Thermohydraulic experiments on a supercritical carbon dioxide–air microtube heat exchanger

• Published in: International journal of heat and mass transfer 2023-04, Vol.203 (C), p.123840, Article 123840
• Main Authors: Jin, Kaiyuan, Krishna, Akshay Bharadwaj, Wong, Zachary, Ayyaswamy, Portonovo S., Catton, Ivan, Fisher, Timothy S.
• Format: Article
• Language: English
• Subjects: Friction factor; Microtube; Shell-and-tube heat exchanger; Supercritical CO2; Thermal conductance; Thermohydraulics
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2022.123840

•Experiments on a shell-and-tube heat exchanger (HX) with thirty-nine microtubes, 5 unit cells and similar design features to future commercial-scale sCO2 systems.•Detailed analysis of thermohydraulic behavior in the HX in high Reynold number ranges that have not been previously studied.•Performance metrics for multiple sCO2 and air flow rates.•Good overall agreement between experimental results and a recent model. Heat exchangers are critical components in supercritical CO2 Brayton cycles and provide necessary heat input, recovery, and dissipation. Tubular heat exchangers with unconventionally small tube sizes (tube diameters less than 5 mm) are promising components for supercritical CO2 cycles and potentially provide excellent structural stability with wide scope of application. This paper provides essential design and fabrication guidelines for a compact shell-and-tube heat exchanger with microtubes (with an inner diameter equal to 1.75 mm). A heat exchanger test rig is used to evaluate the thermohydraulic performance of this heat exchanger with supercritical CO2 and air as working fluids. Thermohydraulic data are reported for more than forty sets of experiments with varying Reynolds numbers for shell and tube flows. Critical performance metrics are calculated from the data and compared with predictions from a previously described numerical model. The average deviations between the experimental and model results fall within 10% for all critical metrics. This excellent agreement validates the numerical model for supercritical CO2 heat exchanger optimization and scale-up.