Investigation of the effect of the top and the bottom temperatures on the performance of humidification dehumidification desalination systems

摘要

Humidification dehumidification process is an attractive small scale water desalination technique in which desalinated water is produced by mimicking the nature's water cycle. Various modifications to the basic HDH system can be vital in improving the productivity and reducing the production cost of the fresh water. In this study, a closed-air-open-water water-heated (CAOW-WH) cycle and a closed-air-open-water air-heated (CAOW-AH) cycle are modeled and optimized. Effects of mass flow ratio, humidifier and dehumidifier effectiveness, relative humidity, top and bottom temperatures (main concern of study) on the gain output ratio (GOR), the recovery ratio (RR), entropy generation in the system have been analyzed and presented. It has been observed that an optimal mass flow ratio exists for both the cycles, which maximizes the GOR of the system. Moreover, effectiveness of the humidifier and the dehumidifier is an important parameter, which determines the productivity of the systems. Furthermore, a higher GOR can be obtained at low T_(min) and high T_(max) and at high T_(min) and low T_(max) for systems heated by a water heater, whereas the GOR of the air heated HDH system increases with increasing both the T_(min) and the T_(max) for values of humidifier and dehumidifier effectiveness of 0.8. This study provide extended design charts for building an optimum HDH system to produce a pre-determined rate of desalinated water.