Effect of mechanical polishing of aluminum alloy surfaces on wetting and droplet evaporation at constant and cyclically varying pressure in the chamber

Abstract

Improving the mechanical polishing of engineering surfaces in terms of the wetting and droplet evaporation theories is important for increasing the efficiency of modern equipment. Depending on the function of engineering surfaces, the mechanical polishing allows changing the wetting, as well as the liquid droplet evaporation rates and modes. However, the prediction of the processes occurring at the liquid/gas/solid contact line becomes more complicated after modification of metal surfaces, as well as under changing the environmental conditions. This work focuses on the study of wetting and evaporation of liquid droplets from polished aluminum alloy surfaces at constant and cyclically varying pressure. Wetting and droplet evaporation are key processes in equipment of the thermal power industry, in particular, operating at constant and cyclically varying high pressure: water-water steam generators, water vapor separators, droplet catchers, etc. Therefore, we investigated droplet wetting and evaporation modes after mechanical processes of surfaces, including polishing by tumbling, satin finishing, grinding and polishing by disks and pastes. We determined the condition when polishing of aluminum alloy surfaces by these methods does not affect the wettability by liquid droplets. Moreover, we established the effect of constant and cyclically varying high pressure on the droplet evaporation rate and evaporation modes. The pressure was found not to affect the characteristics of water droplet evaporation under conditions of periodically varied pressure in the chamber from the atmospheric (0.1 MPa) to high (0.5, 1.0, 1.5, and 2.0 MPa) values.