Heat transfer properties of dusty radiative cooling surface: Modeling and experimental studies

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Radiative cooling has shown great potential for energy saving in different sectors. However, performance of a radiative cooling surface is easily affected by dust deposition at outdoors. In this work, we employed the equivalent particle model and the Rosseland diffusion approximation model to predict the heat transfer properties of radiative cooling surface with three different levels of dust deposition (low / medium / high). The models were then validated by experimental data. Theoretical and experimental results show that at low level of dust deposition, the reduction of net cooling power is about 7.1 W/m2 for every 0.1 mg/cm2 increase of dust mass. At medium level of dust deposition, the heat flow characteristics of dusty radiative cooling surface changes from outflow (i.e., cooling) to inflow (i.e., heating). The net heat gain is about 6.4 W/m2 for every 0.1 mg/cm2 increase of dust mass. At high level of dust deposition, the net heat gain gradually increases to a constant value with the increasing of dust mass, and even if the surface is fully covered by dust, it could still reduce the net heat gain by at least 10% in comparison with the concrete roof. This work could provide new insights into the heat transfer processes of dusty radiative cooling surface.