海水中动态污垢组成及影响因素的实验研究

Experimental Study on Composition and Influencing Factors for Dynamic Fouling of Seawater

海水冷却水有诸多优势,但是存在结垢的弊端。本文搭建了一套海水动态结垢实验装置;通过污垢热阻的变化来表征加热管外表面污垢结垢量的变化,并使用X射线衍射(X-ray Diffraction,XRD)、扫描电镜(Scanning Electron Microscope,SEM)和X射线能谱(Energy Dispersive X-Ray,EDX)法对海水动态污垢进行物相与形态分析;通过实验研究分析热流密度、Re数、进口温度和不同材料对海水结垢的影响。结果发现,动态海水在不锈钢表面形成污垢的主要成分是水合氢氧化镁铝;最长诱导期出现的工况是进口温度为50℃,Re数为1,600,热流密度为1×10~5 W/m^2;100 h内1×10~5 W/m^2热流密度下的平均热阻是0.5×10~5 W/m^2的1.93倍;Re数为6,283的海水污垢热阻大于Re数为1,600的海水污垢热阻;随着海水流体温度升高,结垢量下降;铜管的抗垢性能优于不锈钢管。

There are many advantages of seawater used as cooling water,but there are still some disadvantages of fouling.An experimental apparatus for testing seawater dynamic fouling was built in this paper.The change of fouling amount on the outer surface of heating pipe was characterized by the change of fouling resistance.The phase and morphology of seawater dynamic fouling were analyzed by XRD(X-ray Diffraction),SEM(Scanning Electron Microscope)and EDX(Energy Dispersive X-Ray).It was also studied by experiments about the effects of heat flux,Re number,inlet temperature and different materials on seawater fouling.The results show that,the magnesium hydroxide hydrate is the main constituent of fouling on the surface of stainless steel;the working conditions of the longest induction are the inlet temperature of50℃,the Re number of1,600,and the heat flux of1×105W/m2;the average fouling resistance within100hours at heat flux of1×105W/m2is1.93times as that at heat flux of0.5×105W/m2;the fouling resistance of seawater with Re number of6,283is bigger than that with Re number of1,600;with the increase of the seawater temperature,the amount of scaling decreases;the scale resistance of copper pipe is better than that of stainless steel pipe.