Development of SiC-SiC Heat Exchangers for High Temperature Heat Transfer

A Department of Energy grant (DE-SC0020741) was awarded to NovaTech to develop a robust, resilient heat exchanger design that would efficiently integrate industrial energy users with the advanced (Gen 4) nuclear power plants now under development. NovaTech examined the use of silicon carbide composite heat exchangers for use in Integrated Energy Systems (IES) tied to industrial energy users, energy storage systems, and energy conversion systems. These facilities would produce electricity and process heat needed to support industrial processes. While some industrial processes rely on low temperature process heat, many including petrochemical, metals, cement manufacturing, and some hydrogen production processes require process heat at 800°C or above. To do this, new materials and designs are needed to produce long-life heat exchangers. These materials and designs are also applicable to advanced fossil, or Concentrated Solar Power (CSP) plants, stand-alone industrial heat exchangers, and very-high temperature Brayton cycle plants including supercritical CO2 power systems. In the Phase I SBIR contract, NovaTech developed a conceptual design for a SiC composite heat exchanger to operate in conjunction with a very-high temperature gas cooled reactor, transferring energy to a molten salt loop for industrial process heat. The heat exchanger was also designed to minimize the use of ceramic composites while operating at temperatures >800°C and to allow periodic in-service inspection to meet the intent of NRC Regulatory Guide 1.83 and ASME Section XI. This resulted in a bayonet tube arrangement with SiC composite tubes providing the only non-metallic pressure boundary. In the Phase II effort, we continued developing the technology. First, Framatome identified changes to their ANTARES nuclear system to operate at temperature up to 1000°C and identified requirements for an intermediate heat exchanger to transfer core power to a molten salt loop for industrial process heat. NovaTech and CTP then fabricated key heat exchanger components and tested them to demonstrate feasibility. This was followed by revising the heat exchanger design to meet Framatome functional requirements and to incorporate the component data that was obtained from the Phase II test program. In the Phase IIB proposal, NovaTech proposes to continue this development via the following activities: NovaTech and CTP will identify changes to the component designs to streamline fabrication and reduce the associated cost and schedules, NovaTech and CTP will test ways of joining SiC composite tubes, NovaTech and CTP will design, fabricate, and test a subscale prototype heat exchanger (four tube) to demonstrate operability and performance. This will demonstrate key features of the nuclear intermediate heat exchanger designed in Phase II but will operate at lower pressures consistent with a high-temperature industrial air recuperator; the targeted near-term market, and Framatome will work with ASME B&PV Section III code committees to identify a process that can lead to the certification of SiC composite tubes. This is vital for the commercialization of ceramic heat exchangers.