新型纵流壳程换热器夹套式变截面导流筒流场分析与结构优化

【作者】 夏立荣；

【导师】 董其伍； 刘敏珊；

【作者基本信息】 郑州大学 ， 化工过程机械， 2004， 硕士

【摘要】 对换热器中的流体流动与传热过程进行分析与研究有助于开发可靠、高效、经济的换热器结构。传统的换热器研究多采用实验方法来进行，但由于实验方法所固有的实验费用高、周期长、限制多、模型变换复杂及无法得到细观信息等不足，使得其难以跟得上换热器研究、发展的需要。而随着当前计算流体力学、计算传热学及计算机软硬件技术的不断提高，使用数值模拟方法对换热器进行分析与研究已成为可能。随着数值模拟方法的不断投入使用，越来越多的人认识到数值分析是一个节省投资、减少浪费、方便可行的途径，现在已有越来越多的学者使用该方法进行科学研究。 对高效节能纵流壳程换热器的进一步深入研究，是当前的一个重要课题。本中心在研究纵流壳程换热器设备总体结构的基础上进一步对其进行结构优化，开发出了由杆圈(杆栅、圈)支撑、变截面导流筒与夹套三元件组合的新结构——夹套式变截面导流筒折流杆换热器(国家专利：ZL91219300X)。工业实际应用证明：该新型纵流壳程换热器的传热效率高，与传统折流板换热器相比，其综合指标α／△_p提高了50％左右，而设备重量减轻了20％～40％。目前，该新型纵流壳程换热器已广泛应用于生产实践中，并取得了较大的经济效益与社会效益。 导流筒装置是为强化管壳式换热器传热效率、改进壳程结构而开发出的一种新型结构。设置导流筒不仅可以防止入口处高速流体对管束的直接冲击，并且可以使得壳程流体达到较均匀分布，从而使壳程进口段管束的传热面得到充分利用，并起到减少传热死区及防止进口段可能会出现的流体振动的作用。鉴于传统的导流筒装置结构的复杂性，本中心顺应工业发展需要而开发出的夹套式变截面导流筒装置则从结构上大大简化了传统的导流筒结构。该装置采用变截面结构，使得导流筒成斜口形状，从而能够保证流体沿周向均匀进入壳体。同时这种结构还可以克服等长圆筒形导流装置所存在的介质进入壳程时流体阻力不同的缺点，使大部分介质进入管束间的流体阻力相同，而不是只从接口附近直接进入壳体内。目前，斜口形导流筒的高、低端的长度等结构参数尚且没有标准可依，但有一点可以肯定，就是高端处必须有足够的高度以遮挡住进口端处。正是由于该类郑州大学硕士学位论文导流筒在工业中应用日渐广泛，因此尽可能确定该类导流装置的结构参数、优化该结构，已成为这类问题的研究重点。 本文采用数值模拟方法对该新型纵流壳程换热器的新型流体均布装置—变截面导流筒装置内的流体流动情况进行了计算、分析与比较，从而根据其内部流体的流动情况来对其结构做进一步优化设计。 本论文的主要工作和创新点如下: 1.本文首次实现了新型纵流壳程换热器变截面导流装置内的三维流体流动数值模拟计算，该工作在前人的工作中未见文献报道。 2.本文应用大型通用商用CFD软件—FLUENT软件研究了新型纵流壳程换热器变截面导流筒装置内的流体流动特性，获得了采用实验方法无法获得的流体流动的细观信息。 3.本文分析了新型纵流壳程换热器变截面导流筒装置中各结构参数的变化对其内部流体流动均布性的影响，得出导流筒的结构参数与壳程内筒进口处流体流动状况的相应关系，从而便于对导流装置内流体流动状况进行深入细致的了解，同时也为变截面导流筒的结构设计提供了一定的依据。利用数值模拟方法来对新型纵流壳程换热器的变截面导流筒内的流动状况进行分析，进而得出其结构参数对流体流动状况的影响关系未见文献报道。 4.本文对数值模拟的结果处理采用图形与统计计算相结合的方式表达。对模拟结果采用图形方法表示有利于读者对模拟结果的直观、清晰、定性的理解;而采用统计计算的方法来表示则便于读者对模拟结果定量的分析比较，便于对模拟结果进行总结、归纳，得出一定的数值关系。采用FLUENT软件计算的模拟结果往往是用图形的方式来表达的，本文采用的图形与数值统计相结合的结果表达方法及评价标准既保留了图形表达的直观性，又兼顾了定量分析的客观准确性，这点在相关的工作中少见报道。 5.本文在建模过程中没有因为模型几何形状比较复杂而一律采用一般网格划分中常用的混合型非结构网格。这种网格虽然对模型几何形状的适应性较强，但是其本身故有的网格质量难以保证、占用内存大、对计算机硬件要求较高等问题使得该网格的使用受到了一定的限制。为保证计算结果的精确性，本文充分考郑州大学硕士学位论文虑网格的质量，故此多采用了结构化网格，只是在极少数的地方采用了非结构网格，从而既满足了计算要求，又保证了网格的质量。这种网格划分的方法并未见多用，但对其他具有复杂几何模型的模型计算很有参考价值。 本论文的主要工作成果如下: 1.利用大型商用CFD软件—FLUENT软件进行数值计算，获得了不同结构参数(不同的L、0、H)条件下的新型纵流壳程换热器变截面导流筒装置内的流场情况及流动规律。 2.通过对不同结构参数的变截面导流筒的流场分析及内筒进口截面的速度均布性的分析、计算与比较，我们发现:改变L、0及H中任意参数都会对导流筒进口截?更多还原

【Abstract】 The analysis and research of fluid flow and heat transfer in heat exchangers are helpful in the development of safe, high efficiency and economical heat exchanger structure. In conventional research of heat exchangers, experimental method is mostly employed. However, it cannot keep pace with the requirement of research and development of heat exchangers because of its intrinsic disadvantages such as high experimental expense, long period, strict limit, complication in model transition, incapacity of getting detailed information, etc. Currently, with the advancement of computational fluid dynamics, computational heat transfer and computer technology, it is possible to use numerical simulation method to analyze and study heat exchangers. As numerical simulation method is used more widely, more and more people are getting to think that numerical analysis is a feasible approach to save investment and decrease waste and employ it in scientific research.It is an important topic to carry out further study on high efficiency energy-saving heat exchangers with longitudinal flow of shellside fluid(HELFSF). Based on the research of gross structure of HELFSF equipments, our research center optimizes it and develops a new structure which is the combination of rod-ring(rod grid, ring) support, tapered flow distributor and jacket-jacketed rod-baffle heat exchanger with tapered flow distributor(Patent Number: ZL91219300X). It is demonstrated in industrial practice that the new type HELFSF has higher heat transfer efficiency with comprehensive parameter a / A p 50% up and lighter weight 20%-40% down. At present, the new type HELFSF has been used widely in industrial production and brought distinct economic and social efficiency.The setup of flow distributor is a new structure developed to enhance the heat transfer efficiency of shell-and-tube heat exchangers and improve shellside structure. By installing flow distributor, not only the direct impact of high speed fluid on tube bundle at inlet can be prevented but also the distribution of shellside fluid can be improved. As a result, the heat transfer area of tube bundle near inlet can be used fully and the possible flow-induced vibration near inlet can be prevented. Due to the complexity of conventional flow distributor, our research center has developed the jacketed tapered flow distributor, which simplifies greatly the conventional structure of flow distributor. Since tapered structure is used in the flow distributor, the inlet has a sloping section which overcomes the shortcoming of conventional flow distributor that the fluid resistance of media entering shellside is different and makes fluid enter the shell more uniformly. Presently, there is no standard to comply with for the parameters of the new structure such as the length of high and low end of the flow distributor, etc. However, it is certain that the high end of the flow distributor must cover the inlet. Because such flow distributor is used increasingly widely in industry, it has become the emphasis of research on flow distributor to make certain the structural parameters and optimize the structure.In the paper, the numerical simulation method is employed to compute, analyzeand compare the fluid flow condition in the new type flow distributor setup of HELFSF-tapered flow distributor. Further optimal design is carried out according to the flow condition of fluid in the flow distributor.The main work and innovative points in the paper are as follows:1. In the paper, three-dimensional numerical simulation of fluid flow in the tapered flow distributor of new type HELFSF is accomplished for the first time, which is not found in previous work by others.2. In the paper, large universal commercial CFD software-FLUENT is employed to study the characteristics of fluid flow in the flow distributor of new type HELFSF and detailed information of fluid flow is obtained, which cannot be obtained by using experimental method.3. In the paper, the effect of the alteration of structural parameters in the tapered更多还原