Performance improvement of spray flash evaporation desalination systems using multiple nozzle arrangement

Abstract This research aims to improve the performance of the spray flash evaporation as a key component of Discharge Thermal Energy Combined Desalination (DTECD) systems using a multi-nozzle head in various arrangements for the first time. Two novel nozzle arrangements were proposed and compared with the conventional single nozzle. The injection of saline water inside the vacuum chamber was performed under various operating conditions including inlet flow rate, pressure injection, superheat degree, and salinity. Furthermore, the droplet sizes and distribution were observed and analysed using shadowgraph imaging. A similar outcome was reached between the droplets measurement analysis and measured evaporation rate and gain output ratio which implied the most efficient arrangement. The proposed arrangement in which five nozzles are located in the farthest distance totally improved the efficiency of the system under various conditions up to a maximum 28% compared to the conventional single nozzle for the same flow rate. In addition, it was found that the number of nozzles plays a more significant role than their arrangements for a certain pressure injection. Moreover, the optimised maximum superheat degree for the most efficient arrangement was found to be 19°C. These results provide new fundamental understanding in the area of spray flash evaporation and reveal that increasing the number of nozzles and placing them in the farthest distance apart can improve the efficiency of the system.