Experimental investigation of spray cooling on flat and enhanced surfaces

The heat transfer during spray cooling was studied experimentally using deionized water to investigate the effects of the spray characteristics, flat and enhanced surfaces with micro-structures and the surface roughness on the heat transfer. The shadowgraph technique was used to measure the droplet parameters with the results showing that the droplet sizes decreased while the velocities and droplet number density increased as the flow rate increased. The spray cooling experiments further showed that the heat transfer was enhanced in both the single and two phase regions for enhanced surfaces compared with the flat surface and that the enhanced surface with smaller feature sizes had better heat transfer rates. Thus, the enhanced surface effectively improves the spray cooling heat transfer. There is an optimal flow rate and optimal orifice-to-surface distance for spray cooling on both flat and enhanced surfaces, with the optimal flow rate increasing and the optimal orifice-to-surface distance decreasing as the groove size decreases. The heat transfer performance is best for a spray inclination angle of 0° and the heat transfer rate increases with surface roughness.