Waste-heat recovery from a vapor-absorption refrigeration system for a desalination plant

The waste-heat of vapor-absorption refrigeration (VAR) cycles could efficiently power humidification-dehumidification (HDH) desalination systems for freshwater production. The integrated systems reported in the literature relied on water-heated HDH cycles, in which the waste-heat of VAR systems heats the HDH saline water before entering the humidifier. This paper assesses the coupling of an air-heated HDH system with a double-effect (DE) VAR system by circulating the HDH air to cool the absorber and condenser of the DE-VAR system and concurrently driving the HDH system. In addition to less corrosive issues compared to water-heated HDH systems, the proposed air-heated HDH based system can produce higher freshwater and achieve better performance. Under the investigated conditions, the proposed system produces water amounts of about 2100.0 L/h and a cooling effect of 104.0 tons of refrigeration, with a gained output ratio (GOR) of 4.7, coefficient of performance (COP) of 1.2, energy utilization factor (EUF) of 5.9, water cost of 2.5 $/m³, and cooling effect cost of 0.0037 $/kWh. In addition, the suggested integrated system outperforms the standalone air-heated HDH system in terms of water production, GOR, EUF, and water cost reduction by a factor of 2.3, 2.4, 3.0, and 2.4 times, respectively. Compared to a standalone DE-VAR system, the integrated system shows less cooling capacity by about 10.0% but with a significant reduction in the cooling cost by 3.8 times and improved EUF by 4.2 times. Additionally, the present system shows excellent economic feasibility under different salinities.