a b s t r a c tIn this study, an experimental investigation is performed on a two-stage dehumidification water desalination system utilizing a humidification-dehumidification process that has been accomplished using heat pump. The air is heated by means of heat pump condenser to increase its ability to efficiently humidify, while condensation takes place at the heat pump evaporator section. Additionally, in order to enhance the dehumidification efficiency a per-dehumidification process was performed to the humid air, using a cooling water heat exchanger and that was utilized prior to the evaporator. Raw water is sprayed at a constant flow rate of 2.2 L/min using cross, counter, and parallel flow spraying systems. The mass flow ratio between water and air is varied from 0.091 to 0.14 via the change in the air flow rate. The inlet cooling water temperature of the heat exchanger dehumidifier is changed from 15 to 25°C. Results of the experiments showed that the parallel flow spraying system has the highest productivity in both single and two stage dehumidification with a productivity of 2.34 L/h and 4.44 L/h respectively. The results show an extra ordinary influence of the heat exchanger on productivity intensification. The maximum specific productivity including all power consumption elements is 2.02 L/kWh.

In this paper, an experimental and theoretical investigation is performed on a novel water desalination system based on a humidification–dehumidification technique using a heat pump. An ultrasonic water atomizer is used in the humidification process in order to improve the humidification system. In addition to that, a new configuration is employed in the humidification process (hybrid atomization system), which combines the traditional spraying atomization system and the ultrasonic water atomizer. The new humidification system performance is investigated and compared with the spraying water atomizer system in terms of humidification effectiveness and freshwater productivity. The results show that the ultrasonic water atomizer has enhanced and improved humidification effectiveness, and consequently, the productivity of freshwater. The maximum humidification effectiveness and productivity achieved by the ultrasonic water atomizer are 94.9% and 4.9 kg/h, respectively, meaning an increase of 25.2% and 18.8%, compared to the traditional spraying atomization system. The hybrid system increases humidification effectiveness and productivity by 3.8% and 8.2%, respectively, in comparison with the stand-alone ultrasonic water atomizer. A cost analysis was also carried out in this paper in order to perform an economic comparison of different humidification processes (spraying, ultrasonic; and hybrid atomization systems). The minimum production cost of one liter of freshwater amounts to $0.0311 with the spraying system, $0.0251 with the ultrasonic system, and $0.0250 with the hybrid atomization system. These results reveal the profitability of the new configuration.

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