Experimental and theoretical investigation of vacuum-based seawater desalination system driven by ultra-low temperature heat source

Sustainable freshwater plays a key role in human life and the rapid growth of industry. However, freshwater sources are limited, as seawater constitutes most of the available water on the earth. Converting seawater into freshwater via desalination, particularly using low-grade heat, presents a promising solution for sustainable freshwater production. This paper proposes a theoretical and experimental investigation of a thermally driven vacuum desalination system (TDVDS). The primary objective is to demonstrate the system’s ability to produce freshwater when driven by an ultra-low temperature heat source (50 – 70°C), while the heat sink is maintained at 30°C. A mathematical model is developed to predict freshwater production and assess the TDVDS’s working characteristics. An experimental test rig is constructed to provide validation data. The simulated results are validated against experimental data under identical working conditions to demonstrate the model’s accuracy. The TDVDS is found to operate stably and provide acceptable performance, producing freshwater with a thermal efficiency of 54 – 67%. An discrepancy of around 5 – 10 % is observed between simulated and experimental freshwater production and thermal efficiency. Freshwater production increases linearly with distillation time, indicating a constant evaporation rate under steady-state operation. Increased heat source temperature results in higher freshwater production and improved thermal efficiency. The mathematical model proved to be an efficient tool for assessing the system’s working characteristics. The contributions of this work serve as a reference case for further development and practical application of the TDVDS, for which sustainable freshwater is a major achievement.