【作者】 王红；

【导师】 刘明言；

【作者基本信息】 天津大学 ， 化学工程， 2006， 硕士

【摘要】 在实际沸腾换热过程中,换热面上很容易生成污垢。污垢的存在,会使换热器的传热效能降低,流动阻力增大,能耗和物耗增加,并带来严重的安全隐患。研究表明,污垢的形成和污垢与传热表面之间的附着力有关,而附着力的大小和材料表面的表面能密切相关,表面的表面能越大,附着力就越高。因此降低传热表面的表面能可在一定程度上使附着力减少,从而降低壁面污垢的形成概率。通过表面处理技术对换热表面进行表面处理,可降低传热表面的表面能。由于采用表面处理技术对传热表面实施表面处理,既由于所处理之表面厚度极薄,不会对换热表面热阻产生不良影响,又可达到降低表面能的效果,故本文作者在对换热表面上污垢形成的机理及目前的研究现状进行综合分析的基础上,采用液相沉积法对传热表面进行处理,对所获得的处理表面的表面能、接触角、薄膜厚度等进行了测量和表征,得到了薄膜厚度和表面能的关系。研究结果表明对加热面进行一定的表面处理,可降低表面的表面能,并且薄膜处理厚度越薄,表面能越低。在本文所用的流动沸腾实验装置中,应用自行开发的数据微机自动测试采集系统,对表面有不同厚度二氧化钛薄膜的加热面的传热和抗垢性能进行了研究。研究结果表明,在传热实验中,与未处理表面相比,当处理薄膜厚度为1587nm时,加热表面传热系数值是未经过表面处理表面传热系数值的106%～114%,当薄膜厚度为141nm时,加热表面的传热系数值是未处理表面传热系数值的110%～144%;在防垢实验中,薄膜厚度为141nm加热表面的传热系数随时间几乎不发生变化,薄膜厚度为1587nm加热表面的薄膜厚度的传热系数随时间稍稍有所下降,而未经过表面处理的表面的传热系数随着时间的变化迅速下降。经过处理的加热面的传热和防垢效果优于未经过表面处理的表面,并且薄膜越薄的表面的传热和防垢效果越好。这是由于表面经过表面处理,使得加热表面的表面能降低,从而减小了表面的润湿性,污垢与表面的附着力变小,因此传热和防垢效果好。此外,在本文中还考察了操作参数如热通量、主体流速等对传热和防垢的影响。随着热通量的增加、主体流速的增加,传热系数也增加。更多还原

【Abstract】 The fouling easily is formed on the heat transfer surface in the boiling process. The efficiency of heat transfer will fall down while the consumption of energy and material will increase for the existence of fouling.Research shows that the formation of fouling is related with the adhesion between fouling and heat transfer surface .While the adhesion is related with the surface energy, the bigger the surface energy, the bigger the adhesion. So if reduce the surface energy, it will reduce the formation of the fouling on the heat transfer surface. Treating the heat transfer surface with surface treatment technology can reduce the surface energy. In this paper, the mechanics of fouling formation are summarized; The heating surface is treated by using liquid deposition. That is used to the research of anti-fouling. The surface energy, contact angle of the treated surface and thin film thickness are measured and attributed to get the relationship between the thin film thickness and the surface energy. The results show that as the heating surfaces are treated properly so to reduce the surface energy.The thinner the layer, the lower the surface energy. The research on heat transfer and fouling are made by flow boiling device, the process of heat transfer and fouling formation on the different heating surface are studied by automatic data acquisition system. The experiment results show that when the thin film thickness is 1587nm, as compared with the untreated heating surface its heat transfer coefficient is 6%-14% bigger than the untreated surface, when the thin film thickness is 141nm, as compared with the untreated surface its heat transfer coefficient is 10%~44% bigger than the untreated surface. In the fouling experiment, when the thin film thickness is 141nm, its heat transfer coefficient almost dose not change within a certain time.When the thin film thickness is 1587nm, its heat transfer coefficient drops a little within a certain time, while the heat transfer coefficient of the untreated heating surface drops quickly within the operating time. Heating surface is treated by liquid deposition, its effect of heat transfer enhancement and anti-fouling is good. The experiment results also show that the thinner the layer, the better the effect. The surface energy is reduced so to reduce the wetting effect of heating surface, where upon the fouling can not easily is formed on the surface.更多还原