Investigation of heat pump-driven humidification–dehumidification desalination system with energy recovery option

This paper presents a vapor compression heat pump-driven humidification–dehumidification process with energy recovery option. Two systems with different applications of recovered energy are proposed. System A recovers energy for preheating inlet feed water to the heat pump condenser, while system B recovers energy for preheating the humidifier inlet air. The system performance metrics such as gained output ratio (GOR), recovery ratio (RR), productivity, specific electrical energy consumption (SEEC) and the cost of freshwater production are investigated based on variations in mass flowrate ratios, humidifier effectiveness, seawater temperature, brine heat exchanger effectiveness, unit cost of electricity and expected plant life. The thermo-economic performance of the proposed system is compared with system “C” without energy recovery option. Findings reveal the need to recover thermal energy associated with the discharged brine for humidification and dehumidification desalination system having ineffective/poor component effectiveness, especially the humidifier. The proposed system shows that the cost of freshwater for system C can be reduced by about 15.23% with energy recovery in system A. The GOR of system C is improved by about 23.1%, whereas the RR, productivity and SEEC of system C are improved by about 23.3% each. The conditions at which the energy recover is effective are also shown in the results.