Engineering Commons^™

Thermal Transport To Impinging Droplets On Superhydrophobic Surfaces, Jonathan C. Burnett

Theses and Dissertations

An analytical model is developed to quantify the heat transfer to droplets impinging on heated superhydrophobic (SH) surfaces. Integral analysis is used to incorporate an apparent temperature jump at the superhydrophobic surface as a boundary condition. This Thesis considers the scenario of both isotropic and anisotropic slip, as would be realized on post-cavity style and rib-cavity style SH surfaces. This thermal model is combined with a hydrodynamic model which incorporates velocity slip at the surface. Use of the two models allows determination of the overall cooling effectiveness, a metric outlined in contemporary work. The effect of varying velocity slip and …

Computational Sodium Heat Pipe Simulation In Three Dimensions For Transient Nuclear Reactor Analysis With Variable Surface Heat Flux, Valerie Jean Lawdensky

UNLV Theses, Dissertations, Professional Papers, and Capstones

Heat pipes are used to transfer heat through phase change in a liquid/vapor contained in a metal tube. They are passive devices that require no pumps to circulate the fluid and can transfer heat far more efficiently than a solid copper rod of the same diameter. They are commonly used in laptop computers where copper heat pipes filled with water take heat away from the CPU and transfer the heat to air through a heat exchanger. Heat pipes were also used in the Kilopower nuclear reactor where higher temperatures required sodium as the working fluid with stainless steel tubes. Computer …

Analyzing The Non-Isothermal Multiphasic Flow In Porous Media Through Strongly Coupled Thermo-Hydro-Mechanical Modeling., Mohammadreza Mir Tamizdoust

Electronic Theses and Dissertations

Underground geo-structures and climate change can trigger coupled heat, moisture, and vapor flow in shallow and deep subsurface which is frequently referred to as non-isothermal multiphase flow. The coupled multiphasic flow in soil may induce volumetric shrinkage or expansion deformation depending on the thermo-hydraulic loading condition. In saturated porous media, temperature gradient and heat transfer may affect pore fluid pressure and/or pore fluid flow depending on thermal, mechanical, and hydraulic properties of the media and the saturating fluid. In vadose zones, the prediction of coupled nonisothermal multiphase flow in porous media has been the subject of many theoretical and experimental …

Investigation Of Microdroplet Generation, Morphological Evolution, And Applications Under Quasi-Steady And Dynamic States, Li Shan

McKelvey School of Engineering Theses & Dissertations

Microscale droplets are commonly encountered in the fields of materials processing, thermal fluids, and biology. While these droplets are naturally occurring, recent advances in microfabrication have enabled researchers to harness their enhanced transport characteristics for numerous laboratory and industrial applications from controlled chemical synthesis to inkjet printing and thermal management. Smaller droplets have larger specific surface area and a greater perimeter-to-area ratio when resting on a surface (i.e., sessile), which accelerates processes occurring at droplet surfaces like evaporation, chemical reaction, or combustion. The demand for microdroplets with smaller and more uniform sizes has motivated investigation of how such droplets can …

Investigation On The Interaction Of An Impinging Jet With Cylinder Wakes, Karthik Krishna

Doctoral Dissertations and Master's Theses

Jet impingement cooling is a widely used cooling method due to the high heat transfer rates associated with it. Research for improving heat transfer rates for this cooling is still being carried out due to its broad application in various fields like gas turbine blade cooling, electronic component cooling, and paper drying. The unsteady jet oscillation effectively enhances the stagnation region and the time-averaged heat transfer rates. It is shown that a novel passive jet oscillation technique can be achieved using the vortices periodically shed from a cylinder placed upstream in a channel with an initial crossflow. Preliminary CFD results …

Theoretical And Experimental Analysis And Optimization Of Thermal Conduction In Electrochemical And Latent Heat Energy Storage Systems, Amirhossein Mostafavi

Mechanical and Aerospace Engineering Dissertations

Phase change materials (PCMs) are used commonly for energy storage purposes. Thermal energy can be stored in a PCM with a variety of configurations such as PCM slabs, cartesian and cylindrical finned systems. Heat transfer in PCM storage systems can be from a heat transfer fluid (HTF) or a heat source at constant temperature to adjacent PCM. The rate of heat transfer is limited by thermal properties. Fin insertion can improve the heat transfer inside the PCM. Chapters 2 and 3 derive and solve the governing energy equations to determine the transient temperature distribution in the PCM due to the …

Optimizing Heat Pipes With Partially-Hybrid Mesh-Groove Wicking Structures And Its Capillary-Flowing Analysis By Simulation, Guanghan Huang

Theses and Dissertations

Heat pipes are known as efficient two-phase heat transfer devices and widely utilized in thermal management of power plants and electronics. The hybrid mesh-groove wick promises to attain a higher thermal performance of the heat pipe by balancing the permeability and capillarity. However, traditional fully hybrid mesh-groove wick presents considerable condensation thermal resistance due to the condensed quiescent working fluid and thick, saturated wick.

In this study, a novel partially hybrid mesh-groove wick has been proposed to enhance the evaporation of L-shaped copper-ethanol heat pipes. L-shaped heat pipe promotes high-efficient draining of condensed liquid by gravity, while traditional straight-shaped heat …

Computational Investigation Of Perforated Plate Film Cooling Utilizing Conjugate Heat Transfer, Jonathan Sippel

Doctoral Dissertations and Master's Theses

The accuracy of modern state-of-practice computational fluid dynamics approaches in predicting the cooling effectiveness of a perforated plate film-cooling arrangement is evaluated in ANSYS Fluent. A numerical investigation is performed using the Reynolds Averaged Navier Stokes equations and compared to NASA Glenn’s available Turbulent Heat Flux 4 experimental measurements collected as a part of the Transformational Tools and Technologies Project. A multiphysics approach to model heat conduction through the solid geometry is shown to offer significant improvements in wall temperature and film effectiveness prediction accuracy over the standard adiabatic wall approach. Additionally, localized gradient-based grid adaption is analyzed using the …

Binary Particle Mixtures As A Heat Transfer Media In Shell-And-Plate Moving Packed Bed Heat Exchangers, Chase Ellsworth Christen

Boise State University Theses and Dissertations

Solid particles are being considered in several high temperature thermal energy storage systems and as heat transfer media in concentrated solar power (CSP) plants. The downside of such an approach is the low overall heat transfer coefficients in shell-and-plate moving packed bed heat exchangers caused by the inherently low packed bed thermal conductivity values of the low-cost solid media. Choosing the right particle size distribution of currently available solid media can make a substantial difference in packed bed thermal conductivity, and thus, a substantial difference in the overall heat transfer coefficient of shell-and-plate moving packed bed heat exchangers. Current research …

Relationship Between Thermal Conductivity And Free Electrons In Metal, Yansong Liu

Senior Theses

An experiment was designed and conducted to explore the relationship between thermal conductivity with free electrons in metal. In the experiment, copper, iron, aluminum, and titanium rods with close diameters were used to carry out the experiment. Each rod was heated up by a heat unit at one end while cooled on the other end with a heat sink to maintain a steady state. DC current was applied to rods in the direction along, as well as against, the heat flow. Thermal conductivities were measured in these two situations for each rod. Results showed electrons do dominate thermal flow inside …

Accuracy And Computational Cost Assessment Of Radiation Solvers For Combustion Simulations, Chloe David

Master's Theses (2009 -)

High-fidelity combustion simulations necessitate the accurate and efficient calculation of radiative heat transfer. A successful radiation calculation requires the use of a spectral model, which describes the variation of radiative properties across the entire electromagnetic spectrum, and a radiative transfer equation (RTE) solver, which solves the governing equation for radiation transport. Three primary categories of RTE solvers are the discrete ordinates method (DOM), the spherical harmonics method (SHM), and the photon Monte Carlo (PMC) method. The accuracy and computational cost of each type of RTE solver is compared in detail in this work. The PMC RTE solver is considered the …

Flow And Heat Transfer Characteristics Of Turbulent Swirling Impinging Jets [Thesis], Muhammad Ikhlaq

Theses: Doctorates and Masters

Numerous industrial applications rely on impinging jets to impart convective heat and mass transfer in processes ranging from the cooling of electronic devices and gas turbine blades to drying of paper and food products. Conventionally, non-swirling impinging jets have been employed, but some studies have shown that inducing swirl allows better control of uniformity and improved convective fluxes. A better understanding of the underlying physical mechanisms that lead to such behaviour warrants deeper insights into the flow and heat transfer characteristics of impinging jets, both swirling and non-swirling. Whilst important to achieve, the flow field of an impinging jet is …