Investigations into the feasibility of high-heat flux, evaporative spray cooling in a single-component, closed-system are reported. A spray cooling heat exchanger was designed, manufactured, and tested. Three specific areas were investigated. These were: (1) the effects of noncondensable gas on the heat transfer. (2) the maximum heat flux and heat transfer coefficient. (3) the effects of variation in spray characteristics.The experiments conducted in the saturated, single-component, closed-system demonstrated heat removal rates in excess of 1000 W/cm2 with only a 27 ºc superheat. It was shown that removing the air from the system had little effect on the evaporation heat transfer efficiency. However, as expected, the condensation heat transfer efficiency improved greatly when the air was removed.The effects of nozzle size, flow rate, and average droplet diameter and velocity are explained through analysis of the experimental data. The measurements of the spray characteristics lend insight into the mechanisms responsible for causing critical heat flux.