换热管内插圆锥扭带强化传热数值模拟

发布时间：2018-06-06 06:31

本文选题：圆锥扭带 + 数值模拟　；参考：《昆明理工大学》2015年硕士论文

【摘要】：随着工业的发展,换热器强化传热技术不断取得了显著的改进和发展。近几年在国家节能减排的背景下,以能源消耗强度低、有效利用率高为特点的新型节能换热器,成为未来换热器强化传热技术研究的新方向。从强化传热机理的角度而言,目前国内外所开发出的各种异型扭带均是以壁面强化扰流为特点,以增加流体的湍流度达到强化换热的目的,纵然这些异型扭带在一定程度上提高了换热管的热交换率,却也因此使得流体的压降过高,导致流体输送功耗成倍增加,有时甚至超过强化传热所带来的效益。本文从另一角度出发,基于全新的核心流强化传热原理提出了新型低阻力扭带——圆锥扭带,采用数值模拟的方法分析了圆锥扭带在湍流状况下插入光管及波纹管内的流动与换热特性。首先,分析了光管内插入扭曲比δ=3.0,锥角θ分别为θ=1：3.6、8=1：5、8=1：7、8=1：9的圆锥扭带在Re=4000～14000范围内的传热和阻力特性,并与传统光滑直扭带进行了比较。通过对管内的温度场、压力场进行分析,并运用综合强化传热性能评价指标(PEC)指标对其进行分析,得出了在模拟的范围内,圆锥扭带在保持一定的扰流强化传热性能的前提下,能够有效减小流体的流动阻力,具有更佳的综合换热性能。其次,针对圆锥扭带几何参数(锥角θ)对传热和阻力特性影响进行了分析,得出了锥角0=1：5的圆锥扭带PEC值达到峰值,具有最佳的综合强化传热性能,使得换热和阻力达到最佳匹配。该结果从另一方面反映出：持续增加湍流流体的扰流,将使得扭带对换热和阻力的贡献值发生逆转,造成换热管的换热性能在无明显改善的情况下所耗费的流体输送能量急剧上升。因此针对湍流区内的流体,单纯地依靠增加流体扰动强度的传统强化传热措施存在一定的局限性,内插件的扰流性能的强弱与换热管的综合换热性能并无直接联系,而具有核心扰流特性的圆锥扭带则具有更加优异的综合强化传热性能。最后,本文结合第三代复合强化传热理论,研究了锥角8=1：5,扭曲比δ分别为δ=2.0、δ=4.4、δ=6.0的3种不同扭曲比的圆锥扭带在波纹管和光管内的传热和流阻特性,并探究了扭曲比δ对其换热和阻力特性的影响。得出扭曲比6越小的圆锥扭带,其综合换热性能越高。并且将同一扭带在光管与波纹管内进行比较,发现圆锥扭带在波纹管内的综合换热性能更高,并对其中的原因进行了解释。最终证明圆锥扭带在复合强化传热中仍具有相当广泛的运用价值,为新型高效节能换热器的设计及传统换热器的升级改造提供了一定参考。
[Abstract]:With the development of industry, the heat transfer technology of heat exchanger has been greatly improved and developed. In the background of national energy saving and emission reduction in recent years, a new type of energy saving heat exchanger with low energy consumption intensity and high effective utilization rate has become a new direction for the research of heat transfer enhancement technology in the future. At present, all kinds of special-shaped torsional bands developed at home and abroad are characterized by wall intensification turbulence, which can increase the turbulent degree of fluid to achieve the purpose of strengthening heat exchange. Even though these twisted tapes increase the heat exchange rate of the heat transfer tubes to a certain extent, the pressure drop of the fluid is too high and the power dissipation of the fluid is multiplied. In this paper, based on the new core flow strengthening heat transfer principle, a new low resistance torsional band, conical torsional belt, is proposed from another point of view. The flow and heat transfer characteristics of the tapered torsional band in the turbulent flow and the bellows are analyzed by numerical simulation. The characteristics of heat transfer and resistance in a conical torsional band with a twist ratio of [delta] =3.0 and a cone angle theta (theta) of theta =1:3.6,8=1:5,8=1:7,8=1:9 respectively in the range of Re=4000 to 14000 are analyzed. The comparison is made with the traditional smooth straight torsional band. By analyzing the temperature field and pressure field in the tube, the comprehensive heat transfer performance evaluation index (PEC) is used. According to the analysis of the index, it is concluded that in the range of simulation, the conical torsional band can effectively reduce the flow resistance of the fluid and have better comprehensive heat transfer performance on the premise of maintaining a certain heat transfer performance. Secondly, the influence of the geometric parameters of the tapered torsional band (cone angle theta) on the heat transfer and resistance characteristics is analyzed. The PEC value of conical torsional band of cone 0=1:5 reaches its peak value, and it has the best comprehensive heat transfer performance, which makes the heat transfer and resistance reach the best match. In the case of improvement, the energy of fluid transport is rising rapidly. Therefore, there are some limitations on the traditional heat transfer measures for the fluid in the turbulent zone, which simply relies on the increase of the intensity of the fluid disturbance. The strength of the disturbing flow performance of the internal plug-in is not directly related to the heat transfer of the heat transfer tube, but has the core disturbing characteristics. The tapered torsional band has a more excellent comprehensive heat transfer performance. Finally, this paper studies the heat transfer and flow resistance characteristics of the cone angle 8=1:5, the twist ratio Delta =2.0, Delta =4.4 and delta =6.0 in the bellows and light tubes, and explores the distortion ratio Delta for the change of the twisted ratio Delta. The influence of heat and resistance characteristics is obtained. It is found that the taper twisted belt with smaller twist ratio 6 has higher comprehensive heat transfer performance. And the same twisted belt is compared with the bellows in the light tube. It is found that the comprehensive heat transfer performance of the tapered torsional band is higher in the bellows, and the reasons are explained. Finally, it is proved that the tapered torsional belt is in the compound strengthening heat transfer. It still has a very wide range of application value, and provides a reference for the design of new energy-efficient heat exchanger and upgrading and upgrading of traditional heat exchanger.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK172.4

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