蜂窝型蓄热体传热过程热工特性的数值研究

介绍了高温空气燃烧过程中蜂窝型蓄热体的工作原理和损毁原因 ,并建立蓄热体三维非稳态传热数学模型。采用代数雷诺应力模型和修正的速度 -压力耦合算法SIMPLEC ,耦合蓄热体内流体的流动和换热过程 ,用数值计算的方法研究了蜂窝型蓄热体的传热特性和格孔壁面上的应力变化规律。结果表明 :适当降低流过蓄热体的气体流速 ,缩短四通换向阀的切换时间 ,可降低烟气的出口温度 ,提高系统的余热回收率。频繁的蓄热和释热过程变换 ,使蓄热体格孔壁面交替受到拉应力和挤压应力的作用 ,换向时间越短 ,应力交替作用的影响越大 ;流体的流速越大 ,应力变化越大     

耦合边界条件下蜂窝陶瓷传热及气体流动特性的数值模拟

通过建立蜂窝陶瓷传热及气体流动的三维非稳态模型,运用计算流体力学(CFD)软件,在耦合边界条件下对蜂窝陶瓷的工作过程进行数值模拟,得到了启动过程中蜂窝陶瓷热端和冷端的气体温度及压力变化规律,以及稳定工作期内蜂窝陶瓷内气体温度、速度和压力的分布规律。为采用蜂窝陶瓷作为蓄热体的高温空气燃烧技术的开发提供了一定的理论依据和指导。     

蜂窝陶瓷蓄热体的抗热震性研究进展

本文针对高风温燃烧技术和煤矿乏风瓦斯氧化技术的蜂窝陶瓷蓄热体,系统地综述了影响蓄热体抗热震性的因素,数值模拟分析了蓄热体在热冲击下的温度场和热应力场的分布特点,总结了蜂窝陶瓷蓄热体热震损伤机理等的研究进展情况,并提出今后的研究及发展方向。     

蓄热氧化炉中蜂窝陶瓷损坏机理及改进措施

结合蓄热氧化技术的工作原理,介绍了蓄热氧化炉关键部件蜂窝陶瓷蓄热体的损坏形式,分析了蜂窝陶瓷蓄热体的损坏原因及影响因素,并提出了延长蜂窝陶瓷蓄热体使用寿命的措施,指出了有待进一步研究的问题,为开发高性能、长寿命的新型蓄热体提供参考。     

蜂窝陶瓷蓄热体的研究现状

介绍了蜂窝陶瓷蓄热体在蓄热节能技术中的发展及应用,详细讨论了蜂窝陶瓷蓄热体的研究现状,尤其是在材质结构以及换热性能的发展及应用中存在的问题,指出了蜂窝陶瓷蓄热体在节能、环保方面的发展方向.     

微波能、有机粘合剂对蜂窝陶瓷快速稳定干燥的影响

本文介绍了蜂窝陶瓷体在干燥过程中,有机粘合剂在微波场的作用下,产生凝固、收缩,并且在蜂窝陶瓷体内形成网络结构,使蜂窝陶瓷体内部存在的应力和缺陷得到分散和固定,从而达到稳定干燥的目的;蜂窝陶瓷体自身吸收微波能产生热量,其热量流动方向与水份迁移的方向一致,为快速稳定干燥提供了重要条件;以及在负载量、材料性质一定的情况下,蜂窝陶瓷体的壁厚是影响其干燥速度的重要因素,而与蜂窝陶瓷体的形状、尺寸没有很大关系。     

莫来石蜂窝陶瓷的阻力特性

本文以实验为基础,通过搭建的蜂窝陶瓷蓄热体阻力特性实验台,对莫来石蜂窝陶瓷的阻力特性进行了实验研究。研究表明:蜂窝陶瓷的阻力损失随蓄热体长度增加而增大,随孔隙率增加而减小;在蜂窝陶瓷的长度一定时,其阻力损失随雷诺数增加而增大,随气体流速增加而增大。根据实验数据得到了蜂窝陶瓷蓄热体摩擦阻力系数实验关联式,为煤矿乏风氧化装置的设计提供了数据支持。     

蜂窝陶瓷蓄热体中的辐射传热

蜂窝陶瓷是由贯穿本体非常密集的小孔构成,当载热气体沿孔隙通过蜂窝体时,则其中每一单孔可看作非等温空腔。在前期模型的基础上,以圆形孔道的辐射蜂窝体为研究对象,建立了考虑辐射、对流与热传导复合传热时的能量控制方程。使用FlexPDE软件数值计算出蓄热陶瓷氧化床的温度分布以及辐射对氧化床温度的影响。结果表明,氧化床轴向温度呈梯形分布;辐射具有平滑氧化床温度梯度的作用。所得模拟结果与实验结果较为吻合。     

蜂窝陶瓷蓄热体的研究现状

综述了高温空气燃烧系统的关键部件之一——蜂窝陶瓷蓄热体的主要发展历程,制备要求以及国内外对蜂窝陶瓷蓄热体热工性能的实验研究和数值模拟现状。可以看出,深入研究蜂窝陶瓷蓄热体的特性对我国发展和应用蓄热式高温空气燃烧技术具有重要意义。     

陶瓷蓄热体的研究现状及应用

陶瓷蓄热体作为陶瓷蓄热技术中的关键部件，它的性能决定了余热回收体系的整体性能。着重对蜂窝陶瓷蓄热体在制备及使用过程中存在的主要问题及解决措施进行了较详细的论述。同时对新型的潜热型复合相变蓄热体的研究现状及发展趋势进行了简单论述。     

Thermal shock resistance behavior of auxetic ceramic honeycombs with a central crack or an edge crack

In this paper, the thermal shock resistance of an auxetic ceramic honeycomb plate is studied based on the fracture mechanics concept for the cases of a central crack or an edge crack. The transient temperature field and transient thermal stress field are obtained for both auxetic and non-auxetic structures. The relationship between the thermal stress intensity factor (TSIF) and the internal cell angle, crack length and time is determined and the critical temperature for the initiation of crack propagation is predicted. Results show that compared with the non-auxetic ceramic honeycombs which are at an internal cell angle of 30°, the critical temperature of the auxetic ceramic honeycombs whose cell are orientated at an angle of −30° increases by 78.5% and the TSIF at the crack tip decreases by 40%, respectively. Hence, the auxetic structures have better thermal shock resistance. This study indicates that auxetic ceramic honeycombs have significant potential applications in harsh temperature environments.     

扩缩方孔蜂窝蓄热体强化传热的数值模拟

为提高烟气余热回收率,提出一种扩缩方孔蜂窝蓄热体,通过用户自定义函数(UDF)实现烟气和空气周期切换时流体种类和进口速度、温度等参数的改变,基于ANSYS Fluent软件建立了新型蓄热体的三维非稳态传热数值模型。通过比较模型预测值与文献实验值进行了模型验证。利用模型研究了新型蓄热体方孔扩缩角、扩缩节距和总长度对其传热和流阻性能的影响。通过温度云图分析了扩缩通道强化蓄热体性能的机理。结果表明,缩放通道能有效提高蜂窝蓄热体的传热性能,在压力损失增加不多的前提下,蓄热体效能最多提高约5个百分点。扩缩方孔蜂窝蓄热体长度越长,其传热性能越好;对于一定长度的新型蓄热体,扩缩节距(或扩缩角)不变时,蓄热体传热性能随扩缩角(或节距)增大而增强。扩缩角过大时,新型蓄热体流动阻力很大,综合性能不佳。     

Heat and mass transfer in monolithic honeycomb catalysts—I.

The body of information presented in this paper is directed to engineers and scientists concerned with control of automobile emissions and exhaust gases from some industrial processes. The differential equations describing heat and mass transfer in a monolithic honeycomb catalyst are developed. Following transport mechanism is considered: convective heat and mass transfer in the holes of the structure, longitudinal thermal conductivity of the honeycomb support and gas-to-solid heat and mass transfer. The magnitudes of governing parameters for monolithic modules in use are discussed. Two methods for the numerical solution of a system of coupled, nonlinear ordinary differential equations with split boundary conditions are proposed. The first method-shooting procedure can be used only for problems with low values of Peclet number. For high values of Peclet number finite-difference approach along with the Newton-Raphson algorithm is suggested. It is shown that two stable steady states exist in certain regions of operation of a particular monolithic structure. The all-metal monolithic supports are more prone to multiplicity of steady states than the ceramic ones. For ceramic supports the two-phase piston-flow model is sufficiently accurate.     

High-temperature alloy/honeycomb ceramic composite materials for solar thermal storage applications: Preparation and stability evaluation

SiC_w/Al₂O₃ honeycomb ceramics were engaged as sensible shell materials for encapsulating Al-Si alloys (latent heat materials) in the honeycomb holes to obtain alloy/ceramic composite materials with a high thermal storage capacity for high-temperature solar thermal storage applications. The stability evaluation between the sensible honeycomb ceramics and the latent alloys had been conducted and the failure mechanism for the latent alloys was investigated. Results indicated that the addition of the latent alloys could improve the thermal storage capacity of the sensible honeycomb ceramics significantly by >114% and the thermal storage densities of honeycombs containing Al-12Si and Al-20Si alloys were 1141.3 kJ/kg and 1106 kJ/kg (400–900 °C), respectively. The composite materials exhibited excellent physical and chemical stability. No cracks formed in the honeycomb ceramics and no leakage of alloys was discovered after the composite materials were exposed to 100 thermal cycles in a high-temperature testing environment. The oxidation of Al at >600 °C would lower the latent heat of alloys and the thermal storage densities decreased to 1039.9 kJ/kg and 1013.2 kJ/kg after enduring 100 thermal cycles. This study not only provides a sensible-latent system of thermal storage materials with excellent stability but also gives an insight into the protection of metal containers against the corrosion from Al-based alloys.     

基于数值模拟的马蹄焰玻璃窑蓄热室热效率研究

蓄热室是马蹄焰玻璃窑余热回收、能源循环再利用的重要设备,它对于降低玻璃窑炉整体能耗有着重要的作用。热效率低的蓄热室不但会造成大量的能源浪费,还可能会减少玻璃窑炉的使用寿命,提高蓄热室的热效率已经成为了玻璃产业亟待解决的问题。为了研究蓄热室参数对热效率的影响规律,首先运用计算流体力学理论和多孔介质模型建立了蓄热室的数值仿真模型,然后结合热平衡分析和气体热力学性质变化规律,建立蓄热室热效率模型,最后运用Fluent对不同参数下蓄热室内部温度场与速度场进行仿真,同时从温度场中采集热效率计算数据并分析各参数对蓄热室热效率的影响规律。结果表明：在保证燃料燃烧充分的前提下,减小助燃空气进口速度、格子体孔隙率、格子砖当量直径有利于增大空气与格子体的传热量,提高蓄热室的热效率,而烟道口进口面积在0.9～1 m²时蓄热室的热效率较高。