采用辐射管加热的辊底式热处理炉数值仿真及其分析

以某公司拟建的采用辐射管加热的辊底式热处理炉为研究对象,在详细分析其传热机理的基础上,建立了炉内钢坯加热过程的二维传热数学模型.采用交替隐式格式的TDMA数值计算方法,开发出了采用辐射管加热的辊底式热处理炉钢坯加热过程二维传热模型计算机数值仿真系统,并进行了大量的数值仿真计算.所得结论为该公司即将开展的辊底式热处理炉模型优化控制奠定了坚实的理论基础.     

辊底式连续热处理炉钢坯二维传热过程数学模型的研究

以某公司拟建的辊底式连续热处理炉为研究对象,在详细分析其传热机理的基础上,针对其钢坯厚度变化较大的特点,建立了钢坯在炉内连续加热和摆动加热过程数学模型,采用数值计算方法对其进行了仿真计算,并利用设计大纲提供的数据间接验证了所建模型的正确可靠性。所开发的辊底式热处理炉计算机数值仿真系统可以动态模拟不同燃料、不同规格的钢坯在炉内的运行状况及其钢坯各典型点的温度变化规律;可以确定在不同的热处理工艺制度下、不同规格的钢坯所需要的最佳运行方式和最佳工艺制度。     

辊底式热处理炉加热模型的研究与应用

为确保钢板的加热质量,以明火加热的辊底式热处理炉为研究对象,建立了钢板加热过程数学模型,通过研究分析炉内传热机理,开发出辊底式热处理炉加热模型控制系统。此加热模型控制系统投运后,先后通过埋偶实验及生产实践检验,其结果表明模型计算精度较高,在线控制系统运行稳定,满足生产的需求。     

微型计算机在测量热处理炉热损失中的应用

在节能工作中,为减少热处理炉炉墙的导热引起的热损失,须首先知道热处理设备的热损失状况。在对企业开展能量平衡的工作中,碰到了计算炉墙导热损失中的关键问题是层间温度的估算。因为层间温度无法直接测量,根据“能量平衡统一规定”的要求,层间温度采用试算法。试算法盲目性大、计算繁杂、且要凭经验。采用该法估算一面炉墙     

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。     

耐火纤维热处理炉阶段试验总结

近二十来年国外大型热处理炉已采用硅酸铝纤维毯作炉墙。这种热处理炉大大改善了炉子性能,具有节约燃料、节约钢材、减少基建投资、缩短施工周期、减少炉子占地而积等优点。我厂容器车间和设计一院、二院、八院一起对3.5×16米热处理炉作了多次试验,总结了国产各种耐火纤维作炉墙的试验,从而获得备项试验数据,以供改进大型热处理炉的参考。     

内壁多凸起式火焰加热炉的应用

一、工作原理 在火焰炉内,对物料的加热是在火焰、炉墙内面和被加热物料三者间的复杂热交换中完成的。火焰的温度最高,被加热物料的温度最低,炉墙内面的温度在二者之间。在热交换过程中,火焰和高温烟气以辐射和对流的方式把热量分别传给被加热物料和炉墙内面,炉墙内面又以辐射和反射的方式将所得到的大部分热量向炉膛传出(一小部分热量在墙体内传导至外表面,构成散热损失)。来自炉墙内面的辐射热通过炉膛空间时一部分被火焰和烟气吸收,其余部分射向被加热     

低温明火炉内钢板加热温度的均匀性实验研究

为研究低温回火热处理炉加热的温度均匀性,搭建低温明火炉实验平台,在实验炉内采用高速烧嘴脉冲燃烧加热,获得了实测的炉膛温度分布和炉内钢板表面温度,试验结果表明在合理布置炉内烧嘴和合理的供热方式条件下,不采用循环风机也可满足炉内钢板加热温度均匀性要求。     

铸铝轿车轮子的先进热处理设备

铸铝轿车轮的热处理设备由固溶热处理炉及人工时效炉组成,固溶热处理炉采用直接燃气加热,炉壳由4.76mm碳钢板制成,背衬为127mm厚的矿渣棉和     

轴承套圈余热退火辊底炉生产线

轴承套圈余热退火辊底炉生产线是一高度机械化自动化的特大型加热设备。由于受厂房长度限制，设计成长方形的闭环结构，这是本设计的特点之一。从热镦机出来的红热套圈进入料筐、以及热处理各工序的进行、料筐内套圈的翻卸、空料筐的返回等各个阶段全自动运行，构成一热处理生产线的闭环系统。由于是热装炉，可显著节约能源。本生产线另一特点是：加热段采用煤气辐射管加热，而控制降温段和球化段则采用电热辐射管加热，这可显著降低     

Effects of radial thermal dispersion on fully-developed forced convection in cylindrical packed tubes

The fluid flow and heat transfer characteristics of a fully-developed forced convective flow in a cylindrical packed tube with symmetric heating are analyzed in this paper. The Darcy—Brinkman—Ergun model is used as the momentum equation, with the radial porosity variation of the packed column approximated by an exponential function. The method of matched asymptotic expansions is applied to construct a composite solution for the axial velocity profile of a hydrodynamically fully-developed flow. The interaction of inertial and wall channeling effects on the pressure drop and the axial velocity profile is illustrated. The effects of radial thermal dispersion and variable stagnant thermal conductivity are taken into consideration in the energy equation for a thermally fully-developed flow in the packed tube, which is heated circumferentially with constant heat flux or constant wall temperature. A wall function is used to model the wall effect on the transverse thermal dispersion process, and the predicted Nusselt numbers agree with existing experimental data. Numerical results of the corresponding heat transfer characteristics in the packed tubes, without introducing the wall function, are also presented for comparison.     

Dual-phase-lag heat conduction in a furnace wall made of functionally graded materials

In this article, the transient heat transfer in a furnace wall, which is made of functionally graded materials (FGMs), is investigated based on the hyperbolic-type dual-phase-lag (DPL) heat conduction model to consider the microstructural interactions in the fast transient process of heat conduction. All material properties of the furnace wall are assumed to vary following a power-law form along the radial direction with arbitrary non-homogeneity indices. For simplicity, the values of the phase lags are taken constant. A semi-analytical solution for the temperature field is obtained in the Laplace domain. The transformed temperature solution is inverted to the physical quantity by using numerical inversion of the Laplace transform. A comparison between the hyperbolic-type DPL model and thermal wave model in the temperature responses of the furnace wall is made. Effects of different phase-lag values on the behavior of heat transfer are also investigated.     

Estimation for inner surface geometry of furnace wall using inverse process combined with grey prediction model

In this work the inner surface geometry of a cylindrical furnace wall is estimated using inverse process method combined with grey prediction model. In estimating process a virtual area extended from the inner surface of furnace wall is used for analysis. The heat conduction equation and the boundary condition are first discretized by finite difference method to form a linear matrix equation; the inverse model is then optimized by linear least-squares error method and the temperatures of virtual boundary are obtained from a few of measured temperatures in furnace wall using the linear inverse model; and finally the temperature distribution of system is got by direct process and the inner surface geometry of furnace wall can be estimated accordingly. The result shows that using inverse process combined with grey prediction model the geometry can be exactly estimated from relatively small number of measured temperatures. Moreover, the effects of measurement error, location, and number of measured points on the estimation for inner surface geometry of furnace wall are discussed in detail.     

A heat transfer model for the analysis of transient heating of the slab in a direct-fired walking beam type reheating furnace

A mathematical heat transfer model for the prediction of heat flux on the slab surface and temperature distribution in the slab has been developed by considering the thermal radiation in the furnace chamber and transient heat conduction governing equations in the slab, respectively. The furnace is modeled as radiating medium with spatially varying temperature and constant absorption coefficient. The steel slabs are moved on the next fixed beam by the walking beam after being heated up through the non-firing, charging, preheating, heating, and soaking zones in the furnace. Radiative heat flux calculated from the radiative heat exchange within the furnace modeled using the FVM by considering the effect of furnace wall, slab, and combustion gases is introduced as the boundary condition of the transient conduction equation of the slab. Heat transfer characteristics and temperature behavior of the slab is investigated by changing such parameters as absorption coefficient and emissivity of the slab. Comparison with the experimental work show that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace.     

环形加热炉热工过程CFD数值模拟及其应用

借助CFD商业软件CFX，考虑流动、辐射、燃烧等，对宝钢环形加热炉的热工过程进行了数值模拟，得到了炉膛内的温度、速度矢量等热工参数的分布图。通过简化处理，对环形加热炉各控制段内的加热过程进行了模拟分析，并根据所得到的管坯表面辐射热流、热电偶温度及管坯表面温度研究了各个段总括热吸收率的分布情况，主要分析了总括热吸收率在管坯圆周方向、长度方向以及各个段之间的变化规律。     

Effects of viscous dissipation on the heat transfer in a forced pipe flow. Part 2: Thermally developing flow

In this part of the study, consideration is given to thermally developing laminar forced convection in a pipe including viscous dissipation. The axial heat conduction in the fluid is neglected. Two different thermal boundary conditions are considered: the constant heat flux (CHF) and the constant wall temperature (CWT). Both the wall heating (the fluid is heated) case and the wall cooling (the fluid is cooled) case are considered. The distributions for the developing temperature and local Nusselt number in the entrance region are obtained. Results show that the temperature profiles and local Nusselt number are influenced by the Brinkman number (Br) and the thermal boundary condition used for the wall. Significant viscous dissipation effects have been observed for large Br.     

Investigation of the slab heating characteristics in a reheating furnace with the formation and growth of scale on the slab surface

In this work, the development of a mathematical heat transfer model for a walking-beam type reheating furnace is described and preliminary model predictions are presented. The model can predict the heat flux distribution within the furnace and the temperature distribution in the slab throughout the reheating furnace process by considering the heat exchange between the slab and its surroundings, including the radiant heat transfer among the slabs, the skids, the hot combustion gases and the furnace wall as well as the gas convection heat transfer in the furnace. In addition, present model is designed to be able to predict the formation and growth of the scale layer on the slab in order to investigate its effect on the slab heating. A comparison is made between the predictions of the present model and the data from an in situ measurement in the furnace, and a reasonable agreement is found. The results of the present simulation show that the effect of the scale layer on the slab heating is considerable.     

Heat and fluid flow characteristics of gases in micropipes

In this study, laminar forced convective heat transfer of a Newtonian fluid in a micropipe is analyzed by taking the viscous dissipation effect, the velocity slip and the temperature jump at the wall into account. Hydrodynamically and thermally fully developed flow case is examined. Two different thermal boundary conditions are considered: the constant heat flux (CHF) and the constant wall temperature (CWT). Either wall heating (the fluid is heated) case or wall cooling (the fluid is cooled) case is examined. The Nusselt numbers are analytically determined as a function of the Brinkman number and the Knudsen number. Different definitions of the Brinkman number based on the definition of the dimensionless temperature are discussed. It is disclosed that for the cases studied here, singularities for the Brinkman number-dependence of the Nusselt number are observed and they are discussed in view of the energy balance.     

间歇式热处理炉传热计算与分析

建立了台车式热处理炉炉膛传热数学模型和辐射换热器工作模型,分析了换热器的传热特性（空气预热温度、壁温、传热系数）随炉况的变化。结果表明,辐射换热器的传热特性随炉子的升温及保温过程变化而波动很大,因而对炉子的热工性能产生了影响。     

板坯加热炉内加热特性的数值分析

以某公司热轧厂常规与双蓄热烧嘴组合供热的板坯加热炉为研究对象,建立该加热炉炉内流动、传热、燃烧和板坯运动吸热过程的三维物理数学模型,运用CFD仿真技术对其进行详细的数值计算,得到炉内稳态的速度场和温度场分布规律、板坯的升温曲线以及板坯温度分布均匀性,计算结果与"黑匣子"实验测量数据吻合良好。本文给出的板坯加热特性计算方法为研究加热炉新工艺、优化板坯加热温度制度提供了科学依据。