Modeling of Strip Temperature in Rapid Cooling Section of Vertical Continuous Annealing Furnace

 The strip temperature is affected by many factors in rapid cooling section (RCS) of the vertical continuous annealing furnace (VCAF). They can be divided into four types: the physical properties of cooling gas, the geometry characteristics of configuration of cooling equipment, the heat transfer between the strip and the cooling gas, and the conductivity of the strip. It aims to model the strip temperature in the cooling section based on the fundamental heat transfer theory and the four aspects factors. The model for transient Nusselt number is obtained by considering Reynolds number, Prandtl number and geometry characteristics of RCS. Then cooling model of the strip transient temperature is built by Nusselt number, heat transfer coefficient and heat conductivity of the strip. The results are compared with the data from production line. The comparisons indicate that the model can well predict cooling temperature of the strip. It is hoped that the proposed model can be used for design and control of the vertical continuous annealing furnace.     

CSP辊底加热炉供煤气量随坯厚、坯温变化规律的模拟研究

研究了CSP辊底加热炉内的传热过程及其规律.采用数值模拟的方法,在进行合理简化后,建立总能量平衡基础上的炉内热过程数学模型,其中辐射传递方程的求解采用离散坐标法.自主开发了该炉型的通用热过程模拟软件,采集包钢CSP薄板坯连铸连轧厂的生产数据进行验证计算,计算所得钢坯温度与实际温度的相对误差小于1%,表明该模型假设合理,建模正确;该软件能够应用于该类型加热炉的设计、管理和研究等领域,为确定CSP生产线高拉速(提高入炉坯温)、多钢种的生产工艺参数创造了条件.     

辐射管的传热模型及实验研究

本文以数学模型和实验为手段，研究了在不同操作参数的条件下，辐射管壁面温度和管内气体温度的分布状况及变化规律。实验表明，理论计算值与实验结果吻合较好，可以用本文结果指导辐射管的现场操作，以延长辐射管的使用寿命．提高辐射管对带钢的加热质量。     

热电偶测温误差分析

针对工业加热炉，详细分析了热电偶测温过程，由于热电偶热端与炉墙内表面之间的辐射换热，以及热电偶本身因热端和冷端温度不同造成的导热总是存在，因此热电偶测温存在误差。本文从理论上分析了热电偶测温误差的来源，提出了热电偶测温误差计算模型，并导出了测温误差的近似计算公式，还结合实例讨论了减小测温误差的措施。     

薄板坯连铸连轧辊底加热炉内传热过程的数学模型

研究了包头钢铁(集团)公司薄板坯连铸连轧厂辊底加热炉内的传热过程,在辐射平衡态的条件下建立了炉内辐射与板坯、炉衬固体壁相耦合求解的炉内热过程数学模型,其中辐射传递方程的求解采用离散坐标法.采用控制体积法对数学模型进行离散,自主开发了辊底加热炉型的通用热过程模拟软件,经计算得到炉气、板坯温度沿炉长的分布,炉子出口处板坯温度与生产实测值的最大误差小于10%.该软件对理论研究和生产实践具有一定的指导意义.     

立式炉内转向辊传热过程数学模型

应用粗糙表面间接触换热数学模型,建立了带钢连续热处理立式炉内转向辊辊室传热过程数学模型,综合考虑了接触换热、对流换热、辐射换热等换热方式.对转向辊辊室传热的仿真分析表明:转向辊辊面温度变化层的厚度不超过10mm,同时在带钢连续热处理立式炉中,可以忽略转向辊传热对带钢温度的影响.     

Analysis and calculating for preheat temperature and average convection heat change coefficient in the continue annealing furnace

The aim of the thesis is to utilize essential theory of heat transfer,to use correlative expressions to calculate average convection heat change coefficient and heating temperature of strip in Jet Preheat Furnace （JPF）,make the calculating results accordant with production data,and make the calculation to be used the process of production.The method is to collect:entry temperature and speed of strip,temperature and speed of N₂ - H₂,to analyse heat transfer according to length and thickness of strip,jet hole and mutual position of jet piping in JPF,to analyse heat transfer and built the physical model.In mathematic model, Martin correlative expressions are tried to calculate using the data from production,and are modified in part properly.At the same time,heat boundary condition is analysed with theory of impact jet and production data.The conclusion is obtained that boundary condition is rarely average numerical value of temperature of strip and N₂ - H₂ with impact jet condition,instead of a relation of function of temperature of strip, temperature and speed of N₂- H₂,array of jet holes,diameter of hole,distance between hole and strip,and acquired a calculating expression.In calculation of examples,the thesis collected and calculated 15 kinds of strips.The thickness of strips are 2=0.51¹.41 mm,material DQ - IF、DDQ,EDDQ,SEDDQ and 340DDQ.Main assess numerical value is temperature value after strip is heated with certain speed and within section of time.Maximum error in 9 groups of numerical value in the thesis is 3.36%comparing with production data.The correlative expressions can be used in production to adjust temperature of strip through changing speed and temperature of N₂ - H₂ and speed of strip.The correlative expressions are compiled computer process.The process can be applied in on line control of production by rapid calculating speed.     

立式连退炉快冷段氢气含量对带钢温度的影响

立式连续热处理炉快冷段混合气的氢气含量,对换热系数和带钢温度有很大的影响,体现了冷却气体物理性质与换热系数和带钢温度之间的关系。在其他条件相同而氢气含量不同的条件下,对带钢传热状态进行分析,利用冷却设备几何结构、努塞尔数与换热系数的关系,得到带钢瞬时冷却温度计算公式,为生产及工程设计提供了一定的依据。     

考虑辐射影响的接触传热模型与分析

应用GW统计接触模型,建立了粗糙表面之间的接触导热模型.与实验数据的对比分析表明:该模型能够正确地反映接触导热现象.在此基础上,对接触表面进行了合理的简化,建立了接触界面间的辐射传热模型.数值计算表明:当接触表面的温度高于400K时,辐射的影响已不可忽略;载荷对接触导热热导的影响明显大于对辐射热导的影响,导热热导随载荷的增大迅速增大,而辐射热导以及等效辐射系数均随载荷的增大有所减小,这主要是由接触界面的空隙面积减少造成的;在接触面几何参数中,粗糙峰等效斜率对等效辐射系数起着主导作用,在相同的量纲1的载荷情况下,粗糙峰等效斜率越小,等效辐射系数越大;通过对本文提出的等效辐射系数的误差检验,结果表明其最大相对误差为10^-3数量级,说明等效辐射系数仅仅为接触界面黑度、几何特性和接触载荷的函数,而与接触界面温度水平和温差无关,同时也间接证明了本文提出的等效辐射系数可以较为合理地描述接触界面间的辐射换热强度.     

The Influence of Oxide Scale on Heat Transfer during Reheating of Steel

The present work presents methodology and development of a mathematical model for prediction of the influence of oxide scale on heat transfer during reheating of steel in an industrial furnace. In this developed model, temperatures inside the steel billet were measured and with thermocouples at selected places and were collected by a water cooled computer that was traveling inside the slab. CFD is used to calculate the flow field inside of a furnace. The mass‐transfer coefficient of the scale formation is obtained by solving the convection mass‐diffusion equation across a boundary layer to the surface of a flat plate. A model for inverse heat conduction is employed to calculate the local surface temperature and heat flux on top of the growing oxide scale layer on a slab moving through a walking beam reheating furnace. By using the inverse method, the transient temperature and heat flux was firstly determined on the surface of the steel. During subsequent computations, the growth of the scale was calculated and the surface temperature of the oxide scale was extracted by using the Cauchy data from the previous calculations. The sensibility of the model on steel physical parameters is studied, and suitable parameters were obtained for heating a low carbon steel plate in the reheating furnace. Results show that the oxide scale layer should not be neglected in reheating models.     

高炉炉缸炉底内衬的等效冷却条件计算方法

建立了高炉炉缸炉底冷却的二维有限元传热模型.该模型能计算紊流水冷冷却器以等效对流换热系数表征的冷却参数,能反解服役炉缸实际冷却强度.等效冷却条件参数可用于缩小多维炉缸传热模型的计算域和规模,且不失边界条件精度.文中设计了参数化有限元建模及分析的计算程序,基于管内紊流水努赛尔特征数,定义一个物性综合系数,构造了更为简明的对流换热系数计算表达式.     

Estimation of the Transient Surface Temperature,Heat Flux and Effective Heat Transfer Coefficient of a Slab in an Industrial Reheating Furnace by using an Inverse Method

In the steel industry it is of great importance to be able to control the surface temperature and heating or cooling rates during heat treatment processes. In this paper, a steel slab is heated up to 1300°C in an industrial reheating furnace and the temperature data are recorded during the reheating process. The transient local surface temperature, heat flux and effective heat transfer coefficient of the steel slab ares calculated using a model for inverse heat conduction. The calculated surface temperatures are compared with the temperatures achieved by using a model of the heating process with the help of the software STEELTEMP® 2D. The results obtained show very good agreement and suggest that the inverse method can be applied to similar high temperature applications with very good accuracy.     

蓄热式连续加热炉数学模型的研究

应用封闭灰腔辐射理论,建立蓄热式连续加热炉数学模型.根据模型研究了加热炉炉内温度分布;产量及燃料分配比变化对钢坯温度的影响;空气消耗系数对加热炉生产率和单位热耗的影响.结果表明,模型能真实地反映加热炉的温度制度、供热制度及空气消耗系数与加热炉生产指标的关系.     

炉缸冷却壁对流换热系数计算及烘炉传热特性

 炉缸冷却壁冷却性能主要体现在冷却水与水管间的对流传热。因为工程上常用计算对流换热系数的经验公式不能满足不同的水流状态从而导致炉缸热应力分析误差较大，所以以某高炉炉缸结构为例，首先利用传热学准数方程推导出冷却水处于不同流动状态时对应的综合对流换热系数表达式，同时探讨了对流换热系数经验公式的适用范围；然后通过迭代计算推导出了冷却水处于层流状态下考虑衰减热阻时的综合对流换热系数表达式；最后对烘炉状态下炉缸侧壁传热模型进行瞬态传热与冷却分析，得到了微水烘炉甚至闭水烘炉的热工依据，可为初步制定高炉烘炉制度进行评估和完善。     

环形加热炉管坯三维传热数学模型的研究

针对某公司环形加热炉的实际生产情况,建立了管坯加热过程的三维传热数学模型。采用交替隐式格式的TDMA（三对角矩阵）数值计算方法,开发了环形加热炉管坯加热过程三维传热数学模型计算机数值仿真系统。利用管坯内部温度黑匣子实验对所建立的数学模型进行了验证。结果表明：所建模型正确可信,同时也证明了利用管坯二维传热过程数学模型实现在线计算机优化控制的可行性。所做工作为某公司即将开展的管坯加热过程计算机优化控制奠定了坚实的理论基础。     

带钢连续退火炉加热室传热计算方法

对带钢连续退火组(CAPL)退火炉加热室传热进行了分析,提出了一种简化辐射管辐射的方法,并利用该法建立了带钢加热数学模型。用此模型,对某厂的CAPL加热室仿真计算结果与现场实测数据吻合较好。     

Improvement of Prediction Method for Strip Coiling Temperature

Thecoilingtemperatureisoneoftheimportanttechnologicalparametersaffectingthefinalmechani calpropertiesofstrip[1,2 ] .The purposeofcoilingtemperaturecontrolistomakestripcooltorequiredcoilingtemperaturefromhighertemperatureforap propriatemicrostructureandmechanicalproperty .Atpresent ,thecontrolmodelofcoilingtemperatureforBaosteel 2 0 5 0millisaself adaptingempiricalmodel.Thoughthecontrolissatisfactory ,theout of toleranceofcoilingtemperatureisstillobservedinproduction .Itwasconcludedbytheinvest…     

Thermal performance of annealing line heating furnace

Abstract

In the present study, a stepwise model based on the enclosure concept has been applied to an annealing line heating furnace. The model has been satisfactorily tested using three industrial manufacturing data sets. As temperature measurement inside the furnace is difficult, the model could be used to improve control and to obtain the outlet temperature of the steel strip, the heat transfer rate loss and the strip heat transfer rate throughout the length of the furnace. Variations in the thermodynamic properties included in the model and in the operational conditions, which cannot be accurately known, have been tested to ascertain their effects on the evolution of the strip temperature. It is found that precise knowledge of the heat capacity and heating power introduced in the furnace are important to obtain good results in application of the model.     

硅钢连续退火炉无氧化加热段辐射换热研究

以能量平衡和辐射换热理论为基础,通过合理假定,建立了硅钢无氧化加热炉数学模型.采用数值计算的方法,通过自编程序,完成对带钢加热过程温度场的仿真.结果显示：数学模型能够反映带钢在无氧化炉内的加热过程,其升温曲线能够与工艺曲线相吻合;现行炉温分布并非最优,数学模型能够为炉温分布的优化、炉段的设计提供理论依据.     

高炉冷却壁与炉气之间的换热特性

 基于边界条件替换方法建立了高炉冷却壁本体和捣打料与炉气之间的换热系数计算模型。用试验测量冷却壁近热面温度来推算冷却壁热面温度，与冷却壁温度场计算模型结合，确定了炉气温度在500~1 248 ℃范围内，高炉冷却壁与炉气之间的换热系数。结果表明，本模型的计算值与前苏联学者的试验结果吻合。