顺列光管管束烟气颗粒通过率的研究

以不同管径、横向管距和纵向管距的顺列光管管束以及不同速度和粒径的飞灰颗粒为研究对象,通过数值计算,分析了烟气颗粒横掠顺列光管束的运动规律,建立了飞灰颗粒通过率的数学模型,为循环流化床锅炉尾部顺列布置的卧式空气预热器、过热器、再热器和省煤器的减轻磨损提供了设计依据。图6表1参2     

螺旋槽管式空气预热器在1OO MW机组锅炉上的应用

论文介绍了一种新型的节能传热元件--螺旋槽管,分析了螺旋槽管的传热特性,阻力特性.并介绍了螺旋槽管在一台100MW机组锅炉的低温级空气预热器应用情况,以及工业性试验结果.     

螺旋槽管式空气预热器在100MW机组锅炉上的应用

论文介绍了一种新型的节能传热无从-螺旋槽管,分析了螺旋槽管的传热特性,阻力特性。并介绍了螺旋槽管在一台100MW机组锅炉的低温级空气预热器应用情况,以及工业性试验结果。     

50286型锅炉空气预热器的改造

使用管式空气预热器产生一系列的问题 ,采用螺旋槽管式空气预热器是一种有效的改造措施。文中针对管式空气预热器的检修空间不足的情况 ,介绍了改为螺旋槽管空气预热器的方案及其实例     

换热器节能新途径：螺旋槽管强化传热技术

介绍了螺旋槽管强化传热技术的原理，在锅炉空气预热器及发电厂高压加热器的应用实例。节能效果显著，值得在电力、化等行业推广应用。     

螺旋槽管束管外对流换热特性的数值模拟

针对烟气横掠顺列螺旋槽管束外侧的流动传热问题,利用CFD技术、通过改变顺列螺旋槽管束的横向、纵向间距、螺距、槽深等结构参数,对烟气横掠螺旋槽管管外的流动传热特性进行数值模拟,分析多几何参数对螺旋槽管管外流动传热特性的影响,得出强化传热的原因和合理的结构参数。研究表明:螺旋槽管束管外传热特性数Nu比光管管束高7%-20.6%;随横向间距的增大,管外传热特性数Nu减小,烟气流动阻力也随之减小;纵向间距的增大使管外传热特性数Nu和烟气流动阻力均增大;增加螺距或减小槽深都可以强化换热,但烟气流动阻力也会增大;综合考虑,螺旋槽管束的横、纵向间距分别取s1/d=1.75-2,s2/d=1.5-1.75,螺距P取25-30 mm,槽深e取0.4-1 mm。     

热管和内螺纹管在低温空气预热器中的应用

结合目前低温空气预热器存在的问题和实际应用的结果，通过对光管、内螺纹管和热管的传热，流动阻力以及壁温（低温腐蚀）性能进行对比分析，阐述了内螺纹管和热管换热器作为空气预热器的优点，并说明了它们的适用条件。     

螺旋槽管凝结换热器的研究与应用

通过对螺旋槽管凝结换热器的试验研究,得到了螺旋槽管涉及相变时管内对流换热、管外凝结换热准则关联式以及管内流动阻力关联式,并依据试验结果,将螺旋槽管应用于电站凝结换热器,取得了满意的效果。     

空气横掠管束换热实验研究

扩展传热面是提高单位体积内传热面积最常用的方法。以空气为介质,对三种给定的肋片管束(H型、纵肋肋片、螺旋肋片)进行了顺列和错列的换热和流动阻力实验。实验结果表明:错列布置的管束换热效果优于顺列布置的管束,但流动阻力相应增加;错列布置时,综合考虑换热和阻力因素,螺旋肋片管有较好的换热经济性。通过对实验数据进行拟合回归,得出了实验条件下各肋片管束顺列、错列布置的换热关联式。为肋片管束的工程应用、优化选取及进一步的实验研究提供了理论依据。     

H型鳍片管性能优化的数值研究

基于Fluent平台,利用Realizable k-ε湍流模型对H型鳍片管的传热特性、阻力特性和综合性能进行了数值研究.结果表明:当烟气流速越高、翅片高度越小、翅片节距越小、管束横向节距越大、管束纵向节距越大时,H型鳍片管的传热系数越大;当烟气流速越高、翅片高度越大、翅片节距越小、管束横向节距越小、管束纵向节距越大时,H型鳍片管的流动阻力越大;当相对翅片高度为h/d=2.105、翅片节距越小、管束横向相对节距为s1/d=2.237、管束纵向节距越小时,H型鳍片管的综合性能最好.     

顺排与叉排套片式换热器的热力性能对比研究

套片式换热器的管束排列形式一般都是叉排,顺排非常少见。由于顺排形式的套片式换热器通常比叉排的流动阻力更小,因而对一些流动阻力有限制的场合,可以考虑使用顺排形式的套片式换热器。为论证这一点,对某种结构形式的顺排套片式换热器和叉排套片式换热器的热力性能进行了对比研究。为便于对比、分析,两个换热器试件的纵向管间距及管排数设计成相等。结果显示:两个试件的热力性能非常接近。分析表明,在某些应用场合,套片式换热器排列成顺排是更合适的选择。图7参6     

Thermal–hydraulic analysis of a steam boiler with rifled evaporating tubes

Rifled evaporating tubes are applied in the steam boilers with the aim to increase the steam–water mixture turbulization and to prevent the burnout of tubes walls. The rifled evaporating tubes and the working fluid forced circulation are applied in the steam boiler at the Thermal Power Plant “Kolubara B” that is being built by the Electric Power Utility of Serbia. In order to investigate operating characteristics of the steam boiler of such an advanced design, a simulation and analysis of complex coupled thermal processes on the furnace gas side and thermal–hydraulics inside the evaporating tubes were performed for the whole range of plant operating loads. In this paper a methodology for hydraulic calculations of both forced and natural circulation loops is presented. The increased thermal safety margin of rifled tubes is predicted and compared with the safety margin of smooth tubes for uniform and variable heat loads among walls of the boiler furnace. The rifled tube provides an acceptable temperature of its wall even under a high void fraction of the coolant and prevents the occurrence of critical heat transfer conditions. The influence of the rifled tubes on an increase of the hydraulic resistance in the circulation loop is analyzed. Also, a range of operating conditions under which there is no need for the circulation pumps operation is determined.     

Experimental study of post-dryout with R-134a upward flow in smooth tube and rifled tubes

A study of post-dryout heat transfer was performed with a directed heated smooth tube and rifled tubes using vertical R-134a up-flow to investigate the heat transfer characteristics in the post-dryout region. Three types of rifled tube having different rib height and width were used to examine the effects of rib geometry and compare with the smooth tube, using a mass flux of 70–800 kg/m² s and a pressure of 13–24 bar (corresponding to an approximate water pressure of 80–140 bar). Wall temperature distribution in all tubes was strongly dependent on pressure and mass flux. Wall temperatures of the rifled tubes in the post-dryout region were much lower than for the smooth tube at same conditions. This was attributed to swirl flow caused by the rib. Thus, the thermal non-equilibrium, which is usually present in the post-dryout region, was lowered. The empirical correlation of heat transfer in the smooth tube of the post-dryout region was obtained. The heat transfer correlation for rifled tubes was also obtained as a function of rib height and width with the modification of the smooth tube correlation.     

传热强化管管内熵产分析与热力性能评价

根据热力学第二定律,对传热强化管管内热力过程进行熵产分析,建立了基于流动与传热过程熵增原理的管内传热熵产方程,导出恒热流和恒壁温2种常见工况下的无因次熵产数表达式.在不同雷诺数和进口温差条件下,对2种螺旋槽管和光管进行恒壁温工况的熵产分析和热力性能评价,分析了传热和流动摩阻引起的熵产变化规律及2种不可逆损失占总熵产的份额.结果表明,熵产分析可用于评价传热强化管的综合热力性能,确定合理的运行工况、结构参数及强化换热形式,为强化管的应用评估及优化设计提供参考.     

Experimental and computational performances of heat exchangers functioning in wet regime by using the film method

In this paper, we present a method of calculation by partial or total condensation of the water vapour contained in the humid air, over the smooth or finned tubes-heat recuperators. This study presents an implementation of the film method in a computer code developed here. The mathematical model used is validated by our experimental approach, using tubes bundles in staggered and aligned arrangements. The temperature of the humid air varies between 100 °C and 350 °C. The determination of the fin portion, which functions in wet regime was carried out by the calculation of temperature field over a circular fin. The heat transfer coefficient by convection around the fin is supposed to be constant. The computer code predicts the heat flux exchanged in a range of 20% and 5%, in wet and dry regime, respectively. The apparent heat transfer coefficient by condensation can exceed 10 times the value of the heat transfer coefficient.     

螺纹槽管错排管束的传热特性及流动阻力特性研究

1引言近年来,随着市场经济的发展,换热设备迫切需要节约能源、节省材料和降低成本的优化设计,因此强化传热技术受到了国内外的广泛重视。螺纹槽管是一种有效的强化换热管型,由于螺纹槽管的粗糙表面,可以有效地防止烟气在管内积灰而造成换热能力的下降,可以提高壁温以避免低温腐     

Simulation of Thermal and Flow Phenomena in Smooth and Internally Rifled Tubes

This paper puts forward modeling thermal and flow phenomena in smooth and internally rifled tubes. The proposed model is a distributed parameter model based on solving balance equations describing the principles of the mass, momentum and energy conservation. The model enables an analysis of transient-state processes. The aim of the calculations is, among others, to find the distribution of the fluid enthalpy, mass flow and pressure in smooth and internally rifled tubes and to determine the heat transfer coefficient. The analysis concerns tubes arranged vertically and operating at supercritical steam parameters. The numerical calculation results will be compared to values obtained from computational fluid dynamics.     

三维变形管与三维内肋管在管式空气预热器上的应用研究

本研究对比分析了三维内肋管及三维变形管的结构特点和强化传热机理,在相同工况下,揭示了光滑圆管、三维内肋管及三维变形管用于管式空气预热器时的传热性能和流动阻力性能,三维内肋管和三维变形管传热性能均优于光滑圆管,三维变形管管内传热系数和流动阻力系数随短长轴B/A的减小而增大,三维内肋管可增加每米肋数、肋宽和肋高以强化传热效果,但流体流动阻力也将增加,低Re下,三维变形管管内综合传热性能优于三维内肋管,三维变形管管外自支撑而防止管束振动的特点可以实现在管内外的冷热流体纯逆流动,提出一种传热温差高的逆流三维变空间管式空气预热器,在相同工况条件下,空气预热器重量减轻,体积减小约65%,节省大量的生产和运输成本以及安装空间,三维变形管空气预热器在烟气余热利用中具有推广应用价值。     

Thermal energy recovery from high-temperature blast furnace slag particles

Dry granulation is an attractive alternative to water quenching because of saving energy and reducing water consumption. In many dry granulation technologies, the high-temperature molten slag is atomized to slag particles, and the thermal energy from high-temperature slag particles is recovered by physical and chemical methods. In the present study, a technique for thermal energy recovery from high-temperature slag particles using a gravity bed waste heat boiler was exploited. The heat transfer characteristics of a laboratory-scale gravity bed waste heat boiler were investigated. An increase in Reynolds number (Re) showed no effect on the heat transfer coefficient or recovery efficiency. However, the heat transfer coefficient and recovery efficiency increased with a decrease in particle diameter and an increase in the velocity of descending particles. Compared with those observed with an aligned arrangement of the boiler tubes, the heat transfer coefficient and the recovery efficiency were higher in a staggered arrangement. The semi-empirical relations regarding the heat transfer coefficient between slag particles and boiler tubes were obtained based on experimental data and can be used to calculate the heat transfer coefficient within a certain range.