环柱形颗粒填充床传热参数

在一可同时测定轴向与径向温度分布的壁冷式固定床实验装置上 ,通过实验测定了球形、圆柱形和环柱形填充颗粒的径向有效导热系数和壁给热系数 .采用计及内、外环外表面积的颗粒等比表面积当量直径 ,将这些传热参数与Reynolds数相关联 .     

气体流动条件下钴基催化剂固定床的传热

在气体流量4~8 Nm3/h、气体分布器进口温度190~210℃、加热管壁温约240℃的条件下,对气体流动时活性组分呈蛋壳型分布的钴基催化剂固定床的传热进行了实验研究,建立了二维拟均相传热模型,利用正交配置法和Levenberg-Marquardt法对其求解,得到了钴基催化剂床层径向有效导热系数及壁给热系数的关联式,并将传热参数与由气体处于静态时固定床的有效导热系数计算而得的固定床传热参数值进行了比较,在气体入口温度范围内考察了其对固定床传热参数的影响. 结果表明,实验所得传热参数与文献值的最大偏差绝对值均在15%以内.     

二○○二年第16卷总目次

题 目 作 者 期 页 间歇过程能量平衡和 平衡分析方法的研究 李志红, 宋子明, 袁志敏 1 1 笼式反应器中的流动与混合特性 周贤爵, 戴干策 1 7 气升式环流反应器强制振荡周期对传质影响的研究 徐圆圆, 刘德华, 谢东明 1 13 搅拌槽内近桨区流动场的数值研究 周国忠, 施力田, 王英琛 1 17 异形多通孔催化剂工程研究(III)——12孔及24孔颗粒固定床传热参数测定 樊蓉蓉, 甘 霖, 朱炳辰, 徐懋生 1 23 紫外光辐射下臭氧在水中的…     

低流量下微细颗粒固定床的温度分布及有效传热参数研究

为探索微小型热生物传感器中反应器内部的传热特性,研究了恒壁温(60℃)条件下,低流量(5,3和1 mL·min-1)和微细颗粒直径(平均直径分别为1,0.75和0.45 mm)对固定床内部温度分布的影响,并结合二维均相传热理论模型,获得了有效径向导热系数和有效壁面传热系数等重要参数。研究结果表明,即使在流量非常小(如1 mL·min-1)的情况下,固定床入口段温度分布也很不均匀,存在明显的"入口段效应",但随着床层的增高,这种效应快速减弱;实验所采用树脂颗粒的导热系数很低,颗粒直径越小,接触热阻和流动阻力也越大,导致其有效传热参数越小,不利于热生物传感器中微量反应热信号的检测;在相同Rep时,本研究的有效径向导热系数明显小于文献值,而有效壁面传热参数与多数文献值比较接近。     

异形多通孔催化剂工程研究(Ⅰ)12孔及24孔颗粒当量直径测定

引　言异形多通孔催化剂载体的外形为薄壁环柱形 ,多通孔由薄片分隔而成 ,是一种组合成形的薄片载体 .对于活性组分呈均匀分布的催化剂 ,多通孔载体有利于减小内扩散过程影响 ,提高选择性 ;对于外表型分布的催化剂 ,外表面积增大有利于增加活性组分负载量 ,提高催化剂活性 .异形多通孔催化剂还具有强化传热和降低反应器床层压力降的优点 .文献 [1,2 ]针对三叶草、蜂窝状载体等异形催化剂颗粒的传热性能及选择性的提高等方面进行了实验研究 .本文具体研究异形多通孔催化剂对床层压力降的影响 ,并测定了异形多通孔颗粒的当量直径 .催化剂颗粒…     

活性焦传热系数的测定

为研究活性焦传热性能,把床层径向传热简化为径向有效导热,将轴向传热看成轴向有效导热和流体流动传热2项组成,自制传热系数测定装置,改变扰流气体流速,测定床层轴向和径向温度分布,利用Matlab软件,采用正交配置法进行数据处理,通过赋予初值,采用最优化方法求解模型偏微分方程,得出径向有效导热系数Ker及壁给热系数Hw。试验结果表明:活性焦有效导热系数约为1.39 W/(m·K),壁给热系数随着颗粒雷诺数的增加而增加。试验测定的壁给热系数与低传热系数材料的壁给热系数经验公式较吻合。     

A301氨合成催化剂工程参数研究与测定Ⅱ床层传热参数的实验测定

实验测定了Ａ３０１氨合成催化剂填充床内的二维温度分布。采用正交配置法求解拟均相二维传热数学模型,获得了床层的径向有效导热系数和壁给热系数。并将其与雷诺数关联得到了可在实验条件范围内使用的经验关联式。     

固定床有效导热系数及壁给热系数的实验测定及其关联式

在固定床反应器设计时,需要计算床层温度分布及热点位置,因此测定传热参数数值具有重要意义。本文作者在直径为φ76×4mm长1040mm,内部充填φ4.5mm刚玉球的固定床实验装置上测定了床层不同高度,不同径向位置上的温度分布值,并分别用理论解法、有限差分法及最优化法求得床层径向有效导热系数K_e及壁给热系数H_w值。作者认为最优化法求出的K_e、H_w值准确可靠,计算温度和实测温度较为吻合。     

固定床内传热参数的估计与分析

本文在系统地考察了各种因素对床层径向有效导热系数和壁传热系数影响的实验研究与计算机模拟的基础上,对文献中发表的固定床内传热参数估值离散的原因进行了分析。结果表明,Bi取值在5.0左右时,对床层出口温度比较敏感,是造成h_(?)估值离散的重要原因之一。床层填充的随机性影响床层温度分布,低床层、低Re_p条件下估计参数误差要大。d_(?)取值范围不同,壁冷却和壁加热条件下估计出的参数均会不同。     

钴基催化剂固定床有效导热系数

在165~265℃及常压条件下,采用稳态法测定了气体处于静态时活性组分呈蛋壳型分布的钴基催化剂固定床的有效导热系数,并根据稳态法理论,拟合实验数据获得了固定床有效导热系数与气体导热系数和催化剂导热系数之间的关联式. 实验数据与拟合结果的最大偏差和标准偏差的绝对值分别为1.74%和0.43%. 将实验数据与前人的相关预测模型计算值进行了比较,结果表明,二者吻合良好. 利用气体处于静态时固定床的有效导热系数、Re和Pr,获得了气体流动时固定床径向有效导热系数的计算式.     

PPH治疗混合痔的护理体会

目的探讨混合痔行PPH的护理方法。方法99例混合痔患者均行PPH,手术前向患者介绍住院环境、住院须知,告知治疗方法及护理上需要的配合,饮食、排便的注意事项,术前准备等;术后体位及恢复饮食时间,大小便情况观察及各种外用药的使用,出血护理及伤口护理,肛门功能锻炼;制定入院评估,印制出院指导。结果99例患者痔核明显回缩,顺利出院。结论混合痔PPH的术前术后护理对患者顺利康复有重要意义。     

Crosslinking of styrene-butadiene rubber with polyurethanes bicapped with benzyocyclobutene

Summary A polyurethane prepared from 1,9-nonanediol and toluene-2,4-diisocyanate with M_n=11,840, was capped on both ends in a reaction with 4-(benzocyclobutenyl) methanol. The polyurethane was used to crosslink styrene-butadiene rubber through Diels-Alder reactions on the benzocyclobutene functionality. The synthesis and characterization of 4-(benzocyclobutenyl) methanol, a molecule not reported previously, is presented. The crosslinking reaction was carried out on intimate mixtures of the telechelic polyurethane and SBR at elevated temperature and pressure. Various physical properties of the crosslinked material were studied.Work done at the Department of Chemistry, University of Akron, Akron, OH 44325, USA     

Dehydrochlorination of propylene chlorohydrin with sodium hydroxide and with catholyte

Dehydrochlorination of an aqueous solution of propylene chlorohydrin with sodium hydroxide (12·5 and 30% by weight), with catholyte (5 or 10% by weight NaOH + 14% by weight NaCl) and with milk of lime (15% by weight) were compared. The use of catholyte (10% by weight NaOH + 14% by weight NaCl) enables propylene oxide to be obtained in a yield of 94·3%, with 100% conversion of chlorohydrin. The concentration of 1,2-propylene glycol in the waste is 0·07% by weight.     

复合扰流柱的螺旋内构件反应器内流体的宏观混合

在管式反应器内插入复合扰流柱的螺旋型内构件,采用脉冲示踪法测定了反应器内流体的停留时间分布,研究了器内流体的宏观混合特性,分析了该内构件强化混合的机理. 结果表明,复合扰流柱的螺旋型内构件反应器内的流体流动更接近于活塞流,其轴向扩散模型参数Pe为螺旋型内构件反应器的1.02~1.28倍,为不带内构件反应器的1.35~1.77倍. 复合扰流柱的螺旋型内构件能显著增强器内的二次流动,从而强化了宏观混合效果.     

Reaction of CH-acidic compounds with thiacumulenes and alkylation with dihaloalkanes

Dithiocarboxylation of CH-acidic compounds 1 and stepwise alkylation of primarily formed dithiolates 2 yielded ketene dithioacetals 5a,b or methylenebis(dithiocarbonates) 12a–c. Reaction of 5a,b with nucleophiles afforded thiophene 7 and dithioacetals 8, 9a,b, 11, respectively. 1,3-Thiazetidines 14a,c,e and thiazolidines 14b,d,f were prepared by thiocarbamoylation of 1b,c,e and subsequent alkylation with dihaloalkanes.     

Copolymerization of acrylonitrile with maleamic acid derivatives and with carboxyphenylmaleimide

Acrylonitrile was copolymerized with two N-arylmaleamic acids and with N-3-carboxyphenylmaleimide in dimethylformamide (DMF) using azobisisobutyronitrile as initiator. The reactivity ratios and the Q-e parameters of these monomers were estimated, and the resulting copolymers were characterized by viscosity measurements and thermal analysis. Thermogravimetry and differential thermal analysis data showed an improvement in the thermal behaviour of the investigated copolymers compared with that of poly(acrylonitrile). Mechanisms illustrating the role of both the acidic group and the maleimide ring in the nitrile oligomerization were proposed. The produced copolymers showed an excellent affinity towards basic dyes and better color fastness towards UV light.     

Syntheses of bismaleimides with ester units and their polymerization with diamines

Five structurally different bismaleimides were synthesized by reaction between 3(4)‐maleimidobenzylchloride with various diphenols. They were characterized by infrared (IR) and proton nuclear magnetic resonance (¹H‐NMR) spectroscopy. Thermal characterization of monomers and their polymers was accomplished by differential scanning calorimetry (DSC) and dynamic thermogravimetric analysis (TGA). Polyaminobismaleimides having inherent viscosities of 0.1–0.4 dL/g were prepared by Michael addition of diamines to bismaleimides. The polymers are soluble in solvents as DMF, NMP, and DMSO, and afforded film from their solutions. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 750–757, 2002; DOI 10.1002/app.10294     

单双切向环流式旋风除尘器的比较

以粉煤灰 空气为实验物系 ,测定了单、双切向环流式旋风除尘器的除尘效率和压降。实验结果表明 ,双切向环流式旋风除尘器的除尘效率比单切向环流式旋风除尘器的除尘效率有所提高 ,压降比单切向环流式旋风除尘器的压降低 2 0 0Pa ,处理量有所增大     

Wettability enhancement of polystyrene with electron cyclotron resonance plasma with argon

Polystyrene cell‐culture substrates were treated with argon glow discharge to make their surfaces hydrophilic. The process was novel in that it used a microwave electron cyclotron resonance (ECR) source for polymer surface modification. The substrates were processed at different microwave powers and time periods, and the surface modification was assessed with by measurement of the water contact angle. A decrease in contact angle was observed with increasing microwave power and processing time. Beyond a certain limit of power and duration of exposure, however, surface deterioration occurred. The optimum conditions for making the surfaces hydrophilic without deterioration of the samples were identified. The plasma parameters were assessed by Langmuir probe measurement. Fourier transform infrared spectroscopy with attenuated total reflectance showed evidence for the induction of hydrophilicity on the surface. The surface micromorphology was examined with scanning electron microscopy. The results prove that the ECR glow discharge was an efficient method for enhancing the wettability of the polymer surfaces. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1618–1623, 2003