矩形翅片椭圆管热交换器流动和换热特性的数值模拟

利用CFD计算方法,对矩形翅片椭圆管热交换器进行了数值模拟,得到其在不同风速下的流动和换热特性,并就椭圆管和圆管之间阻力与换热特性进行了计算比较,分析讨论了片距及管排数对阻力特性的影响,为风洞热交换器设计提供依据。     

变角度翅片结构对散热器性能的影响分析

为提升散热器的综合性能,以开窗角度为27°、翅片波距为2. 4 mm的百叶窗翅片散热器为基础,提出基于此结构改良的8种变角度翅片结构。采用Fluent软件进行数值模拟,通过对5种入口风速下8种变角度翅片结构的传热因子j与阻力因子f进行分析,探讨8种变角度翅片结构的优劣。研究表明,各变角度翅片结构均有效提升了散热器的传热性能,均对翅片的阻力性能影响较小,其中对散热器翅片综合性能提升最大的攻角渐变值Δθ=1. 2°,采用变角度翅片结构的散热器最高可提升6. 54%的传热性能,最高可增加1. 5%的散热量。     

空调器铜翅片专用多工位级进模的设计

通过对热交换器工作环境的分析和对其性能的研究,以铜翅片替代铝翅片既可以提高空调器制冷效率、又可增加防腐蚀能力。在参考国内铝翅片加工级进模研究理论的基础上,设计了铜翅片加工专用模具。整套模具采用子模分立式的设计方案,各凸、凹模采用分开加工方法,使相同结构尺寸的模具具有结构互换性。通过加工试验验证了此模具结构的合理性和可行性。     

翅片热板散热器的传热数值模拟研究

采用有限元法,应用ANSYS软件的热分析功能对翅片热板散热器的传热性能进行了数值模拟,并计算出该散热器表面的瞬态温度变化曲线,与实验测试结果吻合得较好.最后的研究结果表明:所研制的新型功率电子元器件翅片热板散热器散热性能良好,具有良好的启动性能和等温性能.     

顺排H型翅片圆管的传热与流动分析

通过模拟计算并比较数据得出结果：随着迎面风速增大,Re 数增大,Nu 数增大,摩擦系数f 减小,传热热阻R 也减小;随着翅片间距增大, Nu 数减小,摩擦系数f 减小,对传热热阻R 的影响较小;随着翅片厚度增大,Nu 数增大,摩擦系数f 明显减小,传热热阻R 也显著减小;随着翅片高度增加,Nu 数增加,摩擦系数f 也增加,而传热热阻R减小,在本文中研究的影响因素中优先考虑的因素为：翅片间距、翅片厚度及翅片高度。     

强制对流开槽翅片的传热性能研究

实验研究了强制对流条件下光滑翅片、水平槽翅片、竖直槽翅片及交叉槽翅片的传热性能。结果表明,四种翅片中,交叉槽翅片的平均对流传热系数最高,比光滑翅片高出１５％～２５％。分别得出了四种翅片的努塞尔特数、雷诺数、翅片高度与间距之比以及翅片长度与间距之比表示的无量纲传热准数关系式。     

一种高效多用的翅片机--CDZ翅片机

简要介绍了CDZ翅片机的结构、工作原理、电气控制;该翅片机在实际使用中具有操作简便、运行稳定、适用范围广、生产效率高等特点.     

典型波纹翅片单元流动与传热特性的数值研究

以两种典型的波纹翅片单元为研究对象,在合理简化条件下给出了物理模型和数学模型,通过流固界面的传热耦合,对不同进口风速下波纹翅片单元的流动及传热和阻力特性进行了数值研究.通过对传热系数,Nu数、压降以及涡量分布的对比分析,结果表明:人字形翅片的传热性能优于波浪形翅片,而流动阻力性能却没有明显的劣势,其主要原因是翅片流场中涡流的产生与耗散存在差异.     

空调热交换器生产线专用设备的研制

一、概述众所周知,制冷技术的心脏是“一机加二器”。“一机”即制冷压缩机,“二器”即冷凝器,蒸发器,通称热交换器。长期以来,生产热交换器的专业厂一直是采用单机手工作业的方式,生产效率低,质量较差。为了彻底改变这种现状,在国家机械电子部的领导下,近些年来,辽宁省机械研究院致力于热交换器生产线专用设备的研制工作。并于一九八七年首次为我国广东某厂研制成功了热交换器生产线专用机床。技术专家认为:这些设备结构先进,自动化程度高,其装机质量达到了国外引进设备水     

错列排布S型翅片流道内流动与传热特性数值研究

对错列排布的S型翅片流道内的流体流动与传热特性进行了数值计算研究,考查了局部、流场分布,分析了不同雷诺数下局部传热系数分布,随着雷诺数增加,传热系数升高.同时从场协同的角度分析了传热系数变化的原因.与传统波纹翅片结构进行对比,S型翅片结构协同角降低,场协同程度提高,对流传热系数增加.     

基于板翅式换热器的百叶窗高翅片的设计与制造

百叶窗翅片的制造高度过高会造成翅片强度不足,导致换热器产品的强度不足,无法使用。传统百叶窗翅片的制造高度限制在10 mm以下。通过对连续型折弯式百叶窗高翅片的设计与制造进行尝试,设计了一种全新的翅片结构,并给出了翅片的制造方法。采用上述制造方法,可以得到,弯折角度0°~45°可控、翅片高度9~19 mm可控、翅片峰距1.5~4 mm可控的任意组合的翅片,提高了翅片的原料利用率和换热器的传热效率。     

New optimization method, the algorithms of changes, for heat exchanger design

Heat exchangers are widely used in the process engineering such as the chemical industries,the petroleum industries,and the HVAC applications etc.An optimally designed heat exchanger cannot only help the optimization of the equipment size but also the reduction of the power consumption.In this paper,a new optimization approach called algorithms of changes (AOC) is proposed for design and optimization of the shell-tube heat exchanger.This new optimization technique is developed based on the concept of the book of changes (I Ching) which is one of the oldest Chinese classic texts.In AOC,the hexagram operations in I Ching are generalized to binary string case and an iterative process,which imitates the I Ching inference,is defined.Before applying the AOC to the heat exchanger design problem,the new optimization method is examined by the benchmark optimization problems such as the global optimization test functions and the travelling salesman problem (TSP).Based on the TSP results,the AOC is shown to be superior to the genetic algorithms (GA).The AOC is then used in the optimal design of heat exchanger.The shell inside diameter,tube outside diameter,and baffles spacing are treated as the design (or optimized) variables.The cost of the heat exchanger is arranged as the objective function.For the heat exchanger design problem,the results show that the AOC is comparable to the GA method.Both methods can find the optimal solution in a short period of time.     

A tribo-testing method for high performance cold forging lubricants

A tribo-testing method based on inducing different deformation patterns at the tool–workpiece interface developed by the authors was used in rating the performance of high quality lubricants. Dies which can induce different levels of maximum surface expansion under localized rod drawing set up were used. The maximum local surface expansion induced ranged from 20 to 500%. The basic feature for this test lies under the assumption that the surface expansion is proportional to the lubricant thinning and breakdown at the tool–workpiece interface. The experimental set up is coupled with die heating facilities used to raise the temperature at the interface so that the influence of temperature on the performance of the lubricant is studied. The performance of several coating-based lubricants was studies under this method. One of the goals of screening the lubricant was to identify possible lubricant candidates for replacing zinc phosphate coating based lubricant for medium forging processes. The results have demonstrated that, the effectiveness of the lubricants varies considerably with changes in the maximum local surface expansion induced at the interface and the change in the interface temperature. Of the six lubricants studied, two lubricants based on calcium and sodium soap were found to be at the same performance level as the conventional zinc phosphate coating + metal soap.     

基于单元化建模的换热器管板系列化设计

首先阐述了单元化建模基本思想,参数化拼接原理,给出了图形单元的分类,然后建立了描述系列化浮头式换热器管板布管区的数据结构,创建了相应的数学模型,采用AutoCAD二次开发技术,在VisualC＋＋6,0和ObjectARX的环境下结合具体图例介绍了单元化建模及参数化拼接原理的实现过程,最后利用该系统中的图形单元建模技术进行实例研究。实践证明,这是一种行之有效的设计方法。     

热交换器用铝合金高频焊管接头组织与性能分析

管材所用铝合金带料为三层复合材料,外层为Al-Si钎料层,中间为Al-Mn芯材,内层为Al-Zn防腐层.带材经成型机组成型后再经高频焊接而成焊管.利用金相试验方法对一系列高频焊工艺焊接接头进行显微组织分析,并通过爆破试验对该接头进行力学性能测试.结果表明:利用高频焊接铝合金管是一种理想的焊接工艺.     

Impacts of fouling and cleaning on the performance of plate fin and spine fin heat exchangers

An experimental study was conducted to investigate the effects of air-side fouling and cleaning on the performances of various condenser coils used in unitary air-conditioning systems. A total of six condenser coils with different fin geometry and row number were tested. Performance tests were performed at three different conditions: clean-as-received, after fouling, and after cleaning. In all cases, it was observed that the fouling was mostly confined to the frontal face of the heat exchanger as reported in the previous investigations. The amount of deposited dust was more dependent on fin geometry for the single-row heat exchangers than for the double-row heat exchangers. The predominant effect of fouling was to cause a more significant increase in air-side pressure drop than a degradation in heat transfer performance. For the single-row heat exchangers, the pressure drop increased by 28 to 31%, while the heat transfer performance decreased by 7 to 12% at the standard air face velocity of 1.53 m/s depending on fin shape. For the double-row heat exchangers, the pressure drop increased by 22 to 37%, and heat transfer performance decreased by only 4-5% at the same air face velocity. Once the contaminated coils were cleaned according to the given cleaning procedure the original performance of the heat exchangers could almost be recovered completely. The pressure drop could be restored within 1 to 7% and the heat transfer performance could be recovered to within 1 to 5% of the originally clean heat exchangers. Therefore, it is concluded that a periodic application of the specified cleaning technique will be effective in maintaining the thermal performance of the condenser coils.     

锅炉房内高位设置热交换器的方法

论述在锅炉房内设置热交换器的条件及方法。     

A thermal design method for the performance optimization of multi-stream plate-fin heat exchangers

An optimization design method based on field synergy principle is developed for Multi-stream plate-fin heat exchangers (MPHEs) with a segmented differential model. The heat exchanger is divided into a number of sub-exchangers along the main stream, and each sub-exchanger consists of N passages along the height of the exchanger. Compared with the traditional heat exchanger design, this method allows temperature and pressure fields to be obtained via coupling calculation with consideration of variable physical properties and the axial heat loss of the heat exchanger. Finally, the heat exchanger is optimally designed using a temperature-difference uniformity optimization factor based on field synergy principle. This design model can provide an accurate temperature field and pressure field, because the stream properties are determined by the mean temperature and pressure of each local sub-exchanger. Optimum results indicate that the temperature distribution on the cross section of the heat exchanger is relatively uniform and that the temperature difference of heat transfer for each stream is always a small value. These characteristics prove the feasibility and effectiveness of this design model. In this paper, a case of five stream plate-fin heat exchangers for an ethylene plant is designed under a practical cold box operating condition with the proposed model, the structure and heat transfer of which are optimally determined. The design model and optimization method proposed in this work can provide theoretical and technical support to the optimization design of MPHEs.

     

CFD analysis of fin tube heat exchanger with a pair of delta winglet vortex generators

Among tubular heat exchangers, fin-tube types are the most widely used in refrigeration and air-conditioning equipment. Efforts to enhance the performance of these heat exchangers included variations in the fin shape from a plain fin to a slit and louver type. In the context of heat transfer augmentation, the performance of vortex generators has also been investigated. Delta winglet vortex generators have recently attracted research interest, partly due to experimental data showing that their addition to fin-tube heat exchangers considerably reduces pressure loss at heat transfer capacity of nearly the same level. The efficiency of the delta winglet vortex generators widely varies depending on their size and shape, as well as the locations where they are implemented. In this paper, the flow field around delta winglet vortex generators in a common flow up arrangement was analyzed in terms of flow characteristics and heat transfer using computational fluid dynamics methods. Flow mixing due to vortices and delayed separation due to acceleration influence the overall fin performance. The fin with delta winglet vortex generators exhibited a pressure loss lower than that of a plain fin, and the heat transfer performance was enhanced at high air velocity or Reynolds number.     

翅片热板散热器的设计

针对功率电子元器件散热的需要,设计一种新型功率电子元器件新型散热器一翅片式平板热管散热器,并通过强度较核了设计的合理性,通过实验检验了设计的可靠性.