Water Desalination Using a Humidification-Dehumidification Technique—A Detailed Review

Abstract

Solar humidification-dehumidification desalination technology has been reviewed in detail in this paper. This review would also throw light on the scope for further research and recommendations in active distillation system by humidification and dehumidification (HDH). Also in this article, a review has been done on different types of (HDH) systems. Thermal modeling was done for various types of humidification and dehumidification (HDH) distillation system. From the present review, it is found that the humidification-dehumidification desalination process HDH will be a suitable choice for fresh water production when the demand is decentralized. HDH is a low temperature process where total required thermal energy can be obtained from solar energy. Capacity of HDH units is between that produced by conventional methods and solar stills. Moreover, HDH is distinguished by simple operation and maintenance. Also from the present condensed review, it was observed that an increase in evaporator and condenser surface areas significantly improves system productivity. But prior to implementing any techniques in design improvement, it is necessary to optimize the MEH unit by optimizing its component size to understand the effect of feed water and air flow rates. Although a fair amount of simulation studies have been conducted in the past, further design simulation is required to fully understand the complicated effects of air and water flow rates, the optimum size of individual components or modules of the unit and to generate a comprehensive model for the system.

A comprehensive review of solar‐driven desalination technologies for off‐grid greenhouses

“…On the other hand, the air cycles between these columns and converts the SFW into vapor. When the vapor passes through the dehumidifier, it condenses to form the freshwater . Each of these cycles can be open or closed (see Figure ), so the brine can be extracted at every stage of the process, or part of it can be mixed with the SFW, referred to as, respectively, the open‐ and closed‐water cycles.…”

“…Moreover, flat plate and finned‐tube heat exchangers are two main types that are used as dehumidifiers. Finally, humidifiers include wetted‐wall, spray, and packed bed towers, as well as bubble columns, among which packed bed towers have higher efficiency, because of increasing the air and water contact . The humidifier's efficiency is important because in water heated open‐air, closed‐water solar HDH desalinations, the high temperature of the coolant water, entering the dehumidifier, adversely affects the WPR …”

“…The efficiency of HDH systems can be enhanced by multieffect systems (with a GOR of more than 4.5) for water‐heated and air‐heated configurations. In the water‐heated layout, the air is extracted from the humidifier at different points, resulting in balancing the mass and heat exchange and decreasing the consumed energy . Likewise, in the air‐heated layout, the air passes through multiple solar collectors and correlating humidifiers, resulting in higher absolute humidity and productivity .…”

“…Currently, over 21 000 desalination plants around the world produce above 13 million cubic meter per day of freshwater (see Figure B) . These systems are classified into the membrane and thermal processes . In thermal desalination, the saline feed water (SFW) is heated, evaporated, and then condensed to produce freshwater, and its well‐known technologies are multistage flash (MSF) and multieffect distillation (MED) .…”

Single Basin Solar Still with Varying Depth of Water: Optimization by Computational Method

“…Sun, as a warmth source, is utilized to dissipate around 16 million tons of water from land to the climate every second [2].Vapor is conveyed by the winds to where it runs over a low temperature zone and consolidates to shape accelerates as rain, snow. One kg of air can carry around 100 g water vapor at 60 ˚C and it arises to 500 g at 80 ˚C [3]. Solar still (SS) is a device which is utilized to change over saline water into distilled water.…”