水分解制氢中的电解液调控机制

氢气因能量密度高和燃烧产物无污染得到了广泛的关注,如何以清洁高效的方式制备氢能成为研究中的重点。光伏-电解、光催化、光电催化分解水可以利用储量丰富的太阳能和水产生氢气,是很有前景的氢气制备技术。其中,电化学反应是水分解工艺的关键环节,直接决定整个系统能量转换效率的高低。而以往研究多集中于催化材料的开发,往往忽略了电解液的性质对电解性能的影响。因此本文综述了电解质对电催化分解水的影响和意义,根据水分解的基本理论和反应机理,讨论了电化学步骤中电解质pH、离子成分对表面催化过程和物质传输的影响。通过调控电解质来影响固液界面反应,达到在各种水分解系统中提高能量转化效率和稳定性的目的,这有助于开发高效的电催化体系,并为大规模应用提供参考。     

Steady microfluidic measurements of mutual diffusion coefficients of liquid binary mixtures

We present a microfluidic method leading to accurate measurements of the mutual diffusion coefficient of a liquid binary mixture over the whole solute concentration range in a single experiment. This method fully exploits solvent pervaporation through a poly(dimethylsiloxane) (PDMS) membrane to obtain a steady concentration gradient within a microfluidic channel. Our method is applicable for solutes which cannot permeate through PDMS, and requires the activity and the density over the full concentration range as input parameters. We demonstrate the accuracy of our methodology by measuring the mutual diffusion coefficient of the water (1) + glycerol (2) mixture, from measurements of the concentration gradient using Raman confocal spectroscopy and the pervaporation‐induced flow using particle tracking velocimetry. © 2017 American Institute of Chemical Engineers AIChE J, 63: 358–366, 2018     

化工原理课程中三传相似性教学要点分析

单元操作从本质上讲可以分解为动量传递、热量传递、质量传递这三种传递过程或者它们的结合。学习和掌握三传相似性在加强学生对化工原理知识的深入认识、融会贯通方面有着重要的意义。文章就三传相似性的一些教学要点进行了深入剖析,并对教学方法进行了简要探讨。     

Effect of ultrasonic waveforms on gas–liquid mass transfer in microreactors

This study aims to investigate the effect of ultrasonic waveforms on the gas–liquid mass transfer process. For a given load power (P), continuous rectangular wave yielded stronger bubble oscillation and higher mass transfer coefficient (k_La) than continuous triangular and sinusoidal wave. For pulsed ultrasound, the k_La decreased monotonically with decreasing duty ratio (D), resulting in weak enhancement at low D (≤33%). For a given average load power (P_A), concentrating the P for a shorter period resulted in a higher k_La due to stronger cavitation behavior. For a given P_A and D, decreasing the pulse period (T) led to an increase in k_La, which reached a constant high level when the T fell below a critical value. By optimizing the D and T, a k_La equivalent to 92% of that under continuous ultrasound was obtained under pulsed ultrasound at a D of 67%, saving 33% in power consumption.     

Hydrodynamics,mass transfer,and photocatalytic phenol selective oxidation reaction kinetics in a fixed TiO2 microreactor

Photocatalytic phenol dissociation was studied in a microreactor, with a TiO₂ layer immobilized on the reactor inner walls. Experiments were conducted for various residence times, initial concentrations, pH values, and UV light irradiation intensities. The intermediates and products (catechol, hydroquinone, and resorcinol) were quantitatively investigated to determine the predominant reaction pathways for the investigated anatase catalyst. A three‐dimensional mathematical model was used to simulate the heterogeneous photocatalysis reaction conditions with Langmuir–Hinshelwood mechanism, considering the adsorption/desorption thermodynamic equilibria, and for kinetic parameter estimation via regression analysis. The effectiveness factor, Thiele modulus, and the correction function were calculated to determine the pore diffusion effects. The value of pH had the dramatic effect of lowering the reaction rate due to the competitive adsorption of hydroxide ions and protons on the catalyst surface. A phenol conversion of 79.5% was achieved at the residence time of 7.22 min, but without total mineralization. © 2014 American Institute of Chemical Engineers AIChE J, 61: 572–581, 2015     

填料型饱和热水塔气相传质系数与传热系数的计算与应用

导出了计算填料型饱和热水塔气相传质系数和传热系数的方法,分析了应用气相传质系数和传热系数计算填料层高度的方法,给出了计算实例,计算结果与生产实际相符。     

声化学微反应器——超声和微反应器协同强化

微反应器和声化学技术都是化工过程强化的重要手段,但都有优缺点。阐释了“声化学微反应器”的理念--微反应器和声化学技术相互集成,利用超声强化微通道内的混合、传质和预防堵塞等,同样借助微反应器实现声场和气泡场的有效调控并解决声空化过程的放大难题,实现协调强化的目的。同时,深入剖析了声化学微反应器内的声空化行为、声场和气泡场调控规律,以及多相流动体系中的混合与传质强化机制。最后展望了该领域的发展方向,并指出超声空化过程中表界面时空尺度现象和理论是实现并优化超声强化的基础。     

分子识别型智能微囊的制备及其控制释放特性

采用微流控乳化和紫外光照引发制备聚(N-异丙基丙烯酰胺-共聚-丙烯酸)微囊,然后通过缩合反应将氨基化β-环糊精(ECD)引入微囊成功制备得到聚(N-异丙基丙烯酰胺-共聚-丙烯酸/氨基化β-环糊精)(PNA-ECD)微囊。PNA-ECD微囊具有明显的核壳型结构和良好的单分散性。微囊的平均直径为470μm,CV值为2.98%。PNA-ECD微囊在识别模型芳环分子8-苯胺-1-萘磺酸铵盐(ANS)后能等温收缩从而实现对内载药物的控制释放。32℃时,微囊内部的模型药物异硫氰酸荧光素标记葡聚糖(FITC-dextran)在纯水中无明显释放,而在加入2.0mmol/L ANS溶液16min后,微囊内部约70%的FITC-dextran释放到微囊外部。研究结果对制备单分散分子识别型智能微囊及研究其控制释放特性提供有价值的理论指导和实验基础。     

绝热圆腔内4根冷热微管阵列振动强化传热实验

目前针对微细管管外同时有自然对流和周期横向振动存在情况下的混合对流问题鲜有研究。为了探究这种现象, 进而开发一种新型的换热器, 本文提出了一种由4根冷热微细管组成的微管阵列, 将其平行放置于有中间流体的圆形腔体内, 并对管束施加微小横向振动的混合对流传热机理进行研究。详细描述了实验系统及实验方法, 以及后期对实验数据的处理方法, 得到了传热Nu数随管间自然对流强度Ra数, 强迫振动Re_v数等量纲为1参数的变化曲线;揭示了该结构形式下传热特性随冷热管温差、振动频率、微管振幅等传热规律。结果表明, 横向振动在小温差情况下传热强化效果更为明显。将本文实验数据与Lemlich单管振动实验中的数据进行对比, 表明了振动对4根微管阵列的强化传热效果比单根管更明显。     

Graetz和Leveque问题的前进边界理论修正的近似解

<正>1引言 氧合器的开发设计,需要计算血液中O2的传质速率。一般地,由于趴在血液中溶解度的非线性特点,使得趴传质的数学模型为一非线性偏微分方程”,“。但在体外氧合装置中,血液的流道远大于单一红细胞尺寸,故可认为O南血红蛋自（Hb）的反应是瞬时的,据此可用可逆反应理论和前进边界理论“－“两种方法近似描述o。的溶解度曲线,进而求出方程的分析解。对于传质界面固定的膜式氧合器,宜应用前进边界理论,但其解仍为较复杂的级数形式。为简化数学处理,Stfoeve等”’提出了1个求解该模型的近似方法。但与精确解比较,其偏差较大（约15％）。本文对Stroeve的近似解法进行了修正,修正后的结果与精确解的偏差可减小到4．36％。     

肠靶向海藻酸钙基微胶囊的制备及控释性能研究

利用毛细管共挤出技术结合静电吸附和仿生硅化的方法,制备了海藻酸钙-壳聚糖/精蛋白/二氧化硅(ACPSi)复合微胶囊。ACPSi复合微胶囊的平均粒径约3.18 mm,单分散性好,囊壁最外层的二氧化硅层可抑制其在肠液pH环境中的溶胀,增强囊的机械稳定性。将羟丙甲基纤维素邻苯二甲酸酯(HPMCP)肠溶微球作为释药“微阀门”,嵌入囊壁可以更好地控制微胶囊的释药行为。以吲哚美辛为模型药物,当药物浓度为22.5 mg/ml时,ACPSi载药微胶囊在pH 2.5模拟胃液中3 h时累计释药率仅为0.33%,而转移至pH 6.8模拟肠液中19 h时累计释药率为77.78%;囊壁嵌入HPMCP微球后,22 h时累计释药率可提高约4%。因此,该复合微胶囊具有良好的肠靶向作用和控释特性,作为口服肠靶向缓控释制剂具有良好的应用前景。     

亲水无纺布PVC复合规整填料除湿性能实验

将亲水无纺布PVC复合规整填料作为溶液除湿塔芯体,开展亲水无纺布PVC复合规整填料除湿性能实验,分析在不同空气流量、溶液流量、溶液温度下,亲水无纺布PVC复合规整填料除湿率、除湿效率、传质系数和传热系数的变化。在实验条件下,除湿率、除湿效率、传质系数、传热系数最大值分别为11.05 g·kg^-1、86.7%、12.95 g·(m²·s)^-1、10.33 W·(m²·℃)^-1;与CELdek规整填料和塑料波纹孔板填料相比,亲水无纺布PVC复合规整填料除湿性能最优。对实验数据回归分析,得到亲水无纺布PVC复合规整填料除湿效率实验关联式。