一维炉衬不稳定态传热的数值计算

根据能量平衡原理导出利用节点网络方程组求解一维炉衬不稳定态传热的数学模型。按照通常的间歇式工业炉的工况因素，列出３种边界条件（按预定升温制度升、降温，按固定热流升、降温，空炉随炉冷却）用ＦＯＲＴＲＡＮ语言编制成通用程序。为了提高计算结果的精度，程序编制时考虑了对炉衬材料的导热系数和比热的温度修正。计算结果详尽（第一计算所在时间间隔内的计算结果包括炉衬各层分界结点的温度、内表供热流量、外表散热流量、     

全纤维炉衬的稳定态传热计算

用通常的方法计算炉衬稳定态传热时,须先假设炉衬内各层间温度,由此求得相应的导热系数,再复核各点温度是否与假设值相近。耐火纤维的导热系数随温度而剧烈变化,假设的温度稍有出入,就会使导热系数有较大的差别,故常常要多次假设凑算,才能得到满意的结果。本文介绍用导热系数的温度函数式λ=f(t)代入传热公式q=λ(dt/dx)的计算方法,可免多次假设凑算之烦,直接算出炉衬内的各温度及炉衬热损失。文中介绍了根据国外资料用回归分析法整理得的各种耐火纤维导热系数的两种表达式:指数函数式λ=e~(A Bt)及二次函数式λ=a bt~2以及两式的具体数据。通过例题计算,详细介绍了多层层铺式炉衬、叠板式炉衬以及双层叠板式炉衬的计算方法,并以在试验炉上实验测得的数据与计算结果作了对比。     

沥青焦回转窑内温度分布研究

国内某钢铁厂沥青焦回转窑由于无法直接测量炉内燃烧物料以及炉衬温度导致无法对炉内燃烧和炉衬材料选择做出科学的判断,采用数值模拟和现场测试的手段对回转窑的温度场进行了准确的判断,计算值与测试值最大误差在5%以内,计算结果表明在15~35 m煅烧带位置处炉内温度达到1 800 K,此处容易发生损坏。     

大型全耐火纤维炉衬燃油热处理炉

某厂安装了一台１０ｍ×１０ｍ×２０ｍ　全耐火纤维炉衬燃油热处理炉。该炉装有两台燃烧能力为６．２８×１０￣６ｋＪ／ｈ燃油高速燃烧器，用Ｄｃｐ２１１数字程控器和电动调节阀实现升、降温速度自动程序控制和温度自动控制。用１６支热电偶测温，炉温均匀性和控温精度均在±１０℃范围内。     

无心工频感应炉炉衬的物理化学性能及工艺因素对炉衬寿命的影响

本文结合工厂实践对炉衬温度分布、矿物组织及化学成分、膨胀特性等进行过实际检测;对铁水、炉渣与炉衬间的化学反应进行过理论分析与计算,对筑炉材料也进行过理化检验;对炉衬修筑的一些工艺因素进行了讨论,为合理选择筑炉原材料及制订炉衬修筑与使用工艺提供参考。     

立式工频感应再加热炉耐火及隔热炉衬的摸拟试验

立式工频感应再加热炉的常用温度为1250～1350℃。再加热的工件进入该炉的温度为900℃,并要求在短时间内(10分钟左右)迅速再加热到1250～1350℃。感应圈与被加热工件之间的间隙约50毫米。由于感应圈的有机绝缘材料不能耐高温,所以设计要求在工件与感应圈之间应有一个耐火及隔热炉衬,其中最大尺寸约为ф460/ф500×1500毫米。当炉内再加热工件温度为1250～1350℃时,炉衬外型温度能低于一般绝缘材料老化温度,即180℃左右。     

工业加热文摘WJ931558～931581

WJ931558 碱性炉衬钢包的使用效果——《Сталь》,1992,№6,22～24(俄) 作者简单介绍了碱性炉衬钢包的优点,着重叙述了用焦油镁砂砖(230×150×125mm)砌筑钢包炉衬的工艺及砌衬时应注意的事项,要考虑钢包使用的温度—时间方案和提高砌体蓄热程度方案。碱性炉衬与普通粘土炉衬相比可降低耐火材料4.4kg/t钢,钢包炉龄从38炉提高到45炉。图4幅。     

AOD炉蓄热式烘烤过程的数值模拟研究

为研究新型蓄热式AOD炉烘烤器的烘烤效果,对AOD炉烘烤过程的流动、燃烧、传热现象进行数值模拟研究,定量考察了空-燃比、空气预热温度,天然气流量等烘烤工艺参数对炉衬温度的影响规律.结果表明,增加天然气流量和空气预热温度是提高炉壁温度的有效措施,空-燃比变化对温度的影响较小;应用蓄热式AOD炉烘烤器,在满足烘烤温度1 373 K的基础上,温差基本可以控制在50 K以内,烘烤温度均匀性较好.提出了供现场参考的烘烤工艺参数.     

十吨无心工频感应炉炉衬热喷补试验研究

近几年来,二汽十吨无心工频感应电炉,(以下简称“十吨工频炉”)在围绕着如何提高炉衬寿命、机械化震动筑炉机研试初步告一段落之后,又进一步研试“十吨工频炉炉衬的热喷补技术”。对工频炉炉衬(以下简称炉衬)实行热喷补的优点是:1)使炉衬各部位腐蚀均匀,延长炉衬寿命;2)缩短补炉时间;3)改善高温补炉的劳动条件;4)降低修炉材料消耗;5)提高工频炉的有效利用率,实现连续生产。     

无芯工频感应炉炉衬捣筑工艺

§1简介 坩埚炉衬是无芯工频感应炉(以下简称工频炉)的重要部件之一,要求其能长时间的保持金属炉料,并能使之进行改变物理、化学和温度的状态。炉衬除要承受炉料的静压力外,还要能经得起熔融金属由电磁力作用所引起的搅动效应。炉衬的强度不仅取决于炉子的设计,同时也取决于所选用的耐火材料,筑炉方法,炉衬的烧结和炉壁的厚度等等因素。     

The effects of infill on hydrogen tank temperature distribution during fast fill

The temperature rise of hydrogen tank during fast fill poses challenge on the safety of hydrogen-powered vehicles. Researchers have been continuously looking for methods to mitigate the challenge of overheating. In this paper, we proposed an innovative solution by introducing porous infill in gas tanks to slow down gas-to-wall heat transfer. The porosity of the infill is no less than 97% to maintain the volume capacity of gas tanks. To evaluate the impact of infill heat capacity, we modelled the filling process with a lumped-parameter model and obtained various time-independent temperature evolution curves. Then, we set up a 2D and a 3D finite volume model and investigated the spatial distribution of temperature rise. Four cases with different infill properties were simulated and compared. At the end of the fast fill, the infill resulted in lower tank wall temperature at the cost of higher gas temperature. The combined effect of internal gas temperature and gas-phase effective thermal conductivity largely determines the final temperature distribution. The presence of infill effectively slowed down convective heat transfer, yet overly resistive porous infill may overly slow down the gas flow and result in thermal stratification. Further studies on infill design can be done to seek more effective solutions.     

平壁,球形壁砌体非稳态热损失计算

本文对平壁、球形壁砌体的非稳态传热计算用有限差分法进行了分析,提出平壁多层砌体的外表面温度、界面层温度以及砌体内部温度场计算公式。提出球形壁砌体的温度场和外表面层温度计算公式。用计算机进行了实例计算,结果表明,外表面层温度计算值与实测值误差仅为8.6％,吻合较好。     

板式换热器性能的数值模拟

建立了人字形板式换热器冷热双流道的流体流动与传热计算模型,利用计算流体力学软件对5组不同速度工况下换热器内流体的流动和传热进行了数值模拟,分析了换热器流道内的速度场、温度场和压力场.结果表明:数值模拟得到的板式换热器进、出口温差和压降与试验测量值的误差均小于6%;换热器内流体的流动和传热存在明显的不均匀性,导致其进、出口的另一侧出现明显的传热"死区";换热器的总传热系数和流道阻力均随着流体流速的增大而增大.     

下降管反应器内颗粒流动升温过程数值研究

采用数值模拟的手段研究了下降管反应器内包含不同尺寸及密度冷热颗粒混合物的流动传热特性。双流体模型及离散单元法分别被用于描述颗粒混合物的流动过程并与实验结果进行了对比。反应器内气固相间传热,颗粒混合物间碰撞传热,以及壁面与气/固两相间的热量传递采用计算流体力学和离散单元法相耦合的方式进行了模拟,对颗粒到达反应器出口前影响温度变化趋势的因素展开了分析研究。模拟结果表明:在V型下降管反应器内,粒度较小的颗粒以沿壁面向下滑动为主;较大尺寸颗粒向下流动过程中在反应器截面上分布区域较广;当反应器壁面热边界条件发生变化时,颗粒升温过程变化明显,采用恒温壁面冷颗粒升温速率明显提高;同时热载体颗粒数目越多,冷颗粒在下降管反应器内升温越快。     

Heat transfer of a horizontal spiral heat exchanger under groundwater advection

Groundwater flows at approximately 1–3 m under the ground surface in a given region. If groundwater flow is present, the performance of a horizontal ground heat exchanger (HGHE), buried in a shallow trench, is enhanced. Nevertheless, owing to the general depth at which groundwater is present, research regarding the heat transfer of a ground heat exchanger (GHE) under conditions with groundwater flow has mainly focused on vertical GHE systems. To the authors’ knowledge, no such studies have addressed HGHEs. From a system design perspective, a prediction tool is needed to consider the groundwater flow, optimize the size of the horizontal heat exchanger, minimize the initial cost and maximize the operational efficiency. Therefore, in this study, a moving ring source model was established and solved analytically to describe the temperature response of a spiral heat exchanger with groundwater flow. In addition, experiments were carried out to study the soil temperature variation during the operation of a spiral heater with different water velocities. The validity of the proposed model was proven by the good agreement between the experimental and calculated results. The average virtual tube surface temperature variations of single ring sources in two different configurations are discussed. Furthermore, the average virtual tube surface temperatures of multiple ring sources extending from single arrangements were computed and approximation algorithms were introduced to reduce the calculation time. The approximation approach has been proven to run thousands of times faster than the initial method, and the calculation results are in 97% agreement with those of the initial method. In summary, this study provides a useful tool for the design of spiral heat exchangers.     

The study on the heat transfer characteristics of oxygen fuel combustion boiler

According to 350MW and 600MW boilers, under oxygen fuel condition, through the reasonable control of the primary and secondary flow and the correct option and revision of mathematical model, the temperature distribution, heat flux distribution and absorption heat distribution, etc. was obtained which compared with those under air condition. Through calculation, it is obtained that the primary and secondary flow mixed well, good tangentially fired combustion in furnace was formed, the temperature under air condition obviously higher than the temperature under O26 condition. The adiabatic flame temperature of wet cycle was slightly higher than that of dry cycle. The maximum heat load appeared on the waterwall around the burner area. The heat load gradually decreased along the furnace height up and down in burner area. The heat absorption capacity of the furnace under O26 was lower than that under the air condition. The heat absorption capacity of the platen heating surface under O26 was equal to that under air condition. And the heat absorbing capacity of waterwall under O26 was about7%~12% less than that under air condition.     

微型汽车发动机舱散热性优化研究

基于发动机舱内外流场和温度场数值模拟,根据汽车在不同行驶工况下的流场和温度场数值计算结果,对发动机舱的流场特性、散热性能、温度场、进风口设计进行分析;依据仿真分析结果提出发动机舱散热改进设计方案;在相同试验条件下,分别对某微车原车状态和对发动机前舱布局进行相应改进后的状态,进行室内整车环境模拟实验.     

Numerical investigation of the heat and mass transfer in a vertical tube evaporator with the three-zone analysis

A numerical study for the flow, heat and mass transfer characteristics near the inflow region of the vertical evaporating tube with the films flowing down on both the inside and outside tube walls has been carried out. Condensation occurs along the outside wall and evaporation at the free surface of the inside film. The transport equations for momentum and energy are parabolized by the boundary-layer approximation and solved by using the marching technique. In this kind of numerical approach, the accurately predicting the early stage is really important because a small error at the previous step can produce the amplified big error at the next step. To accurately predict the flow at the inflow region of the vertical evaporating tube, the calculation domain of two film flow regions and tube wall is solved simultaneously. The interesting heat transfer characteristics revealed through this three-zone simulation, such as the evaporation delay and the temperature inflection at the very near inflow region are found and discussed along the discrepancy between the inner film inlet temperature and the saturation temperature. The case that the inner film comes in with the saturation temperature shows a good performance. The velocity and temperature fields as well as the amounts of the condensed and evaporated mass in both inner and outer films are predicted for the various conditions.     

荆门重油催化装置外取热器催化剂流动故障原因分析及对策

荆门石化1200kt/a重油催化装置反再结构为高低并列、重叠式两段不完全再生型式,再生器配有一台下流式外取热器。2010年6月26日,外取热器出现催化剂流动故障,表现为催化剂在器内基本停止流动,处于死床状态,影响后果是:由于第一再生器过剩热量无法取出,导致再生器超温,装置处理量和掺渣率大幅下降。技术判断认为:外取热器内有部分衬里脱落,堵塞了催化剂流动通道,使催化剂在器内停止流动。为此,制定不停工在线处理技术方案:铺设中压蒸汽反吹线,将外取热器中脱落的衬里吹入第二再生器,打通催化剂流动通道;精细控制第一再生器催化剂进入外取热器的流量,将外取热器进入第二再生器的阀门全开,使催化剂流动更加顺畅;加大外取热器流态化床层流化风流量和催化剂输送立管松动风流量,目的是消除气阻,加快催化剂流动速度。以上方案实施后,外取热器催化剂流动和取热操作逐渐恢复,装置生产转入正常,该处理方案避免了停工处理损失费用共计160万元。     

Experimental and numerical study of convective heat transfer and fluid flow in twisted oval tubes

Twisted oval tube heat exchanger is a type of heat exchanger aims at decreasing the pressure drop of the shell side. In the present study, heat transfer and pressure drop performances of twisted oval tube have been studied experimentally and numerically. The experimental study of the twisted oval tube shows that heat transfer process can be enhanced but also with an increasing of pressure drop when compared with the smooth round tube. The effects of geometrical parameters on the performance of the twisted oval tube have been analyzed numerically. The result reveals that the heat transfer coefficient and friction factor both increase with the increasing of axis ratio a/b, while both decrease with the increasing of twist pitch length P. The influence of a/b and P on the overall performance of the twisted oval tubes are also studied. Aiming at obtaining the heat transfer enhancement mechanism of the twisted oval tube, secondary flow, total velocity and temperature distributions of flow section are given. From the analysis it can be concluded that the emergence of twist in the twisted oval tube results in secondary flow. It exists in the form of spiral flow when a/b is big, but in the form of up and down when a/b is small. It is this secondary flow that changes the total velocity and temperature distributions of the twisted oval tube when compared with a smooth oval tube with the same sectional geometric parameters. Then the synergy angle between velocity vector and temperature gradient is reduced and the heat transfer process is enhanced.