流化床的强化传热途径探讨

分析了直接法合成甲基氯硅烷的反应特点及反应器内流化床的传热过程。分别介绍了主要传热途径:管内强化传热和管外强化传热。着重提出了改进流化床横向构件的安装方式的建议,即在垂直管束间附着一些随流化床内气流浮动的桨式或梅花形内件,增加床内气固相接触的机会,以改善流化质量。     

分离式热管的传热极限

应用热管理论和自然循环流体动力学理论,对分离式热管内的传热极限作了分析,指出了分离式热管的传热极限与传热过程中的热流密度和热管内的充液量有关,在高热流密度传热和充液量偏多或偏少的情况下,会存在以下几种传热极限：（１）蒸发段的干涸传热极限;（２）蒸发段的沸腾传热极限;（３）冷凝段的凝结传热极限;（４）循环回路的流动传热极限。     

反射炉熔态还原磷矿石的热过程

根据传热传质的原理,建立了反射炉内热传递过程与还原过程的数学模型,对反射炉内炉壁、炉料及炉气的温度分布,烟气传热量的分布和炉内能耗分布进行了数学模拟,并由计算结果对强化反射炉内传热的途径进行了探讨。     

烧结矿余热回收竖罐内气固传热特性

以自制气固传热实验装置为操作平台,实验研究了烧结矿颗粒填充床内的气固传热特性。结果表明:气体表观流速和烧结矿颗粒直径是影响颗粒床层内气固传热过程的主要因素。气体表观流速越大,颗粒直径越小,床层内气固传热系数就越大。当烧结矿颗粒直径和气体表观流速一定时,床层内烧结矿颗粒温度的升高导致床层气固传热系数的增加和传热Nusselt数的减小。由于计算误差较大,现有的经验关联式不适用于求解烧结矿颗粒床层内的气固传热过程。基于量纲分析法,并结合实验测量数据拟合得出了能够描述烧结矿颗粒床层内气固传热特性的实验关联式,平均计算误差为4.22%,显示了良好的预测性能。     

流动沸腾传热的计算方法

本文分析了近年来流动沸腾传热的计算方法，探讨了纯组分及混合物在大尺寸圆管内的流动沸腾传热计算。对目前窄缝通道内流动沸腾传热问题的解决办法给予了介绍。     

内插螺旋线强化糖浆立式降膜蒸发传热

搭建了新型立式单管蒸汽-糖浆降膜蒸发实验平台,进行连续4 h加与不加螺旋线的降膜蒸发运行对比实验,研究管内插入特定结构和工艺参数的螺旋线对变粘性糖浆降膜蒸发传热性能的影响.结果表明,内插螺旋线可明显改善糖浆降膜蒸发传热效果,相同条件下,内插螺旋线时总传热系数比空管提高了25.9%~82.9%,且随时间延长其下降速率明显低于空管;从管内蒸发侧和管外冷凝侧传热角度分析降膜蒸发传热性能,传热温差增大,管内蒸发侧传热性能变好,管外冷凝侧传热性能变差,增大传热温差改变物料物性(粘度减小)可强化传热效果.在非结垢影响的传热时间内,对管内蒸发侧传热系数进行处理,得到了管内综合传热系数与传热温差的实验关联式.     

两相闭式热虹吸管强化传热研究进展

回顾了两相闭式热虹吸管强化传热技术研究现状,将热虹吸管强化传热技术归纳分为4类,即采用高效工作介质、管壁内表面处理、管内设置内插件和其它类。分别阐述了这4种技术的强化传热机理,总结得出大部分技术多局限在实验分析层面上,缺乏理论上的深入分析,暂时没有得到工业生产的大规模应用。并指出了强化传热技术的理论研究、各种参数对传热性能的影响探究以及如何降低工业应用的生产成本将是今后热虹吸管强化传热技术的研究热点。     

波纹管传热强化效果与机理研究

通过有限元数值计算考察了波纹管内的流动与传热性能,研究了不同的流体入口雷诺数Re及结构参数对管内平均传热系数的影响,探讨了其强化传热机理。研究发现,在常见的湍流范围内,波纹管内平均传热系数是相同条件下直管的1.06—3.0倍,最佳强化效果出现在Re=16 000附近;波峰处回流区的存在对波纹管的传热强化起到了决定性的作用。此外还拟合出了波纹管内的传热准则方程,有助于指导波纹管换热器的工程设计。     

一种新型裂解炉炉管强化传热数值模拟

利用计算流体动力学(computational fluid dynamic,CFD)方法对含新型内插件强化传热辐射炉管(fortified induced turbulence,FIT)进行了流体流动与传热特性的研究,采用RNG双方程模型求解了动量方程和能量方程,给出了FIT炉管内的流体流动和传热特性,包括速度场、湍动强度和温度场的分布;计算了FIT炉管的强化传热因子和压降。研究结果表明,FIT炉管内插件迫使流体流动由活塞流转变为旋转流,增强了流动湍流程度,符合流动-能量场协同理论,同时流体边界层由于FIT炉管的特殊结构而减薄。FIT炉管具有增强辐射传热、减薄边界层、增加比表面积和旋流增强等强化传热特性。相比于普通当量圆炉管,FIT强化传热炉管的整体传热能力提高了20%左右,证明该新型炉管强化传热效果显著,可以在工程实际中应用。     

回转干馏炉内颗粒间传热特性的数值模拟

将离散元方法与颗粒热传导模型相结合,研究了页岩灰颗粒与油页岩颗粒在回转干馏炉内的混合传热过程,采用混合指数、颗粒平均温度和温度标准偏差作为评价混合传热效果的指标,分析了填充率、炉体转速、油页岩粒径及抄板形式对颗粒间混合传热特性的影响规律。结果表明,炉体转速和油页岩粒径是影响颗粒混合传热效果的主要因素,而填充率和抄板形式对混合传热效果的影响相对较小。当炉内未设抄板时,随着填充率和油页岩粒径的增大,颗粒间分层现象使混合传热效果变差,而随炉体转速的提高传热效果呈现出先增强后减弱的趋势;设抄板时,抄板形式对炉内颗粒间的混合起到不同程度的扰动作用,从而使传热效果得到显著改善。     

高温高辐射涂料对电加热炉传热影响的计算机模拟

建立了电加热炉内传热方程,根据该方程模拟了高温高辐射涂料对电加热炉炉内传热的影响。通过电热窑内传热模型和计算机模拟发现,高温高辐射涂料无论是在窑体内表面温度高于被加热物体温度还是低于被加热物体的温度,高辐射涂料都不会产生节能效果,反而不利于节能,不利于陶瓷的加速烧成。     

加热炉复合砌筑体界面温度的计算机模拟

依据传热学原理 ,建立了连续式加热炉砌筑体界面温度的传热模型 ,并用有限差分法对模型进行求解 ,利用计算机编程进行数值模拟。该方法对于连续式炉窑的设计及其节能分析具有现实意义     

大型乙烯裂解炉辐射传热的研究

应用概率统计理论尤其是用蒙特卡罗法对裂解炉管外辐射传热过程温度分布多维模型的开发研究,将计算结果应用到新建或扩建大型裂解炉的设计、采购、建设总承包项目和PMC工程项目管理中,可以提高裂解技术水平、降低投资费用并延长裂解炉运行周期。对于已建成并正在运行的大型裂解炉进行完善和优化,使裂解炉平稳运行,并延长裂解炉的使用寿命。     

玻璃窑炉火焰空间系统综合传热数学模型的研究

建立了玻璃窑炉火焰空间系统综合传热数学模型,并根据该数学模型,用计算机模拟窑体内表面温度和黑度,窑体对玻璃配合料的角系数,火焰黑度,玻璃配合料表面温度对于火焰空间系统向玻璃配合料传热的影响。     

The imaginary planes method for the calculation of radiative heat transfer in industrial furnaces

Radiation is usually the dominant mode of heat transfer in furnace enclosures. The imaginary planes method is one of the new methods for calculating the radiative heat transfer in such systems. In this study, a general procedure was developed for its application in furnace modelling. Various case studies were carried out for a number of furnaces, and the results were compared with those of the zone method. It was found that the new method combines good accuracy with low computation time and appears to be a promising method for the determination of heat flux and temperature distributions within furnace enclosures.     

The simulation of an existing ethane/dehydrogenation reactor

This paper is concerned with the mathematical representation of an existing box-type furnace for the thermal dehydrogenation of ethane. The furnace is composed of a preheating convection section and a radiant heated section. The two models considering (i) the tube-side calculation and (ii) the radiant heat transfer in the combustion chamber are independent of each other. A study is made of the effects of pressure, heat flux level and “steam/hydrocarbon” ratio on the effluent composition. A significant improvement in reactor operation if a more uniform heat flux could be achieved is predicted. From the radiant heat transfer computations an unexpected variation in flame temperature in the furnace under study was detected.     

A mathematical simulation of radiant heat transfer in a cylindrical furnace

The radiative heat transfer in a cylindrical furnace was investigated both experimentally and theoretically. The flow pattern within the combustion chamber was measured and found to differ from that of an identical cold model for which extensive theoretical and experimental work had been previously carried out. The Monte Carlo Method was used to solve for the radiative transfer part of the non-linear integro-differential equations describing the combustion and heat transfer in a cylindrical furnace. The radiative heat flux distribution obtained from the simulation agreed well with data obtained from a cylindrical test furnace.     

Heat flux profile of the furnace wall of a 300 MWe CFB boiler

It is important to properly understand and calculate the distributions of the heat flux and the heat transfer coefficient in a furnace for designing a circulating fluidized bed (CFB) boiler, especially for one with supercritical parameters. An experimental study of the heat transfer in a commercial 300 MWe CFB boiler was conducted in this work. The heat flux from the bed to the waterwall was measured by a heat flux meter at four different heights. The influence of suspension density and bed temperature was analyzed by measuring the pressure profile and temperature profile in the furnace. In addition a numerical modeling study on the two phase flow in the furnace was carried out. The results indicate that the density of the solids suspension was non-uniform in the cross section at a certain height, and decreased gradually with increasing furnace height. Consequently, the distribution of heat flux in the horizontal plane was non-uniform and decreased along the height of the furnace. The heat flux showed a decreasing trend near the center.     

辐射管搪烧炉热工性能分析

对辐射管搪烧炉炉内辐射换热和对流换热进行了分析,结果表明,提高辐射管和工件的黑度及炉内介质与辐射管和工件的对流换热系数可显著提高工件表面总热流,而炉幸嘿 度及介质与炉叶流换热系数对工件表面总热流几乎没有影响,此外,加强炉墙绝热可提高工件表面热流,但作用是有限的,尤其是对连续式辐射管炉,这种效果更为有限。