Theoretical evaluation on performance of a novel bubbling humidification–dehumidification desalination system directly heated by concentrating sunlight

This work aims to analyze the heat and mass exchange of complex bubbling. First, an empirical correlation for estimating bubbling heat transfer coefficient in different superficial air velocities is obtained based on previous works. Then, a modified theoretical model is set up and used to discuss the performance of the bubbling HDH system. Results show that higher input power enhances water productivity and thermal efficiency, but a maximum exists. When input power is constant, the influence of air flow rate on water productivity is remarkable when air velocity is not large. More importantly, the system has optimal cooling water flow rate and temperature. The optimal cooling water flow rate increases with input power, whereas the optimal cooling water temperature decreases with input power. When input power is 1000 W, the optimal cooling water flow rate and temperature are 60 L/h and 59 ℃, respectively. In addition, ambient temperature variations show a very small effect on system productivity and thermal efficiency. The results of this paper can provide theoretical reference for the design of a bubbling HDH desalination system.