Evaporation in thin film region of water at ambient temperature under reduced pressure conditions: Flow and interface characteristics

In this paper, the flow and interface characteristics of the thin liquid film region near the contact line of water under reduced pressure conditions are experimentally observed by using a multilayer nanoparticle image velocimetry technique. The results demonstrate that the flow in this region is promoted by reducing the pressure. The average velocities in the top layer of this region are 57.99, 61.52, 65.20, 66.00, and 68.25 mu m/s at the degree of reduced pressure of 10-50 kPa with an interval of 10 kPa. Reducing the pressure shortens the evaporation time and advances the depinning time in the constant contact radius mode. Entering the constant contact angle mode, the initial height of the film increases, the critical height is elevated, and the decrease rate of film thickness increases, which leads to the shortening of the overall evaporation time. This work provides insight into the microscopic transport mechanisms of coolant under reduced pressure conditions.