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Quantification of heat- and masstransfer mechanisms at drops and bubbles in supercritical fluids

超临界流体中液滴和气泡的传热传质机制的量化

基本信息

批准号：
182018169
负责人：
Professor Dr.-Ing. Andreas Bräuer
金额：
--
依托单位：
Institut für Thermische Verfahrenstechnik, Umwelt- und Naturstoffverfahrenstechnik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2010
资助国家：
德国
起止时间：
2009-12-31 至 2016-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/182018169?language=en
关键词：
Quantification heat masstransfer mechanisms drops

项目摘要

Within this renewal proposal heat and masstransport mechanisms between the binary system organic solvent and supercritical CO2 will be analyzed at operation conditions below and above the mixture critical pressure. A modified new experimental setup will allow the analysis of the diffusivities D for the systems ethanol/CO2 and acetone/CO2, for which the diffusivity could not be made accessible during the first project period. The solvent and the CO2 are fed into an available high pressure view cell at operation conditions below the mixture critical pressure, so that two phases are formed, initially not in thermodynamic equilibrium. The diffusion of the solvent from the dense lower phase into the light upper phase and the diffusion of CO2 from the light upper phase into the dense lower phase drive the system (the two phases) to thermodynamic equilibrium. During this period vertical profiles of the partial densities of the involved components are measured simultaneous from the light and the dense phase as a function of time by means of one-dimensional Raman spectroscopy. The partial densities are computed based on a calibration from the acquired Raman spectra. By modelling second Ficks law to the experimentally achieved partial density profiles (their temporal and spatial derivatives), the diffusivities of the involved components in each phase are made accessible. With respect to the system ethanol/CO2 temperature profiles will be measured next to the partial density profiles, which enables a comparison of the vaporization and sorption caused cooling effects estimated in the first project period and the ones measured during the renewal period experimentally and directly.Regarding the analysis of heat and masstransport mechanisms at operation conditions above the mixture critical point, the view cell is filled with the fluids the way described before at pressures below the critical pressure. When the two-phase system has not yet reached thermodynamic equilibrium the pressure is increased above the mixture critical pressure and the vertical profiles of the partial densities of the involved components are detected using Raman spectroscopy. The diffusivities will be computed by modelling the measured temporal and spatial derivatives of the partial densities to Ficks second law. For the system ethanol/CO2 temperature profiles will be measured, too.

在此更新建议中，将在低于和高于混合物临界压力的操作条件下分析二元系统有机溶剂和超临界CO2之间的热和质量传递机制。一个修改后的新的实验装置将允许乙醇/CO2和丙酮/CO2系统的扩散系数D的分析，在第一个项目期间无法访问的扩散系数。在低于混合物临界压力的操作条件下，将溶剂和CO2进料到可用的高压观察池中，从而形成两相，最初不处于热力学平衡。溶剂从致密的下相扩散到轻质的上相中，以及CO2从轻质的上相扩散到致密的下相中，驱动系统（两相）达到热力学平衡。在此期间，通过一维拉曼光谱同时从光和密相测量所涉及组分的分密度的垂直分布作为时间的函数。基于来自所获取的拉曼光谱的校准来计算部分密度。通过对实验获得的部分密度分布（其时间和空间导数）的第二菲克斯定律进行建模，可以获得每个相中所涉及的组分的扩散率。关于系统，将在部分密度分布图旁边测量乙醇/CO2温度分布图，这使得能够比较在第一项目期间估计的蒸发和吸附引起的冷却效果和在更新期间通过实验和直接测量的冷却效果。关于在高于混合物临界点的操作条件下的热和传质机制的分析，在低于临界压力的压力下，以上述方式用流体填充观察单元。当两相系统尚未达到热力学平衡时，压力增加到混合物临界压力以上，并且使用拉曼光谱检测所涉及组分的分密度的垂直分布。将通过将测得的局部密度的时间和空间导数建模为Ficks第二定律来计算扩散率。对于系统，也将测量乙醇/CO2温度曲线。