EXPERIMENTAL AND NUMERICAL ANALYSIS OF SPRAY COOLING IN PHOTOVOLTAIC SYSTEMS

A spray cooling system was established to prevent the decrease in electrical efficiency that occurs when the cell temperature of photovoltaic panels exceeds the maximum operating temperature. The parameters of this spray cooling system were investigated experimentally and numerically. The electrical efficiency of the photovoltaic panel was calculated at 1000 W/m<sup>2</sup> solar radiation and different operating temperatures. Taking into account the decrease in electrical efficiency, the operating temperature ranges were determined as 45-25°C so that the efficiency would not fall below 10%. A DXF-HSI nozzle with a flat spray area was used for spraying with direct and quick cooling features. Heat transfer parameters, such as the Sauter mean diameter (SMD), Nusselt number, and heat transfer coefficient, were calculated in the spray cooling experiments. The air-to-liquid ratio (ALR) value was calculated for all experiments and its effect on spray cooling was investigated. In all experiments, the spraying angle and jet diameter were calculated through the images of the sprays taken using a charged-coupled device (CCD) camera. A computational fluid dynamics (CFD) analysis of spray cooling experiments was also performed in ANSYS Fluent and compared with the experimental results. In the experiments, with a water flow rate of 400 mL/min and an air flow rate of 1.55 m<sup>3</sup>/h, the highest heat transfer coefficient was calculated as 2.32 W/cm<sup>2</sup> K, and the shortest cooling time was measured as 150 s. The smallest SMD was calculated to be 74.06 μm with a water flow rate of 200 mL/min and an air flow rate of 1.75 m<sup>3</sup>/h. It has been observed that the experimental results and numerical results are in good agreement.