Spray-enhanced flash desalination using ocean thermal energy

The geographical coincidence of abundant ocean thermal energy and freshwater scarcity in remote island regions underscores the immense potential of utilizing ocean thermal energy for seawater desalination. However, the efficient harnessing of this energy remains a critical challenge. This study introduces a seawater desalination method based on vacuum spray evaporation technology. A prototype desalination unit was designed and developed, and a mathematical model was established and validated to comprehensively analyze the evaporation characteristics of the spray evaporator. The findings demonstrate that spray evaporation significantly enhances the heat and mass transfer efficiency of the flash evaporation process, substantially increasing water production rates. For instance, increasing the spray height from 0.01 m to 0.25 m boosted water production from 28.5 kg/h to 43.5 kg/h, flash efficiency from 60 % to 92.45 %, and recovery ratio from 0.67 to 1.02, resulting in an overall performance improvement of 52.6 %. Additionally, smaller droplet diameters and initial velocities were found to enhance the flash evaporation rate and shorten the critical distance to achieve evaporation equilibrium. Through Gaussian surface fitting, the optimal critical spray height and its relationship with operational parameters were determined, providing valuable insights for the design and optimization of spray evaporators.