Phase change materials used in building thermal storage systems suffer from low thermal conductivity and slow heat storage rates. This study proposes a synergistic enhancement method combining topology-optimized fins with pulsating flow. The 3D numerical simulations and response surface method are employed to investigate the coupling effects of fin volume coefficient, pulsating velocity, amplitude, and period. The numerical model is validated against experimental data, showing an average error of 5.9%, which confirms its reliability. The NSGA-Ⅱ algorithm is used for multi-objective optimization. Increasing the fin volume coefficient from 0.05 to 0.15 reduces the complete melting time by 75.28%. The pulsation period has a limited effect, with less than 1.5% variation in thermal performance. The optimal parameter combination is a period of 10.23 s, an amplitude of 0.63 m/s, and a velocity of 1.29 m/s, yielding a thermal storage capacity of 194.23 kJ, an energy consumption of 0.72 W, and a complete melting time of 886.92 s. This study provides some reference for efficient phase change thermal storage systems in building heating applications.

This study designs and simulates a high-efficiency compound waste heat boiler capable of operating independently. The boiler is designed to function within a gas-steam combined cycle and can also operate independently without a gas turbine. A three-dimensional numerical model of the boiler is established using computational fluid dynamics(CFD) software to simulate its performance under three steady-state operating modes. In addition, the overall characteristics of the dynamic switching process between different modes are analyzed. The simulation results show that all three modes can meet heat load demands by adjusting the supplementary gas combustion during steady-state operation. During dynamic switching, the control method proposed in this study ensures stable operation of the waste heat boiler throughout the entire transition process. Seamless switching between the three operating modes is successfully achieved.