换热管内置分段式弹簧流动与传热的特性研究

发布时间：2018-07-05 13:34

本文选题：分段式弹簧管 + 流场特性　；参考：《武汉工程大学》2015年硕士论文

【摘要】：换热管内置弹簧插入物作为强化换热技术,广泛应用于实际工程中。虽然该技术可以提高传热系数,但是也会大大地增加管内流体压降和阻力。本文对螺旋弹簧进行分段式处理,主要采用理论分析、数值模拟及实验研究相结合的方法对换热管内置分段式弹簧的流动与传热过程进行初步的研究。主要研究的内容如下:(1)结合以往的研究成果,对内置分段式弹簧强化传热的机理进行探索性研究,通过弹簧动力学理论分析了弹簧的轴向传播速度与弹簧参数之间的关系,得到节距大、中径小、丝径大的弹簧产生的轴向波速大,有利于弹簧发生振动。结合场协同理论,分析了水—水工质下光管和内置分段式弹簧换热管分别在不同雷诺数下的场协同角之间的关系。结果表明采取内置分段式弹簧的办法不仅可以提高传热系数,而且可以降低流体在管内流动受到的阻力,对于提高强化传热的效率具有一定的指导意义。(2)通过流体分析软件Fluent对内置分段式弹簧换热管内的流场进行数值模拟,分析了不同长度的分段式弹簧及弹簧的结构参数(节距、丝径、中径)对管内流场、传热和阻力压降的影响。模拟结果表明,当雷诺数相同时,内置分段式弹簧换热管的Nu数相对于光管提高了2-4倍,内置分段式弹簧管的阻力系数比内置未分段式弹簧换热管的阻力系数减小3倍左右。并通过数值方法分析了不同参数的分段式弹簧对传热的影响,得到采用节距较大,丝径较大,中径较小的分段式弹簧插入换热管将使传热效果更好。该结论与上一章的理论分析相一致,说明采用内置分段式弹簧的方法有利于达到强化传热的目的。(3)搭建了PIV实验平台,通过粒子成像测速技术(PIV)对内置分段式弹簧管管内的流场进行测量,分别研究了不同参数(节距、丝径和中径)的分段式弹簧对管内流场的影响作用。并将所测结果和光管进行对比,结果表明内置分段式弹簧管的涡量场和速度场分布情况比光管的要好,在轴向和径向上的速度均有提高,其中轴向速度提高了约1.2~1.6倍,径向速度呈现出M型的波动变化,管内流体的平均速度与雷诺数呈线性关系。且内置节距大、丝径大、中径小的分段式弹簧管的流动效果最佳,此结果验证了理论分析和数值模拟的正确性。
[Abstract]:Spring inserts are widely used in practical engineering as enhanced heat transfer technology. Although the heat transfer coefficient can be increased by this technique, the pressure drop and resistance of the fluid in the tube will also be greatly increased. In this paper, the flow and heat transfer process of the helical spring is studied by theoretical analysis, numerical simulation and experimental study. The main research contents are as follows: (1) combined with the previous research results, the mechanism of heat transfer enhancement of built-in segmented spring is studied, and the relationship between the axial velocity of spring and spring parameters is analyzed by the theory of spring dynamics. The results show that the axial wave velocity of the spring with large pitch, small center diameter and large wire diameter is large, which is beneficial to the spring vibration. Based on the field synergy theory, the relationship between the field coordination angles of the light tube and the built-in segmented spring heat transfer tube under water and water working fluids at different Reynolds numbers is analyzed. The results show that the method of built-in segmented spring can not only increase the heat transfer coefficient, but also reduce the resistance of the fluid flow in the pipe. It has certain guiding significance for improving the efficiency of heat transfer enhancement. (2) numerical simulation of the flow field in the heat transfer pipe of the built-in segmented spring is carried out by fluent, and the structural parameters of the segmented spring with different lengths (pitch distance) are analyzed. The influence of wire diameter and center diameter on the flow field, heat transfer and pressure drop in the tube. The simulation results show that when Reynolds number is the same, the Nu number of the built-in segmented spring heat exchanger pipe is 2-4 times higher than that of the light tube, and the resistance coefficient of the built-in segmented spring tube is about three times less than that of the non-segmented spring heat exchanger tube. The influence of segmented spring with different parameters on heat transfer is analyzed by numerical method. It is concluded that the heat transfer effect will be better if the segmented spring with larger pitch, larger wire diameter and smaller middle diameter is inserted into the heat transfer tube. The conclusion is consistent with the theoretical analysis in the previous chapter, which shows that the method of built-in segmented spring is beneficial to the enhancement of heat transfer. (3) A PIV experimental platform is built. Particle imaging velocimetry (PIV) was used to measure the flow field in a built-in segmented spring tube. The effect of segmented spring with different parameters (pitch, wire diameter and center diameter) on the flow field in the tube was studied. Compared with the light tube, the results show that the vortex field and velocity field distribution of the built-in segmented spring tube is better than that of the light tube, and the axial and radial velocities have been improved, in which the axial velocity has been increased by about 1.2U 1.6 times. The radial velocity shows the fluctuation of M-type, and the average velocity of the fluid in the tube is linearly related to the Reynolds number. The flow effect of segmented spring tube with large pitch, large wire diameter and small center diameter is the best, which verifies the correctness of theoretical analysis and numerical simulation.
【学位授予单位】：武汉工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.5

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