order to evaluate the heat transfer in the heater and support structure. In general, the Nusselt number at the heater surface was found to decrease with increasing (Fr 1/2 Ga) 1/2 .