Experimental and Computational Studies of Temperature Gradient–Driven Molecular Transport in Gas Flows through Nano/Microscale Channels

Studies at the University of Southern California have shown that an unconventional solid-state device, the Knudsen compressor, can be operated as a microscale pump or compressor. The critical components of Knudsen compressors are gas transport membranes, which can be formed from porous materials or densely packed parallel arrays of channels. An applied temperature gradient across a transport membrane creates a thermal creep pumping action. Experimental and computational techniques that have been developed for the investigations will be discussed. Experimental studies of membranes formed from machined aerogels, activated by radiant heating, have been used to investigate thermal creep flows. In computational studies, several approaches have been employed: the direct simulation Monte Carlo (DSMC) method and discrete ordinate solutions of the ellipsoidal statistical (ES) and Bhatnagar-Gross-Krook (BGK) kinetic models. Beyond the study of Knudsen compressor performance, techniques discussed in this article could be used to characterize the properties of gas flows in nano/microscale channels.