Influence of syngas components and ash particles on the radiative heat transfer in a radiant syngas cooler

Radiant syngas cooler(RSC)is widely used as a waste heat recovery equipment in industrial gasification.In this work,an RSC with radiation screens is established and the impact of gaseous radiative property models,gas components,and ash particles on heat transfer is investigated by the numerical simulation method.Considering the syngas components and the pressure environment of the RSC,a modified weighted-sum-of-gray-gases model was developed.The modified model shows high accuracy in validation.In computational fluid dynamics simulation,the calculated steam production is only 0.63%in error with the industrial data.Compared with Smith's model,the temperature decay along the axial direction calculated by the modified model is faster.Syngas components are of great significance to heat recovery capacity,especially when the absorbing gas fraction is less than 10%.After considering the influence of particles,the outlet temperature and the proportion of radiative heat transfer are less affected,but the difference in steam output reaches 2.7 t·h^(-1).The particle deposition on the wall greatly reduces the heat recovery performance of an RSC.

Analysis of the Erosion-Corrosion Mechanism of the Air Cooler in a Hydrocracking Unit:A Numerical and Experimental Study

Corrosion leakages often occur in the air cooler of a hydrocracking unit,with the failure sites mainly located in the entrance area of the tubes.An analysis of the macroscopic morphology and corrosion products confirmed that the damage was caused by erosion-corrosion(E-C).Numerical and experimental methods were applied to investigate the E-C mechanism in the air cooler.Computational fluid dynamics(CFD)was used to calculate the hydrodynamic parameters of the air cooler.The results showed that there was a biased flow in the air cooler,which led to a significant increase in velocity,turbulent kinetic energy and wall shear within 0.2 m of the tube entrance.A visualization experiment was then performed to determine the principles of migration and transformation of multiphase flow in the air cooler tubes.Various flow patterns(pure droplet flow,mist flow,and annular flow)and their evolutionary processes were clearly depicted experimentally.The initiation mechanism and processes leading to the development of E-C in the air cooler were also determined.This study provided a comprehensive explanation for the E-C failures that occur in air coolers during operation.

Numerical simulation of coupled thermo-electrical field for 20 kA new rare earth reduction cell

To solve the problems of high energy consumption,low efficiency and short service life of conventional rare earth reduction cells,a 20 kA new rare earth reduction cell(NRERC)was presented.The effects of the anode-cathode distance(ACD)and electrolyte height(EH)on the thermo-electrical behavior of the NRERC were studied by ANSYS.The results illustrate that the cell voltage drop(CVD)and the temperature will rise with a similar tendency when the ACD increases.Also,the temperature rises gradually with EH,but the CVD decreases.Ultimately,when the ACD is 115 mm and the EH is 380 mm,the CVD is 4.61 V and the temperature is 1109.8℃.Under these conditions,the thermal field distribution is more reasonable and the CVD is lower,which is beneficial to the long service life and low energy consumption of the NRERC.

The thermo-electric effect of magnetite and the mechanism of geo-electric abnormalities during earthquakes

The thermo-electric coefficients of twenty-six magnetite samples, formed either by magmatism or metamorphism, were tested by the thermo-electric instrument BHET -06. Results showed that the coef- ficient is of a constant value of about -0.05 mV/℃. It is emphasized that because every magnetite grain was tested randomly, the coefficient is independent of the crystallographic direction. This fact means the thermal voltage generated from a single magnetite crystal can be accumulated, and as a result a new thermo-electric field can arise when a gradient thermal field exists and is active within the earth＇s crust. Because magnetite is widespread in the earth＇s crust （generally appearing more in the middle-lower crust）, there is more-thanrandom probability that the additional thermo-electric field can be generated when certain thermal conditions are fulfilled. We, therefore, used the thermo-electric effect of magnetite to study the mechanism responsible for the presence of abnormal geo-electric fields during earthquake formation and occurrence, because gradient thermal fields always exist before earthquakes. The possible presence of additional thermo-electric fields was calculated under theoretical seismological conditions, using the following calculation formula：E= - 0.159（σ×△T×Ф×ρ2×[[（h^2 - 2x^2）cos α ＋ 3hxsin α]/ρ1 （h^2 ＋x^2）^5/2）. In the above formula, σ is thermo-electric coefficient of magnetite, △T is the temperature difference acting on it, Ф is a sectional area on a block of magnetite vertically perpendicular to the direction of the thermal current, ρ1 and ρ2 are the respective resistivities of magnetite and the crust, and h, α, and x, respectively, h is the depth of embedded magnetite block. α means the angle created by the horizontal line and ligature of the two poles of magnetite block, and x is the distance from observation point to projective center point of the magnetite block on earth surface. According to simulations calculated with this formula, additional thermo-electric field intensity may reach as high as n to n × 10^2 mV/km. This field is strong enough to cause obvious anomalies in the background geo-electric field, and can be easy probed by earthquake monitoring equipment. Therefore, we hypothesize that geo-electric abnormalities which occur during earthquakes may be caused by the thermo-electric effect of magnetite.

Experimental Study on the Thermal Performances of a Tube-Type Indirect Evaporative Cooler

The so-called indirect evaporative cooling technology is widely used in air conditioning applications.The thermal characterization of tube-type indirect evaporative coolers,however,still presents challenges which need to be addressed to make this technology more reliable and easy to implement.This experimental study deals with the performances of a tube-type indirect evaporative cooler based on an aluminum tube with a 10 mm diameter.In particular,the required tests were carried out considering a range of dry-bulb temperatures between 16℃ and 18℃ and a temperature difference between the wet-bulb and dry-bulb temperature of 2℃∼4℃.The integrated convective heat transfer coefficient inside the tube in the drenching condition has been found to lie in the range between 36.10 and 437.4(W/(m^(2)⋅K)).

光学舱推进剂补加过程的热分析仿真与试验研究

推进剂补加是确保光学舱在轨长寿命工作的重要功能,补加过程面临的热环境条件比以往任务恶劣,全过程热控制十分必要。针对光学舱推进剂补加过程的复杂传热新问题,建立包含压气机、液冷模块和环路热管等部件的光学舱平台集成热数学模型,进行热分析仿真研究,并开展系统级热试验。对比高温和低温2种补加条件的瞬态热分析和热试验结果,研究传热关系和温度变化规律;针对热试验中垂直热管因重力因素从不运行至运行的瞬态过程,提出一种变热导率仿真方法;提出高温补加优化设计方案并进行在轨预示。结果表明:瞬态仿真结果与试验结果吻合良好,验证了热分析方法和仿真模型的准确性和有效性;在轨补加采用压气机本体预热并启动2套环路热管,压气机的最高温度≤34.1℃,预热总功耗50 Wh,满足指标要求。研究结果对于光学舱停靠空间站期间的推进剂补加流程设计具有一定参考价值。

一种自汲水蒸发冷却器及其关键材料制备

针对蒸发冷却机组高效紧凑化需求,提出一种小型自汲水间接蒸发冷却器结构,并对关键湿面材料的制备和性能进行试验研究。PAN-SiO_(2)导湿纤维采用静电纺丝工艺制造,在20%浓度前驱体溶液中添加SiO_(2)驻极体,使其综合性能达到最优,其中,芯吸速率相比普通腈纶材料提高了250%,湿扩散速率提高了569%,蒸发速率提高了129%。在标准焓差室环境下,通过试验研究了样机性能及入口参数的影响规律。结果表明,进口干、湿球温度为40,21.8℃,风速为1.0 m/s时,湿球效率达到82.6%,能效比达到10.1;通过新型材料自汲补水的结构,取代了常规间接蒸发冷却设备中的重要耗能水泵设备,在保证制冷效率的前提下大大降低了机组能耗,可为蒸发冷却机组小型化探索提供参考。

烧结矿双级冷却工艺及装备技术研发与应用

烧结行业实践应用的余热回收方式主要是环冷机+余热锅炉与竖式冷却+余热锅炉,而将原烧结给料溜槽改为一级竖式冷却的双级冷却技术,可显著回收高品质余热。本文在介绍烧结双级冷却技术工艺及原理基础上,通过FLUENT流体仿真,对比了烧结双级冷却相对传统环冷机流场和温度场分布,并从冷却提效、余热回收增量、烧结矿增产和除尘增效4方面系统阐述了烧结双级冷却技术效果优势。结果表明,该技术可降低环冷机冷却风量约13%,提高过热蒸汽50℃,降低返矿率1%。该技术在湘潭钢铁新一烧360 m^(2)烧结机成功应用也表明,余热锅炉蒸汽产量可由吨矿约34 t/h增长到约40 t/h,增加发电量约为1200 kW·h年经济效益约为400万元。

干湿联合式蒸发空冷器管束腐蚀失效分析及预防措施

干湿联合式蒸发空冷器的传热管束包含预冷管束和蒸发管束,预冷管束采用翅片管,蒸发管束采用蛇形光管。该类型设备在某沿海石化企业使用过程中,蛇形光管U形弯部位出现不同程度的腐蚀穿孔泄漏,为了确定腐蚀泄漏原因,以石脑油加氢装置中石脑油分馏塔顶空冷器为例,采用多种试验手段对腐蚀失效原理进行分析。根据外观检查、水质分析、化学成分检测、力学性能及金相检测、腐蚀形貌观察和产物成分分析等分析结果判断,该空冷器的主要失效原因是浓差腐蚀及电化学腐蚀共同作用的结果,并对此提出了相应的预防措施。

基于热管散热的多级热电制冷器性能分析

为了研究几何结构对多级热电制冷性能的影响,建立了基于热管散热的多级热电制冷器有限时间热力学模型,提出模块利用系数和协调性能系数两个性能评价指标,并采用数值模拟的方法研究了热电偶比例系数和级数对热电制冷器性能的影响,得到了不同几何结构下装置性能指标随工作电流的变化规律。结果表明:比例系数为2的六级热电制冷器的制冷温差和制冷量可分别达到135.3℃和0.34 W;较小的比例系数和工作电流,可以有效实现制冷能力和经济性能的统一。设计制作了基于热管散热的四级热电制冷器样机,当环境温度分别为16℃和26℃时,实测冷端温度分别为-76℃和-69℃。

基于响应面法的矿用翅片管空冷器参数优化

矿用空冷器是矿井降温系统常用的末端设备,优化矿用空冷器换热性能对提升矿井降温系统能效具有重要意义。采用Fluent建立了平直翅片管矿用空冷器模型,研究了翅片间距、翅片厚度、横向管间距和纵向管间距对传热因子、阻力因子和综合性能评价指标的影响规律;采用Box-Behnken响应面法,分析了双参数协同作用下传热因子、阻力因子和综合性能评价指标变化规律。结果表明:随着翅片间距、横向管间距的减小,以及翅片厚度增加,传热因子、阻力因子和综合性能评价指标逐渐增加;综合性能评价指标则随纵向管间距的增加而先增加后降低;横向管间距、翅片厚度是影响空冷器传热及流动性能最显著的两个参数,而翅片间距、纵向管间距的影响最小;得到了平直翅片管矿用空冷器的最优参数,传热因子提升16.3%、阻力因子增加26.3%、综合性能评价指标提升8.3%。研究结果可为矿用翅片空冷器设计参数优化提供指导。

汽油机EGR用超纯铁素体J444E不锈钢高温性能研究

根据汽油机EGR冷却器工况特性和对材料的要求,开发出适应复杂环境下性能优良、成本低廉的超纯铁素体不锈钢材料J444E钢。通过对200~630℃、900~1050℃中高温力学性能及900~1050℃不同温度下100~500 h不同时间及900℃钎焊前后高温氧化性能和氧化层的试验研究和分析,表明该材料在工况环境下具有良好的力学和抗氧化性能。

传感器位置对大型冷库库内温度及风机运行规律的影响

目前,冷库多通过库内布置传感器所采集的温度信号控制冷风机启停,进而维持适宜贮存温度。为探索不同位置传感器对大型冷库库内温度及风机运行时长的影响,本文以一实际使用的大型冷库为为原型构建计算模型,模拟研究了不同传感器位置导致风机运行规律变化,进而引起冷库温度波动情况。结果表明,“冷库升温”过程中,传感器布置在侧墙中部响应效果最佳;“关门降温”过程,传感器平行侧墙布置在冷库中部时,所导致的风机能耗最小;“开门降温”过程,传感器平行布置在冷库中间可以实现风机最佳的响应时间。

重离子储存环CSRe上类钠Kr^(25+)离子的双电子复合精密谱学实验研究

高电荷态离子的双电子复合精密谱学实验研究,不仅对天体等离子体和聚变等离子体的研究具有重要意义,而且可以作为一种新的精密谱学工具,用来检验强场量子电动力学效应、测量同位素移动及提取原子核电荷半径等.在兰州重离子储存环CSRe上,安装了专门用于电子-离子复合精密谱学实验的电子束能量调制系统,质心系下电子-离子碰撞能量的调制范围达到0—1 keV.在CSRe电子冷却器下游安装了自主研制的塑料闪烁体探测器和多丝正比探测器,用于探测复合离子.在此基础上,使用Kr^(25+)离子在CSRe上进行了首次双电子复合测试实验,实验测量了质心系能量0—70 eV的双电子复合速率系数.为了更好地理解实验测量结果,利用FAC(flexible atomic code)程序计算了Kr^(25+)离子的双电子复合速率系数,并与实验做了细致对比,整体符合很好,而且发现3s→41(△n=1)的共振跃迁对实验谱线有很大的贡献.实验结果表明,CSRe双电子复合实验平台具有非常好的稳定性和可重复性,能够为下一步开展更高电荷态离子的双电子复合精密谱学实验、检验强场量子电动力学效应以及原子核性质精密测量等前沿实验提供支持.

Design calculation of porous ceramics tube type dew point indirect evaporative cooler

To improve the wall surface hydrophilicity of a tube type indirect evaporative cooler,a new method adopting porous ceramics is proposed.This method realizes the combination of porous ceramics and the evaporative cooling technique.The design calculation of the porous ceramics tube type dew point indirect evaporative cooler are carried out from such aspects as the volumes and status parameters of the primary and secondary air,the cooler structure,the heat transfer of the solid porous ceramic tubes and the resistance of the cooler.The calculation results show that the design is reasonable.Finally,based on the design calculation,the porous ceramics tube type dew point indirect evaporative cooler is successfully manufactured.

Influence of regenerator flow resistance on stability of pulse tube cooler

Based on the fluid network theory,the possibility of utilizing regenerator flow resistance to suppress the direct current （DC） flow induced by the introduction of a double-inlet in a pulse tube cooler is investigated theoretically. The calculation results show that increasing regenerator flow resistance can lead to a smaller extent of DC flow.Therefore,a better stability performance of the cooler can be realized.On this basis,the stability characteristics of the cooler with various regenerator matrix arrangements are studied by experiments.By replacing 30% space of 247 screens of stainless steel mesh at the cold part of the regenerator by lead balls of 0.25 mm diameter,a long-time stable temperature output at 80 K region is achieved. This achievement provides a new way to obtain stable performance for pulse tube coolers at high temperature and is helpful for its application.

谷物冷却机降温通风粮温变化规律实验研究

科学高效使用通风设备对粮仓通风,可有效控制粮堆温度,保障粮食储藏安全。为探究谷物冷却机通风过程中的粮堆温度变化规律,采用谷物冷却机先后对2个浅圆仓、3个超高大平房仓进行冷却通风对比实验。结果表明,浅圆仓通风效果良好,温度迁移速率约为1.7~1.9 m/d,通风11 d后会降低整仓粮温,无通风死角;平房仓通风过程中会形成风道,打乱粮堆原始冷心,有效降低平均粮温但无法实现整仓粮温均匀降低,存在通风死角。

HC浓度对EGR冷却器沉积层表面微观结构的影响

不同试验条件下沉积在EGR(exhaust gas recirculation)冷却器换热管内表面的颗粒物会形成不同表面微观结构的沉积层。为了量化分析沉积处表面微观结构的分布特征和三维表面的起伏特征,提出采用沉积层表面结构特征面积占比和表面分形盒维数两个参数分析沉积层的表面微观结构变化规律,并利用其分析碳氢化合物(HC,hydrocarbons)浓度对沉积层表面微观结构的影响。结果表明:试验气体中的HC等挥发性物质的析出会影响EGR气体中颗粒物的尺寸,改变沉积层表面凹坑和凸起结构的数量和尺寸分布;随着HC浓度的增加,沉积层表面凸起结构所占的面积百分比逐渐增加,凹坑结构所占面积百分比变化较小;用于表征沉积层表面起伏程度的沉积层表面分形盒维数随试验气体中HC浓度的增加而逐渐增加。

基于LADRC的跑道积冰主动探测装置温度精准控制

对跑道表面积冰主动进行探测,是保障航班安全运行的重要手段,本文针对目前积冰检测多为被动的积冰后检测的弊端,提出一种以热电制冷器为核心的跑道积冰主动探测装置,超前模拟跑道小范围温度条件和积冰状况,实现跑道积冰主动探测.数值分析表明,装置温度控制易受运行过程中内部参数和外部环境扰动的影响,为实现精准温控,提出一种基于线性自抗扰控制(LADRC)的温控方法,并利用时变增益方法改进扩张状态观测器(ESO).仿真结果表明LADRC控制有更好的抗干扰能力,总扰动下的均方误差(MSE)较PID和非线性PID(NLPID)控制分别减少了57.22%和55.77%.低温实验箱及室外低温环境下实验结果表明,装置能够快速响应达到目标温度,稳态误差为0.05℃,能够满足积冰状况模拟及积冰主动探测的需求.

辐射废锅内辐射屏水冷管热变形数值模拟研究

煤气化技术是煤炭清洁高效利用的有效途径,其中带辐射废锅的气流床气化工艺能够有效回收高温合成气显热,提高能源利用率。辐射废锅内部增设辐射屏水冷管,可在保持辐射废锅水冷壁整体结构紧凑的同时提高传热面积。为研究气化炉操作条件下辐射废锅内辐射屏水冷管的热变形,利用流体−结构耦合原理建立三维辐射屏模型进行模拟分析。模拟结果表明:在正常操作工况下,水冷管整体在距顶部5.30 m处温度达到最大值。在周向方向上,最靠近炉膛中心的1号水冷管表面温度成抛物线形分布,向火侧中间位置温度最高,向火侧和背侧最大温差达到60 K;在相邻水冷管的冷却作用下,2~5号水冷管表面温度成双峰状分布。水冷管的空间布置直接影响水冷管表面的温度分布。未加固定的辐射屏水冷管中最靠近炉膛中心的1号水冷管局部变形量最大为5.20 cm,π方向的最大偏移量为4.58 cm,超过相邻水冷管的间距,水冷管之间易发生碰撞。水冷管间增加固定后,水冷管发生整体变形,最大热变形量为3.28 cm,较未加固定的减小36.9%,π方向的相对偏移基本消失,水冷管之间的局部变形远小于管间距。增加固定可有效避免水冷管之间的碰撞。进口合成气温度和表面沉积的变化不同程度影响水冷管表面温度梯度和变形量,偏移方向均为水冷管的π/2侧。