【作者】 吴可君；

【导师】 何潮洪；

【作者基本信息】 浙江大学 ， 化学工程， 2012， 博士

【摘要】 由于微化工技术在精细高附加值化工产品生产、高效传热传质设备、易燃易爆反应过程、危险化工产品生产、强放热反应过程以及燃料电池及其车载燃料系统的微型化等领域广阔的应用前景,有关流体在微管道中的流动和传热的研究也越来越受到人们的重视。常规尺度下的流动和传热理论在微尺度下是否仍然成立,哪些在常规尺度下可以忽略的因素在微尺度下会对流动和传热产生明显的影响等等问题都是在研究过程中需要分析和探讨的。本文采用去离子水、无水乙醇以及六种离子液体水溶液,考察了其在小、微尺度下的不锈钢圆管内的流动特性；采用九种常见的化工溶剂,考察了其在小、微尺度下的不锈钢圆管内的对流传热特性,同时研究了与其相关的共性基础理论和模型。主要研究内容如下：1.在Guggenheim方程的基础上,提出了对应态-基团贡献法估算离子液体表面张力的模型,对本文包含的105种离子液体,1224个数据点,估算精度较好,满足工程应用的需求；在液体黏度绝对速度理论和自由体积理论的基础上,提出了新的离子液体黏度的混合模型,对本文包含的156种离子液体,1073个数据点,估算精度明显优于之前提出的离子液体黏度模型；在Reidel方程的基础上,提出了新的计算离子液体导热系数的模型,针对本文包含的36种离子液体,296个数据点,估算精度小于实验不确定度(3%-5%)。本文提出三个模型都是基于基团贡献法的原理,形式简单,在估算过程中仅需要用到根据文献计算得到的临界温度Tc或沸点温度Tb数据即可。2.在T=(278.15-313.15)K分别测定了1-乙基-3-甲基溴化咪唑([Emim][Br])+H2O体系和1-丁基-3-甲基溴化咪唑([Bmim][Br])+H2O体系的表面张力和密度。在T=(283.15-313.15)K分别测定了1-乙基-3-甲基溴化咪唑+H2O体系和1-丁基-3-甲基溴化咪唑+H20体系的黏度。对这两种二元电解质溶液的表面张力、密度和黏度,分别采用修正的指数衰减方程、Masson方程和Thomas方程进行了关联,并根据实验结果得到了相关的表面过量性质、表观摩尔体积以及流体力学摩尔体积。3.采用去离子水、无水乙醇、三种质量摩尔浓度的1-乙基-3-甲基溴化咪唑水溶液和三种质量摩尔浓度1-丁基-3-甲基溴化咪唑水溶液作为实验流体,研究其在内径为0.353mm不锈钢圆管中,Re=25.1-542.6范围内的流动过程,重点考察了极性和电黏性效应在层流状态下对流动过程的影响。结果表明,实验尺度下,在考虑进出口压力损失以及水力学发展段压力损失基础上的得到实验结果与常规尺度理论吻合较好,与常规尺度的偏差都在实验不确定度范围内,极性和电黏性效应并未对流动产生明显影响。4.采用去离子水、无水乙醇、质量分数为5%的乙醇水溶液、质量分数为50%的乙醇水溶液、乙酸乙酯、环己烷、正己烷、环己酮和环戊酮作为实验流体,研究其在内径为0.353mm、0.597mm和1.045mm不锈钢圆管内层流状态(Re=52-527)下的对流传热过程。实验结果表明,传热特性与常规尺度下有明显差异。根据实验数据,本文在Gnielinski方程的基础上提出了一个经验模型,用于计算不锈钢微管下的努塞尔数。该经验模型将固液界面张力也考虑在内,根据气液表面张力与固液界面张力之间的近似线性关系,采用表面张力数据近似表示固液界面张力的大小。模型关联结果与实验结果吻合较好,满足工程应用的需要。更多还原

【Abstract】 Due to the broad applied prospects of microchemical technology in many fields such as production of high added value product, design of high efficient equipment in heat and mass transfer, flammable and explosive reaction, production of hazardous or toxic chemicals, strong exothermic reaction, and miniaturization of fuel cell and its vehicle-mounted system etc, the investigations of fluid flow and heat transfer in microtubes have been receiving more and more recognition. Problems such as if the conventional theory are still valid in micro scale, what factors which are negligible in conventional scale will have effect on the fluid flow and heat transfer in micro scale, and so on should be analyzed and discussed. In this paper, the liquid flow characteristics of deionized water, ethanol, and six ionic liquids (ILs) aqueous solutions and the heat transfer characteristics of nine common chemical fluids were studied. Meanwhile, the related theory and modeling in these subjects were investigated.The main contents are generalized as follows:1. Based on the Guggenheim equation, a corresponding-states group-contribution method was developed to estimate the surface tension of ionic liquids. For a database of1224data points for105ILs, the calculated surface tensions agree well with the experimental data from literatures, it satisfied the need of engineering appliance; Based on the absolute rate and free volume theories, a new hybrid model was developed to estimate the viscosity of ionic liquids. For a database of1073data points for156ILs, this model can provide a higher estimation accuracy than other models proposed before; Based on the Reidel equation, a new model was developed to estimate the thermal conductivity of ionic liquids. For a database of296data points for36ILs, the estimation accuracy is less than the experimental uncertainty (3-5%). All the three models proposed here are based on the principle of group contribution method with a simple form. Only the critical temperature Tc or normal boiling temperature Tb which can be obtained from the literature are needed during the calculation.2. The surface tensions σ (278.15-313.15) K and densities ρ (278.15-313.15) K of aqueous solutions of1-ethyl-3-methyl-limidazolium bromide and1-butyl-3-methyl-limidazolium bromide and the dynamic viscosity η(283.15-313.15) K of aqueous solutions of1-ethyl-3-methyl-limidazolium bromide and1-butyl-3-methyl-limidazolium bromide have been measured at atmospheric pressure. The modified exponential decay equation, Masson-type equation, and Thomas-type equation were used to correlate the surface tension, density, and dynamic viscosity of aqueous solution of ionic liquids, respectively. From these experimental data, the related surface excess properties, apparent molar volumes and hydrodynamic molar volume were determined.3. The experiments were carried out to examine the flow characteristics of deionized water, ethanol, three kinds of [Emim][Br] aqueous solutions, and three kinds of [Bmim][Br] aqueous solutions in stainless steel microtubes with inner diameter of0.353mm. The Reynolds number varied from25.1to542.6. The effect of polarity and electric viscous on liquid flow was also investigated. It is observed that, in the scale of experiments, the results taking the inlet and exit losses and the developing region loss in account are in good agreement with conventional theory. The influence of polarity and electric viscous is at a level within the experimental uncertainty.4. A series of systematic experiments were carried out under laminar flows (Re=52-527) in stainless steel microtubes using deionized water,5wt%ethanol aqueous solution,50wt%ethanol aqueous solution, ethanol, ethyl acetate, cyclohexane, nhexane, cyclohexanone, and cyclopentanone as working fluids. The inner diameters of stainless steel microtubes are0.353,0.597, and1.045mm, respectively. The characteristics of heat transfer in these microtubes differ significantly from those in conventional tubes. According to the experimental results, an empirical equation based on the Gnielinski equation was proposed to correlate the heat transfer in our microtubes. The effect of solid-liquid interfacial tension was also incorporated. In light of engineering applications, the solid-liquid interfacial tension cannot be easily obtained, thus, the data of liquid surface tension were used to represent the magnitude of interaction of solid-liquid interface. The calculation results are in good agreement with our experimental results, it satisfied the need of engineering appliance.更多还原