Radiative cooling has attracted lots of attention recently due to its electricity-free cooling by reflecting solar radiation and emitting thermal radiation to the cold outer space. However, how to improve heat dissipation performance at above-ambient temperatures is still a challenge for outdoor flexible devices. Here a bilayer structure was designed to achieve a thin and thermal conductive radiative cooling film for local heat dissipation in outdoor flexible devices, the local heating area can be avoided by the high in-plane thermal conductive performance and heat can be efficiently dissipated to the outer environment by daytime radiative cooling. The top layer consisted of porous hBN@PVDF-HFP film (thickness ∼ 100 μm) to realize daytime radiative cooling while the bottom layer was the directional graphene film (thickness ∼ 30 μm) to promote in-plane thermal conductive performance, high solar reflectance R‾solar = 0.944, thermal emittance ε‾LWIR = 0.904, and in-plane thermal diffusivity 185.7 mm2 s−1 were obtained. Under sunlight, the designed radiative cooling film can greatly reduce the local working temperature from 130.6 °C to 63.3 °C compared with the reference radiative cooling film at the same local heating power, which also shows great local heat dissipation performance under a non-flat surface. This work provides a potential approach to developing thermal conductive radiative cooling technologies for outdoor local heat dissipation applications.

中文翻译：

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用于局部散热的导热辐射冷却膜


辐射冷却最近因其通过反射太阳辐射并向寒冷的外太空发射热辐射的无电冷却而引起广泛关注。然而，如何在高于环境温度下提高散热性能仍然是户外柔性设备面临的挑战。这里设计了双层结构，在室外柔性器件中实现了一层薄而导热的辐射冷却膜，用于局部散热，高平面内导热性能可以避免局部发热区域，并且可以通过白天辐射冷却将热量有效地散发到外部环境。顶层由多孔 hBN@PVDF-HFP 薄膜（厚度 ∼ 100 μm）组成，以实现白天辐射冷却，而底层是定向石墨烯薄膜（厚度 ∼ 30 μm）以提高面内导热性能，获得了高太阳反射率 R ̅solar = 0.944，热发射率 ε ̅LWIR = 0.904，面内热扩散率 185.7 mm2 s-1。在阳光下，在相同的局部加热功率下，所设计的辐射冷却膜与参考辐射冷却膜相比，可以将局部工作温度从 130.6 °C 大幅降低到 63.3 °C，在非平坦表面下也表现出很好的局部散热性能。这项工作为开发用于室外局部散热应用的导热辐射冷却技术提供了一种潜在的方法。