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

Taylor-Aris弥散技术已成功地应用于Rochester实验室，测定了二元示踪剂在常温下为液体的超临界稠密流体中的扩散系数。对于在环境条件下为气态的流体，由于溶质在管壁上的吸附和不适当的脉冲注入方法而产生的弥散峰拖尾已被发现对扩散系数测量的准确性产生不利影响。为了解决这些问题，提出了在与弥散管相同的条件下进行管子表面失活和脉冲喷射。改进后的技术将用来收集苯、萘、菲和1，2-苯并茂在近临界和超临界密度二氧化碳、一氧化二氮、三氟氯甲烷和乙烷中的扩散系数。这一结果应该允许分子扩散的粗糙-硬球理论在超临界致密区域进行测试。随着气液临界态的临近，近临界区的扩散数据应该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.