管片式换热器三角形波纹翅片侧流动与传热性能研究

发布时间：2018-03-16 22:36

本文选题：传热　切入点：阻力系数　出处：《兰州交通大学》2016年硕士论文　论文类型：学位论文

【摘要】：作为热量传递过程中的关键设备,管翅式换热器应用在很多场合,它的出现不仅带动了社会的经济发展而且给我们的生活带来了便利,同时管翅式换热器的运行又消耗了非常可观的高品位能量。为了节能及能源的充分利用,就需要研究强化传热技术以进一步提升管翅式换热器的传热特性。管翅式换热器中翅片型式很多,可根据翅片的几何形状把翅片分为:平片型翅片、条缝型翅片、波纹型翅片、百叶窗型翅片以及近年来逐渐兴起的涡发生器型翅片。在该翅片管换热器中,空气侧热阻为其热环节的主要热阻,约占总热阻的70%-90%,也就是说空气侧换热性能的好坏对整个换热器的换热性能起着决定性作用。因此,要提高换热器的总体换热性能,对空气侧的换热性能进行强化。论文通过数值模拟的方法来对三角形波纹翅片管换热器的翅片侧传热性能进行深入的研究。首先建立相应的数学及物理模型,然后选取合适的翅片单元作为计算区域,对计算区域进行合理的网格划分,确定数值计算所用的网格数目的大小,通过数值结果与实验结果的对比确定所用算法的合理性。然后用数值方法获得在各种翅片参数及工作条件下的翅片侧努塞尔数、阻力系数,运用线性回归法拟合出努塞尔数、阻力系数与各几何参数之间的关联式,对比三角形波纹翅片与平直翅片传热性能的区别,例如阻力系数和努塞尔数随雷诺数的变化规律,横向和纵向截面的流场分布等。为了深入揭示三角形波纹翅片的强化传热机理,计算并讨论纵向涡强度、横向涡强度与努塞尔数,阻力系数的关系。研究结果表明:与平直翅片相比,三角形波纹翅片表面的局部努塞尔数较大,三角形波纹翅片的换热性能更好;对三角形波纹翅片与圆管形成的通道内的流场进行了分析,发现在波峰及波谷处,二次流现象十分明显。由于三角形波纹翅片与圆管形成的通道内能够产生纵向涡和横向涡,而纵向涡和横向涡能够强化传热;努塞尔数、纵向涡强度、横向涡强度都随着翅片间距、波纹角、波纹数的增大而增大。阻力系数随着翅片间距、波纹角、波纹数的增大而减小;在同一雷诺数下,三角形波纹翅片的平均努塞尔数及阻力系数都高于平直翅片的,同时还拟合得到了三角形波纹翅片努赛尔数和阻力系数与雷诺数及二次流强度的关联式。
[Abstract]:As the key equipment of heat transfer in the process of tube fin heat exchanger used in many occasions, it not only promoted the development of social economy and bring convenience to our life, at the same time running tube fin heat exchanger and consumes considerable high-grade energy. In order to make full use of energy and energy the need to study the heat transfer technology to further enhance the heat transfer characteristics of fin tube heat exchanger. The tube fin heat exchanger fin type many, according to the geometry of the fin fin is divided into: flat fin, fin, corrugated fin, louver fin and vortex generator fin has gradually emerged in recent years. In the finned tube heat exchanger, the main thermal resistance of air side thermal resistance is the thermal link, about the total thermal resistance of 70%-90%, that is to say the air side heat transfer performance of the heat transfer performance of the heat exchanger Play a decisive role. Therefore, to improve the heat exchanger overall heat transfer performance, the heat transfer performance of the air side was strengthened. Methods by numerical simulation of wavy fin and tube fin heat transfer performance of heat exchanger are discussed in detail. Firstly, the corresponding mathematical and physical model, and then select the appropriate fin unit as the calculation region, reasonable meshing of the computational domain to determine the number of mesh used for numerical calculation of the size of rationality by comparing the numerical results and experimental results confirm the algorithm used. To get the number of fin side Nusselt in various parameters and working conditions of the fin resistance by numerical method coefficient, using linear regression method to fit the Nusselt number, the relationship between the resistance coefficient and the geometric parameters, contrast the wavy fin and flat tube heat transfer performance difference, For example, the resistance coefficient and Nusselt number with Reynolds number variation of transverse and longitudinal section of the flow field. In order to reveal the mechanism of heat transfer enhancement in the wavy fin, discuss the longitudinal vortex intensity calculation and transverse vortex intensity and the Nusselt number, the relationship between the resistance coefficient. The results showed that compared with the straight fin, local Nusselt triangle a large number of wavy fin surface, better thermal performance for wavy fin; flow field of the wavy fin and tube formation in the channel are analyzed, found in the peak and trough, two secondary flow phenomenon is very obvious. Due to the wavy fin and tube formation in the channel can generate longitudinal and transverse vortex the longitudinal vortex, vortex and vortex can enhance heat transfer; the Nusselt number, longitudinal vortex strength, transverse vortex strength with fin spacing, corrugation angle, wave number and gain increases . the drag coefficient with fin spacing, corrugation angle, wave number increases and decreases; at the same Reynolds number, the average Nusselt number and resistance coefficient of wavy fin is higher than the straight fin, also fitted the wavy fin and the Nusselt number and resistance coefficient and Reynolds number and two flow intensity correlation type.

【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK172;TK124

【参考文献】