水平管降膜蒸发管外海水成垢过程实验研究
发布时间：2019-02-14 08:17
【摘要】：海水作为复杂稀溶液,在传热表面的成垢过程受多方面因素影响。海水淡化装置中蒸发器内部传热管表面的结垢现象是影响装置传热效率和限制盐水顶温的主要因素,传热表面成垢过程的研究对减少或延缓传热面成垢具有指导意义。 本文设计搭建了常压下水平管降膜蒸发传热管外成垢研究实验台,选用海水作为实验流体,模拟实际工程中的运行工况进行实验。实验选取喷淋密度分别为0.03kg/m·s、0.06kg/m·s和0.08kg/m·s,传热管表面温度分别为50℃、53℃、60℃、63℃、70℃和73℃,海水浓度分别为3.5%和7%进行研究。通过精密天平称量传热管增重等得到了管表面垢样生长曲线,对比分析喷淋密度、传热管表面温度和海水浓度对传热表面结垢诱导期、结垢速率、达到结垢渐进值的时间和最终结垢渐进值的影响。实验使用DSA接触角测量仪测量了3FL-铝合金管、铝黄铜管和钛管三种材料的接触角,以此计算三种管材的表面能,对比相同工况下三种传热管表面垢样生长曲线,计算结果与实验结果一致,表面能较低的材料抗垢性能好。 利用非抑制型离子色谱分析仪测量了实验海水中各离子浓度,分析可能的结垢产物主要为CaCO3和Mg(OH)2。使用扫描电镜SEM和能量色散X射线分光计(EDXS)测试了实验后传热管的微观形貌,分析了不同喷淋密度、传热管表面温度和海水浓度下管表面的微观形貌,喷淋密度大的情况下表面产物中因冲蚀而含有少量铝元素；传热管表面温度影响结垢产物中Mg(OH)2的含量,温度较低时管表面垢层中主要以霰石状CaCO3为主,随温度升高Mg(OH)2含量逐渐升高,70℃以后Mg(OH)2成为主要成分；海水浓度对结垢产物的影响为随海水浓度升高管表面附着的垢样颗粒增多。同一运行条件下分析不同时间段内管表面垢的微观形貌,发现发生钙镁沉积时,首先是Mg(OH)2薄片附着在传热管外表面,并形成团簇状不断生长和发展,霰石状CaCO3晶体在此基础上积聚生长并逐渐覆满Mg(OH)2垢层的缝隙,而同时Mg(OH)2也在沉积和生长,CaCO3和Mg(OH)2相互作用共同生长最终形成稳定垢层。
[Abstract]:As a complex dilute solution, the fouling process of seawater on heat transfer surface is affected by many factors. The fouling phenomenon on the surface of the evaporator in seawater desalination plant is the main factor that affects the heat transfer efficiency and limits the top temperature of salt water. The study of the fouling process on the heat transfer surface is of guiding significance to reduce or delay the fouling on the heat transfer surface. In this paper, an experimental platform for the study of scale formation outside the horizontal tube falling film evaporative heat transfer tube under normal pressure is designed and built. Seawater is selected as the experimental fluid to simulate the operation conditions of the actual engineering. The spray density is 0.06 kg / s and 0.08kg/m s, respectively. The surface temperature of heat transfer tube is 50 鈩，
本文编号：2422019
[Abstract]:As a complex dilute solution, the fouling process of seawater on heat transfer surface is affected by many factors. The fouling phenomenon on the surface of the evaporator in seawater desalination plant is the main factor that affects the heat transfer efficiency and limits the top temperature of salt water. The study of the fouling process on the heat transfer surface is of guiding significance to reduce or delay the fouling on the heat transfer surface. In this paper, an experimental platform for the study of scale formation outside the horizontal tube falling film evaporative heat transfer tube under normal pressure is designed and built. Seawater is selected as the experimental fluid to simulate the operation conditions of the actual engineering. The spray density is 0.06 kg / s and 0.08kg/m s, respectively. The surface temperature of heat transfer tube is 50 鈩，
本文编号：2422019
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