A new network-level multi-objective optimization of the heat rejection system for megawatt space nuclear power systems

In Brayton, Stirling, or Rankine space nuclear systems, the Heat Rejection System (HJS) represents a critical component. The size and mass of the HJS significantly impact the overall performance of the space nuclear power system. This paper focuses on a three-wing HJS suitable for megawatt space nuclear power systems. The flow calculation model was coupled with the thermal radiation model to form the HJS calculation model, which was validated with an average error of 0.28 %. A novel network-level optimization method is proposed to optimize the mass density, pressure loss, and outlet temperature of the HJS by using flow connectivity and direction between different radiant units within the wings as independent variables. Optimal solutions for each loss function indicate that the outlet temperature has decreased from 390.70 K to 390.33 K, loop pressure loss has been reduced from 365 kPa to 361.38 kPa, and the mass density of the HJS has been reduced from 3.58 kg/m² to 3.33 kg/m². A simplified calculation method for the pre-design process of the HJS within the overall Space Nuclear Power System has been proposed and verified. This research provides valuable insights into the design of the HJS in megawatt-class space nuclear power systems.