换热器表面污垢形成过程模拟研究

发布时间：2018-03-21 00:32

本文选题：结晶型污垢　切入点：阻垢　出处：《苏州大学》2015年硕士论文　论文类型：学位论文

【摘要】：换热器表面形成的污垢会引起大量的能源浪费和成本消耗,众多研究者努力探索污垢生长过程的机理以及减少污垢的方法。在过去几十年的研究中,人们发现可以通过调节换热器表面的物理化学特性,溶液化学成分和操作条件等抑制或阻止污垢生长,但这通常需要大量、漫长的实验过程。如果能有一个的数学模型准确模拟污垢生长过程,将会简化污垢研究的复杂过程。从模型中能够得到全面的三维动态数据,这些数据一般很难通过实验手段获得,这将有助于理解污垢生长过程的机理。本文的研究内容主要包括如下两个方面:1.用一种新型CFD模型模拟结晶型污垢的生长过程。方法是把连续的污垢生长过程用一系列的稳态过程代替。这种特殊的模拟方法涉及连续流体的质量守恒、动量守恒和热量守恒。该模型还考虑了污垢层的变化与流体流动、污垢生长之间的相互作用。模拟研究硫酸钙在换热器表面的污垢生长,模拟数据与实验数据的高度吻合,证明了该模拟的有效性。另外,该模型还定量研究了溶液化学成分和操作条件等对污垢热阻的影响。该模型作为一种有效的工具可被用于探索有效减少污垢甚至消除污垢的策略。2.通过X射线衍射或扫描电镜等设备可以检测到换热器表面的污垢有着复杂的结构。污垢层的结构同时也决定了流体的流动状态,污垢生长动力学和传热过程。然而,到目前为止,研究污垢生长过程的模型都建立在把换热器表面的污垢层看做是流体不能流过的、具有均一孔隙率结构的基础上。为了定量计算污垢层的结构对污垢生长的影响,这一部分研究了四种代表性污垢层的结构:流体不能流过的、均一的孔隙结构(简称Ho Im);流体不能流过的、不均一的孔隙结构(简称He Im);流体能流过的、均一的孔隙结构(简称Ho Pe);流体能流过的、不均一的孔隙结构(简称He Pe)。在相同的操作条件下,这四种模型表现出在流体流动速率、温度分布和污垢热阻方面的明显不同。从四种模型的不同结果可以得出的结论是,研究换热器表面污垢生长过程的数学模型应该把污垢层的结构考虑进去,而最符合实际的污垢层的结构是流体能流过的、不均一的孔隙结构。
[Abstract]:Fouling formed on the surface of heat exchangers can lead to a large amount of energy waste and cost consumption. Many researchers have tried to explore the mechanism of fouling growth and methods to reduce fouling. It has been found that dirt growth can be inhibited or prevented by regulating the physical and chemical properties of the surface of the heat exchanger, the chemical composition of the solution and the operating conditions. A long experimental process. If there is a mathematical model to accurately simulate the fouling growth process, it will simplify the complex process of fouling research. These data are generally difficult to obtain experimentally, This will help to understand the mechanism of fouling growth process. The main contents of this paper are as follows: 1. A new CFD model is used to simulate the growth process of crystallized fouling. Instead of a series of steady-state processes, this particular method of simulation involves the conservation of mass in a continuous fluid. Momentum conservation and heat conservation. The model also takes into account the interaction between the variation of fouling layer and fluid flow and fouling growth. The simulated study on the fouling growth of calcium sulfate on the surface of heat exchanger is highly consistent with the experimental data. The validity of the simulation is proved. The model also quantitatively studies the effects of solution chemical composition and operating conditions on fouling thermal resistance. As an effective tool, the model can be used to explore strategies to effectively reduce and even eliminate fouling. The structure of the fouling layer also determines the flow state of the fluid, and the structure of the fouling layer can be detected by means of a projector or a scanning electron microscope to detect the complex structure of the fouling on the surface of the heat exchanger. Fouling growth dynamics and heat transfer processes. However, so far, models of fouling growth have been based on treating the fouling layer on the surface of the heat exchanger as a fluid that cannot flow through. On the basis of homogeneous porosity structure, in order to quantitatively calculate the influence of fouling layer structure on fouling growth, this part studies the structure of four representative fouling layers: fluid can not flow through, Homogeneous pore structure (Ho Iman for short; fluid impassable, heterogeneous pore structure for short; fluid flow, homogeneous pore structure; fluid flow, Under the same operating conditions, the four models show significant differences in fluid flow rate, temperature distribution and fouling thermal resistance. The structure of the fouling layer should be taken into account in the mathematical model of the fouling growth process on the surface of the heat exchanger.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.5

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