A pulsating jet generated by a pulse combustor has been experimentally demonstrated as a technique for impingement heat transfer enhancement relative to a steady jet. The enhancement factor was as high as 2.5. Despite such potential, further studies of this technique have been limited, let alone industrial applications. The ultimate goal of the Pulsed Air Drying project at the Institute of Paper Science and Technology is to develop this technique to commercialization for industrial applications such as paper drying. The main objective of the research in this dissertation is to provide a fundamental basis for the development of the technology. Using CFD simulations, the research studied the characteristics of pulsating single-slot-nozzle jet impingement flows and heat transfer on stationary and moving surfaces. In addition, in order to understand basic flow characteristics of pulse-combustor jets, a simplified model of Helmholtz pulse combustors was developed. The model was used to recommend a strategy to generate a pulsating jet having large amplitude of velocity oscillation. And based on this model, pulsating jets in the simulations were characterized as those at the tailpipe exit of a pulse combustor. The impingement conditions were similar to those in conventional impingement hoods for paper drying. Parameter studies included the effects of jet velocity oscillation amplitude, pulsation frequency, mean jet velocity, tailpipe width, and impingement surface velocity. Simulation results showed that the amplitude of jet velocity oscillation was the most important parameter for heat transfer enhancement, in which two mechanisms were identified: high impinging jet velocity during the positive cycle and strong re-circulating flows in the impingement zone during the negative cycle of jet velocity oscillation. As for the improvement by the pulsating jets relative to steady jets, the maximum heat transfer enhancement and energy saving factors were 1.8 and 3.0, respectively, which were very encouraging for further development of the technology.

Theoretical aspects of multicomponent superconductivity and systemswith competing interactions are studied using Monte Carlo techniques.Motivated by recent experimental and theoretical results of complex struc-ture formation of vortices in multicomponent systems, possible vortex struc-ture formations due to vortex interactions that are not purely attractive orrepulsive are considered. Vortex structures such as clusters, superclusters,hierarchical structure formation, stripes, gossamer patters, glassy phases, aswell as checkerboard lattices and loops are demonstrated to be possible.The order of the superconducting phase transition is considered for multi-component lattice London superconductors. The phase transition is demon-strated to be either rst-order or continuous depending on the strength of asymmetry-breaking Josephson intercomponent interaction. It is argued thatthe rst-order phase transition is caused by a vortex phase separation due toa uctuation-induced attractive interaction between vortex lines. / <p>QC 20151117</p>

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