Constructal design and optimization of a direct contact humidification-dehumidification desalination unit

► A direct contact humidification-dehumidification desalination unit is modeled and analyzed. ► The constructal theory is incorporated with mathematical modeling to optimize the proposed unit. ► The Genetic Algorithm and Lagrange multiplier methods are used to optimize the fresh water production rate. ► All design parameters change in proportion with the water inlet temperatures of the dehumidifier and humidifier. ► The water to air mass flow rate ratio (saline and fresh water) significantly affects on the main design parameters. ► Recycling ratio is found as an effective way for declining the energy consumption of unit.