Experimental test, numerical analysis and thermal calculation modeling of hundreds kWth-class supercritical CO2 fossil-fired boiler system

Boiler is one of the important parts for supercritical CO2 (S–CO2) power system. Currently, most studies are based on theoretical calculations and lack experimental validation. Besides, low flue gas temperature and high wall temperature significantly enhance convection heat transfer (CHT), resulting in the failure possibility of existing thermal calculation models (neglect CHT). This study aims to construct a thermal calculation model suitable for S–CO2 boiler. Firstly, the hundreds kWth-class S–CO2 diesel/coal-fired boiler system was built, and steady-state experiments were carried out. Secondly, to further evaluate CHT, a numerical model was established, and the reliability of simulation was verified. The results indicate that the proportion of CHT can reach 44.52%. The entrainment effect caused by high-speed jet leads to a negative velocity region near the cooling wall. Furthermore, there are velocity disturbances of non-mainstream direction near the cooling wall. These two lead to great enhancement of CHT. According to the above analysis, a proposed thermal calculation model (DCTCM-1D) considering CHT and wall temperature was constructed. Compared to existing models, DCTCM-1D has the lowest error, with the root mean square error of flue gas temperature, heat load, wall temperature and S–CO2 temperature being 22.54 °C, 0.94 kW/m2, 6.40 °C and 2.29 °C.