铝材退火炉退火过程的传热分析

根据箱式退火炉退火过程的传热特点,分析了铝箔退火炉退火过程各阶段炉膛内传热形式,建立了铝卷导热的数学模型,着重分析和计算了影响炉内空气与铝材间传热的重要参数——对流换热系数,并模拟计算了铝卷的退火过程和温度变化。结果表明,铝卷退火曲线计算值与实测值结果比较吻合。     

全氢罩式炉钢卷退火过程在线数值仿真

在分析全氢罩式退火炉钢卷退火过程传热机理的基础上,建立了适用于钢卷温度在线跟踪的二维传热数学模型,着重讨论了循环气体与钢卷之间对流换热的计算方法。针对强烈影响对流换热计算的循环气体流速分布问题,通过内罩内氢气流场的数值分析,给出了氢气流量的分配规律。应用所开发的仿真软件,实现了钢卷退火过程温度在线跟踪,并得到了实测验证。     

罩式退火炉内罩内加导流翼的强化传热研究

研究了罩式炉内罩强化传热机理,得出通过加强钢卷退火过程中的轴向换热,可以使钢卷中温度场更均匀;在内罩内加导流翼可以增强钢卷的轴向导热,也可以合理地分配内罩内的氢气流量。     

强化管外CFC11与HCFC123沸腾换热系数的对比试验研究

本文通过强化管外CFC11与HCFC123沸腾换热系数的对比试验分析与研究,分别得出了HCFC123与CFC11沸腾换热系数,并对这两种工质的实际应用情况进行了分析。     

全氢罩式炉钢卷埋偶试验研究

介绍了全氢罩式退火炉埋偶测试的试验原理、装置和方法,分析了某炉台退火试验结果。试验结果表明加热期循环气体温度近似等于钢卷表面温度,冷却期二者差别很大。以循环气体温度是否达到退火温度作为加热期结束的判据是合理的,而冷却期缺乏钢卷的温度信息,有必要通过数学模型计算钢卷温度场。     

对流换热系数测定的一种新方法

对流换热系数是求解伴有表面对流换热的热传导问题的重要参数之一。本文提出了一种测定对流换热系数的新方法。此方法是以传热学中非稳态导热求解法中的数学分析法－集总参数分析法为基础设计的,特定环境下的对流换热系数测定方法。本文全面分析了各因素对流换热系数精度的影响,并进行了定量分析。此方法简便可靠,在一般条件下,误差不超过１．６％。     

Helmholtz共振腔强化换热的试验研究

为研究脉动流体对强化换热的影响，设计Helmholtz共振腔并分别在加装和不加装共振腔的情况下进行对比试验，发现水流经共振腔后变成了脉动流体，脉动的水经过单管换热器后强化了换热，在一定的共振腔参数的配合下，换热系数提高约10％～40％。     

高频焊接与激光焊接翅片管传热性能对比试验

对高频焊接与激光焊接翅片管的传热性能进行对比试验,得到了两个试件在不同管外空气流速下的传热数据,运用直接分离法将管外空气侧对流换热系数从总的传热系数中分离,获取管外空气侧换热系数,再通过拟合方法获得管外空气侧换热关联式。研究表明:激光焊接翅片管的传热性能优于高频焊接翅片管,当空气流速为3m/s时,激光焊接翅片管的管外空气换热系数比同翅片尺寸的高频焊接翅片管的管外换热系数约高9%。     

喷流式退火炉炉内卷材尺寸对换热过程的影响

利用FLUENT软件对铝卷材喷流退火过程进行模拟计算,模型耦合求解炉内温度场及流场。讨论退火过程卷材规格不同对卷材截面换热的影响,得到卷重及宽度不同时料卷芯部与端部温升的变化规律。     

Sitrling发动机燃烧及换热分析

基于碳氢燃料燃烧化学平衡反应计算，得到燃烧产物温度及组分成份，在此基础上计算燃气物性，从而计算了热气机外燃系统加热管的对流换热系数，辐射换热系数及后排换热管的肋片换热对燃用空气和液氧两种燃烧情形进行了对比计算。     

A study of heat transfer in high‐performance hydrogen bell‐type annealing furnaces

The mechanisms of heat transfer in high‐performance hydrogen bell‐type annealing furnaces are discussed in this paper. It examines two important parameters, the convective heat transfer coefficient and the equivalent radial thermal conductivity, which have large effects on the overall heat transfer in the furnace. The calculated annealing curves are in good agreement with experimental data. © 2001 Scripta Technica, Heat Trans Asian Res, 30(8): 615–623, 2001     

Effect of Crucible Location on Heat Transfer in Sapphire Crystal Growth by Heat Exchanger Method

A global model of heat transfer, including melt convection, solid conduction, surface radiation, and crystal internal radiation, as well as phase change, is established for a sapphire crystal growing system by a heat exchanger method. Global simulations are carried out to investigate the effects of crucible location on heat transfer and sapphire crystal growth in the growing system. It is found that the crucible location has a significant effect on the heat transfer in the crystal and melt domains. When the crucible rises up, the melt flow is enhanced and the convexity of the melt–crystal interface increases at the crystallization stage. The thermal stress in the growing crystal decreases at the annealing stage. It therefore can be concluded that the crucible should be lowered at the crystallization stage, and raised up at the annealing stage, to obtain high-quality sapphire crystals.     

Numerical investigation on optical and heat transfer characteristics of a rapid thermal annealing system for LCD manufacturing

The objectives of present study are to propose a method to evaluate the quality of polycrystalline silicon film by using the thin film optics analysis, and to investigate heat transfer characteristics in a rapid thermal annealing system for liquid crystal display (LCD) manufacturing. The transmittance of polycrystalline silicon film is calculated by the characteristic transmission matrix method, and predicted results are compared with the experimental data for two different samples. The transient one-dimensional conduction and radiation heat transfer equations are additionally solved to predict the surface temperature of thin films. The two-flux method is employed to evaluate radiation heat transfer, and the ray-tracing method is utilized to take into account of the wave interference effect. As the film thickness increases, the peak transmittance value increases and the wavelength where the peak appears becomes longer due to wave interference. These characteristics can be used for in situ and practical estimation of the extent of crystallization of the silicon film during the process. From the thermal analysis, it is shown that the selective heating in the multilayer film structure acts as an important mechanism during the annealing of silicon film deposited on the glass.     

Unsteady‐state lumped heat capacity system design for tube furnace for continuous inline wire annealing process

A continuous annealing furnace is developed, which incorporates the principle of electric resistance heating for obtaining the desired temperature in the furnace. The concept of lumped heat capacity system is applied for the determination of annealing time of a continuously moving wire through the refractory tube. Also, the heat transfer inside the system and heat losses to the atmosphere are considered using the principles of conduction, convection, and radiation. The parameters related to the dynamics of moving wire are also designed. The designed furnace is fabricated and tested for its working, the observations of which show that 30 minutes are required to reach about 400°C furnace temperature and 30 seconds for annealing 1 m length of wire. The morphological testing of annealed and nonannealed wire is done to study the microstructure, which shows more traces of pearlite in annealed wires than in nonannealed wires. Thus, continuous annealing furnaces are more effective for inline annealing of wires; so as to relieve the internal stresses, induced by the step cold rolling process.     

Simultaneous determination of in- and over-tube heat transfer correlations in heat exchangers by global regression

We propose a method of data reduction that improves the predictions of correlations obtained from heat exchanger measurements. If we define an ideal heat exchanger on the basis of commonly made assumptions, the two heat transfer correlations corresponding to both sides of the heat transfer surface can be simultaneously determined. A local regression analysis, however, gives a multiplicity of possible correlations corresponding to the given data. The best correlations are obtained from this set by using a global regression procedure. Three methods are evaluated for this purpose: genetic algorithms, simulated annealing and interval analysis. All three perform well, with some differences in accuracy and CPU time. The predictions are further improved by correlating the error that is introduced by the assumptions of the ideal heat exchanger. The heat rate predictions are then improved considerably, giving a good idea of the extent to which these assumptions degrade them.     

Mathematical Model and Its Application of Radial Effective Thermal Conductivity for Coil Heat Transfer in HPH Furnace

Temperature uniformity of steel coils in High Performance Hydrogen bell-type annealing furnace has a significant effect on their quality and production. The hot rolled coil can be considered as a periodically laminated material composed of steel layers and interface layers in radial direction. A new formula for the radial effective thermal conductivity has been proposed, which is based on surface characteristic, strip thickness and compressive stress of the rolled coil. Furthermore, it has been used to develop a heat transfer mathematical model for steel coils in the HPH furnace. The calculated annealing curves using this mathematical model are in good agreement with the experimental data.     

Heating and Flow Analysis in Hot‐Rolled Stainless Strip Continuous Annealing Furnace Based on CFD Modeling

A three‐dimensional mathematical model was found for a continuous annealing furnace, the temperature field, and flow field of the furnace and the temperature of the stainless strip could be calculated by using this model. The simulation results were compared with measured data and the accuracy of the model was proved by the predicted temperature distribution. By using this model, the convective heat transfer coefficient and equivalent radiation heat transfer coefficient of the strip surface were also analyzed.     

Optimum thermal performance of microchannel heat sink by adjusting channel width and height

A three-dimensional numerical model of the microchannel heat sink is presented to study the effects of heat transfer characteristics due to various channel heights and widths. Based on the theory of a fully developed flow, the pressure drop in the microchannel is derived under the requirement of the flow power for a single channel. The effects of two design variables representing the channel width and height on the thermal resistance are investigated. In addition, the constraint of the same flow cross section is carried out to find the optimum dimension. Finally, the minimum thermal resistance and optimal channel width with various flow powers and channel heights are obtained by using the simulated annealing method.