板式换热器板片的失效分析

通过垢层电子探针成分分析和金相分析 ,发现板式换热器板片失效的主要原因是由于换热器介质中含有Cl-、S2 -而导致点腐蚀穿孔。并据此提出严格控制磺酸钠溶液的碱度以防止板片失效或采用钛材作为板式换热器以增加材料的耐蚀性的措施。     

板式换热器失效因素分析

板式换热器以其传热效率高、结构紧凑、体积小、重量轻、操作灵活性大等特点,越来越多的应用于各行业的多个领域。本文参照我厂板式换热器多年的使用经验,根据板式换热器的结构特征,一方面从设计制造、设备安装方面的影响因素加以分析;另一方面对工艺操作条件的变化,如压力、温度急剧波动、介质物况的不同及使用和的流道结垢与堵塞、板片腐蚀穿孔等方面对板式换热器密封的影响加进行了分析;对换热器在清洗检修时清洗剂的选择、垫片材质的选择及维护保养方面提出建议。从而总结出式换热器失效是多方面因素造成的,要针对具体的问题进行分析,提出合理可行的解决方法 。     

板式换热器的新颖板片结构

<正> 板式换热器是一种新颖高效的换热设备。随着换热器结构的改进和换热性能的不断提高,板式换热器的应用也越来越广泛。板式换热器最重要的部件是换热板片,其结构和组装形式是影响换热器热力性能的关键因素。对板片结构所作的一系列改进,其目的不外乎是提高传热性能,降低压力损失和减小热损失。     

板式换热器的研究现状及进展

介绍了板式换热器研究现状。针对板式换热器超大型化技术、可靠结构和传热性能兼顾的板片开发、流场精细化CFD研究等问题讨论,为板式换热器未来的发展研究提供参考。     

板式换热器失效的主要原因及相关对策

板式换热器是一种结构紧凑、性能高效的换热器。但板式换热器的各种失效破坏也给使用者造成一定的经济损失,其原因是多方面的。本文分析了板式换热器失效的原因,以及提出了解决板式换热器失效的相关对策。     

关于板式换热器粘接修补堵漏技术问答

板式换热器是化工行业重要的生产设备,以吉林石化公司乙二醇厂使用的丹麦阿法拉伐生产的A15-BWPD型换热器(由432片板片组成,换热面积为324m2)为例,对板式换热器的粘接修补堵漏技术进行详细介绍。     

板式换热器在终冷水换热中的应用

由于板式换热器具有设备基础简单、易按换热面积增减板片、工艺管道简单、检修容易和传热效率高等优点,近年来,已在各种介质的换热过程中得到了广泛的应用。在我厂的终冷水换热中,原设计使用的是列管式换热器,１９９３年我们用螺旋板换热器代替了列管式换热器,但堵塞和腐蚀串漏问题仍难以解决,设备的使用周期较短。１９９７年５月,我们利用终冷水系统改造的机会,用１台板式换热器代替了４台螺旋板换热器。选用的板式换热器的参数如下：型号Ｍ１５—Ｂ板片材质ＡＩＳＩ３板片厚度０．ｓｍｍ换热面积１８８．ｓｉｎ’有效板片数３０４…     

2种CaCO_3溶液配制法下板式换热器的污垢特性

为研究板式换热器碳酸钙的污垢特性,以BR0.015F型板式换热器为实验平台,研究了2种配制碳酸钙溶液方法(碳酸钠与氯化钙和碳酸氢钠与氯化钙)在板式换热器下的污垢特性,并用扫描电镜观察结垢表面的晶体类型。结果表明:在相同的实验条件下,碳酸钠法在板片表面结垢薄、易于清除,污垢没有凝结成块状,板式换热器速度场和温度场对污垢分布的影响不明显,扫描电镜观察污垢粉末多为六面体晶型,单个分布未粘结在一起。碳酸氢钠法在板片表面结垢相对致密、难于清除,污垢凝结成块状,板式换热器温度场的分布对污垢分布的影响明显,结垢量的分布与板式换热器数值模拟的温度场分布基本一致,扫描电镜观察污垢发现污垢晶体紧密的粘结在一起。     

板式换热器常见故障及处理

板式换热器被广泛的应用于各行业领域,但是,由于板片间流通截面狭窄,水质不好形成水垢和污物沉积都容易造成板式换热器堵塞,密封垫片耐温性能差时,容易渗漏和影响使用寿命,形成水垢的主要原因是由于循环水硬度高,要保证板式换热器正常使用,必须保证软化水设备完好,循环水硬度符合标准.     

双波纹板管式换热器流场的数值模拟

介绍了一种用于气气交换的错流式双波纹板管式换热器,它具有单位体积换热面积大,结构紧凑、稳定性好以及换热系数高等特点.运用Fluent软件.对不同尺寸的双波纹板管式换热器的流场进行了模拟,经过分析对比得到换热效果最佳时双波纹板片的形状.研究结果表明,换热板片上双波纹的波幅、周期和板间距决定了板式换热器的换热效果和压降等.     

钛-钢复合板设备的结构优化

近些年,钛制设备在我国的氯碱工业、尿素生产、精细化工、硝酸生产、PTA等行业得到了广泛应用,我国的钛需求量也逐年增高.国内设计、制造、使用钛制设备已有30余年的历史,积累了一些经验,掌握了一些设计、制造和使用技术.而今钛-钢复合板制设备占据了钛制设备的大部分应用,但钛-钢复合板制设备比钢制设备在设计、制造上具有更多的难度,需要将成熟、可靠的结构设计进行传播,并不断探寻更加合理、有效的结构形式.     

Effects of Viscous Dissipation and Rarefaction on Parallel Plates with Constant Heat Flux Boundary Conditions

The effect of viscous dissipation and rarefaction on heat transfer characteristics of hydrodynamically and thermally fully developed flow between parallel plates with constant heat flux conditions is analyzed. Three different types of heat flux boundary conditions, i.e., both plates kept at different constant heat fluxes, both plates kept at equal constant heat fluxes, and one plate insulated, are applied. In all cases, closed form expressions are obtained for the temperature distribution and Nusselt number. Viscous dissipation, rarefaction, and heat flux ratio are found to influence the heat transfer substantially. The present predictions are verified for the cases which neglect the microscale and viscous heating effect. The obtained results are in good agreement with other analytical results.     

两种波纹深度板片传热及阻力特性的对比实验研究

通过实验的方式和对比的方法对两种不同波纹深度板片组成的可拆板式换热器的传热及阻力特性进行研究,每种深度板片组成的板式换热器采用硬板63°/63°、软板29°/29°和混合板63°/29°三种波纹角度组合,此实验采用水/水换热,设置了两种工况,一种是冷热两侧等流速,另一种是固定热侧流速,计算两种工况下传热系数和压降的数值,描绘出对应的曲线。实验证明相同波纹夹角板片组合,该浅密波纹板片的传热系数均高于普通波纹板片,平均高于140 W/(m²·K),即传热系数平均提高1.9%,在混合板中两者传热系数的差别在300 W/(m²·K)以上,提高达4.8%,阻力的变化趋势与传热系数相同。推导出每组设备适用于一定Reynolds数范围的Nusselt数方程和摩擦系数方程,与已有研究成果对比分析,证明了该实验的正确性,同时也揭示这两种波纹板片的传热和阻力性能有优化的余地,为进一步的研究指明了方向。该实验也表明,除深度外的几何尺寸和结构均相同的两种波纹板片,虽然外形接近,但对应的Nusselt数和摩擦系数关系式却不相同,而且差别很大。     

Heat transfer in a reciprocating plate column

A pilot‐scale (5.08 cm internal diameter) reciprocating plate column has been modified by the insertion of a brass test section for heat transfer measurements. Heat is supplied to liquid (water or a glucose solution) in the column from an electrical heating tape wound round the brass section, the walls of which contain thermocouples. Reciprocation of the plates in the column results in up to a seven‐fold improvement In heat transfer coefficient, to single phase liquids. Conditions are turbulent with oscillatory Reynolds numbers up to 20000. The effect of plate reciprocation is much less pronounced when the liquids are agitated by a stream of gas bubbles. The single‐phase heat transfer coefficients have been correlated for 5 different types of plates using approaches already available in the literature for turbulent systems in steady flow. The best‐fit oscillatory flow correlation differs slightly from the existing correlations for steady flow.     

内部热耦合精馏塔的传热及优化

为研究同轴式内部热耦合精馏塔（HIDiC）在不同压缩比下的传热量和传热系数,以乙醇-水为分离物系,在自制中试装置中进行了实验研究。建立了同轴式HIDiC的传热模型即利用闪蒸罐代替塔板,计算进出闪蒸罐物流的焓值差,从而得到精馏段与提馏段板间换热量,并通过划分区域的方法计算了传热系数。以年度总费用（TAC）作为优化指标研究了实现外回流为零时所需的外部换热器的个数。结果表明：当压缩比为2.2时,塔间传热量最大,冷凝器和再沸器的负荷最低,且压缩比与传热系数的关系为负相关;随着精馏段与提馏段板间最小换热温差的增大,所需外部换热器个数不断减少,TAC呈现降低的趋势,当外部换热器个数为1,即热量耦合位置为精馏段第一块板与提馏段第一块板时,TAC最低。     

Thermal Residual Stresses in Adhesively Bonded In-plane Functionally Graded Clamped Plates Subjected to an Edge Heat Flux

In this study we have carried out the thermal residual stress analyses of adhesively bonded functionally graded clamped plates for different edge heat fluxes. The material properties of the functionally graded plates were assumed to vary with a power law along an in-plane direction not through the plate thickness direction. The transient heat conduction and Navier equations describing the two-dimensional thermo-elastic problem were discretized using the finite-difference method, and the set of linear equations was solved using the pseudo singular value method. The plate material properties near the interfaces played an important role in the interfacial adhesive stresses. The compositional gradient affected considerably both in-plane temperature distributions and heat transfer periods. The type of in-plane heat flux had only a minor effect on the temperature profiles but affected both the temperature levels and heat transfer period. Both plates undergo considerable compressive normal strains and stresses, but shear strains were more effective. Peak equivalent strains were observed for a constant heat flux and plates with a metal-rich composition. The compositional gradient and direction played important role in the profiles and levels of normal, shear and equivalent stresses as well as strains. The equivalent stress and strains concentrated along the free edges of the adhesive layer. The adhesive layer experienced a considerable distortional deformation rather than volumetric deformation. The equivalent stress exhibited small changes through the adhesive thickness and along the overlap length. The equivalent stress remained uniform in a large region of the overlap length and increased to a peak level around the free edges of the first plate–adhesive interface, whereas it increased to a peak level in a large region of the overlap length from a minimum level around the free edges of the second plate–adhesive interface. The strains and equivalent strains were higher for a metal-rich material composition. The direction of the material composition of the plates affected both stress and strain levels; thus, the CM–CM and CM–MC plates exhibited lower strain and stress levels than those in the MC–CM and MC–MC plates. However, only the adhesively bonded CM–MC plate configuration could achieve the lowest deformations and stresses in both plates and adhesive layer.     

Thermal model validation of plate heat exchangers with generalized configurations

Thermal models of plate heat exchangers rely on correlations for the evaluation of the convective heat transfer coefficients inside the channels. It is usual to configure the exchanger with one countercurrent single-pass arrangement for acquiring heat transfer experimental data. This type of configuration approaches the ideal case of pure countercurrent flow conditions, and therefore a simplified mathematical model can be used for parameter estimation. However, it is known that the results of parameter estimation depend on the selected exchanger configuration because the effects of flow maldistribution inside its channels are incorporated into the heat transfer coefficients. This work presents a parameter estimation procedure for plate heat exchangers that handles experimental data from multiple configurations. The procedure is tested with an Armfield FT-43 heat exchanger with flat plates and the parameter estimation results are compared to those obtained from the usual method of single-pass arrangements. It can be observed that the heat transfer correlations obtained for plate heat exchangers are intimately associated with the configuration(s) experimentally tested and the corresponding flow distribution pattern(s).     

型板换热器的传热性能和阻力降特性研究

研究一种新型高效型板换热器 ,对型板换热器的传热特性及阻力降性能等进行了实验研究。通过研究发现 ,型板换热器的传热系数比列管式换热器的传热系数高 5 0 %～ 10 0 % ,阻力降值比传统的列管式换热器低 ,与型板内流体流速的 1 4 4次方成正比     

Experimental study of natural convection heat transfer in a non-newtonian fluid: Part II. Horizontal plate

Experimental data on natural convection heat transfer to non-Newtonian fluids from isothermal horizontal flat plates facing both up and down are reported. Emperical expressions for predicting the heat transfer coefficient for fluids as the flow behavior index is varied from 0.19 to 1.0 were developed. These are essentially similar to the vertical plate case and correlate the data with reasonable accuracy.     

聚合物两圆筒环槽切向流传热的简化计算

本文应用有限差分法对聚合物在两圆筒环槽间具有粘滞耗散热的切向流,简化为两平行平板拖动流而进行传热计算.首先得出熔融体拖动流顺流方向的温度分布,并导出两壁面处温度梯度的近似计算式,从而求出两壁面处的努塞尔准数Nu和换热系数α值.本文可供聚合物螺杆机械、剪切机头、以及模腔流道等具有耗散热传热计算时参考.