【作者】 林雄；

【导师】 郭崇志；

【作者基本信息】 华南理工大学 ， 化工过程机械， 2010， 硕士

【摘要】 管壳式换热器是具有结构简单、牢固、操作弹性大、使用经验丰富、可靠性高等优点,是目前应用最广泛的一种换热器。其中弓形折流板换热器是应用最普遍的一种传统管壳式换热器,由于存在时间长,技术相对成熟和完善,加工制造装配容易,虽然存在某些局限性,但仍大量使用。管壳式换热器的热力-水力特性的研究对于换热器的设计计算、改造、提高换热效率、降低能源损耗、延长使用寿命等显得尤为重要。而采用数值模拟的方法对管壳式换热器进行流体流动与传热特性的研究的文献报道日渐增多,已经成为一种趋势,但仍存在着壳程流体划分的网格精度不高,数值模拟只局限于定性研究以及回避或简化掉某些重要流路的建模,从而忽略了这些通道的流动与传热对换热器的影响等问题,而解决这些问题,恰恰会导致网格模型复杂、计算成本高等新的问题,甚至导致问题难以求解。本文针对上述问题和基于预应力换热器要求完成比较精细的数值分析的研究目的,采用分段建模的模拟新技术来处理大模型和提高离散化精度,实现分段模型的精细化,最后综合处理的方法,并成功引入小间隙流路A和E,考虑各流路间隙对传热压降的影响,建立整体流路模型,对折流板换热器进行数值模拟,获得了更为准确和详细的数值模拟结果,为后续预应力换热器实施技术提供了坚实的基础和有力依据。同时分别进行了单一流路E和流路A在不同间隙下换热器性能的数值模拟,初步探讨了流路E和流路A对换热器流体流动与传热的影响特性,并推导出与间隙结构参数相关的定量无因次准数表达式。本文的研究结论是:对换热器整体流路下流体流动与传热特性进行分段建模和综合的数值模拟新方法是可靠的,所得结果与经验计算公式吻合良好。流路E和流路A对换热器性能的影响各有不同,换热器整体传热膜系数随着流路E间隙的增大而逐渐减小且趋于平缓;随着流路A间隙的增大却出现先增大后减小,存在一个间隙最佳值。流路E比流路A对换热器传热性能的影响要大得多。而打开E、A流路都降低壳程总压降,综合来看,流路A对提高换热器综合性能是有利的。更多还原

【Abstract】 Shell and tube heat exchanger is one of the most widely used heat exchanger because of the advantage of it, which mainly concludes the simplicity and security of the structure, the great flexibility of operating and the abroad application of material and the segmental baffle heat exchanger is the most common application of a traditional shell and tube heat exchanger.The heat exchanger has some limitations but still widely be used because it exits for a long time, has the relatively mature technology and easy manufacturing assembly.The heat-hydraulic characteristics research of the shell and tube heat exchanger is very important for design and calculation,reconstruction, improving heat transfer efficiency, saving energy consumption, extending the service life of heat exchanger. The studies of fluid flow and heat transfer characteristics of the shell and tube heat exchanger using the numerical simulation method are reported in the literature more and more and already become a trend, but there are issues including low accuracy shell fluid divided mesh , numerical simulation stopped at the qualitative issues research and avoiding or simplifing the modeling of the some important flow path ,and neglect the influence of flow path flow and heat transfer on heat exchanger.Solving these problems, it will lead to new problems including the grid model precisely complicated and the higher cost of calculation or indeed hard to be solved.Based on the above issues, and the research purposes on completing more detailed numerical analysis of prestressed heat exchanger ,this paper uses new sub-modeling simulation technolgy to deal with large models and improve the discretization accuracy, achieves the refinement of sub-model and at last adopts comprehensive treatment method. The small gaps flow path A and E are successfully instroducted taking into account the impact of heat preesure drop of heat exchange.The numberical simulation of overall flow path model of the baffle heat exchanger will obtain more accurate and detailed simulation data ,which will provide a solid foundation and strong evidence for the subsequent technology implementation of prestressed heat exchanger.At the same time,this paper respectively makes simulaton of the model with single flow path E and single flow path A of different gap size of flow path, Preliminaryly studies on the characteristic for the fluid flow and heat impact of flow path E and A.At last we derive quantitatively multidimensional criterion expression associated with the gap structural parameters.It is conclude that:The numerical simulation method of fluid flow and heat transfer at the overall heat flow path is reliable,and the results obtained are in good agreement with the empirical formula.Flow path E and A have different impacts on the performance of heat exchanger.The overall heat transfer film coefficient decreases with the increase of flow path E gap,but first increases and then decreases with the increase of flow path A gap which has a best value.The impact on heat transfer performance of flow path E has much greater than A.Opening flow path E and A cutts down the pressure drop in shell.The flow path A is favorable for improving the comprehensive performance of heat exchanger.更多还原