Experimental characterization of an additively manufactured supercritical carbon dioxide recuperator

The design, fabrication, and experimental characterization of a high-temperature, high-pressure recuperator heat exchanger for a supercritical carbon dioxide cycle are presented. The heat exchanger core consists of a pin array of different designs on the hot and cold sides. The headers are integrated with the core and feature an interwoven architecture that enables pure counterflow heat exchange in the core. A recuperator with eight pairs of hot and cold passages is fabricated using the laser powder bed fusion method with Haynes 282, a nickel superalloy. X-ray CT scan images were used to confirm that the internal passages were clear of powder and to characterize deviations of printed features from the design. Experiments were performed in a recuperator configuration with the hot side at a nominal pressure of 80 bar and an inlet temperature of up to 800 o C, and the cold side at a nominal pressure of 250 bar and an inlet temperature of 300 o C. Results indicate an effectiveness of 72.3% and a thermal rating of 44.08 kW, with a gravimetric density of 11.7 kW/kg. The experimental results were compared against a one-dimensional steady-state model of the recuperator. When actual measured dimensions of the pin array are used in the model, the mean absolute percent deviation between model and experiments is 2.25% for effectiveness and 2.32% for power. The hot and cold side pressure drop between model and experiments are within 11.2% and 11.6%, respectively. A genetic algorithm-based optimization using the validated model indicates that a total gravimetric density (heat exchanger core + header) of 35.6 kW/kg can be achieved at 80% effectiveness for a 267 kW heat exchanger.