Thermal performance evaluation of an innovative window incorporated with nano-enhanced PCM, reversible design and ventilation

PCM windows are regarded as promising translucent building envelopes due to their ability to store solar heat and enhance thermal comfort. However, limitations in thermal insulation, phase transition rate, and climate adaptability hinder their further development. Hence, a novel triple-glazed window integrated with nano-enhanced PCM, reversible design and ventilation (NPRVTW) is proposed, while its dynamic photothermal transfer model is developed. Based on simulation results for the application in Guilin and Daqing, China, the thermal comfort and energy efficiency of NPRVTW are evaluated across different seasons and climates. The multi-technology coupling mechanisms are also discussed through comparisons with four other window configurations. The influences of physical properties, phase change temperature, and thickness of NPCM, as well as ventilation volume and strategy, are analyzed. The results show that adding nanoparticles to paraffin enhances solar absorption and accelerates phase change. Exhaust air in summer aids in heat removal and PCM solidification, while intake air in winter utilizes solar energy to preheat fresh air and heat the space. The reversible design regulates the direction of discharged heat to meet seasonal thermal demands. It can be concluded that NPRVTW exhibits excellent climate adaptability. In Guilin, the energy-saving rates in summer and winter are 41.84% and 55.62%, respectively, with NPCM4, phase change temperature of 27–29 ℃, a thickness of 20 mm, and a ventilation rate of 0.5 m/s recommended.