封头形状对板翅式换热器入口段流场影响的数值研究

板翅式换热器入口段存在流场分布不均匀,并由此会引起换热效率低下.首先从封头曲线对流体的引导作用出发,进而优化换热器入口段流场均匀性,提出了板翅式换热器一次封头进一步的改进和优化思路和方法.即结合封头截面曲线函数及其导数特性,将前人提出的下抛物型一次封头改进为上抛物型和正切型,并利用CFD数值模拟方法对3种封头条件下换热器入口段的流场分布进行了对比研究.研究结果表明,使用后两种曲线的封头时,换热器入口段的物流分配更为均匀,在入口条件为7 m/s时,流速不均匀度由封头Ⅰ的5.9分别下降到0.5和0.4;流速最大值与最小值之比由封头Ⅰ的73.6分别下降到60.5和41.5.     

铝制板翅式换热器封头大开孔的补强计算

简述板翅式换热器封头大开孔补强计算的几种近似方法,结合实例,阐述铝制板翅式换热器封头大开孔的补强计算与校核,提出复杂结构的封头应采用应力分析。     

板翅式换热器封头型式的改造

采用计算流体力学(CFD)方法研究大型板翅式换热器封头内的流体流动,根据流动特征提出在封头段加入导流分布板改善流动分布均匀性的方法.与未加入导流分布板比较结果显示,加入导流分布板后,流体分布得到改善,传热系数亦有显著提高.     

板翅式换热器两相流封头设计及其分配特性

提出了三种两相流板翅热器封头形式，即水帘式，打孔管式，孔板工，在允许的压降范围内，明显改善了两相流分配的不均匀状况。实验结果表明，孔板式封头的两相分配性能最佳。     

封头结构对板翅式换热器流体分配性能的影响

研究了板翅式换热器封头高度与流体分配之间的关系,实验结果说明板翅式换热器的流体分配与封头高度有很大关系,封头高度越高流体分配就越均匀.引入不均匀参数,以便可以对流体在出口截面的分配特性进行研究,并进一步研究封头结构型式不同对于流体分配的影响,研究表明:换热器内部流体的流速的最大值与最小值的比值由3-4减少到1.1-1.2,其不均匀度也从原来的0.331减少到0.046.     

CFD技术在板翅式换热器设计开发中的应用

介绍CFD软件的应用领域及特点,阐述CFD技术在板翅式换热器设计中进行数值模拟的理论基础、传热与流动分析,指出CFD技术在板翅式换热器设计开发中的研究发展状况。同时,总结了对流体流动进行CFD技术数值模拟的一般步骤,并提出了CFD技术在板翅式换热器优化设计及开发方面的前景与方向。     

铝制板翅式换热器封头的详细设计

简述铝制板翅式换热器和封头的特殊结构,分析封头的焊接设计、强度计算方法和开孔补强。提出当容器部件难以准确计算时,应先采用验证试验分析,再用对比经验设计的观点。     

板翅式换热器设计理论的进展

介绍20多年来板翅式换热器设计理论方面的主要进展。内容包括:翅片表面传热分析,流动阻力分析,传热因子、摩擦因子的理论和试验数据及有关关联式,表面选择及设计优化技术,计算机辅助设计,流体分配不均匀性和两相流动等。图3表1。     

我国板翅式换热器技术进展

阐述了３０年来，我国在板翅式换热器设计，制造和修补与防护等方面所取得的进步，无熔剂真空钎焊取代盐裕浸渍钎焊和８．０ＭＰａ高压板翅式换热器的开发是我国板翅式换热器制造技术上重大突破，总体技术水平达到或接近世界先进水平，最后展望板翅式换热器的前景和发展方向。     

基于遗传算法的板翅式换热器优化设计

以板翅式换热器的质量为目标函数,以换热器芯体外形尺寸和冷热两侧翅片参数为优化变量,分别采用改进遗传算法和基本遗传算法对其结构尺寸进行优化设计.结果表明,与原始数据相比,换热器的质量明显减小,同时证明改进遗传算法的有效性和先进性.     

板翅式换热器翅片效率等问题的探讨

现有文献中提到的以及实际使用的板翅式换热器设计方法中,在板翅式换热器的翅片效率等若干参数的计算方面,存在一些值得探讨的问题。为了不断提高板翅式换热器的设计精确度,指出原有设计方法存在的问题,并结合例题提出新的设计方法。     

板翅式换热器的传热计算

介绍了板翅式换热器的结构形式,通过传热方程式推导出了翅片效率、表面效率以及流动阻力的计算公式,为板翅式换热器的计算提供依据。     

板翅式换热器翅片性能的比较和选择

通过理论分析和实际计算,讨论了翅片节距对翅片性能的影响,并对不同种类、不同规格翅片的性能进行了比较,得出结论:在同样翅片高度的情况下,翅片节距变小、性能有提高的趋势,所以所有翅片应向节距小的方向发展;适当高度和节距的多孔形翅片,性能不亚于锯齿形翅片;同一种翅片在不同的场合使用,会表现出不同的特性。     

Study of flow distribution and its improvement on the header of plate-fin heat exchanger

In order to enhance the uniformity of flow distribution, an improved header configuration of plate-fin heat exchanger is put forward in this paper. Based on the analysis of the fluid flow maldistribution for the conventional header used in industry, a baffle with small holes of three different kinds of diameters is recommended to install in the header. The flow maldistribution parameter S is obtained under different header configuration. When the baffle is properly installed with an optimum length, with stagger arranged and suitably distributed holes from axial line to baffle boundary, the ratio of the maximum flow velocity to the minimum flow velocity drops from 3.44-3.04 to 1.57-1.68 for various Reynolds numbers. The numerical results indicate that the improved header configuration can effectively improve the performance. The conclusion of this paper is of great significance in the improvement of plate-fin heat exchanger.     

PIV experimental investigation of entrance configuration on flow maldistribution in plate-fin heat exchanger

Flow characteristics of flow field in the entrance of plate-fin heat exchanger have been investigated by means of particle image velocimetry (PIV). The velocity fields were measured using the two-frame cross-correlation technique. A series of velocity vector and streamline graphs of different cross-sections are achieved in the experiment. The experimental results indicate that performance of fluid maldistribution in conventional entrance configuration is very serious, while the improved entrance configuration with punched baffle can effectively improve the performance of fluid flow distribution in the entrance. Based on the analysis of the fluid flow maldistribution, a baffle with small holes is recommended to install in the entrance configuration in order to improve the performance of flow distribution. When the punched baffle is proper in length, the small holes is distributed in staggered arrangement, and the punched ratio gradually increases from central axis to the boundary along with the baffle length, the performance of flow distribution in plate-fin heat exchanger is effectively improved by the optimum design of the entrance configuration. The flow maldistribution parameter S in plate-fin heat exchanger has been reduced from 1.21 to 0.209 and the ratio of the maximum velocity to the minimum θ is reduced from 23.2 to 1.76 by installing the punched baffle. The results validate that PIV is well suitable to investigate complex flow pattern and the conclusion of this paper is of great significance in the optimum design of plate-fin heat exchanger.     

CFD simulation on inlet configuration of plate-fin heat exchangers

A computational fluid dynamics (CFD) program FLUENT has been used to predict the fluid flow distribution in plate-fin heat exchangers. It is found that the flow maldistribution is very serious in the y direction of header for the conventional header used in industry. The results of flow maldistribution are presented for a plate-fin heat exchanger, which is simulated according to the configuration of the plate-fin heat exchanger currently used in industry. The numerical prediction shows a good agreement with experimental measurement. By the investigation, two modified headers with a two-stage-distributing structure are proposed and simulated in this paper. The numerical investigation of the effects of the inlet equivalent diameters for the two-stage structures has been conducted and also compared with experimental measurement. It is verified that the fluid flow distribution in plate-fin heat exchangers is more uniform if the ratios of outlet and inlet equivalent diameters for both headers are equal.     

两台同组板翅式换热器的偏流研究

简介空分设备中两台并联板翅式换热器的偏流量的计算,比较不同偏流量所带来的换热效果差别,得出同组两台换热器的偏流量与流体出口温度的关系曲线,最后提出三种解决偏流的方法及其优缺点。     

大型空分设备板翅式换热器偏流问题分析

随着空分设备大型化,为其配套的换热器体积也不断增大,由此带来的偏流问题会降低换热器的传热效率。从板翅式换热器的设计、制造和外围管道布置两方面分析了引起换热器偏流的原因,并提出解决换热器偏流问题的措施。     

MUSE软件在乙烯冷箱板翅式换热器设计中的应用

介绍MUSE软件应用于板翅式换热器设计中的计算过程和结果,以某套乙烯装置用板翅式换热器为例,完整地介绍了用MUSE软件设计板翅式换热器的具体应用,分析MUSE软件设计板翅式换热器在乙烯冷箱设计中的优势。