热油载体锅炉对流管束三维参数化设计

文章基于Solidworks API的二次开发,研究总结了Solidworks参数化设计的方法和过程,并以热油载体锅炉对流管束三维参数化设计为例,提出了一套新产品开发和产品系列化的先进、快捷的集成型计算机辅助设计方法。     

表面粗糙度标注的参数化设计

以标注表面粗糙度为例，介绍了在微机上进行机械设计过程中标注的方法，用类似的方法设计人员可以对CAD进行二次开发，编制对设计者有用的一些程序，表面粗糙度标准参数化设计在计算机上调试半通过，已经在机械设计过程中使用。     

利用AutoCAD软件包二次开发曲轴零件参数化绘图处理程序的研究

本文介绍了以Auto CAD软件包为基础的二次开发以及实现机械零件CAD参数化绘图的方法;并以发动机曲轴零件为例,着重论述了如何采用AutoCAD内部的Autolisp语言及其它功能,更有效地、更灵活地实现计算机参数化绘图。     

空冷器管束用Incoloy 825复合钢板设计厚度的探讨

介绍了空冷器管束用Incoloy 825复合钢板的设计厚度与复合后的成品厚度之间的差异,可能造成不满足设计要求的严重后果,并提出了设计制造时的注意事项。     

空冷器管束换热管与管板胀焊并用连接的制造工艺探讨

简要叙述了空冷器管束换热管与管板胀焊并用连接的制造工艺,并提出了控制其连接质量的方法。     

一种新的柴油机螺旋进气道参数化设计方法

通过建立螺旋进气道螺旋段曲线方程及启用曲线关联特性,研究出一种全新的进气道参数化设计方法,建立了结构复杂的螺旋气道参数化模型.采用数值模拟计算和稳流气道试验相结合的方法,在验证了计算模型可靠性的前提下,引入性能结构参数K和θ,研究了各设计方案结构参数与气道性能之间的关系,通过分析和比较各气道方案的计算结果表明:改变θ角度大小,气道涡流强度变化十分明显;将比例因子K控制在0.84左右,流量系数和涡流比均可维持在较高水平.通过调整这两个参数的数值大小,可以有效控制气道性能的变化趋势,从而确立了气道结构与性能之间的定量关系.     

产品设计的参数化方法

介绍了产品设计过程中参数化技术的概念、基本原理及实现方法。     

活塞专用加工机床模块的参数化设计方法研究

为了适合活塞专用加工机床模块化方案设计的需要,提出用参数化设计方法来进行模块创建,建立了参数化模块模型创建的一般过程和方法并应用于实践。     

活塞专用加工机床模块的参数化设计方法研究

为了适合活塞专用加工机床模块化方案设计的需要,提出用参数化设计方法来进行模块创建,建立了参数化模块模型创建的一般过程和方法并应用于实践。     

内燃机中系列标准螺母的参数化建模设计

从实际应用角度,通过在Microsoft Visualc＋＋6．0编辑器中运用类c＋＋语言创建表达式文本文件,详细介绍了在一维工程设计软件UGNX中实现零件参数化建模设计的方法。针对不同的产品系列,零件结构形体的相似性,向读者揭示了可以构建相应的表达式文本文件,应用相应的建模方法实现快速有效的参数化设计建模。     

Simulation of cross-flow-induced vibration of tube bundle by surface vorticity method

A fluid-structure interaction model based on Surface Vorticity Method (SVM) was used to study flow-induced vibrations of tube bundles in medium space ratio. The flow-induced vibrations of four tubes in a rotated square and a staggered tube bundle in three-row and five-column arrangements were simulated in the high sub-critical Reynolds number (Re) range. The results on fluid forces, tube responses and vorticity maps were presented. The vorticity maps of the four rotated-square tubes changed dramatically when the rigid tubes were replaced by the flexible tubes. From the vorticity maps and vibration responses of the staggered tube bundle of different structural parameters, it was found that with the decrease of tube natural frequency, the maximal vibration response moved from the third row to the first. The results also showed that when more flexible tubes are used, the flow pattern changed drastically and the fluid-structure interaction imposed a dominant impact on the flow.     

Numerical simulation of horizontal tube bundle falling film flow pattern transformation

It is important to study the falling-film pattern of a horizontal tube bundle in order to set up a heat and mass transfer model accurately. The falling-film pattern of a horizontal tube bundle is simulated in this paper. The technique is based on computational flow dynamics (CFD) for the two-phase flow of gas and water. The experimental results were used to validate the mathematical model. It indicates that the simulation results accord with experimental data well. The simulated results show that the flow pattern varies with different flow rates. Under the different flow rates, it observes the droplet, droplet-columnar, columnar, columnar-sheet and sheet flow patterns. The critical value is 0.0125 kg/s between droplet and columnar, and the critical value is 0.02 kg/s between columnar and sheet.     

Effect of fins on forced convection heat transfer around a tube in an aligned‐arranged tube bundle

The effect of fins on heat transfer around a tube in an aligned‐arranged tube bundle was investigated experimentally, and the obtained results were compared for three arrangements, i.e., single tube, single tube row, and staggered‐arrangement. It was found from the experiment that the effect of fins begins to appear in an aligned‐arrangement with larger fin spacing than in a staggered‐arrangement. The degradation in the local heat transfer coefficient due to fins can be recognized not only on the rear region of the tube, as observed in other arrangements, but also on the frontal region. As a result of this phenomenon, the degradation in the average heat transfer coefficient in an aligned‐arrangement becomes larger than in other arrangements with the same fin spacing. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(8): 555–563, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20091     

Particle image Velocimetry measurement of flow across tube bundle in waste heat boiler

IntroductionShell-and-tube heat exchanger is the key componentof waste boiler applied abundantly in industry. Becauseof the extfCme flow complexity, it is very difficult topredict the heat transfer and pressure drop characteristics.The vortex and flow stagnation will lead to thedeterioration of heat transfer, deposition of scale andcormsionll]. So the investigation of the characteristics offlow across the tube bundle in shell side is of practicalimportance. Moreovef, it is of theoretical impo…     

氦气冲刷螺旋管束传热的数值研究

采用CFD软件对氦气冲刷螺旋管束的传热特性进行了数值模拟。计算时采用了轴对称简化模型;湍流模拟采用低Re k-ε模型。通过与实验数据对比,发现低Re模型比壁面函数法更适合计算冲刷管束类型的流动。计算结果表明,顺排管束前几层平均Nu高于叉排管束,而深层管平均Nu低于叉排管束;管列距离较大时排列方式对深层管的传热影响很小;管束与边界距离约为管束中心部分氦气流道宽度的一半时,各列传热管传热和氦气出口温度都较为均匀;管束横向位置发生偏移将导致管束内流动、传热出现不均匀。结果对于螺旋管蒸汽发生器设计具有参考意义。     

微细管束换热器结霜及流动对流换热特性实验研究

利用可视化换热器性能实验台测试了微细管束表面在无换热、大温差、凝露条件下不同风速工况的流动损失与空气侧换热系数。同时探究了超低温工况下,相对湿度和风速对微细管束换热器流动换热特性影响。相对湿度增大,湿空气释放潜热增加,结霜量增大,换热器前后压损增加。高速气流具有剪切作用,风速增大会导致结霜迟滞。     

CAD技术在舰用燃气轮机设计中的应用

本文论述了计算机辅助设计(CAD)技术及其在舰用燃气轮机设计工作中应用的前景,并提出了舰用燃气轮机CAD 系统实现的方案和方法。     

Condensation of organic binary mixtures flowing horizontally in a horizontal tube bundle

Both heat and mass transfer in the gas phase and heat transfer in the liquid phase are examined experimentally for film condensation of organic binary mixtures such as ethanol-water and methanol-water. Experimental results on the average heat flux, vapor-liquid interface temperature and liquid-phase Nusselt number are compared with analytical solutions based on stagnant film theory and heat-transfer relationships for film condensation from a pure vapor. Experimental heat transfer results agree well with the analytical solutions, except that the experimental liquid-phase Nusselt numbers under conditions of low mass fraction of water are considerably higher than predicted by the analytical solutions. This high value of the liquid-phase Nusselt number is considered to be caused by dropwise condensation in the liquid phase. However, its effect on the tube bundle is not so remarkable compared with that in gravity-controlled condensation on a vertical surface. This is considered to be caused by the condensate inundation effect. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(6): 342–361, 1996     

Tube bundle replacement for segmental and helical shell and tube heat exchangers: Experimental test and economic analysis

In this investigation, the second test analysis with more comprehensive evaluation with a focus on fouling mitigation, increased running-time and economic analysis are shown and then, the thermal design procedure for tube bundle replacement of critical heat exchanger of Butene-1 unit in Petrochemical Company as a case study are described. Finally, experimental data for the average heat transfer coefficient and pressure drop of shell-side in segmental and helix bundles are measured and calculated for the mass flow rate of 14.24 kg/s and then these data are compared with the data from code and EXPRESS. Moreover, additional comparison between code and EXPRESS results are provided to ensure the accuracy of calculation program in various mass flow rates. Based on the same shell in the case studies, the results showed that in addition to improved heat transfer performance of the helix bundle over segmental bundle, helix bundle achieved two to three times longer operational run times. From economic point of view, the results for replacement of segmental bundle with a helix bundle showed that initial and installation costs of helix bundle to segmental bundle could be increased, but maintenance and operating costs can be decreased in the helix bundle, 60% and 20%, respectively. Comparison between code and EXPRESS results with experimental data for the mass flow rate of 14.24 kg/s showed that the deviation in heat transfer coefficient and pressure drop are quite reliable for segmental and helix bundles.     

A new performance evaluation method and its application in fin-tube surface design of small diameter tube

In this paper, a simple yet efficient performance comparison method is proposed based on the assumptions of constant properties and identical frontal area. For this method, no correlations are required, and a small number of discrete data are sufficient. To illustrate the feasibility of the proposed approach, a new slotted fin with 4 mm tubes is designed to replace the original louvered fin with tubes of 7 mm. The orthogonal design method is adopted in the fin design to reduce the number of computational cases significantly, and yet a nearly optimum combination of major geometric factors can still be obtained. The reasonable parametric combination of 3 global parameters is obtained by analyzing the numerical results of 16 plain plate fins. Based on this result, 3 new slotted fins with different fin pitches are studied. The slotted fin with a fin pitch of 1.4 mm is recommended after considering the heat transfer, comprehensive performance, and cost of material and operation. The result shows that compared with the original louvered fin, the recommended fin not only increases the heat transfer rate by 2.2%, 22.5%, and 13.7% under an identical flow rate, identical pressure drop, and identical pumping power constraint, respectively, but also saves approximately 36% of the copper tube materials.