Comparative thermo-economic assessment of a novel CCHP Brayton system with dual-stage reactor heat recovery and variable cross-section straight type PCHE modeling

The supercritical carbon dioxide Brayton cycle is considered a promising solution for coupling with gas-cooled nuclear reactors due to compactness and high efficiency. In this paper, a novel combined cooling, heat and power (CCHP) Brayton system with dual-stage reactor heat recovery structure is proposed. A key component in the system is a printed circuit heat exchanger (PCHE) and a method for modeling the variable cross-section PCHE is proposed. Based on the derived positions of hypothetical adiabatic planes, the PCHE modeling method achieves an average length deviation of 4.2 % for single-side etched PCHEs and 2.7 % for double-side etched PCHEs. Results shows that the system can fully recover the reactor heat through dual-stage heat recovery structure. When coupling with the ALLEGRO reactor, the optimized system achieves an artificial net power of 29.0 MW, an artificial energy efficiency of 53.7 %, an artificial exergy efficiency of 65.6 %, and a levelized cost of energy of 44.5 USD/(MW·h). Compared to the recompression-reheat Brayton cycle, the system exhibits a 139.7 % higher artificial net power and a 28.9 % lower levelized cost of energy. Finally, when coupling with the GT-MHR reactor, a top cycle in the system exhibits a 24.6 % increase in energy efficiency, a 24.3 % improvement in exergy efficiency, a 24.6 % enhancement in power output, and only a 23.0 % increase in levelized cost of energy compared to the recuperation Brayton cycle. Therefore, the system demonstrates favorable thermo-economic advantages when coupled with the reactors featuring large-scale thermal energy rate.