Droplet Vaporization on Warm Surface in Rapid Decreasing Pressure: An Experimental Study

Herein, we experimentally addressed the size variation in droplet vaporization on copper surfaces.The influence of the vaporization conditions, including the pressure decrease-rate, surface warmness (25~30℃) and hydrophilic/hydrophobic properties, on the droplet's size variation was investigated with the experimental setup, equipped with charge-coupled device (CCD) video cameras. The results show that the vaporization conditions had a major impact. To be specific, the vaporization on went through four distinctive stages:the initial, rapid vaporization, constant contact radius and rapid contraction stages. The droplet survived much longer on the hydrophobic surfaces because a larger number of bubbles significantly slowed down the shrinkage of the droplet contact radius.On the hydrophilic surfaces, the droplet vaporized much faster with an increase of surface temperature and with a decrease of pressure, resulting in a longer time of constant contact radius vaporization stage.