Energy and exergy analyses of circulatory flash evaporation of aqueous NaCl solution

In present study, an experimental system for circulatory flash evaporation was designed and built. Energy and exergy analyses of circulatory flash process were carried out. Basing on the first law of thermodynamics, the gained output ratio of circulatory flash evaporation (GORCFE) was defined as an energy ratio between latent heat carried away by flash steam and input excess energy of working fluids. The performance ratio of circulatory flash evaporation (PRCFE) was defined as the mass flow rate divided by exergy destruction rate. The Effects of main factors, namely, superheat degree, circulating flow rates, equilibrium pressure, initial water level and salinity on GORCFE and PRCFE were studied. Results suggested that GORCFE decreased rapidly at the initial stage, then increased with the increase of superheat degree and became flat eventually. The optimal superheat degree was determined wherein the maximum performance ratio was reached. According to the comparison of gained output ratio and performance ratio, the maximum performance ratio was obtained when gained output ratio was great enough and temperature difference was minimal.