Thesis (M.S.)--Boise State University, 2009. / Includes abstract. Includes bibliographical references (leaves 66-69).

The effects of shock wave impact on unsteady turbine heat transfer are investigated. A numerical approach is developed to simulate the flow physics present in a previously performed unsteady wind tunnel experiment. The windtunnel experiment included unheated and heated flows over a cascade of highly loaded turbine blades. After the flow over the blades was established, a single shock with a pressure ratio of 1.1 was introduced into the wind tunnel test section. A single blade was equipped with pressure transducers and heat flux microsensors. As the shock wave strikes the blade, time resolved pressure, temperature, and heat transfer data were recorded. / Ph. D.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 77-83). Also available on the World Wide Web.

Dissertation (Ph.D.) -- Worcester Polytechnic Institute. / Keywords: ignition; fire; flammability; burning; scalability; heat flux oxygen; mass loss rate. Includes bibliographical references (p.44-49).

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (p. [116]-122).

Thesis (Ph.D.)--University of Missouri-Columbia, 2007. / 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 March 10, 2009) Includes bibliographical references.

Phase-change heat transfer involves the exchange of thermal energy when a substance transitions between different phases, such as solid to liquid (melting), liquid to vapor (boiling), or vice versa. During phase-change, energy is absorbed or released without a change in temperature. In particular, boiling is highly efficient due to the large latent heat of vaporization, allowing for dissipative heat fluxes on the order of q′′ ∼ 10–100 W/cm². However, during boiling, once the temperature exceeds a critical threshold, a vapor film forms between the heated surface and the liquid, suppressing effective nucleate boiling which reduces heat transfer efficiency so that q′′ ∼ 1 W/cm². This critical temperature limitation prompted our exploration of three-phase heat transfer. In three-phase heat transfer, energy is transferred between the solid, liquid, and vapor phases; all of which coexist simultaneously. In this study, we define and investigate three-phase heat transfer by examining ice on a superheated substrate. We explore the use of ice as a quenchant and our findings indicate that dissipative heat fluxes for our three-phase system are an order of magnitude larger than for classical boiling (q′′ ∼ 1,000 W/cm²). This is due to the inherent 100 °C temperature differential across the meltwater film, which dissipates q′′ ∼ 100 W/cm² via conduction (and subsequent ice melting) and an additional q′′ ∼ 100 W/cm² for sensible heating of the meltwater. We propose experiments to measure the dissipative heat flux of a tall and pressurized ice column during three-phase heat transfer. Furthermore, we discuss potential avenues for future research of three-phase heat transfer at high superheats. / Master of Science / Phase-change heat transfer involves the exchange of heat when a substance transitions between different phases, such as solid to liquid (melting), liquid to vapor (boiling), or vice versa. During phase-change, energy is absorbed or released without a change in temperature. For example, in boiling, water molecules act like tiny magnets. When water changes from one phase to another, the distance between these tiny magnets changes. When they are pulled apart, like when water turns into steam, they need some extra energy to do that. This energy, termed latent heat, is the reason lots of heat can be transferred during phase-change. However, during boiling, once the temperature of the heated surface exceeds a critical threshold, a vapor film forms between the heated surface and the liquid, which suppresses effective boiling and reduces the efficiency. This critical temperature limitation prompted our exploration of three-phase heat transfer. In three-phase heat transfer, energy is transferred between the solid, liquid, and vapor phases; all of which coexist simultaneously. In this study, we define and investigate three-phase heat transfer by observing ice on a heated surface. The vapor film is avoided for a while because a majority of the heat is used to melt the ice and warm the meltwater, leaving only a little left for vaporization. We propose experiments to measure the heat transfer capabilities of a tall ice column pressed into a heated surface. Furthermore, we discuss potential avenues for future research of three-phase heat transfer at high superheats.

The thermal boundary condition to a fire exposed surface was quantified with a hybrid heat flux gage. Methods were developed to determine the net heat flux through the gage, incident heat flux, cold surface heat flux, convective heat transfer coefficient, adiabatic surface temperature, and the separated components of radiative and convective heat flux. Experiments were performed in a cone calorimeter with the hybrid gage flush mounted into UNIFRAX Duraboard LD ceramic board. The results were then compared to results obtained with a Schmidt-Boelter gage and a plate thermometer. The hybrid heat flux gage predicted a cold surface heat flux within 5% of cold surface heat fluxes measured with a Schmidt-Boelter gage. Adiabatic surface temperature measurements compared well with the plate thermometer measurements at steady state. Hybrid gage measurements were performed on flat plate samples of Aluminum 5083, Marinite P, and UNIFRAX Duraboard LD ceramic board. The gage and sample assemblies were exposed to mixed-mode heat transfer conditions in a cone calorimeter. Temperature measurements were performed at the top, center, bottom surfaces of the marinite and ceramic board samples. A single midpoint temperature was performed on the aluminum. Boundary condition details obtained with the hybrid gage were then input to the commercial finite element analysis package Abaqus. Abaqus was used to create the flat plate geometries of the sample and variable temperature dependent material properties were used for each material. Measured temperatures were then compared to the model predicted temperatures with good results. Hybrid gage measurements were verified using a new experimental apparatus. The apparatus consisted of an impinging jet assembly, a tungsten lamp, and a gage holster assembly. The impinging jet was used to expose the gage to isolated convection and the lamp was used to expose the gage to isolated radiation. The gage holster assembly was used to water cool the gage when desired. Measurements performed with the gage water cooled in isolated convection allowed for the convective heat transfer coefficient to be determined. Two methods were developed to determine the convective heat transfer coefficient in mixed-mode heat transfer conditions. These methods were then verified by comparison to the isolated heat transfer coefficient. Similarly, the incident radiation was isolated by water cooling the gage while only the lamp was on. The components of heat flux were then separated for mixed-mode comparisons and were verified against this isolated radiation. The hybrid gage predicted convective heat transfer coefficients within 10% of the isolated heat transfer coefficient and incident heat fluxes within 11% of the isolated radiation. / Master of Science

No description available.

During the development of flight tests of a spacecraft, heat exchange occurs among the many physically separated subsystem surfaces through the phenomenon of thermal radiation. Considering the increasing complexity of the geometrical forms and shapes in the design of such systems, the monitoring and control of the radiative heat fluxes taking place in the multi-reflecting, absorbing and emitting heat transfer environment are very critical. Because the analytical solution of thermal radiation in such geometrically complex three-dimensional systems is not practical, extensive numerical modelling techniques are widely used to predict radiative heat fluxes on the many thermally active surfaces. From experience, it is found that this can be very difficult and not at all commensurate with fast feedback unless the analysis is from a simple system layout. Considering that a relatively new approach dedicated to the basic analysis of radiative heat flux has been developed by the heat transfer community as a numerical approximation called the Discrete Ordinates Method (DOM), a first question did arise in terms of how well an enhanced and more comprehensive formulation based on this concept would fulfil the task of achieving faster results whilst still accurately predicting radiative heat transfer in three-dimensional, more complex geometries.