Optimization of a heat pipe-radiator assembly coupled to a recuperated closed Brayton cycle for compact space power plants

Abstract

• Analysis of recuperated closed Brayton cycle conditions is carried out. • Brayton cycle and heat pipe-radiator models are numerically coupled. • Heat source and cold heat exchanger inlet temperatures are optimized. • The specific mass minimization is used as the objective variable. • Optimization provides cycles with specific masses ranging from 40 to 50 kg/kW. Compact and efficient energy conversion systems for space applications enable the appearance of new mission opportunities and technological discoveries resulted from space exploration. Besides energy availability, another crucial factor of any energy conversion system for space purposes is its total mass and size. Focusing on a recuperated closed Brayton cycle (CBC), thermodynamic modeling of a CBC is proposed. Moreover, a thermal model is carried out to predict the overall properties of the cold side of the system (i.e., heat pipes and radiator) for different CBC conditions. Both models are coupled and their conjunct solution provides operational data for the design of the heat rejection system, such as the number of heat pipes (HP), total assembly mass, length, and second-law efficiency. Furthermore, by means of this coupling, the heat source temperature and the cold heat exchanger (CHE) inlet temperature are defined, using an optimization procedure where the specific mass (i.e., radiator mass to cycle power ratio) is minimized. Based on this objective variable, the optimized heat source temperature of 1200 K is achieved, while the CHE inlet temperature of 513.2 K is obtained. Such temperature conditions ensure the future design of a space energy conversion system that aligns good efficiency and compactness.