Thermodynamic analysis of an energy-efficient thermal-desalination based on coupling absorption chiller, freeze and humidification-dehumidification

Abstract

Existing absorption chiller and humidification-dehumidification desalination systems typically utilize lithium bromide-water solutions, limiting cooling temperatures to 5 °C and constraining desalination performance. To overcome these limitations, this study introduces an ammonia-water-based absorption chiller, enabling sub-zero cooling for freeze desalination, which is integrated with HDH desalination to form an efficient hybrid system. In this configuration, cold energy supports both freeze desalination and low-temperature dehumidification, while waste heat from the AC's condenser and absorber enhances seawater humidification. A comprehensive thermodynamic analysis is performed by coupling the ammonia-water absorption chiller, dual seawater flow streams, and the HDH loop. Results indicate that maximizing the ammonia concentration in the AC's strong solution enhances its coefficient of performance to 0.45, significantly improving desalination productivity. The proposed system achieves a combined output of 750 kg/day using 17.1 kW of input heat, with a specific energy consumption of 400 Wh/kg. Key findings recommend maintaining lower generator and absorber temperatures (60 °C and 25 °C, respectively) and optimizing ice recovery ratios to balance freeze and HDH desalination outputs. The results demonstrate that the proposed system significantly outperforms existing AC-HDH designs, offering an efficient solution for hybrid desalination.