Performance assessment and optimization of a humidification dehumidification (HDH) system driven by absorption-compression heat pump cycle

Abstract

Feasibility investigation of a humidification dehumidification (HDH) desalination system driven by an absorption-compression heat pump cycle (ACHPC) is carried out in this paper. The proposed hybrid desalination system uses both heating capacity of the discharged brine as a waste heat for the ACHPC and mechanical power of the ACHPC for the HDH system. The system's performance is investigated under different optimal design modes, using genetic algorithm (GA) as the most robust tool for optimization. A steady-state mathematical model based on the mass, energy, exergy, and exergoeconomic balance equations for components of the proposed system is developed and the predicted results are validated using the available experimental and numerical data. The results indicated that the proposed hybrid system can produce the maximum freshwater of 0.647 kg/s with the gain output ratio (GOR) and exergy-based GOR (EGOR) of 9.02 and 3.04%, respectively. In this optimal mode, the cost of produced freshwater and specific work consumption (SW) are estimated 7.13 $/l and 262.9, respectively. Furthermore, a comprehensive parametric study is conducted leading to the determination of the proposed system's behavior due to any variation in the key thermodynamic parameters. It is found that the GOR and EGOR can be maximized with the desalination top temperature, desalination mass flowrate ratio, and compression ratio, while the cost of freshwater can be minimized with the absorber terminal temperature difference and compression ratio. At last, multi-variable regression analysis is employed to correlate the main performance criteria of the system with the key thermodynamic parameters.