Mathematical study of spray flash evaporation in a spray-assisted seawater desalination chamber

Abstract

Spray flash evaporation is a method for the new desalination technology driven by renewable energy. This paper studies the flash evaporation phenomenon of the seawater jet sprayed into a low-pressure chamber. A droplet flash evaporation model has been developed to enable an in-depth understanding of the flash evaporation. This model is capable of predicting the spray flash speed, the evaporated mass rate and the flashing efficiency under different working conditions. Applying this model, the effects of different operating variables on the flash evaporation process are investigated. Results from the developed model reveal a larger Jakob number, Reynolds number and Weber number all lead to the increase of the production rate. The flashing efficiency can attain values larger than 0.9 with the nozzle diameter ranging 5–14 mm when the flash chamber is 150 mm height. The flashing efficiency with nozzle diameter of 5 mm is larger than 0.9 when the flash chamber is 25 mm height. The flow velocity of 10 m/s is recommended for the current case to obtain a large production rate. A flash chamber larger than 500 mm height is needed for complete evaporation considering the presence of dissolved salt in sea water.