High intensity, supercritical CO2 heat exchangers capable of operating at temperatures between 800 and 1100 ˚C and pressures in excess of 80 bar are considered a critical component for ultra-high efficiency power generation and a range of next generation industrial processes.Our team is currently developing compact plate-type heat exchanger components made via additive manufacturing (AM) of oxide dispersion strengthened (ODS) nickel-based alloys. Plates are equipped with AM features to generate turbulence, enhance heat transfer and provide mechanical strength. In order to experimentally test and validate these components, we have developed a flow-loop capable of temperatures up to 1100 ˚C at 80 bar on the high temperature/low pressure side and 800 ˚C at 250 bar on the low temperature/high pressure side. The flow loop is capable of nitrogen flow rates up to 0.007 kg/s. It consists of i) a 3 kW, low temperature (300 ˚C), high pressure heater (250 bar), ii) a high pressure enclosure holding the heat exchanger plates, and iii) a 3 kW, high temperature (1100 ˚C), medium pressure (80 bar) heater.The low temperature high pressure heater (i) consists of a thick-walled ultra-high pressure stainless steel tube and the pipe is heated via direct Joule heating using a 3 kW power supply. The heater is insulated via two fibrous insulation boards and encased in an aluminum enclosure for hazard protection. It has been successfully tested under nominal (300 ˚C, 80 bar, 0.04 kg/s) conditions. A high pressure enclosure consisting of a set of flanges and gaskets contains the heat exchanger plates. It is pressurized to avoid complex sealing requirements. The high temperature heater consists of a stainless steel flanged cylindrical pressure vessel with a design pressure of 263 bar. The pipe is internally insulated and houses a graphite heating element with a nominal power rating or 3 kW at 12 V. The stainless steel vessel is externally water-cooled to keep its temperature close to ambient. The heaters feed into the high temperature and low temperature inlets of the heat exchanger respectively. The high temperature (1100 ˚C) piping is internally insulated via an open pore alumina insulation.To our knowledge, this is the first time that heat exchanger testing at such extreme conditions (1100 ˚C / 80 bar, 800 ˚C / 250 bar) has been made possible. Currently scale-up design of the flow-loop is ongoing to accommodate testing of heat exchangers capable of transferring up to 50 kW of heat.

Test Flow-Loop for Extreme Pressure and Temperature Supercricitcal Co2 Heat Exchanger

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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