Coupled modeling of combustion and heat transfer process of a supercritical CO₂ boiler

In this paper, the heat transfer process of high temperature heating surfaces in a 20 MW_th supercritical CO₂ (S-CO₂) boiler is integrally modeled by combining the one dimensional (1D) analytical model for supercritical CO₂ and the three dimensional (3D) CFD model for combustion and heat transfer process of flue gas. The 20 MW_th S-CO₂ boiler is designed for a 5 MWe S-CO₂ power generation platform being constructed by Xi'an Thermal Power Research Institute Co., Ltd. The numerical results indicate that the tube wall temperature of gas cooling wall increases gradually along the S-CO₂ flow direction, and the maximum wall temperature appears at the outlet region of the Front wall where the temperature reaches 907 K. The maximum temperature of tube wall in superheater and re-heater is around 950 K. The heat flux and temperature distributions of tube walls in superheater and re-heater are extremely non-uniform, which makes the traditional design method not practical in designing S-CO₂ serpentine heat exchangers. The integral modeling method put forward in this work has the ability to capture the non-uniform heat transfer process in superheater and re-heater, and hence it is an efficient tool to study the sophisticated phenomena in S-CO₂ boiler.