Synthesis, characterization and application of SiO2 and CuO nanofluid in spray cooling of hot steel plate

The current work uses SiO2 and CuO mono, mixed nanofluid to improve very-high mass-flux spray cooling performance. At first, the modified sol–gel method based SiO2 and wet-chemical method based CuO nanoparticles are prepared. The prepared nanoparticles' density, crystalline/amorphous nature, functional groups, compositions, morphology, and particle size are characterized. The SiO2 and CuO nanofluid are prepared using one-step and two-step methods, respectively. The nanofluid thermophysical properties, particle size distribution, and stability are determined. The heat transfer performance of applied nanofluid is assessed in terms of parameters cooling rate, heat flux, and heat transfer coefficient, which are estimated using inverse heat conduction analysis. The cooling performance improvement is observed with concentration enhancement for all nanofluids. However, for mono CuO and mixed SiO2-CuO nanofluid at their highest concentration, the cooling enhancement percent decreases compared to their second highest concentration. The highest cooling rate of 164 °C/s is observed for mixed nanofluid at the highest concentration. The average surface heat flux, critical heat flux, and average heat transfer coefficient improvement are maximum at 1.80 MW/m2, 2.36 MW/m2, and 2.67 kW/m2K, respectively, for mixed nanofluid highest concentration. Therefore, nanofluid inclusion leads to spray cooling performance improvement, with slight performance reduction after nanoparticle loading enhancement in some cases.