Evaporation rates and temperature distributions in fine droplet flash evaporation sprays

Abstract This study reports an experimental investigation of a flash evaporation system based on low-temperature thermal desalination (LTTD) technology. Low temperature liquid in the range of 60–80 °C becomes superheated by injecting it through a nozzle into a depressurized chamber. Previous studies have not attempted to establish a correlation model between the temperature distributions and the evaporation rate. Moreover, this study presents for the first time the temperature distribution in fine droplets (small nozzle, 0.8 mm) sprays upward flash evaporation sprays over a range of conditions. The effect of the operating parameters on the temperature distribution and evaporation rate of flashing spray is also investigated and comparisons are made between the results of the present experiments and flash evaporation jets. The dimensionless temperature introduced (ϴemp) follows an exponential decaying curve and is found to also match temperature distributions in a range of other works covering different nozzles (sprays or jets), in both upward and downward flash evaporation. It is also found that flow rate has a different effect on the evaporation rate depending on whether spray or jet flash evaporation is taking place. Increasing the flow rate in sprays leads to higher flash evaporation, but lowers the evaporation rate in jets.