Cold-side temperature optimization of a recuperated closed Brayton cycle for space power generation

Abstract

Regarding space exploration, an adequate design of an energy conversion system for power generation is essential and plays an important role in the mission feasibility, having low total mass and size as key features that differ space power plants from grounded power stations. The waste heat system of space power plants consists of heat pipes attached to a radiator panel and, as they are responsible for the highest size proportion of the total energy conversion system, special attention must be directed to these components during the design phase. Considering these aspects, this short communication aims the optimization of the cold-side temperature of a recuperated closed Brayton cycle for space power production. For this purpose, an endoreversible thermodynamic modeling is proposed, based on overall thermal conductances of heat exchangers and heat pipes, whereas a set of algebraic equations characterized the compressor and turbine performance. The ratio of the cycle power output per radiator area was considered as the objective function which is maximized. For a fixed heat input of 157 kW and heat source and sink temperatures of 1150 K and 200 K respectively, it was evidenced an optimum operating temperature ranging from 450 to 500 K for the cold heat pipe. Based on this range of operation, heat pipes made of titanium-water with rectangular grooves as the wick structure were chosen as reference for design modeling and assembly of the heat rejection system.