某空间站的集成全局热数学模型

为评估某空间站对接飞船后的整体热性能，建立一个集成全局热数学模型。用NEVADA软件建立了空间站在轨运行状态的辐射模型，获得了空间站的外热流及内部辐射交换系数；用FLUENT软件模拟密封舱内部的空气流动情况，获得了舱内空气的速度分布情况及空气与壁面的换热系数；最后用SINDA／FLUINT建立了该空间站的集成全局热数学模型。集成全局热数学模型综合反映了空间站在轨运行时的整体热行为，可以用来评估空间站不同组成部分及不同热控措施对系统整体热性能的影响，也可以用于分析热控系统的地面试验验证方法及系统的故障模式等。

空间站集成全局热数学模型的建模和分析

为了分析某空间站的综合热性能,建立了该空间站的集成全局热数学模型(IOTMM)。文章介绍了该空间站的物理模型、工作模式、热节点网络模型和流体网络模型,其中流体网络模型主要由氨外回路、低温水回路、中温水回路、舱内通风回路和舱间通风回路组成,最后利用IOTMM分析了空间站在载人飞行模式下各种设备的温度变化情况。

弹性气藏中气体渗流的气—固—热耦合数学模型

综合应用渗流力学、岩石力学、热力学理论 ,建立起以气体压力、岩石固相质点位移、绝对温度为基本变量的全新的气—固—热耦合数学模型。该模型假设气藏岩石骨架是可变形的 ,气藏内热量按热力学定律自由传递 ,模型包括完全耦合的气体渗流方程、温度场方程和岩石变形方程。文章所建立的模型实现了气藏中渗流、变形、变温三者间真正意义上的耦合 ,较之已有的气藏渗流模型更能反映气藏实际 ,是对气藏传统渗流理论和流固耦合力学理论的发展 。

加热炉供热系统优化的数学模型研究

本文首先建立了加热炉内钢坯加热过程的数学模型，根据变化的轧制生产情况，即可得出钢坯的准确温度分布，通过建立在给定条件下尽可能地提高加热质量、降低燃耗和钢坯氧化烧损的优化加热模型和加热炉区域热平衡模型，结合钢坯加热过程数学模型，应明分割技术采用FORTRAN编程计算出了加热炉最佳供热的Q－P模型。在现场实验数据的基础上，结合操作经验与理论计算，制定相应的待轧策略．这些研究结果可进一步用于加热炉的计算机控制系统的开发。

防火服热湿传递数学建模及人体皮肤烧伤预测

为了研究防火服内热湿传递规律,首先根据织物结构内部热湿传递的质量守恒和能量守恒等物理学定律,考虑消防水对热传递的影响,在已有热传递模型基础上加入湿传递方程,建立高温高湿环境下多层防火服-空气层-人体皮肤系统中的热湿耦合传递数学模型。然后利用有限差分方法求解该模型,得到防火服各层关于温度和水蒸气浓度的分布图。最后将热湿传递模型与皮肤烧伤模型相结合,通过计算烧伤积分值,预测了人体皮肤达到各级烧伤的时间。数值模拟表明:一定量的湿传递能够有效减缓温度上升的速度,延长皮肤达到各级烧伤的时间。该模型为高温高湿环境下防火服的设计提供了一定理论依据。

航天器真空热试验用加热板的数值仿真

文章针对加热板在航天器热试验中的传热特点,利用Thermal Desktop软件建立了加热板和空间模拟器热沉的热数学模型,分析了电热丝数量、加热板材料和液氮管路布置方式对加热板升、降温时间和温度分布的影响;建立了模拟星、加热板和热沉的热模型,分析了加热板和星表间距对模拟星表面温度的影响。根据分析研究结果,提出了加热板设计及其在航天器热试验中的应用方法建议。

空间站热分析综述

作为空间站研制、试验和运行管理的重要基础,系统级热分析已在国内外广泛开展。文章对空间站舱内空气流动分析、温湿度控制分析和以流体回路为核心的整体热建模分析等进行了综述,以国际空间站为重点介绍了这些技术的发展、实施方法、技术特点和作用。

空间站热收集方式的气压适应性研究

热管理系统是保障空间站正常运行的关键系统,其热量收集通常涉及多种传热方式。空间站舱内气压下降将削弱空气的对流换热能力,从而造成热收集方式的气压适应性差异。分析了这种差异及其对空间站热管理的影响。设计了两种针对密封舱的热量收集方式,第一种单纯用空气强制对流,第二种通过在密封舱内加装冷板,同时采用强制对流、导热和辐射进行热量收集。首先利用简化的密封舱换热模型给出了描述两种热量收集方式气压适应性的分析解,然后利用集成全局热数学模型分析给出了热管理系统采用这两种热量收集方式时压力下降对空间站温度控制的影响。结果表明,当热管理系统以空气对流为主进行热量收集时,气压下降可能导致舱内温度大幅升高;当同时采用导热、辐射及对流等多种途径收集热量时,热管理系统的气压适应性较强,有利于空间站的稳定运行。

多孔介质中高温气体非稳态渗流传热数值计算

针对水平导管中填充颗粒物料层内的高温气体渗流传热现象 ,考虑渗流与传热的相互作用并采用局部非平衡假设建立多孔介质中的瞬态渗流传热物理数学模型。研究不同情况下填充物料中的渗流速度和气固温度分布。计算结果表明 ,高温热气体对水平导管中移动颗粒料层的热渗透主要发生在渗流入口端区域 ,随着渗流时间延长 ,热渗透深度沿导管推进。增大入口渗流速度以及减小出料速度 ,将导致物料温度沿导管慢速下降 ,热渗透深度扩大 ,热渗透作用区域内的物料温度水平提高。在热渗透作用区域 ,孔隙率对流场和温度场有很大的影响。研究结果对于高温反应器的颗粒输运和给料器的设计与运行有一定的参考作用。

直通式太阳能真空集热管的热性能研究

综合考虑影响热损失模型的主要因素,建立了直通式太阳能真空集热管热损失及工质出口温度的数学模型,并提出了该模型的计算方法.利用美国国家可再生能源实验室(NREL)对Schott 2008 PTR70真空集热管的热性能测试结果进行验证,结果表明,热损失模拟值与实验数据值的绝对误差都小于6 W/m,相对误差基本控制在4.5%以内,故建立的数学模型可靠.同时设计了直通式太阳能真空集热管热性能的计算界面,在输入外形、物理参数和气象信息时,可以较快、较准确地输出该集热管的热损失以及工质出口温度,从而进一步完善了真空集热管的热性能模型和计算方法,为指导集热管的设计提供了便利.

液压缸连续驱动摩擦焊接的温度场模拟与试验分析

根据连续驱动摩擦焊的简化模型,推导了焊接过程的热输入数学模型;并通过热过程分析,建立了液压缸连续驱动摩擦焊接三维热分析有限元计算模型;利用有限元软件ANSYS计算获得了液压缸连续驱动摩擦焊接头温度场的分布特征。利用红外测温仪对液压缸连续驱动摩擦焊接接头温度场进行了现场测量,测量结果和数值模拟结果基本一致。

MATHEMATICAL MODEL OF ~4He QUANTUM INTERFEROMETER GYROSCOPE

The mathematical model of 4He quantum interferometer gyroscope is presented. The model includes the driven equation, the current equation and the position equation. Therefore, it can sufficiently describe the gyro- scope system. The driven equation shows the thermally driven gyroscope can work for a long time but the pres- sure driven one cannot. From the current equation, the superfluid currents passing through the weak link contain the AC currents which show the rotation flux, and other currents caused by drive. As shown in the position equa- tion, the displacement of diaphragm is the only detectable parameter in the gyroscope system. The model is tested by the simulations based on experimental parameters, and can be used to research performance of the gyroscope and analyse the gyroscope error.

Mathe matical model and calculation for heat transfer during condensation on surfaces of corrugated plates

A mathematical model was established for condensation on surfaces of verticalcorrugated plates based on the mechanism of heat transfer enhancement to thin down the liquid filmdue to surface tension effect between corrugated plate surfaces and liquid films. The relative heattransfer coefficients of condensation on corrugation plates were calculated in contrast withequivalent vertical plane ones. The heat transfer enhancement effects for the main geometricparameters such as pitch, height, corrugation angle, tilt angle, and fillet radii of corrugationswere analyzed to guide the optimization of corrugation structure for application. A two-scalecorrugation is suggested, which can compromise both the enhanced heat transfer effect and adequatecross section area for flows, and it makes the heat transfer coefficient 1 to 2 times more than thatof an equivalent plane one.

45钢连续驱动摩擦焊的温度场数值模拟及实验验证

根据连续驱动摩擦焊的简化模型,推导了焊接过程的热输入数学模型,并通过热过程分析,建立了连续驱动摩擦焊三维热分析有限元计算模型;利用有限元软件ANSYS计算获得了45钢连续驱动摩擦焊接头温度场的分布特征,并与用红外测温仪测得的接头温度场进行了比较,验证了模拟结果。

Mathematical modelling and numerical optimization of particle heating process in copper flash furnace

A mathematical model of the particle heating process in the reaction shaft of flash smelting furnace was established and the calculation was performed.The results indicate that radiation plays a significant role in the heat transfer process within the first 0.6 m in the upper part of the reaction shaft,whilst the convection is dominant in the area below 0.6 m for the particle heating.In order to accelerate the particle ignition,it is necessary to enhance the convection,thus to speed up the particle heating.A high-speed preheated oxygen jet technology was then suggested to replace the nature gas combustion in the flash furnace,aiming to create a lateral disturbance in the gaseous phase around the particles,so as to achieve a slip velocity between the two phases and a high convective heat transfer coefficient.Numerical simulation was carried out for the cases with the high-speed oxygen jet and the normal nature gas burners.The results show that with the high-speed jet technology,particles are heated up more rapidly and ignited much earlier,especially within the area of the radial range of R=0.3−0.6 m.As a result,a more efficient smelting process can be achieved under the same operational condition.

Microstructure evolution during homogenization of Al-Mg-Si-Mn-Fe alloys: Modelling and experimental results

Microstructure evolution during the homogenization heat treatment of an Al?Mg?Si?Fe?Mn(AA6xxx)alloy wasinvestigated using a combination of modelling and experimental studies.The model is based on the CALPHAD-coupledhomogenization heat treatment model originally developed for AA3xxx alloys(i.e.,Al?Mn?Fe?Si).In this work,the model wasadapted to the more complex AA6xxx system(Al?Mg?Si?Mn?Fe)to predict the evolution of critical microstructural features suchas the spatial distribution of solute,the type and fraction of constituent particles and dispersoid number density and size distribution.Experiments were also conducted using three direct chill(DC)cast AA6xxx alloys with different Mn levels subjected to varioushomogenization treatments.The resulting microstructures were characterized using a range of techniques including scanning electronmicroscopy,electron microprobe analysis(EPMA),XRD,and electrical resistivity measurements.The model predictions werecompared with the experimental measurements,and reasonable agreement was found.

Effect modeling of Cr and Zn on microstructure evolution during homogenization heat treatment of AA3xxx alloys

Both of chromium and zinc could appear as either minor impurities or alloying elements in recycled and commercial aluminum alloys, and they could have detrimental effects on the final product properties if not controlled in an appropriate way. A Kampmann-Wagner numerical modeling approach, built on the basis of computational thermodynamics and diffusion kinetics, is employed to investigate the effect of these two minor impurities on dispersoids precipitation during homogenization heat treatment of AA3xxx alloys. The simulation results obtained from different simulation set-ups were compared. The aim is to demonstrate that the modeling approach has the potential to guide the design or optimization of the chemical compositions and heat treatment parameters of aluminum alloys.

Temperature Distribution in Ethylene Pyrolyzer

A good understanding of the detailed temperature distribution in the furnace plays an important role in the implementation of operation optimization and design improvement of ethylene pyrolyzer. Numerical simulation of the turbulent flow, combustion and heat transfer was carried out to investigate the temperature distribution in industrial furnace. Inhomogeneities of the flue-gas temperature distribution were observed in X, Y, and Z direction of the furnace from the simulated results. Along the height of the furnace, the average flue-gas temperature increased initially and decreased afterward, and reached its peak at the height of 5 m. The reactor tube skin temperature varied not only along the height of the furnace, but also around the circumference of the tube. The heat flux profiles from the furnace towards the reactor tubes followed the shape of the average flue-gas temperature profile. The heat flux of the inlet tubes was constantly higher than that of the outlet tubes at the same height in the furnace.

Analysis of multi-dimensional SAR for determining the thickness of thin sea ice in the Bohai Sea

Flat thin ice (<30 cm thick) is a common ice type in the Bohai Sea, China. Ice thickness detection is important to offshore exploration and marine transport in winter. Synthetic aperture radar (SAR) can be used to acquire sea ice data in all weather conditions, and it is a useful tool for monitoring sea ice conditions. In this paper, we combine a multi-layered sea ice electromagnetic (EM) scattering model with a sea ice thermodynamic model to assess the determination of the thickness of flat thin ice in the Bohai Sea using SAR at different frequencies, polarization, and incidence angles. Our modeling studies suggest that co-polarization backscattering coefficients and the co-polarized ratio can be used to retrieve the thickness of flat thin ice from C- and X-band SAR, while the co-polarized correlation coefficient can be used to retrieve flat thin ice thickness from L-, C-, and X-band SAR. Importantly, small or moderate incidence angles should be chosen to avoid the effect of speckle noise.

Thermodynamic simulation of metal behaviors in Cu_(2+)−Ni_(2+)−NH_(3)−NH_(4)+−C_(2)O_(4)^(2-)−H_(2)O system

To investigate the behaviors of Cu^(2+)and Ni^(2+)with the change of conditions in Cu_(2+)−Ni_(2+)−NH_(3)−NH_(4)+−C_(2)O_(4)^(2-)−H_(2)O reaction system,mathematical models of thermodynamics based on the principle of mass conservation were established.The simulation results indicate that the precipitation of metal ions from the aqueous phase is a complicated dynamic equilibrium process,during which the coordination reactions of Cu^(2+)and Ni^(2+)with NH3 forming[Cu(NH3)n]^(2+)(n=3−5)and[Ni(NH3)m]^(2+)(m=3−6)are predominant under high pH conditions,respectively.The pH ranges for the simultaneous precipitation of Cu^(2+)and Ni^(2+)are 2.0−6.5 and 2.0−5.5 when[NH3]T equals 0.6 and 4.2 mol/L,respectively,with the prefixed[C_(2)O_(4)^(2-)]T of 0.6 mol/L.Due to the fractional precipitation of Cu^(2+)and Ni^(2+),Cu−Ni composite is obtained after the thermal decomposition of Cu−Ni oxalate complex salts prepared in a pure water system when pH>7.0.By applying the mixed solvent(water/ethanol)as the precipitation medium,the Cu−Ni alloy rods can be finally fabricated with high purity and crystallinity.