A proposed method of solar-driven spray flash evaporation assisted by MPCM applied to solution regeneration with experimental analysis

Abstract

Solution regeneration belongs to a separation and purification technology for multi-component liquid systems, which is involved in many fields such as liquid desiccant air-conditioning, desalination, and sewage treatment. Solar-driven evaporation technology has enormous energy-saving potential in solution regeneration, but it has the disadvantages of instability and slow regeneration rate. In this work, the method of solar-driven spray flash evaporation assisted by microencapsulated phase change material (MPCM) is proposed for solution regeneration. The spray flash evaporation experimental platform working with NaCl-MPCM suspension is constructed, and the spray characteristics and heat and mass transfer characteristics of NaCl-MPCM suspension are examined under different operating parameters. The results show that the addition of MPCM to the solution can significantly improve its equivalent specific heat capacity, which mitigates dispersed and discontinuous defects of solar energy. Furthermore, it can effectively reduce the severe temperature drop of the solution during the flash evaporation process, which ensures a high driving potential difference between the solution and flash evaporation environment. It is worth mentioning that under the same operating conditions, the regeneration amount per unit mass flow rate of the NaCl-MPCM suspension (wMPCM = 10 wt%) is 24.8 g/kg, which is about 19 % higher than that of the NaCl solution. Additionally, the flash performance of the NaCl-MPCM suspension can be further improved by reducing the initial fluid velocity at the nozzle or the flash evaporation pressure. This study aims to provide guidance for the efficient utilization of solar-driven flash evaporation assisted by MPCM.