This paper proposes a parallel-connected double-effect mechanical vapor recompression (MVR) evaporation crystallization system, which combines the falling film evaporator with the forced circulation evaporator. With the purpose of treating high salinity wastewater, the circulation process of the system was designed and mathematical models were established according to the mass and energy balance as well as thermodynamic properties in the heat transfer process. Model calculation was conducted using 5% sodium sulfate solution, based on which the effects of evaporation temperature, feed concentration, and temperature difference between saturated boiling solution and condensate on the system performance were analyzed by a parametric study. The results showed that the optimal values of evaporation temperature and saturation temperature difference could be determined based on a trade-off between power consumption and heat transfer area. After that, the performance of the proposed system was compared with that of a traditional multi-effect evaporation crystallization system, and it was revealed that the coefficient of performance (COP) and exergy efficiency of the proposed system were 21.4 and 49.1%, respectively, 82.2% and 51.5% higher than those of the traditional system under the same working condition. Meanwhile, the exergy destruction of the proposed system was 24.7% lower than that of the traditional system, indicating that the new system performs better regarding energy saving and thermodynamic perfection.

本文提出了一种并联连接的双效机械蒸汽压缩（MVR）蒸发结晶系统，该系统将降膜蒸发器与强制循环蒸发器结合在一起。为了处理高盐度废水，设计了系统的循环过程，并根据传热过程中的质量和能量平衡以及热力学性质，建立了数学模型。使用5％硫酸钠溶液进行模型计算，然后通过参数研究分析蒸发温度，进料浓度以及饱和沸腾溶液和冷凝液之间的温差对系统性能的影响。结果表明，可以根据功耗与传热面积之间的权衡确定蒸发温度和饱和温差的最佳值。之后，将所提出的系统的性能与传统的多效蒸发结晶系统进行了比较，结果表明，所提出的系统的性能系数（COP）和火用效率分别为21.4％和49.1％，在相同的工作条件下，分别比传统系统高82.2％和51.5％。同时，拟议系统的火用破坏比传统系统低24.7％，这表明新系统在节能和热力学完善方面表现更好。