Global cross-scale simulation and experiment of supercritical CO2 boiler tube wall temperature based on bidirectional fluid-thermal coupling

Abstract

sCO₂ cycle power generation, with wide thermal source applicability and flexible maneuverability, is considered one of the transformative technologies for hybrid power generation with renewable energy. sCO₂ boilers, as key equipment, are typically equipped with numerous bundles to adapt load changes under varying conditions. Currently, 0/1D modular furnace models cannot accurately capture the temperature distribution of the cold wall, and it’s unrealistic to build the sCO₂ boiler’s 3D global transient variation model. Some scholars have used 3D + 1D to explore tube wall temperatures, but lack experiments validated and transient predictions. Therefore, this paper establishes a multi-scale transient coupling model of global sCO₂ boiler to predict the tube wall temperature change rate to ensure safe operation under variable operation. It fully considers the structure of the heat exchanger tubes and the deviation of heat transfer between the flue gas and sCO₂, and accurately captures the wall temperature variation. The transient coupling model validated with experiments shows a maximum deviation of 24.26 K and an error margin of 2.82 %. And the highest tube wall temperature tends to occur near the outlet of the No. 80 heat exchanger located in the middle of the combustion chamber. Transient simulations also revealed the heat exchanger tubes near the exhaust side have a higher temperature change rate increase on their outer walls compared to the tubes near the ignition side, while their rate of temperature decrease is lower. This study is important for avoiding thermal fatigue of heat exchanger tubes under variable load regulation of the unit.