有机蒸气-空气分子扩散系数测定的影响因素分析
Effect factors analysis of determination of molecular diffusion coefficient of organic vapor-air
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摘要: 利用自行研发的气体扩散系数测试装置及测定方法，分别测定和分析了常温常压下，不同扩散管径、扩散距离、体系温度、气体进气方式及其流量、扩散时间等对气体扩散系数测定的影响情况。基于拟稳态扩散模型，得出气体扩散系数测定的合理条件：扩散距离为9~14 cm；吹气流量为0.22~0.33 m3·h-1；体系温度应低于液体沸点且不要太接近沸点；扩散时间根据液体挥发性情况，一般不小于12 h，具体以能够明显观测到测定前后液面高度差为基准；扩散管管径应在保证扩散管截面积较小、液面以上气体以单向自然扩散为主、液体蒸发速度相对较慢的范围内选取。研究结果确定了气体扩散系数测定的合理条件，对加深油气空间传质机理的认识以及确保扩散系数测定的准确度具有重要指导意义。Abstract: Effects of several factors such as diffusion tube diameter,diffusion distance,system temperature,gas inlet pathway,and flow and diffusion time on the determination of the gas diffusion coefficient under normal temperature and pressure were determined using a novel experimental device and determination method. Based on the quasi-steady-state diffusion model,reasonable conditions for determining the diffusion coefficient were obtained:a diffusion distance of 9 to 14 cm,air flow of 0.22 to 0.33 m3·h-1,and system temperature that is substantially less than the boiling point of the liquid. The diffusion time should generally be at least 12 h depending on the volatility of the liquid,and it should be benchmarked against the liquid surface height difference before and after the measurement. The diffusion tube diameter should be selected based on the observation that as the cross-sectional area decreases,the gas above the liquid surface becomes dominated by one-way natural diffusion,slowing the evaporation of the liquid. The results provide reasonable conditions for determining the diffusion coefficient and will play an important role in obtaining an in-depth understanding of the oil and gas mass transfer mechanism of space and ensuring the accuracy of diffusion coefficient measurements.
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