Conceptual Study on Radiator Area Reduction of Brayton Cycle Solar Dynamic Power

Higher on-board energy levels will be needed at the turn of the century for the many developing space programs. Among the many solar-powered energy conversion systems, a recuperated closed Brayton cycle (CBC) is the most promising one. This study investigated several aspects of a solar dynamic CBC system; an assessment of a reference 25 kWe system, simulation studies related to various operating conditions, and heat-rejection studies related to the radiating area required to transfer the Brayton cycle waste heat to space. In addition, particular attention is paid to the significance of the reduction of system mass required for radiation of waste heat from a closed Brayton cycle to space. Conceptually the radiator area can be reduced by rejecting the heat from the radiator at a higher temperature level than that of the waste heat of the CBC, operating a kind of heat pump by using a fraction of generated power. Consequently, an optimum radiator area is obtained. Also, for high radiator-to-waste-heat temperature ratios (greater than 5), the total radiator area is remarkably reduced. Further, the required mass resulting from the inclusion of the heat pump is estimated.