Humidification-dehumidification (HDH) is a cost-effective thermal desalination system that utilizes low-grade energy to extract freshwater from high salinity seawater with minimum maintenance. A robust method is presented using an innovative definition for energy effectiveness to facilitate the practical utilization of HDH modeling in the design process. This definition is mainly based on representing the flow stream on the temperature-enthalpy diagram to locate the pinch point and overcome the terminal-based definition limitation accordingly. The possible violation of the Second Law of Thermodynamics is the main drawback of the previous definitions due to the temperature-cross inside the humidifier, which defeats the purpose of air heating and humidification. The closed-air open-water HDH model is examined thermodynamically, and its design characteristics are explored at different operating conditions. The proposed definition is compared with analogous data from the literature. It showed an excellent agreement with a maximum discrepancy of 2.30%. Furthermore, a direct and straightforward design scheme is provided to estimate the dehumidifier and humidifier sizes based on the location and amount of freshwater needed. A case study for a system that produces 5 kg h⁻¹ of freshwater in Dhahran is presented. The optimal energy effectiveness is found to be 78%, where the average minimum and maximum temperature of seawater in the system are assumed to be 25 and 70 °C, respectively.

加湿除湿（HDH）是一种经济高效的热脱盐系统，该系统利用低品位能源从高盐度海水中提取淡水，且维护成本最低。提出了一种鲁棒的方法，使用了创新的能源效率定义，以促进在设计过程中HDH建模的实际利用。该定义主要基于在温度-焓图上表示流，以定位收缩点并相应地克服基于终端的定义限制。由于加湿器内部的温度交叉，可能会违反热力学第二定律，这是先前定义的主要缺点，这不利于空气加热和加湿的目的。对空气露天HDH模型进行了热力学研究，并在不同的工作条件下探索其设计特性。所提出的定义与文献中的类似数据进行了比较。它显示出极佳的一致性，最大差异为2.30％。此外，提供了直接和直接的设计方案，以根据所需淡水的位置和数量估算除湿机和加湿机的尺寸。产生5 kg h的系统的案例研究^达兰的淡水为^-1。发现最佳能源效率为78％，其中假定系统中海水的平均最低和最高温度分别为25和70°C。