Design and experimental investigation of a heat pump-assisted double-effect evaporation system using ethanol as the working fluid

Abstract

Most existing studies on the evaporation process of ethanol solutions focus on the microscopic scale, with a lack of research on design calculation methods and operational characteristics targeting macroscopic systems. This study proposes a heat pump-assisted double-effect evaporation concentration system using ethanol solution as the working fluid, develops a mathematical model integrating heat balance, mass balance, phase equilibrium, and heat transfer correlations, and presents an iterative solution method based on the average evaporation capacity of the system as the criterion. An experimental platform was designed and constructed, and the experimental results verified the accuracy of the model: the instantaneous evaporation rate of the system decreased by 62.06% during the stable operation stage, with an average evaporation rate of 3956.56 kg/h, and the deviation from the simulation value was approximately 2.02%. The design parameters of each heat exchanger in the system met the actual operation requirements. Under the intervention of the control logic, the heat transfer efficiency of the system decreased, and the heat pump compressor operated at a moderate pressure ratio of about 2.5, with the system coefficient of performance (COP) exceeding 4.65, indicating that the system operation efficiency exceeded expectations. This work presents a robust and energy-efficient solution for concentrating heat-sensitive organic solvents, with strong industrial application potential.