Performance evaluation of a solar humidification dehumidification desalination system employing a multistage bubble column dehumidifier

Abstract

In humidification-dehumidification desalination (HDD) system, conventional dehumidifiers require a large condensing area due to the additional thermal resistance to the heat transfer caused by high concentrations (60–95% by mass) of non-condensable gases present in the air. In a bubble column dehumidifier (BCD), condensation of humid air via direct contact with cold water in a column can significantly decrease condensing area and cost. Hence, in this study, a solar-powered HDD using a multistage BCD is designed and tested in the climatic conditions of Kerala, India. Single-stage and two-stage configurations are investigated in BCD. A mathematical model based on the energy and mass balance of each component is also developed. The model results are observed to be in good agreement with experimental measurements. The results showed that the daily freshwater yield, day average gain output ratio (GOR), and average BCD effectiveness of HDD system with two-stage BCD are 4.571 kg/m2, 0.79, and 0.9, respectively. Furthermore, upgrading the single-stage configuration of BCD to a two-stage configuration increases freshwater yield, day average GOR, and BCD effectiveness by about 6.24%, 6.75%, and 17%, respectively. Detailed water quality analysis revealed that freshwater quality is well within drinking water standards. The cost of freshwater is about 0.0716 $/liter.