中国物理B ›› 2023, Vol. 32 ›› Issue (11): 114401-114401.doi: 10.1088/1674-1056/acdac0
Yang-Chun Zhao(赵洋春) and Yong-Min Zhou(周勇敏)†
Yang-Chun Zhao(赵洋春) and Yong-Min Zhou(周勇敏)†
摘要: Passive daytime radiative cooling is achieved by radiating heat into outer space through electromagnetic waves without energy consumption. A scalable double-layer coating with a mixture of TiO2, SiO2, and Si3N4 micron particles for radiative cooling is proposed in this study. The finite-difference time-domain algorithm is used to analyze the influence of particle size and coating thickness on radiative cooling performance. The results of the simulation show that the particle size of 3 μ can give the best cooling performance, and the coating thickness should be above 25 μ m for SiO2 coating. Meanwhile, the mixture of SiO2 and Si3N4 significantly improves the overall emissivity. Through sample preparation and characterization, the mixture coating with a 1:1 ratio addition on an Al substrate exhibits high reflectivity with a value of 87.6% in the solar spectrum, and an average emissivity of 92% in the infrared region (2.5 μ m-15 μ m), which can be attributed to the synergy among the optical properties of the material. Both coatings can theoretically be cooled by about 8 °C during the day and about 21 °C at nighttime with hc=4 W·m-2·K-1. Furthermore, even considering the significant conduction and convection exchanges, the cooling effect persists. Outdoor experimental results show that the temperature of the double-layer radiative cooling coating is always lower than the ambient temperature under direct sunlight during the day, and can be cooled by about 5 °C on average, while lower than the temperature of the aluminum film by almost 12 °C.
中图分类号: (Thermal radiation)