Performance evaluation of a novel humidification-dehumidification desalination system operated by a heat pump

Abstract

Decentralized and small-scale desalination technologies can effectively address the limitations associated with large-scale desalination systems and contribute to solving the issue of fresh water scarcity. However, low energy efficiency remains a primary obstacle in their widespread application. To tackle this challenge, this paper introduces a novel heat pump humidification-dehumidification desalination system, in which humid air from the dehumidifier enters the heat regenerator and heat pump evaporator in sequence, enabling deep dehumidification. Subsequently, the cold air is reheated by the heat regenerator and subcooler before entering the humidifier. This sequential process can increase not only the energy efficiency of heat pump but also the fresh water productivity. Models are proposed and calculated for the theoretical evaluation of the novel system. Firstly, heat pump design parameters are optimized. Subsequently, performances of the novel system under different operation conditions are compared with those of the conventional system. The results indicate that optimizing heat pump system design parameters can significantly improve system performance. When compared to the conventional system, the novel system exhibits significant improvements. It achieves a maximum fresh water productivity of 39.73kg/h, representing an increase of 12.83%, and a maximum gain output ratio of 6.52, which is 13.39% higher. The lowest fresh water production cost is 9.52 $/m3, also a reduction of 5.15%. Additionally, both the novel and conventional systems possess optimal feed temperature and mass flow rate ratio. At last, the optimal performances of the novel system are compared with the reported results, which further validates the thermodynamic and economic advantages of the novel system.