An improved radiative cooling flat-plate collector: Numerical simulation and experimental study

Abstract

• An improved radiative cooling flat-plate collector (RCFC) was designed. • The device heated air to a higher temperature than a flat-plate collector. • Parametric analysis on cooling performance was carried out. This study aims to develop a structure combining solar heating and radiative cooling without thermal efficiency reduction. A technical scheme for radiative cooling by reforming a flat-plate collector (FPC) is proposed. A glass cover was attached to a polyethylene terephthalate film, which transformed it into a radiative cooling surface; thus, it was able to cool the air through night sky radiation. A polyethylene film covered the top of the device as a windscreen to reduce unwanted heat loss. The heat transfer model of the device was established in MATLAB, and this model for radiative cooling was verified using experimental data. The experimental results also show that the improved radiative cooling flat-plate collector (RCFC) demonstrated improved solar collecting performance compared to a typical FPC; the maximum temperature rise of the RCFC was increased by 40%. The cooling efficiency of the RCFC was essentially between 48% and 54% in Chongqing. Numerical analysis was used to investigate the effects of ambient temperature, humidity, mass flow rate, selective emissivity, and other factors, on cooling performance. The results indicated that by multiplying the airflow by a factor of 2 or by utilizing the ideal film, the cooling power was approximately increased by 50%.