平板膜式氧合器中氧传质系数近似计算的积分法

应用Graetz-Leveque问题的前进边界理论的修正近似解,进一步分析了半透膜阻力对氧传质速率的影响,获得了与Graetz-Leveque问题精确解非常接近的(相对偏差在6.58%以下)用于计算平板膜式氧合器中氧传质系数的简单分析表达式.并提出了基于氧传质速率计算的该类氧合器通道长度设计的临界判据.     

用Na2SO3溶液吸收O2模拟血液氧合的传质性能

直接用血液进行体外血液氧合传质性能的实验研究既不方便且价格昂贵。采用化学性质稳定的Ｎａ２ＳＯ３溶液代替血流模拟氧合器的吸氧性能，不仅需要控制的实验变量少，而且由于Ｎａ２ＳＯ３价格低廉，可免去脱氧操作。本文作者在Φ１００ｍｍ的填料式氧合器中，分别采用血液和Ｎａ２ＳＯ３溶液进行了吸收氧的实验研究。结果表明，用Ｎａ２ＳＯ３溶液代替血液模拟氧合器的传质性能是可行的。     

MCI法计算固体溶质在超临界CO2中溶解度的研究

修正了杂原子原子点价（Ai^E）的计算方法，提出了一个新的分子连接性指数（^kχ^E）。该指数物理意义明确，易于计算，具有良好的结构选择性。用MCI法研究了固体溶质在超临界CO2中的溶解度与其结构之间的关系，研究结果表明溶质的分子连接性指数（^4χPC^E）可用来关联溶质苯环上取代基的种类、位置、长度对溶解度的影响，计算结果表明修正杂原子点价计算方法后的模拟结果比用原来的原子点价计算得到的偏差降低了5．01％。     

平板膜式氧合器中氧传质过程的数学模型

本文对平板膜式氧合器中的传递过程进行了研究,提出了伴有瞬间可逆氧合反应时卡森流体的对流传质模型,并用有限差分方法获得了模型的数值解.当将卡森流体简化为牛顿流体时,其物理吸收的计算结果与文献值完全一致.本文采用猪血进行了氧合实验.实验数据与理论计算的结果相吻合.当血液按牛顿流体和卡森流体处理时,发现两者的计算结果相差甚微,因而认为,在氧合器的研制中可将血液作为牛顿流体处理.     

血液透析过滤传质动力学的简化模型

血液透析（HD）、血液过滤（HF）和血液透析过滤（HDF）是目前临床上治疗慢性 肾功能衰竭最常用的 3种疗法。以往人们对 HD的传质动力学作了较多的研究l’，‘］，而对 HF、HDF的研究则较少。虽然PopoviCh等门、Jaffrln等M相继提出了描述HF、HDF 传质动力学的一、二维模型，但文献囚的模型仅适用J” HD和 HDF；而巳，其解的形式     

填料式氧合器填料传质与溶血特性的研究

本文在直径5.2 cm的有机玻璃填料式氧合器中,分别填充几种自制小填料(6mm不锈钢O网环,6 mm PVC拉西环,以及7 mm PTFE拉西环等填料),进行血液-O_2的物理吸收实验。以体积传质系数k_Lα和溶血程度作为填料的性能指标,对所用填料进行综合评价与筛选。实验结果表明:在所选填料中,以7 mm PTFE拉西环的性能为最佳。     

注塑冷却分析BEM模型中积分项的计算

注塑冷却分析最终归结为求解模具表面温度场BEM方程组,方程组中存在大量的积分项,这些积分项很难用解析式表示,因此无法求得它们的精确解析解,多采用高斯数值积分获得近似数值解,计算精度较低。本文采用近似解析解和半解析解代替原来的数值解,使得关键部位积分计算的精度提高了10％以上,不仅有利于提高冷却分析的精度,也有效地改善了边界元方程组的性态。     

基于多孔介质模型的膜式氧合器内部流场分析

膜式氧合器内部流体运动特性对其性能有重要影响，利用计算流体力学（CFD）对氧合器模型进行流体动力学分析是预测其性能的重要方法之一。本文基于压降实验计算氧合器纤维束的黏性阻力系数，建立了各向同性多孔介质模型。采用RNGk-ε湍流模型对不同流量下氧合器内部流场进行计算，得到了血液速度、压力和壁面剪切应力分布云图。发现随着流量的增加，氧合器内部速度梯度分布形式基本保持不变，压力分布呈倾斜状态且逐渐减小，大部分压力损失位于纤维束内，其中53.3%位于氧合室，42.6%位于变温室。氧合器血液的入口及出口位置为血液损伤的高发区域。采用溶血数值预估模型计算得到了氧合器的标准溶血指数NIH。结果表明：在低流量1.65～3.00L/min下，各向同性多孔介质模型的模拟结果与实验结果基本一致，模拟数值与实验数值的偏差会随着液体流量的增加而变大；流量为1.65～6.00L/min时，标准溶血指数NIH为0.0084～0.0835g/100L，满足人体生理允许的使用范围。     

三种开孔环形填料传质性能的研究

本文介绍了在φ600mm的实验装置内,对Dg50mm聚丙烯鲍尔环（井）、聚丙烯鲍尔环（米）、聚丙烯阶梯环（Ⅰ）填料,用空气脱吸CO_2水溶液,测得的传质性能数据,并用此数据对液膜传质系数的不同关联方法进行了核算、对比。认为:恩田等所提出的计算液膜传质系数的关联式,在计算新型开孔环形填料时偏差较大,主要是由于他们所提出的形状系数a_td_p,未能反映这些新型填料的形状特征对其传质性能的影响。本文用形状修正系数ψ来代替a_td_p,这样恩田等的计算液膜传质系数的关联式,其应用范围被扩展到新型开孔环类型填料的范围。 采用新的形状修正系数ψ后,液膜传质系数的计算式改写为 k_L(ρ_L/μ_(Lg))~1/3=0.0095(L_G/a_ωμ_L)~2/3(μ_L/ρ_LD_L）~(-1/2)ψ~0.4对各种不同类型填料其形状修正系数值为 本式可适用于Dg50mm以下的上述各类填料的计算。     

不可逆热力学分离过程理论

将热力学原理和理论扩展到不可逆过程 ,形成不可逆热力学理论 ,并应用于扩散传质分离过程 ,建立不可逆热力学分离过程理论 ,其核心为描述多组分物系组分间相对运动的普遍化麦克斯韦尔 -斯蒂芬方程。该理论可合理地解释一些传质“奇异”现象 ,计算非理想物系传质扩散系数 ,预测多组分分离过程的传质速率和级效率 ,其模拟计算结果与实验测定值能很好地吻合。不考虑组分间的交互作用 ,视各组分效率相等的模型计算结果与实验测定值存在偏差 ,物系的非理想程度越大 ,偏差越大。     

MASS TRANSFER COEFFICIENTS FOR REACTIVE FLUIDS FLOWING IN CONDUITS WITH SEMI-PERMEABLE WALLS

The advancing front theory is an approximate solution for mass transfer into a reactive fluid when the reaction can be assumed to be very fast. The theory has had considerable use in predicting mass transfer characteristics for reactive fluids flowing in conduits. In this paper, the mass transfer coefficient, in the form of the local, fluid-side Sherwood number, is derived for reactive flow in conduits with semi-permeable walls. The local, fluid-side Sherwood number is given as a function of the Graetz number, the wall Sherwood number, and a dimensionless reaction strength parameter. The limiting cases of both the constant wall concentration boundary condition (Sh_w?∞) and the constant wall flux boundary condition (Sh_w?∞)are investigated. Comparisons of the results with the classical Graetz and Leveque theories give conclusions about the accuracy of the advancing front theory for the worst possible case.     

AN ADVANCING FRONT MODEL OF TRANSPORT INTO PULSATING LAMINAR FLOW

The diffusion and transport of a gas species is analyzed for a slowly pulsating fluid in laminar tube flow. It is assumed that the fluid velocity is in phase with the pulsating pressure gradient. A reversible chemical reaction within the fluid is modeled using advancing front theory. The pulsation is assumed to affect only the diffusion boundary layer thickness, which may be out of phase with the flow pulsation. The solution is approximate for small perturbations of the boundary layer thickness. With these assumptions a closed form solution for the bulk transport is obtained. The results are expressed as differences in the bulk transport relative to a steady flow having the same average flow conditions. The pulsation effect is expressed as a function of the non-dimensional flow amplitude and frequency parameters for various average conditions. Comparison with experimental measurements of oxygen diffusing into water and hemoglobin solutions shows good agreement. For the range of parameters used for the measurements, there is no effect of the pulsation on time-averaged transfer rates.     

Kinetics of mass transfer in a liquid phase under laminar film flow conditions

Comparative analysis of exact and approximate solutions to the problem of mass transfer in a liquid phase under conditions of laminar film flow on vertical surfaces under homogeneous and inhomogeneous boundary conditions is given. It is shown that the rate of mass transfer in the liquid phase derived from an exact solution is considerably lower than the rate determined from the known approximate solutions. Equations for calculating the Sherwood number derived from exact and approximate solutions are given and compared.     

Numerical simulation of CO2 absorption into aqueous methyldiethanolamine solutions

The CO₂ absorption rate into aqueous N-methyldiethanolamine solutions was measured using a stirred cell with a flat gas-liquid interface. The measurements were performed in the temperature range of 293.15 to 333.15 K for various amine concentrations and CO₂ partial pressures. A numerical model of mass-transfer with complex chemical reactions based on the film theory was developed to interpret the experimental results. The model predictions have been found to be in good agreement with the experimental values of CO₂ absorption rates. A comparison is made between the enhancement factor predicted from the detailed model and the approximate solution of mass transfer equations with chemical reaction. The numerical results indicate that under the present experimental conditions, the effect of the reaction between CO₂ and OH^? on the observed mass transfer rates is negligible. The detailed mass transfer model was used for simulating the CO₂ absorption process in terms of the enhancement factor under a variety of operating conditions.     

2-乙基-1，3-己二醇萃取硼酸的传质系数

单液滴法因其测量结果精确与实验设备简单等优点广泛应用于萃取过程中的传质研究。应用此方法研究了硼酸在2-乙基-1,3-己二醇-甲苯/卤水体系中的传质系数。结果表明：传质系数随着有机相2-乙基-1,3-己二醇浓度、卤水相硼酸浓度及温度的增加而增大。通过双膜传质理论分析,并引入修正的传质系数关联式,将双膜传质模型应用到此萃取体系中,建立了新的针对此体系的传质系数模型。新模型的计算值与实验值的平均相对误差为7.59 %,两者吻合良好,因此,该模型可用于2-乙基-1,3-己二醇-甲苯体系萃取硼酸过程的设计与放大。     

Modeling Study of the Influence of Porosity on Membrane Absorption Process

Abstract

A theoretical model based on the advancing front model was developed to analyze the influence of porosity on membrane absorption process. Perturbation solutions were obtained and a nonlinear transformation was applied to increase the accuracy of the solutions. The concentration profile of the solute in the liquid side near the membrane surface was simulated for different operation conditions. The influencing factors on the diffusing rate of the solute concentration profile were analyzed qualitatively. In the case of the rapid mass transfer system, the time of reaction front to reach the midpoint of two proximate pores is relatively long, which means that the concentration layer of solute overcasts the whole surface of membrane slowly, there is a “dead” area for mass transfer, so the influence of porosity should be taken into account. In the case of slow mass transfer system, the time can be ignored compared with the overall experiment time, and the influence of porosity is negligible. The absorption rates were calculated based on the developed model and the calculated results agreed well with the literature results.     

MDEA-MEA混合有机胺水溶液吸收CO_2

研究了N-甲基二乙醇胺(MDEA)和一乙醇胺(MEA)混合有机胺水溶液吸收CO_2的过程.根据双膜理论,导出了简化近似宏观动力学模型,用以预测混合有机胺水溶液吸收CO_2的速率.该模型考虑了化学反应之间的交互作用,用三次多项式近似表示反应组分在膜中的浓度分布.在各种条件下测定了搅拌反应器内MDEA/MEA水溶液吸收CO_2的速率.模型计算值与实验测定值符合良好.     

Extraction of formic acid with G/O/W microdispersion system

The enrichment of formic acid in dilute solution was achieved by complex extraction method. An extraction system with high partition coefficient was determined. The continuum model was then applied for describing mass transfer process and predicting the mass transfer characteristics in O/W system. The rate-limiting step was determined to be mass transfer of formic acid in aqueous phase, by comparison of mass transfer rates between extractant in organic phase and solute in aqueous phase. The effect of dispersion size of organic droplets on mass transfer characteristics in O/W systems was determined, indicating inefficient extraction process with low mass transfer coefficients and surficial area in O/W systems. Inert gas was introduced into extraction system and a G/O/W system was developed. The calculation of mass transfer performance in G/O/W system indicates the addition of microbubbles effectively enhances the mass transfer process. Also, suitable volumetric fraction of inert gas was optimized. According to the calculation, a double-membrane-dispersion-device was designed, with which G/O/W double emulsion was prepared and effective enrichment of formic acid from its dilute solution was realized.     

G/O/W微分散体系实现甲酸/三辛胺-正辛醇体系萃取分离

以络合萃取法实现了稀溶液中甲酸的富集。确定了高分配系数的萃取体系。根据传质基本方程建立了传质模型，计算并分析了油/水体系中的传质过程，确定传质控制步骤为甲酸自水相至水/油界面的传质。计算了分散尺寸对体系传质性能的影响，结果表明，由于水/油相比高，体系的传质系数低，界面积小，以油/水微分散乳液实现萃取过程，传质效率仍不高。引入惰性气体，并构建气/油/水体系，计算并分析了气/油/水体系中的传质过程并优化了气相加入量，结果表明，气相的加入可以有效促进传质过程。设计了双重膜分散设备，制备了微米尺度的气/油/水双重乳液，并以此实现了稀溶液中甲酸的高效富集。