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实验研究了板翅式换热器封头结构对其内部流体分配及换热特性的影响,实验结果表明,目前工业应用的板翅式换热器内部存在流体分配极为不均匀的严重问题,造成了其换热效能的严重下降。研制了各种新型孔板封头结构,并且实验研究了新型封头的各种参数,如孔板长度、开孔的分布规律和小孔直径对板翅式换热器流体分配及换热的影响。研究结果表明,孔板封头从根本上改善了换热器内部流体的分配问题,流体不均匀度从0.208减小到0.035,最大与最小流速比由改进前的2—3倍降低到1.1—1.2倍,温度分布不均匀度从0.826减小到0.601。孔板型封头结构增加了换热器的流动阻力,错排孔板型封头在改善换热器流体分配的同时,也较好地抑制了阻力损失的增加,得到了不同封头结构的流动阻力与雷诺数之间的关系。 相似文献
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针对板翅式换热器封头内部流场分布不合理和流道流量不均匀分配的现象,提出了一种新型导流翼封头结构的改造方案。采用CFD方法对该封头结构改进前后的流场进行数值计算与分析,证明了导流翼的应用使换热器封头流道的流量分配的均匀性得到很大改善,使得封头内部流场分布更加合理。模拟研究还发现通过改变导流翼片的安装参数可有效地改善换热器封头内部物流分配特性,当导流翼角为70°、翼片顶端安装距离为6 mm时为最佳导流翼片结构安装参数组合,文中原始模型的模拟结果与相关文献中封头的实验结果数据吻合很好,从而验证了该数值模拟研究中物理模型与数值模型的合理性与准确性,此封头结构的研究结论对板翅式换热器的优化设计具有重要意义。 相似文献
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纵向传热、温度场与物流分配不均匀对换热器效能的影响具有耦合关系,其中物流分配的不均匀会加剧其内部温度场分布的不均匀,增大换热器的纵向传热,导致其效能的下降,所以物流分配的不均匀在三者中对换热器效能的影响最为重要.因此,对引起物流分配不均匀的因素进行研究是板翅式换热器优化设计的重要内容.针对板翅式换热器内部流动特性对封头结构的影响进行了深入研究.研究发现:封头结构的影响主要体现在垂直于总管流动方向上.发现了封头结构的改进方法,通过改变封头结构的设计可以有效地改善换热器内部的物流分配. 相似文献
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《化工进展》2015,(10)
以一种板壳式换热器壳程为研究对象,建立了几何模型并进行了数值模拟,通过对各流道的流量偏差和相对标准差的计算,分析了壳程物流分配的特性,并总结了物流分配特性对换热器的传热效率、整体效能以及压降的影响。模拟与分析结果显示:换热器壳程存在严重的物流分配不均匀现象,这种现象会造成换热器整体效能的下降,同时造成压降的大幅升高,但是对于传热效率的影响很小,总换热量偏移不足3%。为了改善物流分配带来的影响,提高换热器的性能,通过在入口处设置封头和圆弧状条纹板对换热器壳程来进行优化设计。优化分析结果表明:该设计可以改善换热器物流分配不均匀性,并能使换热器效能下降明显降低,压降相对减小,可以为板壳式换热器的优化提供参考。 相似文献
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在数值模拟的基础上,利用粒子图像测速仪(PIV)对板翅式换热器原始封头A和3种改进的顺排孔板型封头结构(B、C、D)的流场进行了可视化的实验,获得了封头内部不同截面处流场的速度流线分布图.比较了Re=6.22×104时原始封头A和一种改进型封头B的出口物流分配以及3种不同中孔面积比率的改进型封头对出口物流分配的影响.结果表明:改进型封头结构能有效地改善物流分配的均匀性;C型封头的不均匀参数SU和最大流速与最小流速之比θU最低;流量分布和中孔面积比率之间存在着一个最佳值. 相似文献
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The flow distribution through a plate‐fin heat exchanger is studied by using a computational fluid dynamics (CFD) code, FLUENT. The flow distribution through any heat exchanger affects its performance. In designing a heat exchanger, it is assumed that the fluid is uniformly distributed through the heat exchanger core. In practice, however, it is impossible to distribute fluid uniformly, because of an improper inlet configuration, imperfect design, and a complex heat transfer process. The CFD simulation of the flow distribution in the header of a conventional plate‐fin heat exchanger is presented. It is found that the flow maldistribution is very serious in the y‐direction of the header. A modified header is proposed and simulated using CFD. The modified header configuration has a more uniform flow distribution than the conventional header configuration. Hence, the efficiency of the modified heat exchanger is seen to be higher than that of the conventional heat exchanger. 相似文献
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Flow characteristics in the entrance of plate-fin heat exchanger have been investigated by means of particle image velocimetry (PIV). The flow field was measured using the two-frame cross-correlation technique. Streamline and velocity contour graphs at different cross-sections were obtained in the experiment. The experimental results indicate that flow maldistribution in the conventional header is very serious, while the improved header configuration with punched baffle can effectively improve the uniformity. The flow maldistribution parameter in plate-fin heat exchanger has been reduced from 1.21 to 0.21, and the ratio of the maximum velocity to the minimum is reduced from 23.2 to 1.8 by installing the punched baffle. The results suggest room for the optimum design of plate-fin heat exchanger. 相似文献
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The flow maldistribution and the effect of different inlet configuration on the flow distribution in platefin heat exchangers were studied experimentally. It is found that the flow maldistribution is serious because of the defects of inlet configurations, while the inlet configuration and Reynolds number are the main factors affecting the flow distribution. The improved inlet configurations, which are the header with a two-stage distributing configuration and the guide vane with a fluid complementary cavity were proposed and tested in this paper. The experimental results show that the improved inlet configurations can effectively improve the performance of flow distribution in heat exchangers. 相似文献
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A fluid flow model of distributor was set up to investigate the effectof distributor configuration on the fluid flow distribution in plate- fin heat exchanger. At the same time, a mathematical equation was developed to generate different types of fluid flow maldistribution models considering the possible deviations in fluid flow. Using these fluid flow models, the fluid flow distributions in plate- fin beat exchanger were calculated for different configurations and operating conditions. The computational results show that nonuniform inlet velocity, inlet angle, and orifice diameter on the fin are the main factors affecting the distribution performance of distributor. The fluid flow distribution in plate- fin heat exchanger can be effectively improved by changing the distributor configuration. The distributor reaches the best distribution performance when the orifice diameter is 2 mm. The computational results are in good agreement with experimental ones. 相似文献