Engineering Research Equipment Grant: Binary Tracer Diffusion in Near-Critical and Supercritical Dense Gases

在罗切斯特实验室，泰勒-阿里斯分散技术已成功地用于测定超临界致密流体中二元示踪剂的扩散系数，该流体在环境条件下为液体。对于在环境条件下为气态的流体，由于溶质吸附在管壁上和不适当的脉冲注入方法引起的分散峰尾迹会对扩散率测量的准确性产生不利影响。为了解决这些问题，建议在与分散管相同的条件下进行管表面失活和脉冲注入。改进后的技术将用于收集近临界和超临界稠密二氧化碳、氧化亚氮、三氟氯甲烷和乙烷中的苯、萘、菲和1,2-苯并蒽的扩散系数。结果应允许在超临界致密区测试分子扩散的粗-硬球理论。随着气液临界状态的逼近，近临界区域的扩散数据将动态临界现象的理论置于更广阔的视野中。

The Taylor-Aris dispersion technique has been successfully employed in the Rochester laboratory to determine binary tracer diffusion coefficients in supercritical dense fluids that are liquid under ambient conditions. For fluids that are gaseous under ambient conditions, dispersion peak tailing arising from solute adsorption ont tube walls and from inappropriate pulse injection methods has been found to adversely affect the accuracy of the diffusivity measurement. To redress these problems, tube surface deactivation and pulse injection under conditions identical to those prevailing in the dispersion tube are proposed. The modified technique will be used to gather diffusion coefficients of benzene, naphthlene, phenanthrene and 1,2-benzanthracene in near-critical and supercritical dense carbon dioxide, nitrous oxide, chlorotrifluoromethane and ethane. The results should permit a rough-hard-sphere theory of molecular diffusion to be tested in the supercritical dense region. Diffusion data in the near- critical region should place theories of dynamic critical phenomena in a broader perspective as the gas-liquid critical state is approached.