点坑型扁管换热性能研究

发布时间：2018-01-23 12:03

本文关键词： 点坑换热器数值模拟阻力系数　出处：《湖北工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：换热扁管是换热器中最重要的换热元件,是其换热的载体。换热扁管的换热和流阻性能的优良直接决定了换热器的工作效率。点坑结构是近年来发展起来的一种新型强化换热结构,大量的实验证明了点坑型流道的综合换热效果要好于光滑流道。同时,与其他强化换热技术相比较,它能在增强换热的同时又不会产生太大的流动阻力,因此在工业上得到了越来越广泛的应用。本文建立了点坑扁管的物理模型和数学模型,并根据研究对象的特点和不同的流态,分别选取了RNGκ-ε湍流模型和层流模型,以空气为介质在不同工况下对多种换热扁管进行了数值模拟研究。首先针对多种不同几何结构参数的点坑扁管在高雷诺数工况下进行模拟,细致的分析了不同点坑深度、点坑宽度、点坑间距、流道高度对扁管换热和流动阻力以及综合换热性能的影响和变化规律,还得到了不同工况下扁管换热和流阻达到最佳匹配时的结构参数,并探讨了点坑扁管的强化换热机理。研究认为,一方面,由于点坑的存在有效的增加了换热面积,使得换热增强。另一方面,点坑破坏了流体的边界层,导致了涡旋的产生,使得流体的局部湍流程度显著增加,在点坑的附近,换热效果明显要增强。相较于光滑的扁管,点坑扁管的综合换热性能增强因子在1.5~2.2左右,明显要好于光管。然后还针对低雷诺数工况下的窄缝点坑扁管,研究了在层流的状态下,点坑深度、点坑纵向间距、点坑横向间距、点坑宽度对综合换热性能的影响,并进行了正交试验,最后得到了最优方案。本文研究了不同工况下和不同几何结构的点坑型扁管的换热效果,探讨了其流动和换热机理,为进一步设计与开发提供了依据。
[Abstract]:Flat tube is the most important heat transfer element in heat exchanger. It is the carrier of heat transfer. The excellent heat transfer and flow resistance performance of the flat tube directly determine the working efficiency of the heat exchanger. The spot pit structure is a new type of enhanced heat transfer structure developed in recent years. A large number of experiments have proved that the integrated heat transfer effect of point pit channel is better than that of smooth channel. In addition, compared with other enhanced heat transfer techniques, it can enhance heat transfer without causing too much flow resistance. In this paper, the physical model and mathematical model of point crater flat pipe are established, and according to the characteristics of the object of study and different flow patterns. RNG 魏-蔚 turbulence model and laminar flow model are selected respectively. The numerical simulation of a variety of heat transfer tubes was carried out under different conditions using air as the medium. Firstly, the point pit flat pipes with different geometric parameters were simulated under high Reynolds number conditions. The influence and variation law of different point pit depth, point pit width, spot pit spacing, channel height on heat transfer, flow resistance and comprehensive heat transfer performance of flat pipe are analyzed in detail. At the same time, the structural parameters are obtained when the heat transfer and flow resistance of the flat tube reach the optimum matching under different working conditions, and the mechanism of strengthening the heat transfer of the flat pipe with a point pit is discussed. The existence of spot pits effectively increases the heat transfer area and makes the heat transfer increase. On the other hand, the point pits destroy the boundary layer of the fluid, resulting in the production of vortex, which makes the local turbulence of the fluid increase significantly. In the vicinity of the spot pit, the heat transfer effect is obviously enhanced. Compared with the smooth flat tube, the enhancement factor of the comprehensive heat transfer performance of the spot pit flat tube is about 1.5 ~ 2.2. It is obviously better than the light tube. Then, the depth of the spot pit, the longitudinal distance of the spot pit and the transverse distance of the spot pit are studied under the laminar flow condition for the narrow slot crater flat tube under the low Reynolds number working condition. The effect of point hole width on the comprehensive heat transfer performance is studied, and the orthogonal test is carried out. Finally, the optimal scheme is obtained. The heat transfer effect of point pit type flat pipe under different working conditions and different geometry structures is studied in this paper. The mechanism of flow and heat transfer is discussed, which provides the basis for further design and development.
【学位授予单位】：湖北工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK172

【相似文献】