MVR系统中离心式蒸汽压缩机与蒸发器的匹配特性研究

Study on matching characteristics of centrifugal vapor compressor and evaporator in MVR system

为了保证机械式蒸汽再压缩(mechanical vapor recompression,MVR)系统的运行经济性和稳定性,对MVR系统中离心式蒸汽压缩机与蒸发器的匹配特性进行研究。针对蒸发器换热系数在新投、工作和结垢工况下的变化,提出了蒸发器运行温阻特性线的概念,并将其与离心式蒸汽压缩机的温升特性线叠加,从而开展离心式蒸汽压缩机与蒸发器的匹配分析。通过分析发现,离心式蒸汽压缩机的设计流量偏大或蒸发器的换热面积过小会导致匹配不足,易发生喘振,从而影响MVR系统的运行稳定性。而离心式蒸汽压缩机的设计流量偏小或蒸发器的换热面积过大会导致匹配过度,致使MVR系统的运行经济性差,甚至可能造成MVR系统无法建立热力自循环。结果表明,离心式蒸汽压缩机在MVR系统启动过程中会出现不稳定的喘振现象,可以通过系统参数的临时调节或采取辅助措施来避开不稳定区。设计时应保证离心式蒸汽压缩机的喘振裕度大于20%,蒸发器换热面积的设计裕度为30%;MVR系统运行时实际蒸发温度与设计温度的偏差应控制在±5℃以内。研究结果可为MVR系统的设计和调试提供参考。

In order to ensure the operation economy and stability of mechanical vapor recompression(MVR) system, the matching characteristics of centrifugal vapor compressor and evaporator in the MVR system were studied. In view of the change of heat transfer coefficient of evaporator under new operation, operation and scaling conditions, the concept of temperature resistance characteristic curve of evaporator operation was put forward, and it was superposed with the temperature rise characteristic curve of centrifugal vapor compressor, so as to carry out matching analysis of centrifugal vapor compressor and evaporator. Through analysis, it was found that the design flow of centrifugal vapor compressor was too large or the heat transfer area of evaporator was too small, which would lead to insufficient matching and easy surge, thus affecting the operation stability of MVR system. However, the design flow of centrifugal vapor compressor was too small or the heat transfer area of evaporator was too large, which led to excessive matching, resulting in poor operating economy of the MVR system, and may even cause the MVR system to be unable to establish thermal self cycle. The results showed that the centrifugal vapor compressor had unstable surge during the startup of MVR system, and the unstable area could be avoided by temporary adjustment of system parameters or by taking auxiliary measures.The surge margin of centrifugal vapor compressor should be more than 20% and the design margin of heat transfer area of evaporator should be 30% during design;the deviation between actual evaporation temperature and design temperature during MVR system operation should be controlled within ±5 ℃.The research results can provide reference for the design and debugging of MVR system.