【作者】 史雪菲；

【导师】 张华；

【作者基本信息】 上海理工大学 ， 制冷及低温工程， 2013， 硕士

【摘要】 不论是在客观存在的大自然，还是在主观控制的日常生活和生产过程中，凡是在有换热设备存在的情况下，都会有污垢形成的现象。污垢的存在不仅使换热设备的换热效率下降，浪费能源、资源，产生巨大经济损失，而且使很多能源高效利用的技术方法失去可行性，如低品位能源的利用、高效强化换热技术等。这就使得我们在对换热设备进行设计或优化时，不仅仅要考虑污垢在流体中的形成、扩散和在换热表面的粘附等因素，还要考虑生长过程，从而寻求抑制和防止污垢形成的方法，达到强化换热、高效节能的目的。本实验采用静态沉淀反应法，在无流体流动的扰动和重力作用下，将换热设备常用的四种金属材料制备成实验挂片垂直悬挂于碳酸钙过饱和溶液中，来研究换热材料(紫铜、黄铜、不锈钢304和不锈钢316)和流体性质(溶液温度，碳酸钙浓度，溶液pH值)对碳酸钙析晶垢微观形貌的影响。通过实验，得到了大量表征CaCO3析晶垢的生长特性的数据，包括换热表面结垢量、CaCO3的晶型、晶体尺寸以及析晶垢的诱导期等。实验结果表明：当流体中碳酸钙处于过饱和状态时，系统中成垢粒子其中一部分通过扩散和吸附沉积在换热表面上而异相成核以及晶核生长。在相同的工况下，结垢量最小的是黄铜，其次是紫铜，不锈钢316，表面结垢量最大的是不锈钢304；溶液性质不仅会对换热表面碳酸钙垢的种类产生影响，而且能影响到生成晶粒尺寸，进而影响换热表面沉积析晶垢的结垢量。随着溶液温度的升高，结垢量和晶体的尺寸均会有减小的趋向，并且文石晶型出现的比例增大。随着pH值的升高，结垢量和晶体的尺寸有减小的趋势，碳酸钙的主要晶型是稳定的方解石。随着碳酸钙浓度的增大，结垢量增大，但晶体的尺寸减小，碳酸钙的主要晶型是稳态的方解石。更多还原

【Abstract】 Fouling in heat exchange equipments is an extraodinary abnormal phenomena．Itlies in many fields, such as in nature, in our daily life and widely in industrial processes.It not only reduces the heat transfer efficiency of heat transfer equipments, but alsowastes energy and resources, and even makes the technologies and methods ofhigh-efficient energy use infeasible.So the processes and characteristics of the foulingform and diffusion in fluid, then adhesion and growth on heat transfer surface must betaken into consideration when designing the heat equipments in order to inhibit andmitigate fouling,thereby,enhance the heat transfer and save energy with high efficient．Without fluid flow and gravitational settling influence, the experiment adopts staticprecipitation reaction method, the four common used materials was prepared as couponswhich was vertical suspended in the supersaturated calcium carbonate solution,so wecan study the effect of substrate and liquid properties on precipitation characteristic ofCaCO3crystal. The experiment adopts four substrates: copper, brass stainless steel304and316.The fluid propertis includes the temperature, concentration and pH of solution.We got lots of data that characterize growth characteristic of CaCO3crystal, includingfouling mass, crystal morphology, size and induction period of CaCO3fouling crystal.Results of the experiment indicated that when the fluid is supersaturated, a part of scaleions in system precipitate on the heat transfer surface by diffusion and adhesion, andthen the process of heterogeneous nucleation and crystal growth.Under the samecondition,the fouling mass on stainless steel304is the biggest,and then stainless steel316, copper,and the brass is smallest.The fluid properties not only influence the crystalmorphology,but also the size of crystal,and therefor affect the fouling mass. Withtemperatures rising, the fouling mass and size of crystal has the tendency of reduction,and the proportion of aragonite increases. The fouling mass and size of crystal has thetendency of reduction as the temperature rises, the main crysyal morphology iscalcite.When the concentration of CaCO3rises, the fouling mass increases, but the sizeof crystal decreases, and calcite is the main morphology of CaCO3crystal.更多还原