Pinch-based analysis of a humidification-dehumidification desalination system

Abstract Humidification–Dehumidification (HDH) desalination offers a key advantage in handling high-salinity feedwater while utilizing low-grade energy, making it favorable compared to other desalination technologies such as reverse osmosis, multi-effect desalination, and multi-stage flash. Although HDH systems generally exhibit lower energy efficiency, there is potential for improvement. This study focuses on the thermodynamically optimized design of a water-heated HDH cycle. The optimum performance of an HDH system is achieved with the help of pinch analysis based on the thermodynamic balancing concept. This pinch model can be integrated into the design process to estimate mass flow rates and temperatures throughout the cycle under optimal operating conditions. Once the optimum performance is established, the humidifier and dehumidifier can be appropriately sized. A regression-based approach has been developed to streamline the design process. In this method, design parameters such as heat input and enthalpy pinch are normalized to facilitate the development of regression correlations. The procedure relies on predefining certain parameters, including the minimum feedwater temperature and the maximum cycle temperature. A parametric study was conducted to evaluate how variations in these temperatures affect the sizing of both the humidifier and dehumidifier. For instance, increasing the maximum cycle temperature reduced the required size of components. Additionally, this study investigates how the pinch point location within the humidifier shifts under different operating conditions.