Experimental study on static flash evaporation characteristics for ethanol solutions under low-pressure conditions

Abstract

In this study, ethanol solution is employed as the working fluid to investigate its flash evaporation characteristics under varying conditions. The experimental parameters include the initial solution concentration (0-30 %), initial solution temperature (50-70 °C), equilibrium pressure in the flash chamber (8-16 kPa), and initial liquid height (15-45 mm). By systematically adjusting these parameters, the variations in solution temperature, non-equilibrium temperature difference (NETD), non-equilibrium fraction (NEF), flash evaporated mass, solution concentration, and cooling rate are comprehensively analyzed. The influence of initial conditions on each parameter is thoroughly examined. The results demonstrate that higher initial solution concentration, greater superheat, and lower liquid height significantly enhance sensible heat release. Specifically, increases in superheat, reductions in liquid height, and elevated initial solution concentrations lead to maximum NEF(t_f) reductions of 16.46 %, 35.7 %, and 21.5 %, respectively, thereby facilitating a more complete and efficient flash evaporation process. Simultaneously, the onset of flashing occurs earlier, with flash time shortened by 11.65 %, 23.4 %, and 37.6 %, respectively. The flash evaporated mass also increases under these conditions. Furthermore, a quantitative model is established to assess the influence of superheat, initial solution concentration, and liquid height on the cooling rate. The model predictions exhibit good agreement with the experimental data, with a maximum relative error ranging from −11.3 % to 4.3 %, confirming the model’s reliability.