离子液体型新工质溶液降膜吸收过程传热传质及其强化机理研究

The new working fluids composed of phosphoric imidazolium ionic liquids and refrigerants are suitable in absorption refrigeration and heat pump cycles because of ionic liquids having the advantage of non-volatility，wide liquid range, thermal stable, non-corrosive tendency, green and environmental friendly. In this project the effects of surfactants(2-ethyl-1-hexanol) and nano-particles (Cu, CuO, NCT)on thermo-physic properties of new working fluids, Marangoni convection, heat and mass transfer coefficients in falling film absorption will be researched. The suitable additives and nano-particles which can match the new working fluids will be chosen and the basic thermo-physical data on these new working fluids and the correlation equations on heat and mass transfer in falling film absorption will be obtained. The force fields for all atom and united atom will be constructed and the parameters in these force fields will be optimized based on the quantum chemistry methods. The enhanced effects of surfactants and nano-particles on heat and mass transfer in falling film absorption for the working solutions will be researched by molecular dynamics simulation. The microscopic structure of interface layer between vapor and liquid phases such as the distribution density function and the orientation of molecules or radicals, interactions between different radicals ( hydrogen bond and adsorption to the interface) will be analyzed. The diffusivity and conductivity of some molecules in binary working solution or in binary nano- particles fluids will be predicted by Gibbs ensemble. This research will enrich and expend the theory and practices on heat and mass transfer of new working solutions and provide the fundamental and necessary data for the industrial applications of new ionic liquid working solutions.

磷酸酯咪唑离子液体不挥发、液程宽、热稳定、不腐蚀、绿色环保，可作为冷媒（水、醇）的新型吸收剂，构成吸收循环新型工质溶液。研究表面活性剂（异辛醇等）和纳米粒子（Cu，CuO,NCT等）对新工质溶液热物性（黏度、表面张力、导热系数等）以及降膜吸收冷媒蒸汽过程中的液膜形态、马拉戈尼对流、传热、传质速率的影响规律；筛选出与离子液体溶液相匹配的表面活性剂和纳米粒子，获得新工质溶液体系基础热物性数据以及传热、传质膜系数关联式；构建全原子力场或联合原子力场模型，利用量子化学方法优化模型参数。利用分子动力学方法，从分子层面上研究表面活性剂、纳米粒子强化热、质传递的机理；分析汽液界面层的微观结构、表面活性剂和纳米粒子在界面层中的分布密度和空间取向，揭示界面吸附/吸收的物理本质，利用Gibbs系综，理论计算新工质溶液的热物性数据。丰富和拓展工质溶液热质传递的研究内容，为离子液体新工质的工业应用提供理论依据。

以离子液体水溶液[Emim][DEP](1)+H2O(2)，[Emim][DMP](1)+H2O(2)及其为基液的单壁和多壁碳纳米管（SWCNT，MWCNT）流体作为吸收制冷和热泵循环的新型工质对，对其热物性（密度，粘度，导热系数）进行了实验测量和数据关联。采用分子动力学方法研究了热物性随着溶液组成和碳纳米管含量的变化规律。结果表明：单壁碳纳米管的增强效果明显高于多壁碳纳米管。多壁碳纳米管纳米流体导热系数的增强比为8-9%，单壁碳纳米管的增强比可达到30%左右。利用Gaussian 09A.01软件，分析了离子液体溶液[Emim][DMP](1)+H2O(2)体相中的阴，阳离子以及水分子径向分布函数，所形成的氢键键长和键角。结果发现：纯离子液体[Emim][DMP]中阳离子中的H2原子同阴离子中的O21原子所形成的氢键最强。在离子液体溶液[Emim][DMP](1)+H2O(2)中，最强的氢键产生在阴离子中的双键氧原子O21，同水分子中的氢原子之间。并且随着水分子摩尔数的增加而变弱。当水的摩尔分数低于0.6时，水分子全部同离子液体阴离子形成氢键，没有自由水形成。离子液体水溶液表现为更像纯离子液体，当水的摩尔分数高于0.6时，溶液中含有自由水分子，溶液的性质更像水。 利用分子动力学方法，研究了离子液体水溶液[Emim][DMP] (1)+H2O(2) /水蒸气界面的微观结构。分析了离子液体及其溶液的界面层中阴、阳离子和水分子的分布密度和方向序。结果表明：离子液体溶液的界面层是具有分层结构的，离子液体的阴离子分布在界面的最外层，其次是阳离子，水分子位于最内层。这种分布结构有利于离子液体溶液吸收气相中的水蒸气。研究发现:离子液体阳离子的咪唑环处于与界面相垂直的位置，咪唑环上的大部分乙基链朝向气相，而大部分甲基链则朝向液相。对离子液体二元工质溶液[Emim][DEP](1)+H2O(2)进行了垂直降膜吸收制冷循环性能实验研究。结果表明，二元工质溶液[Emim][DEP](1)+H2O(2)的确具有吸收制冷功能，但制冷系数和降膜吸收传热系数较低。主要原因是离子液体粘度较高，导热系数偏低。添加一定量LiBr到[Emim][DEP](1)+H2O(2)溶液中，实验表明，所构成的三元溶液的制冷系数，降膜吸收传热系数明显得到增强，吸收温度进一步降低。