Performance analysis of heat and mass transfer, thermodynamic and economic of high gravity direct contact evaporation system

Abstract

Based on the problem of low heat and mass transfer efficiency and low heat utilization rate in the process of efficient utilization and treatment of low-grade waste heat, the high gravity direct contact evaporation (HG-DCE) system driven by industrial waste heat is proposed. The heat and mass transfer properties in HG-DCE process were studied by simulated with hot water and air at room temperature, and the thermodynamic and economic properties were further analyzed in detail. Results showed that the evaporation intensity of the HG-DCE system could reach 1523 kg/(m3·h), and the volume heat and mass transfer coefficients could reach 270.77 kW/(m3·°C) and 12.23 kg/(m3·s), respectively. According to the established analysis models of entropy generation and exergy loss, the rule of irreversibility of system was obtained, and the highest exergy efficiency was higher than 90.0 % at the gas-liquid mass ratio of 1:1. Simultaneously, the evaporation heat of system accounted for 40.0 % of the supplied heating enthalpy, and the evaporation cost about 0.094 $/kg could be easily achieved. The perfect performance and advantages of HG-DCE system were further confirmed, which provided a new method for using low grade heat for seawater desalination and wastewater treatment.