Parametric study of an integrated organic rankine/reverse Brayton refrigeration cycle and multiple-effect desalination unit

This study explores the opportunity of a combined cooling, desalination, and power (CCDP) unit that is thermally driven using low-to mid-grade heat input of 1,940 kW_th (enthalpy of vaporization of steam at 200°C and mass flow rate of 1 kg/s). The proposed CCDP system is comprised of a Rankine cycle that partially drives a gas refrigeration cycle by means of shaft work and thermally drives a multiple-effect distillation (MED) unit by harnessing the rejected heat of condenser. Based on our thermodynamic model, the proposed CCDP system is more efficient from an energy-saving viewpoint compared with stand-alone systems that deliver the same services provided if there are ≥8 MED effects (units). Furthermore, the proposed polygeneration system is able to produce nearly 188 kW_e of electrical power output, 116 kW_th of cooling capacity, and 25.6 m³/h of freshwater capacity when water is employed as a working fluid and air as a refrigerant. In addition, the CCDP system attains an exergy efficiency of ≈42% and a primary energy-saving ratio of 28%. Because an organic Rankine cycle is promising for the conversion of low-and mid-grade heat to electricity, various organic working fluids are investigated. The results show that when propane is used instead of water, the freshwater capacity rises by 3.4%.