Performance evaluation of bubble column humidifier using various air distributors in a humidification-dehumidification desalination plant

Abstract

A humidification-dehumidification (HDH) system using a bubble column humidifier was optimized using response surface methodology (RSM). The humidifier was integrated with four types of air distributors entitled the horizontal cuts (H-cuts) and vertical cuts (V-cuts) spargers with the same total hole area, as well as the multiple orifice nozzles (M-orifice) and perforated plate with equal hole diameters. The experimental investigation consisted of a parametric study, optimization using RSM, and bubble characteristics using image analysis. The effects of a qualitative parameter (i.e., the type of air distributors) and quantitative parameters (i.e., the inlet water temperature, superficial air velocity into the humidifier as well as the water height inside the humidifier) on the absolute humidity of the air leaving the humidifier were studied. The H-cuts and M-orifice spargers were found as the best air distributors in their subclasses due to higher gas holdup, specific interfacial area, and lower Sauter mean diameter. The humidifier performance was optimized in the lowest superficial air velocity (0.195 m/s), the highest water height inside the humidifier (50 cm) and the inlet water temperature to the humidifier (90 °C). It was concluded that the H-cuts and M-orifice spargers at the optimum values of the quantitative parameters achieved the maximum absolute humidity of about 0.18 and 0.143 kg water vapor/kg dry air, respectively.