Experimental study on a solar assisted heat pump desalination unit with internal heat recovery based on humidification-dehumidification process

On-going study on the humidification-dehumidification (HDH) desalination has proved that internal heat recovery is a significant and potential method for improving the system performance and reducing the fresh water cost. In this paper, a novel solar assisted heat pump (SAHP) with internal heat recovery desalination system based on HDH process is proposed and studied experimentally. The objective of this study is to investigate the ability of heat recovery in improving the system performance and obtain the optimal operating parameters. Based on the experimental results, it can be concluded that the fresh water cost of the two-stage HDH desalination system is reduced by 17.36%, and system productivity and gained-output-ratio (GOR) are increased by 15.51% and 55.64%, respectively compared with those of the single-stage. Particularly, benefiting from energy cascade utilization, the distribution ratio is introduced to further improve the system performance, which is affected strongly by the cooling seawater flow rate. Furthermore, a comparison of the humidifier materials between plastic polyhedron empty balls (PPEBs) and honey-comb paper indicates that the increment in system productivity by PPEBs is 27.76% lower than that by honey-comb paper with a reasonable specific surface area.