Nowadays, access to freshwater has become a major concern for many people around the globe. The
Humidification-dehumidification (HDH) is a desalination method that has recently been developing
for use on a small scale in rural areas. According to the literature review, a few numbers of researches
done in this field include the Carnot system and thermodynamically balanced systems with air
injection from the humidifier to the dehumidifier. It should be noted that the Carnot system considers
a water desalination system through a thermodynamic analysis of a general control volume without
including the details of the desalination method. Therefore, the maximum value for the energy
efficiency obtained from this analysis provides an upper limit for the performance of all of the
thermal desalination systems and is not specific to the humidification-dehumidification method. In
humidification-dehumidification systems with infinite number of air injection from the humidifier
to the dehumidifier, one step is taken forward (compared to the Carnot system) in terms of including
the details of the desalination system, however, in thermodynamic analysis of those systems, the
conditions of saturated air (100% relative humidity) and thermal equilibrium between humid air and
saline water in humidification tower are assumed simultaneously which is thermodynamically
impossible. Because from the phase equilibrium analysis it can be shown that the humid air in
contact with saline water will have a relative humidity less than 100% when the thermal equilibrium
condition is invoked. Therefore, the main purpose of this study is to enhance the prediction of the
maximum energy efficiency (ideal) specific to the humidification-humidification method. In order
to achieve this goal, in this study, two nearly reversible HDH desalination systems are proposed by
removing the entropy production sources (heat transfer with finite temperature difference and mass
transfer with finite concentration differen