Biomedical and cooling applications of micro flows

Official URL: http://192.168.1.20/record=b1378272 (Table of Contents)

Micro flows find applications in a variety of topics covering biomedical, cooling, electronics and MEMS (micro-electro-mechanical-systems) applications. In this work, the destructive effects of hydrodynamic cavitation for biomedical treatment, heat transfer enhancement with nanostructures and nanofluids for small scale cooling applications were investigated. The research performed in this study includes results from bubbly cavitation experiments and findings showing the destructive effects of bubbly cavitating flow on selected solid specimens, live cells and proteins. Our results showed that cavitation could induce damage both on chalk pieces (and possibly kidney stones) and leukemia/lymphoma cells while the secondary structure content, the hydrodynamic diameter and enzymatic activity of lysozyme were unaffected by cavitation. For the purpose of making compact and efficient heat exchangers, heat transfer enhancement with nanostructures could be considered as a futuristic candidate. Thus, heat transfer characteristics of nanostructured plates, on which an array of vertical and tilted copper nanorods with an average diameter ranging from 100 to 150 nm and length 500 to 600 nm are integrated to a planar copper thin film coated silicon wafer surface, were compared to planar copper thin film coated silicon wafer surfaces via three different heat transfer techniques (pool boiling, forced convection and jet impingement). Three different heat sinks were developed for this purpose. Surface temperatures were measured and heat transfer coefficients were calculated for the designed heat sinks and an average of 22% single-phase heat transfer enhancement was realized with the nanostructured plates. A miniature heat transfer enhancement system is also developed based on the actuation of magnetic nanoparticles dispersed in a base fluid (water). The ferromagnetic particles within the pool were actuated with the magnetic stirrers and this resulted in an average heat transfer enhancement of 37.5% compared to the stationary fluid. In the light of the performed stuides, hydrodynamic cavitation was shown to be a strong heat-free and energy efficient future alternative to ultrasonic cavitation which is being extensively used in biomedical treatment. Also nanostructured surfaces and magnetically actuated nanofluids were proven to contribute to heat transfer enhancement significantly.