Freshwater and cooling production via integration of an ethane ejector expander transcritical refrigeration cycle and a humidification-dehumidification unit

Abstract

Despite the fact that humidification-dehumidification (HDH) desalination systems can be driven by various renewable or waste heat energies, many of the available renewable technologies are expensive in some parts of the globe. Hence, proposing and developing high-efficient mechanical-based HDH units can be an encouraging alternative which is more highlighted in recent investigations. In pursuance of this objective, three innovative mechanical-driven HDH units are simulated and the results are compared with each other. The simulated hybrid desalination system consists of a HDH unit and an ethane ejector expander transcritical refrigeration cycle (ethane-EETRC). The simulated hybrid systems can produce freshwater and cooling load, simultaneously. The main difference between each system is the proposal of using two-stage compression and humidification-dehumidification processes at different scenarios. The results display that a maximum freshwater of 17.3 m3/day can be achieved when a two-stage HDH unit is used with a single-stage compression ethane-EETRC, resulting in CGOR (cogeneration-based gain output ratio), exergy efficiency, and cooling load of 6.56, 17.13% and146.9 kW, respectively. However, to achieve as high cooling load as 161.8 kW - with CGOR, exergy efficiency, and freshwater of 5.19, 18.1% and 11.97 m3/day, respectively - a configuration with two HDH units coupled with a two-stage ethane-EETRC is highly commendable. Moreover, the cost evaluation results indicated that unit overall cost of the product (UOCP) of the hybrid system with two HDH units integrated with a two-stage ethane-EETRC and the hybrid set-up with a two-stage HDH unit integrated with a single-stage ethane-EETRC is calculated 8.2 $/GJ and 8.93 $/GJ, respectively. At last, an intensive parametric evaluation of some influential parameters is presented.