A Scalable Compact Additively-Manufactured Molten-Salt to Supercritical Carbon Dioxide Heat Exchanger for Solar Thermal Application

An additively-manufactured molten salt (MS) to supercritical carbon dioxide (sCO2) compact primary heat exchanger (PHE) for solar thermal power generation is presented in this paper. The PHE is designed to handle temperatures up to 720 °C on the MS side and an internal pressure of 200 bar on the sCO2 side. Within the core of the PHE, MS flows through a three-dimensional periodic lattice network, while sCO2 flows within pin arrays. The PHE design includes integrated sCO2 headers located within the MS flow, allowing for a counter flow design of the PHE. The dimensions of the internal features of the core section are determined through finite element simulations and the headers are configured in a way that optimizes the flow distribution in each sCO2 plate and minimizes obstruction of the MS side. The overall design of the heat exchanger allows AM scalability both horizontally and vertically due to an integrated header architecture. Details of structural and thermofluidic design are presented. An experimentally-validated, correlation-based sectional PHE core model is developed to study the impact of flow and geometrical parameters on the PHE performance, with varied parameters including the mass flow rate of sCO2 and MS sides, the channels width, and the PHE overall height, width, and length. The model results show that a heat exchanger with a power density of 18.6 MW/m3 (including sCO2 header volume) and effectiveness of 0.88 can be designed achievable at a Cr ratio of 0.8.