Iranian Association of Chemical Engineering (IAChE) Iranian Journal of Chemical Engineering (IJChE) 1735-5397 21 1 2024 02 01 Theoretical study of multi-stage and multi-feeding variable pressure humidification-dehumidification (VP-HD) desalination systems 17 29 186626 10.22034/ijche.2024.420681.1504 EN Zohreh Rahimi-Ahar Department of Chemical Engineering, Engineering Faculty, Velayat University, Iranshahr, Iran 0000-0001-6804-9474 M. Sadegh Hatamipour Chemical Engineering Department, Faculty of Engineering, University of Isfahan, Isfahan, Iran 0000-0002-6752-9449 Journal Article 2023 10 14 <em>Humidification-dehumidification (HD) desalination has been identified as a sustainable, reliable, and energy-efficient technology for producing freshwater on a small scale. VP-HD systems operated at one-stage, multi-stage, and multi-feeding vacuum humidification-over atmospheric pressure dehumidification arrangements can be the recent modifications of an HD system. The present study offers a theoretical investigation and experimental verification of two VP-HD systems, encompassing both sub-atmospheric pressure humidification and over-atmospheric dehumidification. Two designs are evaluated, one comprising a three-stage humidification setup and the other featuring a three-feeding one-stage humidification apparatus. The results show which design has better performance than previous conventional and variable pressure HD systems. The parametric analysis reveals that an upsurge in freshwater generation is observed with an increase in air temperature, feed salinity, and a decrease in humidifier pressure. Additionally, an optimal water-to-air ratio is identified. The study further highlights that multi-stage humidification yields better results concerning freshwater productivity and specific power consumption. Three-stage humidification is found to be the most efficient in terms of freshwater production and specific power consumption, achieving the highest values of 1.93 L h<sup>-1 </sup>m<sup>-2</sup> and 0.21 kWh L<sup>-1</sup>, respectively. The agreement between theoretical and experimental outcomes is deemed satisfactory</em><em>.</em> Multi-stage humidification Multi-feeding humidification Dehumidification Freshwater productivity Specific energy consumption https://www.ijche.com/article_186626_fea7f15378a1fd8cde1cc74eaae663cb.pdf