A physical model and a numerical solution procedure has been developed to predict heat transfer behaviour in supercritical fluids. A major area of concentration was the modelling of the turbulent components of shear stress and heat flux. Traditionally, the turbulent fluxes are modelled by algebraic expressions such as the familiar mixing length methods. However, the use of this technique has not been entirely satisfactory. Newer methods for constant-property flows which model turbulent fluxes by considering the transport of quantities such as turbulent kinetic energy and the dissipation rate of turbulence have been extended to supercritical fluids. This involves the solution of two additional partial differential equations that are solved simultaneously with the equations of continuity, energy, and momentum. The numerical scheme has been developed on a completely two-dimensional basis by extending the Pletcher-DuFort-Frankel finite difference method. Computed results for velocity and temperature profiles as well as wall temperature distributions exhibited reasonable agreement with previous experimental data and therefore indicate the viability of the present method. Computations were carried out for supercritical carbon dioxide flowing through a circular duct in the reduced pressure range 1.0037 to 1.098. A consideration of the influence of buoyancy on the mean momentum balance permitted the calculation of unusual velocity profiles in this investigation. The existance of such velocity profiles had been accepted previously but the nature of their growth along a pipe has probably not been suggested previous to this work. No attempt was made to include buoyancy generated turbulence or additional fluctuating property correlations in this work, but suggestions are made regarding possible avenues of approach. Some of the incidental outcomes of this work were a new continuous universal velocity profile implicit in cross stream distance an a new mixing length distribution for turbulent pipe flows. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The purpose of this study was to develop and demonstrate a method for experimentally determining the convective heat transfer in a rigid vessel while air was being injected. The heat transfer took place between the air in the pressurized vessel and the surrounding walls which were maintained at a temperature of 32 F. with a circulating ice water bath. The study considers the effects of injection geometry and injection flow rate on the heat transfer process. The problem of heat transfer after injection has been considered by Means (1), and was responsible for establishing this study. The experimental technique used in this thesis provides a method by which Means may establish the heat transfer just after the injection period.

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Presented in this paper is the first known experimental assessment of a single-phase natural convection in a cylindrical, vertical channel subjected to non-uniform or uniform heat flux. This work was conducted at the University of Central Florida in the College of Engineering. The results of this experimental study were compared with theory. The experimental values of Nusselt numbers (Nu = hD/K) in the entrance and fully-developed regions were somewhat lower and higher, respectively, when compared with theory.

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published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Kwok Chun-yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves [121]-122). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Experimental data --- p.7 / Chapter 2.1 --- Turbulent Convection using Helium --- p.7 / Chapter 2.2 --- Turbulent Convection using water --- p.8 / Chapter 3 --- Probability Distribution and Scaling behavior --- p.9 / Chapter 3.1 --- PDF of YT --- p.9 / Chapter 3.1.1 --- Helium Convection --- p.10 / Chapter 3.1.2 --- Water Convection --- p.26 / Chapter 3.1.3 --- Comparison between helium data and Water data --- p.34 / Chapter 3.2 --- T -dependence of the moments of XT --- p.39 / Chapter 3.2.1 --- Helium Convection --- p.39 / Chapter 3.2.2 --- Water Convection --- p.47 / Chapter 4 --- Hierarchical Moment Relation --- p.50 / Chapter 4.1 --- Method of Analysis --- p.50 / Chapter 4.2 --- Results and Discussion --- p.53 / Chapter 4.2.1 --- Helium Convection --- p.53 / Chapter 4.2.2 --- Water Convection --- p.81 / Chapter 5 --- Discussion and Conclusion --- p.95 / Chapter 5.1 --- Passive Scalar --- p.96 / Chapter 5.2 --- Comparison between Turbulent Convection and Passive Scalar --- p.99 / Chapter 5.3 --- Scaling behavior for length scale above and below the Bolgiano scale for turbulent convection using Helium gas --- p.100 / Chapter 5.4 --- Conclusions --- p.107 / Chapter A --- The lognormal model --- p.108 / Chapter B --- Definition of XT --- p.110 / Chapter C --- Reasons for analysis of (xTp) for p≤ 12 --- p.112 / Chapter D --- Functional form of μp implied by the hierarchical relation --- p.119 / Bibliography --- p.122