膜孔径分布对直接接触式膜蒸馏传质速率的影响

膜蒸馏用膜是一种孔径不均一的多孔介质。文中考察孔径分布的存在对直接接触式膜蒸馏跨膜传质速率的影响。按“熵最大”原则导出了膜孔面积的取值服从指数分布规律,其不对称性可能导致按平均孔径预测的传质速率与考虑孔径分布时预测的传质速率有差异,后者应该更接近于真实情况。模拟计算结果表明,按这两种方法预测的传质速率确实存在不容忽视的差别。两种聚四氟乙烯(PTFE)平面膜的直接接触式膜蒸馏实验结果表明,考虑孔径分布的传质速率预测值更接近于实测值。因此,考虑孔径分布的质量传递模型能更准确地描述直接接触式膜蒸馏的跨膜传质过程。

Effect of pore size distribution on mass transfer in direct contact membrane distillation

The membrane employed in membrane distillation process is a porous medium with a certain size distribution. The influence of pore size distribution on mass transfer in direct contact membrane distillation (DCMD) was investigated. According to the rule of "maximum entropy", it is deduced that the values of the pore area follows an exponential distribution. Its asymmetry indicates that the mass transfer rate predicted with the pore size distribution should be different from that with the mean pore size. This was verified by the results of the calculation based on the equations derived. DCMD experiments were performed for further verification, and the results show that the mass transfer rates obtained are much more close to the value predicted with the pore size distribution than that with the mean pore size. It may be concluded that the membrane pore size distribution should be taken into consideration in predicting the mass transfer rate in DCMD.