Water–air–energy nexus analysis of a sustainable rotary wick humidifier

This study investigates the design, fabrication, and performance evaluation of a vertically aligned rotary humidifier utilizing a capillary-driven wick medium of varying thicknesses. Experimental analyses were conducted by systematically varying the rotational speed of the motor-driven shaft from 30 to 90 rpm and adjusting the wick thickness between 3 mm and 6 mm. Key fluid properties, including effective force balance per unit thickness and capillary rise, were quantified, and found that they exhibited a direct correlation with both wick thickness and rotational velocity. The results demonstrated that humidification efficiency improved with increasing wick thickness, accompanied by a corresponding rise in pressure drop. The optimal operational speed was identified at 70 rpm, yielding a peak evaporation rate (ER) of 0.46 g/s and a maximum coefficient of performance (COP) of 5.83. Indoor air quality was assessed through the measurement of gaseous pollutants such as CO₂, total volatile organic compounds (TVOCs), and formaldehyde, revealing a reduction in pollutant concentrations with increasing wick thickness. Long-term performance evaluation indicated a progressive accumulation of contaminants within the wick matrix, leading to a degradation in system efficacy, evidenced by a 23.91 % decline in evaporation rate and a 14.23 % reduction in COP. Overall, the rotary humidifier demonstrated effective air cooling and humidification capabilities, with performance subject to material degradation over extended operation.As a sustainable system, it plays a significant role in advancing SDG 7 (Affordable & Clean Energy) and SDG 11 (Sustainable Cities & Communities).