Energy Conversion and Management 228 (2021) 113694 0196-8904/© 2020 Elsevier Ltd. All rights reserved. An experimental investigation on a portable bubble basin humidifcation/ dehumidifcation desalination unit utilizing a closed-loop pulsating heat pipe Latif Aref a , Rasoul Fallahzadeh b , Vahid Madadi Avargani c, * a Chemical Engineering Department, Faculty of Engineering, Shomal University, Amol, Iran b Chemical Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran c Chemical Engineering Department, Faculty of Engineering, Yasouj University, Yasouj 75918-74831, P. O. Box 353, Iran A R T I C L E INFO Keywords: Renewable energy Desalination Humidifcation/dehumidifcation Closed-loop pulsating heat pipe Bubble basin ABSTRACT The present work aims to enhance the performance of a solar energy-driven HDH desalination system. An experimental apparatus consisting of a novel closed-loop pulsating heat pipe (CLPHP) assisted by a bubble basin HDH system was investigated. To evaluate the productivity of the fresh water, tests have been properly designed and conducted in outdoor and indoor modes during June and July of 2020, under local weather conditions of Mashhad, Iran. A closed air-heated confguration is introduced into the HDH desalination system, to recover the condensation latent heat. The air leaving the dehumidifer is pre-heated and pre-humidifed using CLPHP before entering the humidifer of the desalination unit. Also, an air injection system is used to enhance the mass and heat transfer rate by generating bubbles. In the experiments, the infuence of the operating conditions such as radiation and air mass fow rate on the performance of the desalination unit was investigated. Furthermore, a comparison between the bubble basin and bubble column types was carried out. Based on the results, the bubble basin type presented a higher yield compared to the bubble column type that was obtained as 0.83 and 0.70 (kg/ (hr.m 2 )), respectively. Besides, it was observed that by increasing the radiation and air mass fow rate, pro- ductivity is improved. The maximum obtained yield of the proposed system was achieved as 8.7 L/(day.m 2 ). 1. Introduction Desalinating seawater and brackish water is becoming a necessity for the sustainable development of many regions in the world. It is predicted that in two decades, solar energy will become the cheapest desalination technology with a price of 0.00045 $/L of treated water [1]. Various methods have been studied on water desalination such as multi-effect desalination (MED) [2], multi-stage fashing (MSF) [3], reverse osmosis (RO) [4,5], solar stills [6,7], humidifcation/dehumidifcation processes (HDH) [8], etc. HDH desalination system is a promising technology to address water scarcity issues in rural regions and is known as an appealing process for small and medium scales, and high-salinity water desalination [9]. HDH process due to its wide range of advan- tages such as moderate working pressure and temperature, easy system construction using low-cost materials, and effortless system operation is considered as the most effective method for desalination process [10]. HDH systems can be classifed under two broad categories [11]: 1. Cycle confguration: closed air-open water (CA-OW), open air-open water (OA-OW), and open air-closed water (OA-CW) systems. 2. Type of heating systems: air heated or water-heated systems. Closed cycles of water/air improve energy recovery since the input energy used for water/air heating is preserved in the process. CA-OW air heated cycle usually surpasses OA-OW [9–12]. HDH units have three main sections: humidifer, dehumidifer, and heat source. A humidifer can be a wetted wall column, packed bed containing different packings, spray tower, or bubble column. Bubble column humidifers (BCH) are promising for HDH, offering higher heat and mass transfer rates by direct mixing of air with water at low cost and have low maintenance requirements [9,12,13]. The ultimate purpose of an HDH desalination unit is to obtain a higher rate of fresh water. To enhance productivity, various bubble HDH arrangements have been investigated in the literature. A summary of the conducted works has been provided. Fallahzadeh et al. [14] introduced a modifed pyramid-shaped solar * Corresponding author. E-mail address: v.madadi@yu.ac.ir (V. Madadi Avargani). Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman https://doi.org/10.1016/j.enconman.2020.113694 Received 7 September 2020; Received in revised form 21 November 2020; Accepted 23 November 2020