【作者】 崔延军；

【导师】 顾平道；

【作者基本信息】 东华大学 ， 供热、供燃气、通风及空调工程， 2012， 硕士

【摘要】 热交换器作为热量传递中的过程设备,在工业领域中应用极为广泛。伴随着各种能源日益紧缺的局面,热交换器的合理设计、运转和改进对于节省资金、材料、能源和空间而言是十分重要的。翅片管换热器作为一种紧凑式换热器,在动力、化工、制冷等工业领域中有广泛的应用,并有很高的换热效率,通常情况下,其基管为圆管,经研究发现,椭圆管具有更小的阻力损失,因此对于矩形翅片椭圆管的研究将对其在工程中的实用效果有更好的指导意义。本文首先采用数值模拟方法对翅片椭圆管的翅片结构进行数值分析及结构优化,通过正交试验组合数据,得出翅片结构的最佳组合为：翅片长度55mm,翅片宽度32mm,翅片厚度0.3mm。通过采用数值分析方法,从管排横向间距、纵向间距、翅片间距、空气流速、空气温度、材料方面对4排错排翅片椭圆管束进行结构优化分析,得出：横向管排间距、纵向管排间距增大,综合评价因子提高,并且变化幅度与进口空气流速有很大关系；翅片间距增大,综合评价因子提高,但是当翅片间距增大到一定值时,其增大幅度减小。通过采用数值分析方法,从管排横向间距、纵向间距、翅片间距、空气流速、空气温度、材料方面对4排错列翅片椭圆管束进行结构优化分析,得出：当纵向管排间距小于16mm时,Nu/Eu增长幅度较小,且当流速达到7.57m/s时,出现性能下降情况；当纵向管排间距大于16mm时,Nu/Eu逐渐增大。随着横向管排间距的增大,Nu/Eu呈线性递增趋势,当间距达到78mm时,趋于平缓,说明继续增大横向间距对换热性能基本没有影响；当横向管排间距位于66mm-78mm时,Eu较为稳定,Nu/Eu呈增长趋势,所以最优结构尺寸应当为横向间距78mm。随着翅片间距的增大,换热性能减弱,当翅片间距增大到一定值时,翅片间距对换热性能的影响变小。入口空气流速的增大可以增强换热,但是阻力增大幅度相对更大；进口空气温度的升高使得换热效果变差,阻力增大；材料的导热系数越好,换热效果越好；入口空气流速一定时,随着管排数的增加,每排管的换热系数是逐渐减小的,随着进口空气流速的增大,整个温度场比较均匀,整体换热效果增强。通过采用数值分析方法,对相同体积下两种换热结构的模型的热力性能比较,得出错列翅片椭圆管束的力能系数较大,最大值约高于错排翅片椭圆管束38%左右,并且错列翅片椭圆管束能以较少的金属材料获得较好的换热效果。更多还原

【Abstract】 As a process equipment of heat transfer, the heat exchanger is widely used in the industry. With the situation of shortage of all the energy, the reasonable design, operation and improvement of heat exchanger is very important for saving money, materials, energy and space. As a kind of compact heat exchanger, the finned tube heat exchanger is widely used in the industry, such as power, chemical industry, and refrigeration industry, and it has a high efficiency of heat exchange. Usually, the base pipe is circle pipe, research shows that the elliptic tubes have smaller resistance losses, so it will have better guidance significance for the study of rectangular finned elliptical tube heat exchanger for its Practical effect in the project.In this paper, we had done a numerical simulation and structure optimization on the fin structure of the rectangular elliptical tube, by the combination data of the orthogonal experiment; we concluded that the best combination of the fin structure is fin length for 55mm, fin width for 32mm, and fin thickness for 0.3mm.By using the method of numerical analysis, we have done the structure optimization and analysis on a four rows of elliptical tubes with rectangular fin in staggered row arrangement from the tubes horizontal spacing, longitudinal spacing, fins spacing, air velocity, air temperature, and the material aspects. The results show that with the increase of the tubes horizontal spacing and longitudinal spacing, the comprehensive evaluation factors get improved and the extent of improvement has a great relationship with the entry air velocity; as the fin spacing increases, the comprehensive evaluation factors get improved, however, while the fin spacing reaches to a certain value, the increase rate becomes small.By using the method of numerical analysis, we have done the structure optimization and analysis on a four rows of elliptical tubes with rectangular fin in staggered column arrangement from the tubes horizontal spacing, longitudinal spacing, fins spacing, air velocity, air temperature, and the material aspects. The results show that while the tubes longitudinal spacing is less than 16mm, the growth rate of Nu/Eu is small, and when air velocity reaches 7.57 m/s, the performance shows descending tendency; when the tubes longitudinal spacing is greater than 16mm, the Nu/Eu is increasing. With the increase of the tubes horizontal spacing, the Nu/Eu shows increscent tendency, but while the tubes horizontal spacing reaches 78mm, it tends towards stability that shows keeping on increasing the tubes horizontal spacing has basically no influence on the heat exchange; when the tubes horizontal spacing is between 66mm and 78mm, Eu is stable, the Nu/Eu is increasing, so the optimization structure size should be 78mm. Along with the increase of the fin spacing, the performance of heat exchange wears off, and while the fin spacing reaches a certain value, the influence of the fin spacing for heat exchange becomes small.Although the increase of air velocity of the entrance can enhance the heat transfer, the increase amplitude of resistance is relatively greater. The increase of air temperature of the entrance makes the heat transfer effect poor, and the resistance also increases. The bigger of the thermal conductivity of the materials, the better of the heat exchange effect. While the air velocity is fixed, with the increase of the tube rows, the heat transfer coefficient is decreasing gradually, and as the air velocity increases, the distribution of the temperature of the entire flow field is even, the heat transfer effect of the whole flow field is enhanced.By using the method of numerical analysis, this paper made comparisons between the two different structural models in the aspect of thermal performance. The results show that the Eo of staggered column arrangement of the elliptical tubes with rectangular fin is higher relatively, and the maximum is about 38% higher than that of staggered row arrangement of the elliptical tubes with rectangular fin, in addition, the former can get a better heat transfer effect with less metal materials.更多还原