纵/横向组合涡强度描述与其强化传热对应关系研究

Promoting energy conversion and utilization rate is a very important means of keeping national economy to be in sustainable growth as well as improving the ecological environment of our country. In the energy conversion and utilization, there are many heat transfer processes involved. To reduce high level energy consumption during heat transfer process, enhancing convective heat transfer is a very effective way of saving energy and is constantly paid much attention by researchers. In various convective heat transfer augmentation technologies, vortex is a kind of effective heat transfer enhancement technology and is widely used. So, the vortices or swirls formed by different means can be used to enhance heat transfer. If taking the main stream direction of the fluid as reference direction, the vortices are classified as transverse vortices, longitudinal vortices as well as the combination of transverse vortices and longitudinal vortices. Though the heat transfer enhancement induced by transverse vortices and longitudinal vortices have been studied for many years, the mechanisms of heat transfer augmentation caused by transverse vortices and the combination of transverse vortices and longitudinal vortices have not been understood deeply. Hereby, the present project is going to carry out the study in following four aspects: (1) the properties of hybrid vortices when transverse vortices and longitudinal vortices come together such as in transverse wave passage and in rectangular cross section passage roughed by ribs; (2) the heat transfer properties in transverse wave passage and in rectangular cross section passage roughed by ribs; (3) the method for describing the transverse vortex strength as well as the combined vortex strength when the transverse vortices and the longitudinal vortices exist at the same time; (4) the relationship between the transverse vortex strength as well as the combination of transverse vortex and the longitudinal vortex strength with heat transfer enhancement. The predictive results of the project are: (1) the corresponding relationships between heat transfer enhancement with the combination of transverse vortices and longitudinal vortices; (2) inducing the guidelines for use of vortex to enhance convective heat transfer; (3) revealing the heat transfer mechanism in the presence of both transverse vortices and longitudinal vortices. The study results of the project can lay firm foundation for reasonably designing heat transfer structure by using vortex mechanism, the results will have high academic value and wide application prospect.

提高能源转换及利用率是在保持经济增长的同时能改善我国生态的重要措施。能源转换和利用中涉及诸多传热过程。为了减少传热过程中高品位能量消耗，强化对流传热成为研究热点。涡被广泛用来形成强化传热技术。参考流动主流方向，涡按其旋转的中心轴方向分为横向涡、纵向涡及纵/横向组合涡。虽经多年研究，还缺乏对横向及纵/横向组合涡强化传热机理深刻认识。据此，本项目拟开展如下四方面的研究工作：（1）横向波纹通道及矩形粗糙元通道内的纵/横向组合涡特性；（2）横向波纹通道及矩形粗糙元通道表面传热特性；（3）横向涡及纵/横向混合涡强度的描述方法；（4）横向涡及纵/横向混合涡强度与强化换热之间的关系。项目旨在获得：（1）纵/横向组合涡强度与强化传热对应关系；（2）归纳出指导涡强化传热的策略；（3）揭示纵/横向组合涡强化传热机理。项目结果还能为设计更加合理的涡强化传热结构奠定基础，具有较高的学术价值和较广泛的应用前景。

涡是粘性流体流动的基本特征，研究表明横向涡和纵向涡都具有强化传热的能力，但对它们之间的内在关系尚缺乏充分的认识。项目采用实验和数值模拟的方法研究了5种通道结构在不同工况、不同几何参数下,通道内流体流动涡强度及其对传热的影响，获得不同通道内传热及阻力特性随雷诺数、传热及阻力特性随涡强度参数变化的规律，拟合出不同结构通道传热及阻力特性与雷诺数、通道结构参数的关系式、涡强度参数与雷诺数、通道结构参数的关系式。.对于三角形波纹矩形通道，在所研究的齿高范围内，当冷却通道的通道高度和三角齿的齿顶角不变时，三角形齿的齿高越小，波纹微通道的换热效果越好，阻力系数也越小。采用热通量方程分析表明，在齿顶附近速度对热通量传输的贡献项、速度梯度对热通量传输的贡献项具有较大的值。对于倾斜肋矩形通道，在相同的几何参数下，涡强度变化趋势与努塞尔数变化趋势相同，说明努塞尔数与涡强度有较强的依赖关系。对于肋化渐缩方形截面通道，努塞尔数随着涡强度的增大而增大，倾斜直肋、V-down型肋、V-up型肋的渐缩通道内纵向涡强度与努塞尔数均存较强的依赖关系。圆管三角形波纹翅片通道内努塞尔数与涡强度有较强的依赖关系；不同结构参数下，阻力系数与涡强度之间关系偏离较大。. 项目研究结果可增进对所研究不同结构通道内流体流动涡特征及其对传热影响的认识，对于相关换热器设计具有指导意义，具有较大的学术意义和较高的工程应用价值。研究成果在国内外学术会议发表标注会议论文8篇，4篇标注论文（含2篇会议论文）分别被工程热物理学报、化工学报、International Journal of Heat Mass Transfer及International Journal of Thermal Sciences 录用；培养硕士研究生9名；获项授权发明专利7项；获甘肃省科技进步奖一等奖1项。