共查询到19条相似文献,搜索用时 234 毫秒
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采用数值模拟技术对错列布置光管及螺旋翅片管、顺列螺旋翅片管的双相流场进行了数值模拟,分析了不同结构、不同排列方式的省煤器的抗磨性能.分析了翅片结构对颗粒运动与流场的影响,指出翅片的存在使烟气中的大颗粒飞灰较难碰撞到基管的表面,增强了省煤器的抗磨损能力. 相似文献
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利用拉格朗日粒子随机追踪模型以及El-Batsh 和Haselbacher提出的粒子沉积模型,对飞灰颗粒横掠管束时的运动轨迹和沉积特性进行了数值研究,获得了管束排布方式以及粒子直径对飞灰颗粒运动轨迹及沉积分布的影响。结果表明:当颗粒的直径小到一定程度时,管束通道内的流场和温度分布对颗粒的运动轨迹影响显著;颗粒在管壁表面的碰撞率和沉积率与管束排布和粒径有关,粒径50.0um颗粒几乎没有沉积;粒径10.0um颗粒沉积主要分布在管壁迎风面;粒径1.0um的颗粒在管壁的迎风面和背风面都有沉积。 相似文献
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H型鳍片管性能优化的数值研究 总被引:1,自引:0,他引:1
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. 相似文献
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为了防止锅炉管束的飞灰磨损,自1959年以来日本就一直从事于有关飞灰磨损的研究和试验。本文论述了这些研究和试验的部分结果。首先,根据试验室中所进行的烟气流动模拟试验的结果,确定了在后墙处存在着局部的高速烟气流。为了防止这种局部的高速烟气流,在包复墙上有规律地布置挡板,已被证明是行之有效的。其次,利用试验设备对锅炉管束的飞灰磨损进行了一系列的基本试验。从这些试验中可显然看到,飞灰对锅炉管束的磨损主要是由大颗粒的飞灰引起的。最后,作为一种防止锅炉管束飞灰磨损的方法,建议在后房管束上安装撞击式分离器。而且通过试验室试验来确定这种分离器的最佳形状、尺寸和布置方式。 相似文献
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一、某SHL6-13A型锅炉结构与计算数据 1.锅炉结构:本锅炉为双锅筒横置式链条炉排锅炉,炉膛敷设有水冷壁管,上下锅筒之间连接有19排顺列对流管束,尾部只设有两段铸铁省煤器,其结构布置简示于图1。 相似文献
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对不同翅片间距Sf、管束横向节距St和管束纵向节距Sl的9组螺旋翅片管束的换热和流动过程进行了试验研究.分析了换热过程的熵产,研究了雷诺数(RP)、翅片间距、管束横向节距和管束纵向节距对管束换热熵产数NsH、流动熵产数NsF和总熵产数Ns的影响.结果表明:对不同布置方式的管束,随着Re的增加,NsH迅速减小,NsF逐渐增加,Ns先减小后增加;翅片间距对NsH影响较小,在高Re下,翅片间距增大时,NsF和Ns均明显降低;横向节距对NsH几乎没影响,但随着横向节距的增加,NsF和Ns均明显降低;管束纵向节距对NsH、NsF和Ns的影响都很小. 相似文献
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采用标准k-ε湍流模型、基于有限体积法,对Ra数1.12×106-1.02×108,Pr数101-127范围内竖排等温管束对原油的自然对流换热特性进行了数值研究。结果表明,随相邻加热管中心距增加,管束整体依次经历了换热恶化、强化、稳定和衰退的不同阶段。底部加热管自然对流诱发的流体流动增大了上层管周围流体的速度,对上层管换热具有强化作用,但同时也改变了上层管周围流体的温度分布,导致上层管换热恶化和Nu数随时间产生波动。此外,存在换热强化和最高换热强度的临界中心距都随Ra数增大而减小,换热强化作用随Pr数增大而减弱,增加上层管数在一定程度上可提高管束的平均换热强度。 相似文献
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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 相似文献
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The excessively increasing environmental concerns along with reducing fossil fuel resources introduce the trend of increasing the efficiency of boiler via implementing waste heat recovery. In the present study, the potential of latent heat recovery is investigated in the middle‐size boiler exhaust flue gas using the shell and corrugated tube heat exchanger. The main purpose of the present study is efficiency growth in flue gases using latent heat recovery of the steam energy. The heat recovery analysis is evaluated by a validated computational fluid dynamics model by a commercial software. For this study, the effect of different tube arrangements, number of tubes, and flow direction in the shell on heat transfer and pressure drop were investigated. The results showed that in‐line arrangement of the tubes in the shell presents better thermal performance and also high pressure drop among the other arrangements. As a result, by considering the thermal performance and pressure drop, radial arrangement shows higher performance. According to the obtained results from Section 2 of the present study, by considering the radial arrangement of tubes in the shell, as the number of tube rises, the thermal performance declines. 相似文献
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Sofia G. Mavridou Demetri G. Bouris 《International Journal of Heat and Mass Transfer》2012,55(19-20):5185-5195
This paper describes the numerical evaluation of a novel cross flow tube bundle heat exchanger that combines tubes of different diameter in an inline arrangement for the purpose of reducing gas side particulate fouling rates while preserving acceptable levels of heat transfer and pressure drop performance. Three arrangements are compared: a common inline tube bundle heat exchanger with cylinders of equal diameter and two other arrangements that consist of alternately placed cylinders with a diameter ratio of d/D = 0.5, at two different transverse spacings. Numerical calculations are performed in order to study heat transfer, pressure drop and fouling rates from flue gases with suspended ash particles. The alternating tube sizes achieve a suppression of the vortex shedding mechanism that has previously been shown to enhance downstream particle deposition. Results show that, compared to the standard arrangement, the tube bundle with unequal cylinders placed at the largest transverse spacing achieves a significant (~30%) reduction in particle deposition rate without sacrificing acceptable values of heat transfer per unit volume and low pressure drop. 相似文献
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Boiling heat transfer of R-134a on a porous, plasma-coated tube bundle was investigated experimentally to determine the effects of the number of tube rows and the total tube number. The bundle consists of up to four tubes with a pitch-to-diameter-ratio of 1.33. Heat transfer coefficients for a single tube with a porous copper coating were up to four times higher than for a smooth tube. Observations showed that the plasma coating enhanced the heat transfer coefficient in tube bundles as well. The bundle factor of the coated tube bundle showed a similar, slightly increased trend as the smooth tube bundles. The enhancement effect of the coated tubes decreases to a certain extent with an increasing heat flux and decreasing saturation temperature. However, it is significantly less pronounced than trends that have been reported from other investigations. The aim of a stable enhanced coating was confirmed by long-term experiments with steady results. 相似文献
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Yuming Chen Manfred Groll Rainer Mertz Rudi Kulenovic 《International Journal of Heat and Mass Transfer》2005,48(11):2310-2322
Pool boiling heat transfer experiments were carried out on a conventional smooth tube and four enhanced tubes with reentrant surfaces using propane, isobutane and their mixtures as working fluids for six saturation temperatures. The heat transfer performance is very different for different surface-fluid combinations. Compared to the smooth tube, the mixture boiling heat transfer degradation is more significant for the enhanced tubes. The current data are compared with available literature data for the same fluids and also with data for R12 and R134a. Experimental results of boiling hysteresis and for twin-tube bundles are also provided. Further explanations for the different heat transfer performances is provided by means of visualization in an accompanying paper [Y. Chen, M. Groll, R. Mertz, R. Kulenovic, Visualization and mechanisms of pool boiling of propane, isobutane and their mixtures on enhanced tubes with reentrant channels, submitted to Int. J. Heat Mass Transfer (H/S 04016)]. 相似文献