Untersuchung überlagerter Effekte von Druckverlust und Totvolumen durch Rekuperation am isobaren Expansionsmotor

The efficiency of heat engines is significantly influenced by heat recovery in recuperators. In the case of the Bush-type isobaric expansion engine (IEE), a heat engine that can be operated with heat sources starting from 60°C, the thermal efficiency increases significantly through the use of recuperators. At the same time, internal fluid volumes of the heat exchanger and the pressure loss arising during operation have a negative effect on the thermal efficiency. In this work, the interaction between dead volume, pressure loss and heat recovery is investigated and recommendations for the operation of recuperators in the isobaric expansion engine are given.     

CERAMIC HEAT PIPES FOR HIGH TEMPERATURE HEAT RECOVERY

Difficulties in finding metal or protected metal components that exhibit both strength and corrosion resistance at high temperature have severely restricted the application of effective heat recovery techniques to process heat furnaces. A potential method of overcoming this restriction is to use heat pipes fabricated from ceramic materials to construct counterflow recuperators. A development program has been initiated to demonstrate the technical and eventually the economical feasibility of ceramic heat pipes and ceramic heat pipe recuperators. The prime candidate for heat pipe construction is SiC. Closed-end tubes of this material have been prepared by chemical vapor deposition (CVD). These tubes were lined internally with tungsten by a subsequent CVD operation, partially filled with sodium, and sealed by brazing a tungsten-lined SiC plug into the open end with a palladium-cobalt alloy.

Heat pipes constructed in this manner have been successfully operated in vacuum at temperatures of 1225 K and in air at a temperature of 1125 K. The heat source used initially for the air testing was an induction heated metallic sleeve in thermal contact with the test unit. Subsequent testing has shown that a silicon carbide heat pipe can be successfully operated with natural gas burners providing the input heat. Methods of fabricating and testing these devices are described.     

Heat integration and operational optimization of an austenitization furnace using concentric-tube radiant recuperators

This paper presents a model-based study of the impact of implementing radiant (radiation-dominated) concentric-tube recuperators on fuel use in an indirectly-fired industrial heat treating (austenitization/quench hardening) furnace. The recuperators recover some of the waste heat from the burner exhaust to preheat the inlet air to the burners, thus reducing the amount of fuel required for combustion. The novelty of this work consists of developing a physics-based model of a recuperator, which captures local gas-to-surface convective heat transfer and long-range surface-to-surface radiation interactions, and using the model to analyze and optimize the energy use of the furnace. An iterative algorithm is proposed to solve the poorly-conditioned energy balance equations. The steady-state system operation is optimized using surrogate models. Extensive simulation studies demonstrate that heat integration reduces fuel consumption significantly without affecting product quality. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16414 2019     

Development of a Ceramic Micro Heat Exchanger – Design,Construction, and Testing

This article presents the development of a ceramic micro heat exchanger. Starting from its geometrical design, results obtained from a simplified simulation of the heat exchanger efficiency will be given. The alumina microcomponents were manufactured by a rapid prototyping process chain. Here, stereolithography was combined with a low‐pressure injection molding process for the rapid and precise manufacturing of ceramic components down to the micrometer range. A micro heat exchanger, joined from sintered components using a glass solder, was applied as a prototype and checked for its performance at a system pressure of 8 bar.     

新型陶瓷换热器用蓄热材料的选择

综述了陶瓷换热器用蓄热体材料的基本性质 ;从材质和形状两个方面详细探讨了蓄热体对陶瓷换热器的热工性能、使用寿命和烟气余热回收率的影响 ,并给出选择合适蓄热体的一些建议 ;同时 ,总结了现有蓄热体的一些性能参数 ,为陶瓷换热器的设计提供了必要的物理、热工数据     

Intensification of Heat Exchange in Recuperators Using Ceramic Coatings

It is shown that coatings with high blackness applied to the hot-front wall surface of recuperators make it possible to increase the temperature of heated air and to reduce the organic fuel rate in a furnace equipped with the appropriate recuperator. Spectral blackness curves for ceramic coatings applied to refractory materials and heat-resistant steels are measured in the range of 0.75 – 9.0 μm, and the advantages of using the coatings to improve performance of ceramic and steel-made radiation recuperators are discussed.     

Evaluation of thermal efficiency for heat regenerators in periodic operation by approximate methods

Thermal efficiency of heat regenerators in periodic operation is one of the most important quantities to the designer and plant engineer. The current procedures for calculation of efficiency are model dependent numerical algorithms which require considerable computational time. In this work approximate formulae, applicable to all model types, have been developed for quick calculation, by algebraic means, of the regenerator efficiency in single pass, cocurrent or countercurrent operation. The formulae require only the knowledge of the variance of the impulse response of a model based on the assumed heat transfer mechanisms in the regenerator. A method is introduced for utilizing the representation of the regenerator thermal impulse response by a gamma probability density function in obtaining the solution and efficiency for cocurrent periodic operation. An analogy to countercurrent heat recuperators and the intergral of the impulse response are used to develop a formula for efficiency for the countercurrent case. The accuracy of the developed approximations is discussed and shown to be well within the accuracy of the parameters of the system.     

新型陶瓷换热器材料的实验研究

从多组实验配方中找出了一种耐热冲击性强、热膨胀性小、烧结致密的最佳配方。研究了几种主要陶瓷成分对陶瓷换热器抗热震性能的影响。     

管壳式换热器的优化设计

管壳式换热器是广泛应用于各个领域的工业设备，在国民经济中具有非常重要的作用，管壳式换热器的效率问题是设计工作的核心。本文利用优化设计原理，建立了以管壳式换热器优化设计模型。分析了影响年总费用的因素．编制了管壳式换热器优化设计计算机程序。最后给出了一个计算实例说明优化设计程序的作用。     

管壳式换热器的优化设计

管壳式换热器是广泛应用于各个领域的工业设备,在国民经济中具有非常重要的作用,管壳式换热器的效率问题是设计工作的核心。本文利用优化设计原理,建立了以管壳式换热器优化设计模型。分析了影响年总费用的因素,编制了管壳式换热器优化设计计算机程序。最后给出了一个计算实例说明优化设计程序的使用。     

高效节能、低污染浇嘴——WDH型燃油、燃气烧嘴

本文首次向国内陶瓷界介绍一种具有九十年代国际先进水平的喷雾燃烧技术——气泡雾化喷雾技术。结合我国目前的陶瓷窑炉烧嘴现状以及WDH型烧嘴在国内各行业的应用情况,介绍了WDH型烧嘴的原理,优点以及推广后的经济效益。     

热管在陶瓷工业窑余热回收工程中的应用初探

介绍了工业窑炉烟气余热回收工程中所广泛应用的热管技术;并结合陶瓷窑炉,对热管换热器在陶瓷工业中的应用进行了初步探索。     

Thermal conductivity studies on Si/SiC ceramic composites

Ceramic heat exchangers are increasingly used in many nuclear power plants. Silicon carbide has been treated as a promising material for heat exchanger application since it has good thermal conductivity and corrosion resistance. In this work, four different types of Si/SiC ceramic composites were prepared by liquid silicon infiltration technique. Thermal conductivities of these ceramic composites at different temperatures are measured by the laser flash thermal conductivity method. Results show that the presence of free carbon and voids are notably affecting the thermal conductivity of these materials.     

换热器中的温度交叉分析

本文通过一个实例,详细计算了换热器在产生温度交叉后的传热效果,并由热容量比和温度效率两参数推导出了温度交叉产生的条件,指出在将单程顺流或逆流型换热器改为多程时应充分注意这种温度交叉现象。     

逆流式微通道换热器设计与操作特性分析

采用一维对流-导热耦合模型对逆流式微通道换热器传热特性进行分析和模拟,考察了结构参数、操作条件和材质热导率对微换热器整体效率的影响.计算结果表明,由于器壁径向和轴向传热的相互影响, 与常规尺度换热器相比,微通道换热器的设计和操作特性有许多明显不同的特征.微通道换热器存在最佳操作流量值,该值可作为标准负荷流量,微换热器不宜在亚负荷状态下操作;操作流量越大,微通道换热器最大换热效率越低;微换热器结构采用大深宽比通道和适当的间壁厚度为佳.     

考虑关键换热器备用的原油预热系统清垢周期优化

原油结垢是原油预热过程面临的一个严峻问题,它使换热器的传热系数降低,影响正常的生产过程。应对原油预热过程的结垢问题最普遍的方法就是对换热器进行周期清洁,并优化清洁周期。许多结垢严重的行业都采用换热器备用的方式来减少因换热器离线造成的热回收减小,但原油预热系统尚未考虑,因而进一步考虑了关键换热器的备用来进行原油预热系统清垢周期优化。首先选取关键换热器,再通过模拟退火算法进行清洁周期优化。应用所提出的方法对简化的原油预热系统进行了清垢周期优化,结果显示,考虑换热器备用时所得到的清垢周期经济效益更好。     

大化肥锅炉的节能改造

A锅炉的燃烧器由船形改为水平浓淡形，空气预热器由回转式改为螺旋管式。改造后锅炉运行平稳，热效率提高，无明显结焦，经济效益显著。     

Electrically Heated Oxide Ceramic Tubes for High Temperature Reactions

Endothermic high temperature reactions are usually carried out in metal tubes heated by gas burners. Electrical heating allows substantial reduction of CO₂ emissions. We propose the usage of a composite tube, where a thin metallic layer is embedded between an inner and outer ceramic layer. While monolithic ceramics suffer from brittleness and low tolerance to thermal stress, only the inner layer is made from monolithic ceramics, while the outer layer is made of fiber reinforced oxide ceramics. In first tests the hybrid ceramic tube was electrically heated to 1250 °C with a maximum heat release of 85 kW m⁻².     

Laser-based investigations of flow fields and OH distributions in impinging flames of domestic cooker-top burners

A thermal performance of impinging flames of widely-used cooker-top burners depends on a complex interaction between flow field and combustion. The critical situation is placed on two typical cooker-top burners having almost the same configurations, but yielding about 10% point difference in thermal efficiency. Therefore, in situ flame measurements of averaged velocity using particle image velocimetry (PIV) and image of averaged OH radicals using planar laser-induced fluorescence (OH-PLIF) are required to obtain insight into the coupling mechanisms during the combustion and heat transfer, and to develop a comprehensive experimental data base to support a phenomenological understanding of the differences in flames of the two burners. A combined study of flow field and combustion forms the basis of a much better understanding of the casual links that couple fluid mechanics, combustion and heat transfer in the two burners. This can provide guidelines for efficient burner design to meet future regulatory requirements.     

多管式换热器的研究及工业应用分析

多管式换热器是一种较为新型的高效换热器，目前对于这种换热器的研究较少，其传热性能的研究也鲜见报道。对多管式换热器做了初步的研究，并以实际工业装置工况为例，采用管壳式、多管换热器和翅片管多管式作为换热器设计的三种方案，利用HTRI软件进行模拟，比较出三个方案在传热和经济方面的性能差异，分析多管式换热器在工业应用中优势，为研究和推广这种新型的换热器提供有价值的参考依据。