Graduate Thesis Or Dissertation
 

The impact of fabrication methods on the mass flux characteristics of contactor membranes in absorption/desorption cycle micro-scale heat pumps

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3n2042516

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  • A key requirement within many microsystem devices is the ability for rapid mixing and gas-liquid absorption. In the past, qualitative results have suggested that micro-manufactured straight-through pores can significantly reduce the pressure drop for gas diffusion across a gas-liquid contactor as compared to the complicated and tortuous flow paths encountered in commercially available membranes. In this study, the mass transfer performance of several micromachined membranes are compared with the performance of conventional membranes. A tortuosity factor is introduced to serve as a standard for comparing the morphology of the different membranes. Two membranes with straight-through pores are micro-manufactured. The first approach involved the deep UV (266 nm) laser micromachining of 75 μm thick Kapton film. The second approach involved the micro-molding of thin polydimethylsiloxane (PDMS) membranes using soft lithography techniques. Pores as small as 5 μm were fabricated with both approaches. A novel technique for producing pores with 3:1 aspect-ratio in PDMS is introduced. Results show that woven membranes provide outstanding mass transfer performance. However, woven membranes are not very stiff and their complex morphology makes their potential for fluidic breakthrough difficult to assess. The laser-machined membranes were also found to give 10 to 30 times the mass flux of conventional membranes. The micro-molded PDMS membranes were found to be unsuitable for mass transfer at pore sizes down to 5 μm due collapsing pores. Several alternatives are presented for improving the performance of micro-manufactured membranes.
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