Compact Additive sCO2 Heat Exchangers

For heat engine power plants used to generate electricity, heat transfer and heat rejection are one of the primary capital expenditures. Due to the highly cost sensitive nature of electrical power generation technologies, it is necessary to develop new heat exchanger technologies for high pressure Supercritical Carbon Dioxide power cycles to reduce these costs while still allowing high temperature, high pressure operation. In the past, the cost and complexity of heat exchangers have been proportional to one another due to the difficulties inherent in manufacturing finely-detailed welded, brazed, or diffusion bonded structures. To address this problem, additive manufacturing is being used to produce a heat exchanger which uses a fractal branching design without any increase in cost. A fractal branching header provides improved flow distribution when compared to standard heat exchanger plenum inlets/outlets by smoothly splitting/combining the flows to thin-walled microtubes in the heat exchanger core. A microtube brazing technique reduces fabrication costs and enables scale up of the heat exchanger beyond the typical size limits of state-of-the-art additive manufacturing without sacrificing mechanical robustness. In the proposed program, designs and produce prototypes for supercritical carbon dioxide recuperator components will be generated. The overall program objective is to design and build a recuperator for installation in a supercritical carbon dioxide power cycle. The heat exchanger will demonstrate specific power substantially better than the state of the art. The overall Phase I objective is to design, build, and test a fully functional laboratory-scale heat exchanger with a tunable heat transfer area. The applications for the additively-manufactured heat exchanger technology include regenerators, condensers, component cooling, and recuperators. The design is not a one-size-fits-all scheme, but instead the general design architecture is readily tailored to purpose. This modularity is due to the parametric design, which allows capacity rate matching between streams, geometric flexibility, and different flow mediums (for example steam, liquid metal, CO2, or molten salt and water). This unique design optimization capability combined with responsive, low cost manufacturing means that the heat exchanger technology could be a replacement for many of the different types of heat exchangers found in power plants and vehicles to reduce cost and volume allocations. Summary for Members of Congress: Existing heat exchangers are very large and heavy with relatively low performance or extremely expensive and represent an opportunity to reduce the cost of electricity generated in thermal power plants. Advances in additive manufacturing allow cost-effective development of advanced heat exchangers with low weight and volume that improve efficiency and cost-of-energy from new power generation plants.