161 |
Numerical Study of Convective Heat Transfer in Flat Tube Heat Exchangers Operating in Self-Sustained Oscillatory Flow RegimesFullerton, Tracy 2011 December 1900 (has links)
Laminar, two-dimensional, constant-property numerical simulations of flat tube heat exchanger devices operating in flow regimes in which self-sustained oscillations occur were performed. The unsteady flow regimes were transition flow regimes characterized by cyclic variations of flow parameters such as stream-wise or cross-stream velocity.
A computer code was developed to perform the numerical simulations. Spatial discretization was based upon a Control Volume Finite Element Method (CVFEM). Temporal discretization was based upon a semi-implicit Runge-Kutta method. Double Cyclic conditions were used to limit the numerical domains to one repeating geometric module.
Nine geometric domains representing flat tube heat exchanger devices were tested over a range of Reynolds numbers. A maximum Reynolds number (Re) of 2000 was established to keep the study within the transition range. For each domain, a critical Reynolds number (Re_crit) was found such that for Re < Re_crit the flow was steady, laminar flow and for Re > Re_crit the flow exhibited cyclic oscillations. For the cases tested, the variation in longitudinal pitch had little impact on the Re_crit value for a fixed transverse pitch. However, for a fixed longitudinal pitch, the Re_crit was increased for decreasing transverse pitch.
The results demonstrate the importance of using unsteady simulation methods for these cases. Nusselt numbers predicted by the unsteady method were on the order of 65% higher than predicted by steady methods for the same Reynolds numbers.
Data for required pumping power versus resultant Nusselt number were collected which showed four distinct operating regions for these devices spanning the low Reynolds number, steady flow region through the self-sustained oscillating flow region. Based on the data, the recommended operating region is the region of self-sustained oscillations as this region is characterized by the highest increase in Nusselt number per increase in required pumping power.
|
162 |
Neutrino oscillations and the early universeBell, Nicole Fiona January 2000 (has links)
We construct a model which provides maximal mixing between a pseudo-Dirac Vµ/VT pair, based on a local U(1)Lµ-LT symmetry. Its strengths, weaknesses and phenomenological consequences are examined. A new intermediate range force is predicted, mediated by the light gauge boson of U(1)Lµ-LT. Through the mixing of µ, T and e, this force couples to electrons and thus may be searched for in precision “gravity” experiments.The generation of relic neutrino asymmetries in the early universe via the mechanism of partially coherent active-sterile neutrino oscillations is considered. We study how an approximate evolution equation for the growth of the asymmetry can be extracted from the exact Quantum Kinetic Equations which describe the evolution of the neutrino ensemble, and examine the nature of some of the approximations employed.
|
163 |
Solar activity and recent climate change evaluating the impact of geomagnetic activity on atmospheric circulation /Palamara, Daniel. January 2003 (has links)
Thesis (Ph.D.)--University of Wollongong, 2003. / Typescript. Bibliographical references: leaf 287-305.
|
164 |
Corrosion of nickel-containing stainless steel in concentrated sulphuric acidLi, Yanxu. Ives, M. B. Coley, Ken. January 1900 (has links)
Thesis (Ph.D.)--McMaster University, 2006. / Supervisors: M.B. Ives, K.S. Coley. Includes bibliographical references.
|
165 |
Theoretical and experimental investigation of oscillating heat pipesLiang, Shibin. January 2006 (has links)
Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 17, 2009) Includes bibliographical references.
|
166 |
Emergent phenomena in classical and quantum systems cellular dynamics in E. coli and spin-polarization in Fermi superfluids /Ellis, Jason Keith. January 2009 (has links)
Thesis (Ph.D.)--Kent State University, 2009. / Title from PDF t.p. (viewed April 9, 2010). Advisor: Michael Lee. Includes bibliographical references (p. 97-101).
|
167 |
Toeplitz Jacobian matrix and nonlinear dynamical systems /Ge, Tong. January 1996 (has links)
Thesis (Ph. D.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 118-125).
|
168 |
The Slichter modes in a realistic earth model /Peng, Zhengrong, January 1995 (has links)
Thesis (Ph.D.)--Memorial University of Newfoundland. / Typescript. Bibliography: leaves 146-154. Also available online.
|
169 |
An experimental investigation of the propulsive thrust of oscillating foils of different planforms /Luznik, Luksa. January 1997 (has links)
Thesis (M. Eng.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 99-101.
|
170 |
The boreal summer intraseasonal oscillation over the south Asian monsoon regionJiang, Xianan. January 2004 (has links)
Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references (leaves 147-156).
|
Page generated in 0.1001 seconds