合成氨二级余热回收换热器改造设计及强化传热研究

发布时间：2018-02-02 22:21

本文关键词： 合成氨余热回收换热器改造设计 T型翅片管强化传热　出处：《华东理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：合成氨尿素工业废气经过一级余热回收后仍然拥有很高的能量,将其直接排放会造成极大的浪费。本文针对某合成氨尿素二级废热锅炉改造,结合T形翅片管换热器的结构特点,分析了其沸腾强化传热机理,对其进行了深入的研究,主要包括以下几方面的内容：(1)对余热回收技术及强化沸腾传热技术的研究现状进行了调研,结合沸腾传热机理,阐述了各种沸腾强化传热技术的优缺点。(2)给出了合成氨尿素二级余热回收锅炉的热力模型及工艺计算方法(包括改造前光滑管换热器及改造后T型翅片管换热器),并利用手算和HTRI软件对改造前后两种换热器进行了工艺分析与设计计算,发现现有设备已经无法满足换热要求。从强化传热角度来看,T型翅片管的管内传热系数约为光管的1.22倍,管外沸腾传热系数约为光管的1.24倍,总传热系数是光管的1.6倍。改造后的换热器在满足了设计要求的同时,所需换热面积明显低于改造前,大大节省了改造成本。(3)从换热器流体诱导振动的机理及振动判定依据出发,使用GB151附录E流体诱导振动计算对改造前和改造后的余热回收换热器进行了流体诱导振动分析。并对比了改造前后两台设备的流体诱导振动分析结果。计算结果表示,改造后的新型换热器壳程不会产生因卡门漩涡或紊流抖振产生管束振动,也不会发生声振动,与改造前相比具有更好的抗振性能。(4)利用大型计算流体力学软件Fluent对T型翅片管和光滑管管外流动沸腾进行了数值模拟研究,结合T型翅片管的结构特点,进一步说明了该换热管的强化沸腾传热机理。在本文研究的范围内,T型翅片管管外沸腾传热系数最大时高于光滑管23.2%,强化传热效果明显。同时,综合评价了T型翅片管强化传热和增加压降的性能。结果表明,其强化传热综合性能评价因子在不同流速下均大于1,说明T型翅片管有很好的强化传热效果。本文通过对该换热器上述问题的研究,完成了合成氨二级余热回收换热器的设计改造工作,同时深入探讨了改造后换热器的强化传热机理,对于同类余热回收热交换器的改造设计有很强的参考价值。
[Abstract]:The waste gas of ammonia urea industry still has very high energy after the first stage waste heat recovery, and it will cause great waste when it is discharged directly. This paper aims at the revamping of the secondary waste heat boiler of a synthetic ammonia urea. Combined with the structural characteristics of T-shaped finned tube heat exchanger, the mechanism of boiling enhanced heat transfer is analyzed, and the mechanism of boiling enhancement heat transfer is studied deeply. The research status of waste heat recovery technology and enhanced boiling heat transfer technology has been investigated, combined with boiling heat transfer mechanism. The advantages and disadvantages of various boiling heat transfer enhancement techniques are described. (2) the thermodynamic model and process calculation method of the secondary waste heat recovery boiler for ammonia synthesis urea are given. It includes smooth tube heat exchanger before revamping and T finned tube heat exchanger after revamping. The process analysis and design calculation of the two kinds of heat exchangers before and after revamping have been carried out by using manual calculation and HTRI software. It is found that the existing equipment can no longer meet the requirements of heat transfer. From the point of view of enhanced heat transfer. The in-tube heat transfer coefficient of T-shaped finned tube is about 1.22 times of that of the smooth tube, and the boiling heat transfer coefficient outside the tube is about 1.24 times of that of the smooth tube. The total heat transfer coefficient is 1.6 times of that of the smooth tube. The heat transfer area of the modified heat exchanger is obviously lower than that of the former. The cost of revamping is greatly saved. (3) based on the mechanism of fluid-induced vibration of heat exchanger and the basis of vibration determination. The fluid-induced vibration analysis of waste heat recovery heat exchangers before and after revamping was carried out by using fluid-induced vibration calculation in appendix E of GB151, and the results of fluid-induced vibration analysis of two equipments before and after revamping were compared. The result of the calculation indicates. The shell side of the modified heat exchanger will not produce tube bundle vibration or acoustic vibration due to Carmen vortex or turbulent buffeting. Compared with before modification, it has better anti-vibration performance.) numerical simulation of flow boiling outside T-shaped finned tube and smooth tube was carried out by using large computational fluid dynamics software Fluent. The mechanism of enhanced boiling heat transfer of the tube is further explained by the structural characteristics of the T-shaped finned tube. The boiling heat transfer coefficient outside the T-shaped fin tube is higher than that of the smooth tube 23.2% when the maximum boiling heat transfer coefficient is obtained in this paper. The effect of heat transfer enhancement is obvious. At the same time, the performance of enhancing heat transfer and increasing pressure drop of T-shaped finned tube is comprehensively evaluated. The results show that the comprehensive evaluation factor of heat transfer enhancement performance is more than 1 at different flow rates. It shows that T-fin tube has a good heat transfer enhancement effect. Through the study of the above problems of the heat exchanger, the design and transformation of the two-stage waste heat recovery heat exchanger for synthetic ammonia have been completed. At the same time, the mechanism of enhanced heat transfer of heat exchangers after revamping is discussed, which has a strong reference value for the retrofit design of similar waste heat recovery heat exchangers.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ113.25;TQ051.5

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