Thermodynamic study on an enhanced humidification-dehumidification solar desalination system with weakly compressed air and internal heat recovery

• Published in: Energy conversion and management Vol. 181; pp. 68 - 79
• Main Authors: Xu, H., Sun, X.Y., Dai, Y.J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2019; Elsevier Science Ltd
• Subjects: Compressed air; Compression; Condensates; Dehumidification; Dependence; Desalination; Drinkable water; Drinking water; Energy consumption; Equalization; Evaporation; Fresh water; Freshwater environments; Heat; Heat exchangers; Heat pumps; Heat recovery; Heat recovery systems; Heat sources; Humidification; Humidification-dehumidification (HDH); Mechanical vapor compression; Moist air; Seawater; Solar energy; Spraying; Temperature effects; Vapors; Moist air; Drinkable water; Humidification-dehumidification (HDH); Heat recovery
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2018.11.073

•A novel enhanced HDH with weakly compressed air and internal heat recovery is proposed.•Additional heat is no more required benefited from the evaporative-condenser.•Cooling water is no need any longer in comparison with traditional HDH process.•The latent heat of condensation can be lossless recycled by the redesigned evaporative-condenser. Humidification-dehumidification (HDH) process has proved to be a promising technology for obtaining drinkable fresh water. Traditional HDH process exhibits limitations in steady working due to the dependence in the stability of heat and cold sources. A combination of heat pump and HDH has been proposed to solve effectively above challenge. However, the energy equalization between heat source and cold source must be guaranteed to maintain the continuing water production. A novel enhanced HDH method with weakly compressed air and internal heat recovery based on traditional mechanical vapor compression is therefore developed, in which moist air instead of vapor is used as the work fluid. Solar energy is required only for the system start-up, and cooling seawater and additional heat sources are no longer needed during steady operation stage. Meanwhile, the restrictions of evaporation and condensation temperature in the HDH process driven by heat pump can also be completely solved. It is found that the system performance can be significantly improved by increasing spraying seawater temperature. When the spraying seawater temperature is 70 °C, the maximum specific energy consumption and gained-out-ratio (GOR) are 18.35 kg/kWh and 12.24 respectively, and GOR is much larger than that of tradition HDH process (normally less than 6) driven by heat pump or solar energy. This new approach provides the possibility for high-efficient, steady and small-scale drinkable water production.