板式换热器运行参数影响结垢的权重及机理分析

对比实验研究了不同工况(冷却水入口温度、流速)下板式换热器松花江冷却水污垢特性,将污垢热阻与这两种运行参数进行了灰色关联分析,并就运行参数对其结垢的影响逐一作了机理分析。结果表明:板内污垢为析晶、生物等污垢共同组成的混合污垢,呈渐近型增长且无诱导期;冷水入口温度比流速更影响结垢;结垢机理为:冷水入口温度的提升,强化了污垢的附着、削弱了污垢层的脱除,结垢由对流传质和表面反应共同控制,低流速以对流传质为主,高流速以表面反应为主;流速对污垢剥蚀的影响强于沉积,故流速增加,净结垢量减少,污垢增长率减小。

Analysis of operating parameters' effect weights and mechanisms on fouling of the plate heat exchanger

The fouling characteristics of Songhua River cooling water in a plate heat exchanger in different operating conditions were investigated through the contrast experiments.And then,based on Grey Relational Analysis,fouling resistances and operating parameters were contacted.Besides,the operating parameters' effect mechanisms were analyzed one by one.The result shows that the fouling,whose type is the composite fouling consisting of crystallization,microbiology fouling and so on,has an asymptotic growth rule and no induce period;and it is the inlet temperature that influences the fouling greater than the flow velocity.At last,the fouling mechanisms are obtained that the rise of inlet temperature of cooling water enhances the attachment of fouling to the wall region and weakens the detachment of fouling layer from the heat transfer surface,and the fouling is controlled by both convective mass transfer which is the main at low flow velocity and surface reaction which is at high one;as a result of flow velocity's greater effect on removal than deposition of fouling,both the net amount of fouling and fouling growth rate decreases when the flow velocity increases.