ABSTRACT
Passive daytime radiative cooling (PDRC), a cooling method that needs no additional energy, has become increasingly popular in recent years. The combination of disordered media and polymeric photonics will hopefully lead to the large-scale fabrication of high-performance PDRC devices. This work aims to study two typical PDRC structures, the randomly distributed silica particle (RDSP) structure and the porous structure, and systematically investigates the effects of structural parameters (diameter D, volume fraction fv, and thickness t) on the radiative properties of the common plastic materials. Through the assistance of the metal-reflective layer, the daytime cooling power Pnet of the RDSP structures is slightly higher than that of the porous structures. Without the metal-reflective layer, the porous PC films can still achieve good PDRC performance with Pnet of 86 W/m2. Furthermore, the effective thermal conductivity of different structures was evaluated. The single-layer porous structure with optimally designed architecture can achieve both good optical and insulating performance, and it is the structure with the most potential in PDRC applications. The results can provide guidelines for designing high-performance radiative cooling films.
ABSTRACT
The risk of fire in the chemical industry's production process is fatal. Gel foam has been widely employed in petroleum storage tanks, oil pools, and other petrochemical equipment for fire extinguishing and thermal protection. Recently, nanoparticles have been doped into gel foam to enhance thermal stability and insulation. However, heat transfer behaviors of the gel foam layer containing nanoparticles are still missing. In this study, a numerical heat transfer model of a gel foam layer containing silica nanoparticles under a radiative heat flux was established. Through simulation, the changes in foam thickness and temperature distribution were analyzed. The effects of the maximum heating temperature, initial gas content, nanoparticle size, and concentration on the thermal insulation behavior of the gel foam layer were systematically studied. The results showed that the thermal stability and insulation performance of the three-phase gel foam layer decreased with the increase in the initial gas content and particle size. Increasing the nanoparticle concentration could enhance the foam's thermal stability and insulation performance. The results provide guidance for a designing gel foam with high thermal protection performance.
