A novel design of a multistage stepped bubble column humidifier for the humidification of air

•A novel multi-stage stepped bubble column humidifier is designed and tested.•A higher system performance with a lower pressure drop is achieved.•Absolute humidity is increased by 7–9% for two-stage bubble column humidifier.•Absolute humidity is increased by 18–21% for three-stage bubble column humidifier. The operating parameters for the optimum performance of a novel multistage stepped bubble column humidifier design were experimentally determined. An improved humidification-dehumidification (HDH) desalination system can be obtained by integrating such a humidifier with a dehumidifier. The relationship between the variation of the pressure drop with varying water column height at different superficial velocities of air was evaluated. A water column height of 1cm and superficial velocity of air of 25cm/s provide the best humidifier performance at the lowest pressure drop. The performance of single-stage, two-stage, and three-stage bubble column humidifiers was evaluated in terms of the absolute humidity when the inlet water temperature is varied in the range of 35–75°C. The absolute humidity increases exponentially with increasing inlet water temperature. The percentage increase in the absolute humidity achieved by the two-stage and three-stage bubble column humidifiers are, respectively 7–9% and 18–21% higher than that achieved by the single-stage bubble column humidifier.