Solar water desalination using an air bubble column humidiﬁer A. Khalil, S.A. El-Agouz ⁎, Y.A.F. El-Samadony, Ahmed Abdo Mech. Power Eng. Department, Faculty of Eng., Tanta University, Egypt HIGHLIGHTS • Desalination using an air bubble column humidiﬁer is investigated. • Effect of water temperature and height, air ﬂow rate and hole diameter is studied. • At inlet water is 62 °C, productivity, efﬁciency and GOR are 21 kg, 63%, and 0.53. • Air bubble column achieves higher performance than that conventional humidiﬁer. • Temperature difference along air column is less than 2.5 °C for all measurements. abstract article info Article history: Received 18 April 2015 Received in revised form 6 June 2015 Accepted 13 June 2015 Available online xxxx Keywords: Humidiﬁcation–dehumidiﬁcation Air bubbles Solar desalination, sieve plate An experimental study of a solar water desalination using an air bubble column humidiﬁer is investigated. The characteristics of the generated bubbles are modiﬁed by using a different sieve plate with different hole size. The effect of water temperature, air ﬂow rate, water height, and sieve's hole diameter on desalination perfor- mance is studied. The results showed that the daily productivity, efﬁciency and gain output ratio are 21 kg, 63%, and 0.53 respectively; at inlet water temperature is 62 °C. The change in the temperature difference along the column is less than 2.5 °C for all measurements. The best performance is observed from sieve with 1 mm hole diameter at which the outlet air from the bubble columns is always saturated. The air bubble column achieves higher performance than that for the conventional humidiﬁer. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Desalination can be achieved by many methods. Thermal method is considered to be the simplest one. In this method, saline water is heated in an evaporator and generates water vapor free of salts. The generated vapor is condensed in a condenser then fresh water is collected. Water, air, or both can be heated by conventional energy source or by renew- able energy source such as solar energy. The latter desalination process can be called solar air humidiﬁcation– dehumidi ﬁcation desalination process. The humidi ﬁcation– dehumidiﬁcation (HD) desalination process is one of the secondary desalination processes. This system is very useful for places which have low freshwater demand. The main advantages of this system are; consume a small amount of energy and simplicity in both plant layout and management. Bourouni et al. [1] presented the technique of air humidiﬁcation– dehumidiﬁcation (HD) process. The principle, technique and state of the art of the HD process were presented. Gahin et al. [2] presented a preliminary design study of a solar collector humidiﬁcation–dehumidi- ﬁcation desalination unit. They studied different parameters affecting the global performance of the unit. Also, they studied the performance of the two most important components of the loop which are humidify- ing and dehumidifying columns or stacks. Farid and Al-Hajaj [3] de- signed and studied experimentally the performance of multi-effect solar air humidiﬁcation desalination unit. The unit had two different loops; air closed loop and water open loop. The results showed that the multi-effect humidiﬁcation–dehumidiﬁcation process, with forced air circulation, was found suitable for water solar desalination. The unit achieved a daily productivity of 12 l/m 2 /d, which was over three times that for single-basin conventional solar still. Al-Hallaj et al. [4] studied experimentally the indoor and outdoor performance of two de- salination units based on air humidiﬁcation desalination. The results showed that water productivity was increased as the feeding water ﬂow rate was increased to an optimum value. Moreover, they concluded that forced air circulation was effective in the unit performance at low operating water temperatures. Ben-Bachaa et al. [5] studied experimen- tally a solar multiple condensation evaporation cycle (SMCEC) desalina- tion technique. The results showed that the pilot units produced as much as 60% of daily water needed for irrigation. Dai et al. [6] conducted experimentally a solar humidiﬁcation and dehumidiﬁcation desalina- tion unit. The performance of the unit was strongly dependent on the Desalination 372 (2015) 7–16 ⁎ Corresponding author. E-mail addresses: Akhalileg@yahoo.com (A. Khalil), elagouz2011@yahoo.com (S.A. El-Agouz), samadony25@yahoo.co.uk (Y.A.F. El-Samadony), eng.a_abdo@yahoo.com (A. Abdo). http://dx.doi.org/10.1016/j.desal.2015.06.010 0011-9164/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal