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Thermally activated shape memory polymers are a desirable material for use in dynamic structures due to their large strain recovery, light weight, and tunable activation. The addition of ferromagnetic susceptor particles to a polymer matrix provides the ability to heat volumetrically and remotely via induction. Here, remote induction heating of magnetite filler particles dispersed in a thermoset matrix is used to activate shape memory polymer as both solid and foam composites. Bulk material properties and performance are characterized and compared over a range of filler parameters, induction parameters, and packaging configurations. Magnetite filler particles are investigated over a range of power input, in order to understand the effects of particle size and shape on heat generation and flux into the matrix. This investigation successfully activates shape memory polymers in 10 to 20 seconds, with no significant impact of filler particles up to 10wt% on mechanical properties of shape memory foam. Performance of different particle materials is dependent upon the amplitude of the driving magnetic field. There is a general improvement in heating performance for increased content of filler particles. Characterization indicates that heat transfer between the filler nanoparticles and the foam is the primary constraint in improved heating performance. The use of smaller, acicular particles as one way to improve heat transfer, by increasing interfacial area between filler and matrix, is further examined.

Advances in microelectronics and nanotechnology have generated tremendous interest in the non-Fourier regimes of heat conduction, where the conventional theories based on local equilibrium no longer apply. The non-Fourier regimes include small length scales, where the medium can no longer be treated using bulk properties due to ballistic transport, and short time scales, on the order of the relaxation time of heat carriers, such as in short pulse laser heating. One of the objectives of this thesis is to clarify some misunderstandings in hyperbolic heat equation (HHE), commonly thought as a remedy of Fourier's law at small time scales. The HHE is analyzed from the stand point of statistical mechanics with an emphasis on the consequences of assumptions applied to the Boltzmann transport equation (BTE) when deriving the HHE. In addition, some misperceptions of the HHE, caused by a few experiments and confusion with other physical phenomena, are clarified. It is concluded that HHE should not be interpreted as a more general equation governing heat transport because of several fundamental limitations. The other objective of this thesis is to introduce radiation entropy to the equation of phonon radiative transport (EPRT) for understanding the heat transfer mechanism on a fundamental level which can be applied to both diffusion and ballistic heat conduction in dielectric solids. The entropy generation due to phonon transport is examined along with the definition of a phonon brightness temperature, which is direction and frequency dependent. A better understanding of non-Fourier heat conduction will help researchers and engineers to choose appropriate theories or models in analyzing thermal transport in nanodevices.

Technological developments in the area of high power LED light sources have enabled their utilization in general illumination applications. Along with this advancement comes the need for progressive thermal management strategies in order to ensure device performance and reliability. Minimizing an LED's junction temperature is done by minimizing the total system's thermal resistance. For actively cooled systems, this may essentially be achieved by simultaneously engineering the conduction through the heat sink and creating a well-designed flow pattern over suitable convective surface area. While such systems are routinely used in cooling microelectronics, their use in LED lighting systems encounter additional constraints which must be accounted for in the design of the cooling system. These are typically driven by the size, shape, and building codes involved with the lighting industry, and thus influence the design of drop-in replacement LED fixtures. Employing LED systems for customary down-lighting applications may require shrouded radial fin heat sinks to increase the heat transfer while reducing the space requirement for active cooling. Most lighting is already in some form of housing, and the ability to concurrently optimize these housings for thermal and optical performance could accelerate the widespread implementation of cost-efficient, environmentally-friendly solid-state lighting. In response, this research investigated the use of conical, cylindrical, square, and pyramidal shrouds with pin/radial fin heat sink designs for the thermal management of high power LED sources. Numerical simulations using FLUENT were executed in order to account for details of the air flow, pressure drop, and pumping power, as well as the heat transfer and temperature distributions throughout the system. The LEDs were modeled as a distributed heat source of 25 - 75 W on a central portion of the various heat sinks. Combinations of device junction temperature and pumping power were used to assess the performance of shrouded heat sink designs for their use in air-cooled, down-lighting LED fixtures.

A Fabric Composite Radiation Heat Transfer Study has been conducted to determine the effective emissivities of specific fabric composite materials. The weave of the fabric and the high strength capability of the individual fiber in combination with the thermal conductivity and chemical stability of specific metallic liner, result in a very efficient light weight heat rejection system. Primary investigation included aluminum, copper, stainless steel and titanium as liner materials, and three different ceramic fabrics - Astroquartz II (a trademark of JPS Co., Slater, SC), Nextel (a trademark of 3M Co., St. Paul, MN) and Nicalon (a trademark of The Nippon Carbon Co., Japan). Experiments showed that fabric composite materials have significantly higher effective emissivities than the bare metallic liner materials. Aluminum and Astroquartz II combination and aluminum and Nextel combination appeared to be the most promising among the tested samples. To simulate deep space the experiment was performed in vacuum where coolant fluid was cirulated at about -10°C. The effective emissivity measurements were conducted at 376 K, 521 K and 573 K. Also high temperature effective emissivity measurements need to be performed. / Graduation date: 1993

A rotating, flat plate condensation experiment has been developed to investigate the heat of the Rotating Bubble Membrane Radiator (RBMR). The RBMR is a proposed heat rejection system for space applications which uses working fluid condensation on the inside surface of a rotating sphere to reject heat to space. The flat plate condensation heat transfer experiment simulates the microgravity environment of space by orienting the axis of rotation parallel to the gravitational vector and normal to the surface of the plate. The condensing surface is cooled to simulate the rejection of heat to cold surface. The working fluid is a super heated steam. The results obtained include relationships between the overall heat transfer coefficient as a function of the temperature difference between the working fluid and a cold environment, both placed in dimensionless groups, and plate angular rotational speeds. This empirical relationship is useful for choosing the optimum rotational speed for the flat plate radiator given a desired heat rejection load. A RBMR prototype, using full sphere shell, was designed and built completely in this research efforts and ready to be tested in future planned experiments in microgravity environment. This RBMR is the first one ever built to investigate the RBMR concepts experimentally. This study also provides the basis for designing new heat rejection systems utilizing centrifugal forces and condensation phenomena in both space and ground applications. / Graduation date: 1993

Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 247-250). Also available in electronic format on the Internet.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Joshi, Yogendra; Committee Member: ghiaasiaan, mostafa; Committee Member: Schwan, Karsten. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 191-196). Also available in electronic format on the Internet.

Exhausting the thermal power from a fusion tokamak is a critical engineering challenge. The life of components designed for these conditions has a strong influence on the availability of the machine. For a fusion power plant this dependence becomes increasingly important, as it will influence the cost of electricity. The most extreme thermal loading for a fusion power plant will occur in the divertor region, where components will be expected to survive heat fluxes in excess of 10 MW/m² over a number of years. This research focussed on the development of a heat sink module for operation under such conditions, drawing on advanced cooling strategies from the aerospace industry. A reference concept was developed using conjugate Computational Fluid Dynamics. The results were experimentally validated by matching Reynolds numbers on a scaled model. Heat transfer data was captured using a transient thermochromic liquid crystal technique. The results showed excellent agreement with the corresponding numerical simulations. To facilitate comparison against other divertor heat sink proposals, a nondimensional figure of merit for cooling performance was developed. When plotted against a non-dimensional mass flow rate, the reference heat sink was shown to have superior cooling performance to all other divertor proposals to date. Results from Finite Element Analysis were used in conjunction with the ITER structural design criteria to life the heat sink. The sensitivity of life to both boundary conditions, and local geometric features, were explored. The reference design was shown to be capable of exceeding the life requirements for heat fluxes in excess of 15 MW/m². A number of heat sinks, based on the reference design, were fabricated. These underwent non-destructive testing, before experimentation in a high-heat flux facility developed by the author. The heat transfer performance of the tested modules was found to exceed that predicted by numerical modelling, which was concluded to be caused by the fabrication processes used.