Water purification experiment by applying flashing method with a rotating nozzle

Abstract

Abstract The flashing process is a way of exposing water in a low-pressure environment by spraying it at high pressure so that the water converts into fine particles. This process is carried out to speed up the evaporation process of water. The evaporation process carried out on freshwater aims to separate the minerals and solids dissolved in water to increase its purity. In this study, the flashing process was carried out through a rotating nozzle that was proven to increase the rate of pure water production. The flashing process experiment is carried out following an experimental design based on the non-dimensional analysis of Buckingham's pi. The rate of pure water production () as the output variable in the flashing process is affected by the nozzle rotational speed (n), nozzle hole diameter (d), feedwater pressure (Pw), vacuum pressure (Pv) and feedwater temperature (T). The feedwater temperature itself can influence the behavior of the feedwater flow in the nozzle, in this case, is density (ρ) and viscosity (μ). Based on these variables, the non-dimensional analysis of Buckingham pi has produced four dimensionless numbers. The generated empirical equations from the flashing process experiments are in the form of quadratic equations. The empirical equation applies to feedwater pressure of 7.6 bar-g, the vacuum pressure of 0.4–0.6 bar-a and nozzle rotational speed of 0–134 rpm. The optimum condensation rate in the flashing experiment was successfully obtained, especially at the nozzle rotation of 27 rpm in all vacuum pressures tested. This success is inseparable from the use of mist-nozzles that convert the feedwater flow into the mist.