Performance evaluation of a humidification–dehumidification desalination system coupled with a composite channel humidifier

Humidification–dehumidification desalination technology is well-suited for renewable energy-driven and small-scale applications. Its relatively low energy efficiency is a critical issue that needs addressing. This paper presents a novel humidifier based on composite channels to improve system energy efficiency. The composite channel consists of a dry channel and a wet channel, respectively for the indirect heat exchange and the direct heat and mass exchange between air and water. It enables modification of thermodynamic process path of the system, thus enhancing energy efficiency. Performance evaluations of the novel system demonstrate its significant improvements in energy efficiency. The maximum energy efficiency improvement reaches 34.6 % compared to traditional systems. Although the influence of perforation holes on energy efficiency varies with working conditions, its influence decreases gradually with the number of perforation holes. Similar to the traditional humidification–dehumidification cycle, there exists optimal system top temperatures and liquid mass flow rates at which the energy efficiency peaks under various cases. The maximum energy efficiency of the proposed system with a single row of perforation holes can reach 1.63 when the dry air flow rate ratio is 0.4.