径向错列翅片管内凝结对流换热数值模拟分析

采用数值模拟方法,对径向错列翅片管内含不凝结气体水蒸气的凝结对流换热及阻力特性进行了综合分析。将编写的自定义函数(UDF)导入ANSYS FLUENT软件,对新型强化管传热性能和阻力性能进行了数值模拟,并根据管长方向壁面上蒸汽质量分数的变化情况,讨论分析了凝结过程中翅片管传热性能的变化规律。分析结果表明:与光管相比,内翅片管的强化传热效果随翅数增多、翅片换热接触面积增大而更加显著;另一方面,翅片管的流动阻力相应增大,对管路换热产生不良影响。在所研究翅型范围内16翅y=2x~2型翅片管综合强化换热效果更优;此外随着换热过程的持续,蒸汽凝结逐渐放缓;入口速度增大导致水蒸气凝结不充分,对换热效果的提升有一定制约。     

一种优化的光盘文件系统

首先简要介绍在光盘存储中应用广泛的文件系统--UDF（Universal Disc Format）,然后详细阐述UDF的组成,分析UDF的优缺点,提出通过增加光盘基本信息分区和刻录信息分区提高文件系统的扫描速度和可靠性。经过实际应用表明,优化后的UDF文件系统容错性能和时间性能都有所增强。     

仿生推进装置翼盘变速运动的数值模拟研究

根据仿生推进装置运动的特点,考虑推进翼盘推进过程中运动速度的变化,运用FLUENT软件,通过自定义非定常入口边界实现推进翼盘在变速运动中的三维流场数值模拟,得到了速度、压强、阻力等流场参数.绘制出不同驱动速度下翼盘的推进力曲线,并分析了负推进力产生的原因.所得结论为仿生推进装置的优化提供了理论参考依据.     

液压悬架系统阻尼特性分析

为研究汽车液压悬架系统的阻尼性能,用CFD方法对液压悬架系统的内部流场进行了瞬态三维数值模拟,并使用自定义函数UDF和动网格技术定义活塞杆的运动速度,获得了不同时刻下活塞杆阻尼力与运动速度关系。研究结果表明:阻尼力幅值与活塞杆运动速度幅值成正比;阻尼力幅值频率与活塞杆运动速度幅值成反比;相同活塞杆运动速度下,阻尼孔半径与阻尼力幅值成反比。     

对夹式止回阀压力脉动对动态特性的影响

以对夹式止回阀为研究对象,用UG软件建立其内部流场三维模型,用ICEM划分非结构化网格。采用FLUENT软件中标准k-ε湍流模型、采用动网格及UDF技术,对该阀门全开流阻特性进行分析计算,并进行相应试验。试验数据与计算结果对比表明,相对误差较小,验证了数值计算的可靠性。采用动网格计算模型可较好地解决因阀瓣运动所导致的计算区域瞬时变化问题,用UDF技术编写阀瓣运动过程速度控制程序,获取对夹式止回阀动态特性曲线,研究入口压力脉动频率、幅值和全开角度对该阀动态特性的影响,为该阀的进一步动态特性优化提供参考。     

The effect of heat transfer characteristics of macromolecule fouling on heat exchanger surface: A dynamic simulation study

At the city gate gas pressure reduction stations (CGSs), to prevent natural gas from forming a hydrate in the throttle valve, the natural gas is heated by the heater before reaching the pressure relief valve. Heat exchangers are an essential component of industrial processes that contribute significantly to total system energy. Since the element impacting heat exchanger performance is the fouling process, all fouling processes and models were dynamically simulated in this study. Through coding in the C++ language and simultaneous use of fluent functions, or, in other words, user-defined function (UDF), fouling-related models were defined for this software. The dynamic simulation was performed, and parameters such as fouling strength and layer thickness were calculated. The effects of changing operating conditions, such as gas inlet velocity, surface temperature, and fouling species concentration on fouling growth, were also evaluated. As the concentration of fouling species increased, the fouling rate also increased. The amount of supersaturation and fouling rate increased as the surface temperature increased. Due to the operational limitations of the system, to reduce the fouling rate, the gas inlet velocity should be as high as possible, and the fluid inlet temperature, surface temperature, and concentration of fouling species should be as low as possible. In this study, the required time to reach the efficiency of 70% of the heat exchanger was calculated using the modelling of this chamber, which was equivalent to 190 days. Additionally, the critical thickness of the fouling layer at this time was 3.5 cm.