Experimental study on productivity intensification of HDH desalination unit utilizing two-stage dehumidification

Abstract

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.

A Novel Humidification Technique Used in Water Desalination Systems Based on the Humidification–Dehumidification Process: Experimentally and Theoretically

“…The proposed theoretical model is related to the spraying atomization method, which was already validated by our previous work [19]. The main results are shown in Figure 6, in terms of the productivity of the desalination unit.…”

“…In the humidification process, the flow of spraying saline water is in parallel with the airflow according to our previous results (El-Maghlany et al [19]), which indicated that the highest humidification effectiveness and productivity were obtained with the parallel spraying system. Therefore, the model of the humidification process is based on a parallel-flow heat exchange between the sprayed saline water and the airflow.…”

“…The basic experimental desalination system was previously proposed by our research group El-Maghlany et al [19]. The system is based on a humidification-dehumidification technique consisting of three main components: a humidifier, a dehumidifier, and a heat pump.…”

“…The distillate flow rate is estimated from a mass balance, taking into account the difference in water content among air inlet and outlet from the dehumidification process, where distilled water is accumulated. This distillation rate is defined as presented by [19]:…”

“…They analyzed different flow directions of the spray water and observed that the highest evaporation rate was achieved by the cross-flow spraying system. Later, El-Maghlany et al [19] improved the desalination system of Hegazy et al [18], increasing the productivity using a parallel spraying flow.…”