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.     

Experimental and modeling analysis of thermal characteristics in carbon fiber wires

To understand the thermal characteristics of carbon fiber heating wires, we tested the heating rules of carbon fiber heating wires with inner core tows of 12k and 24k and different lengths. We found that the surface temperature of the carbon fiber heating wires rose and fell quickly when the power supply was turned on and off by 82.9 and 18.3°C/min, respectively. After the quick rise period, the surface temperature tended to be steady with ±2°C of fluctuation; the steady temperature decreased as the length increased. With an increase in the length from 7 to 12 m, the steady temperature of the 12k and 24k wires reduced from 122°C and 166°C to 53°C and 71°C, respectively. Using the COMSOL Multiphysics software to simulate the carbon fiber heating wires, the simulated surface temperatures were in good agreement with the experimental results, with errors less than 7%. The convective and radiative heat transfer of the simulated carbon fiber electric heating wire decreased with an increase in length and the number of tows, and the convective heat transfer was much higher than the radiative heat transfer to indicate that the convective heat transfer is the main heat transfer mode in the heat dissipation of the carbon fiber electric heating wire. Results indicate that there is a rapid increase in temperature when power is on, and thereafter temperature remains constant. These are the important characteristics of carbon fiber heating wires.     

新型电加热管式高温盐浴回火炉

新型电加热高温盐浴回火炉,主要由热电耦、炉体、电热体、控制台等组成,具有节能、节约铜材、结构简单、炉温均匀、回火质量稳定等优点。     

改善高线加热炉加热质量的技术措施

针对棒线材加热炉在加热质量方面存在氧化烧损及脱碳情况方面损耗量大、加热温度均匀性差等问题,采用全平焰烧嘴、精细化供热分段等多种技术措施,达到进一步改善棒线材加热炉加热质量的目的。     

熔池传热与流动的非定常数值模拟

对受移动激光速间隙加热的工件中的非定常传热与熔体流动进行了数值模拟，对不同热源移动速度下熔池行为的模拟结果进行了比较，当激光束移动速度比较高时形成的熔池浅而短，而移动速度比较较时形成的熔池深而长，所得工件代表点上材料的温度随时间变化以及加热或冷却速率，可以进一步用于研究被焊工件中的热应力或组织结构变化。     

快速丝材加热炉的研制

本文介绍了稀有金属合金丝材拉丝用的快速加热电炉。它可以同时加热合金丝与拉丝模,并使它们分别获得不同的温度。该炉具有升温快,控温准确,炉子短,操作方便等优点。     

钢丝热镀锌机组两项新技术的应用

介绍热镀锌工艺的内加热式镀锌炉和钢丝垂直、斜向引出组合装置等两项新技术在国内某公司钢丝热处理车间设计中的应用。     

低碳钢丝热处理明火炉供热系统分配研究

以现有钢丝热处理明火炉为热工模型,根据低碳钢丝热处理生产过程的工艺特点,分析了低碳钢丝在不同温度阶段沿炉长方向的受热过程,并计算了钢丝及炉体热量吸收、损失,根据所得结果合理布置明火炉供热系统。     

炼油装置加热炉节能途径与制约因素

加热炉是炼油装置的能耗大户,其节能水平对于提高炼油装置的节能水平具有重要意义。介绍了加热炉主要的节能途径：优化换热流程,降低加热炉热负荷;加热炉与其他设备联合回收余热;降低排烟温度、降低过剩空气系数、减少不完全燃烧损失、减少散热损失以提高加热炉热效率。探讨了上述节能途径的主要技术措施及应注意的问题。阐述了进一步提高加热炉节能水平的制约因素：降低排烟温度,要考虑经济性和露点腐蚀;过分降低炉外壁温度,会导致费用过高;预热空气温度过高对环保不利。提出了进一步提高加热炉节能水平的建议;认真净化燃料,降低露点温度;开发新的余热回收工艺;开发并应用“蓄热式高温空气预热贫氧燃烧技术”等新的燃烧技术;加强运行管理。     

基于MATLAB钢丝感应加热模型及其温度场特性的研究

在感应加热理论和热传导理论的基础上，建立了钢丝在线感应加热的模型，并基于MATALB得到了此模型的数值解，通过数值解分析了钢丝在感应加热过程中的温度场分布特性。     

减少钢坯烧损、优化加热工艺的研究

针对包钢高速线材生产工艺加热炉中的钢坯加热温度,加热时间,加热制度,氧化烧损等问题进行了分析。重点对科研课题进行攻关,提出了新颖的高线加热生产的先进操作法。对试验进行测定对比,在优化加热工艺研究后,钢坯氧化烧损、燃耗、产量等取得了成果和显著经济效益。     

普碳钢与某型不锈钢混合加热的可行性初探

以某厂板坯步进梁式加热炉为背景,建立了数学模型,计算出了在相同炉温制度下,普碳钢与某型不锈钢的升温过程,对不同钢种、不同规格的钢坯在炉内混装加热的可行性进行了初步探索。     

Modeling the Occurrence and Methods of Reducing Thermal Deviations of Upper Furnace Heating Surfaces in a 1000 MW Dual Circle Tangential Firing Single Furnace Ultra-Supercritical Boiler

The FLUENT computational fluid dynamics software package was used to model outlet velocity and temperature inhomogeneity in a 1000 MW dual circle tangential firing single furnace ultra-supercritical boiler. These computations allowed a theoretical analysis of thermal deviations at the furnace outlet and suggested means of reducing such deviations. This work involved study of radiative and convective heat transfer of the upper furnace platen superheaters, the radiative–convective heating surfaces above the furnace nose and the convective heating surfaces in the horizontal flue. The results demonstrated that the radiant heat load of the heating surfaces of the platen superheaters is related to the sectional dimensions of the furnace and exhibits a bimodal distribution in the boiler modeled during this work. It was also determined that a large recirculation zone is formed in the central section of the horizontal flue owing to velocity superposition. After establishing the thermal load distribution characteristics and the causes of thermal deviations at the various heating surfaces, further modeling was performed to assess the extent to which thermal deviations could be reduced by decreasing residual rotation at the furnace outlet via horizontally swinging the over fire air (OFA). The effects of OFA swing angles on velocity and temperature inhomogeneity at the furnace outlet were subsequently analyzed, and an OFA swing of ?10° was found to be optimal based on considerations of thermal deviations at the furnace outlet, the airflow field in the furnace, and safe operation of the boiler.     

MHD radiative ohmic heating nanofluid flow of a stretching penetrable wedge: A numerical analysis

The present numerical investigation has focused on the magnetohydrodynamics flow of a viscous nanofluid over a stretching wedge with the boundary convective conditions, thermal radiation, and ohmic heating. Buongiorno's two-component nonhomogeneous nanoscale model was used and a dilute nanofluid with spherical type particles is considered. Similarity transformations are used to render the system of governing partial differential equations into a system of coupled similarity equations. The transformed equations are solved numerically with the BVP4C method. Validation of solutions with previous studies based on special cases of the general model is included. The salient features of fluid velocity profile, temperature as well as concentration profiles are discussed in a graphical manner for various values of selected governing factors. The skin friction coefficient, mass, and heat transfer rates are calculated and summarized. It is worthwhile noticing that the validation results exhibit an excellent agreement with already existing reports. The modeling of the present problem is useful in the thermal processing of sheet-like substances that is a necessary operation in paper procurement, wire drawing, drawing of plastic films, polymeric sheets, and metal spinning.     

Study on dynamic characteristics of the temperature and stress field in induction and laser heating for the semi-infinite body

This study analyzed the dynamic characteristics of temperature and stress fields during induction and laser heating of a semi-infinite body. The semi-infinite body was subjected to a distribution heat flux (induction heating) at a particular depth range and then to a surface heat flux (laser heating). Using the Green function method and the Laplace transform, the temperature and stress fields solutions were acquired for both heating methods. The analytical results of the temperature and stress fields are shown graphically in the time domain for a selected position. It was found that under the same input power conditions, the temperature field acquired is identical in both induction and laser heating in the range of more than one skin depth. The peak dynamic thermal stress from both heating methods increases rapidly along the depth, and converges to a fixed value. Meanwhile, the peak thermal shock stress is relatively small, and quickly decays at a certain position in a very short duration. Therefore, the thermal shock dynamic characteristics are negligible in the two highly variant transient heating methods—induction and laser.     

常减压装置加热炉过程控制不稳定分析及改造

就炼油厂常减压装置中加热炉扩容改造中出现的物料出口的温度控制不稳定问题进行了分析,指出了旧的前馈-负反馈控制系统存在的问题,针对加热炉扩容后出现的控制大滞后问题提出了解决办法,利用霍尼韦尔可编程调节器的组态软件,进行了前馈-增益自适应的Smith预估补偿控制系统改造,保证了主参数的平稳,而且燃料用量也相应减少,满足了工艺的要求,使加热炉出口温度的控制达到了预期的效果。     

基于瞬态非线性分析的中厚板坯加热过程应力场仿真研究

为提高中厚板坯加热效率和防止出现热应力裂纹,需要精确研究中厚板坯加热升温热应力规律。本文在热弹塑性分析理论基础上,采用有限元方法,研究了中厚板坯加热过程中全时域内热应力场变化规律。本文针对实际生产加热工艺,建立了3500板坯加热过程分析模型,考虑了导热系数、比热变化对加热的影响,仿真了中厚板坯的加热过程,得出加热炉温度与加热速度对板坯加热过程热应力的影响规律,具有重要工程应用意义。     

提高延迟焦化装置加热炉热效率的技改措施

洛阳石化1400kt/a延迟焦化装置加热炉采用一炉两塔流程,于2008年6月投产,计算热负荷为45.41MW,加热炉为两室四管程双面辐射箱式结构,加热介质为减压渣油。为降低装置能耗,于2011年9月对加热炉进行改造。改造内容包括更换燃烧器、改造空气预热器、采用先进控制、改造炉墙和增加仪表监测。改造后,利用FLUENT软件,对燃烧室中燃料气的燃烧特性和新型燃烧器某截面的温度场进行数值模拟,分析得出,新型燃烧器大幅降低了燃烧过程中氮氧化物的生成,保证了燃料气在低过剩空气系数下的充分燃烧;计算表明,空气预热器的改造提高加热炉热效率0.92%。先进控制技术的应用,减轻了劳动强度,提高了调节精度和加热炉运行的平稳率,达到了提高加热炉热效率的目的。综合改造后,加热炉热效率高达93.45%,与改造前相比,热效率提高1.81%。     

Efficiency analysis of radiative slab heating in a walking-beam-type reheating furnace

The thermal efficiency of a reheating furnace was predicted by considering radiative heat transfer to the slabs and the furnace wall. The entire furnace was divided into fourteen sub-zones, and each sub-zone was assumed to be homogeneous in temperature distribution with one medium temperature and wall temperature, which were computed on the basis of the overall heat balance for all of the sub-zones. The thermal energy inflow, thermal energy outflow, heat generation by fuel combustion, heat loss by the skid system, and heat loss by radiation through the boundary of each sub-zone were considered to give the two temperatures of each sub-zone. The radiative heat transfer was solved by the FVM radiation method, and a blocked-off procedure was applied to the treatment of the slabs. The temperature field of a slab was calculated by solving the transient heat conduction equation with the boundary condition of impinging radiation heat flux from the hot combustion gas and furnace wall. Additionally, the slab heating characteristics and thermal behavior of the furnace were analyzed for various fuel feed conditions.     

DZL58-1.25/130/70型链条炉低负荷下的燃烧优化

链条炉低负荷运行时,存在热效率低、燃烧不完全等问题。燃烧优化可以达到节能减排的目的。本文认为链条炉的煤层厚度、炉排行进速度通过试验方法进行优化,是链条炉低负荷运行时实现燃烧优化的因素之一。结合在线仪表或采用烟气、煤质分析设备进行实际工况的热平衡测试,以烟气过量空气系数、炉渣含碳量、飞灰可燃物含量、热效率作为评判指标寻求优化值并在低负荷运行时执行。选用一台DZL58-1.25/130/70型链条炉在60%额定负荷运行时进行了煤层厚度、炉排行进速度的优化试验,得到优化数值并在运行中得到应用,使该链条炉低负荷运行时热效率有所提高,达到很好的燃烧优化效果。