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Techniques for the computation of heat transfer and associated phenomena in complex structures are examined with an emphasis on reentry flight vehicle structures. Analysis methods, computer programs, thermal analysis of large space structures and high speed vehicles, and the impact of computer systems are addressed.

We present a unified description of heat flow in two-terminal hybrid quantum systems. Using simple models, we analytically study nonlinear aspects of heat transfer between various reservoirs: metals, solids, and spin baths, mediated by the excitation/relaxation of a central (subsystem) mode. We demonstrate rich nonlinear current-temperature characteristics, originating from either the molecular anharmonicity, or the reservoirs (complex) energy spectra. In particular, we establish sufficient conditions for thermal rectification in two-terminal junctions. We identify two classes of rectifiers. In type-A rectifiers the density of states of the reservoirs are dissimilar. In type-B rectifiers the baths are identical, but include particles whose statistics differ from that of the subsystem, to which they asymmetrically couple. Nonlinear heat flow, and specifically thermal rectification, are thus ubiquitous effects that could be observed in a variety of systems, phononic, electronic, and photonic.

Ever increasing demand from structures makes them to work more in adverse environments. For example, engine components in high performance, high speed new aircrafts are being exposed to much higher temperatures than those in old aircrafts, in different control devices the continuous trend to pack more transistors on a single chip have resulted in an unprecedented level of power dissipation, and therefore higher temperatures at the chip level. Thermal phenomena can adversely affect the performance of these structures. In this project it is investigated whether by designing periodic structures it is possible to manipulate heat transfer directions - increasing heat transfer intensity in one direction while decreasing it in another direction. Such non-uniform heat transfer mechanism utilizing clever design of the periodicity will be useful in designing heat sensitive components. It is shown through numerical analysis that periodicity in structures can steer away the radiation heat energy from its usual propagation direction, thus reducing the energy in one direction while increasing it in another direction. Therefore, structural periodicity can be used to our advantage to manipulate heat propagation directions. Such engineered structures can be used in heat sensitive devices to have more desirable heat transfer characteristics.

Ever increasing demand from structures makes them to work more in adverse environments. For example, engine components in high performance, high speed new aircrafts are being exposed to much higher temperatures than those in old aircrafts, in different control devices the continuous trend to pack more transistors on a single chip have resulted in an unprecedented level of power dissipation, and therefore higher temperatures at the chip level. Thermal phenomena can adversely affect the performance of these structures. In this project it is investigated whether by designing periodic structures it is possible to manipulate heat transfer directions - increasing heat transfer intensity in one direction while decreasing it in another direction. Such non-uniform heat transfer mechanism utilizing clever design of the periodicity will be useful in designing heat sensitive components. It is shown through numerical analysis that periodicity in structures can steer away the radiation heat energy from its usual propagation direction, thus reducing the energy in one direction while increasing it in another direction. Therefore, structural periodicity can be used to our advantage to manipulate heat propagation directions. Such engineered structures can be used in heat sensitive devices to have more desirable heat transfer characteristics.

Evaluation of effective or macroscopic coefficients of thermal conductivity under coupled heat and moisture transfer is presented. The paper first gives a detailed summary on the solution of a simple steady state heat conduction problem with an emphasis on various types of boundary conditions applied to the representative volume element -- a periodic unit cell. Since the results essentially suggest no superiority of any type of boundary conditions, the paper proceeds with the coupled nonlinear heat and moisture problem subjecting the selected representative volume element to the prescribed macroscopically uniform heat flux. This allows for a direct use of the academic or commercially available codes. Here, the presented results are derived with the help of the SIFEL (SIimple Finite Elements) system.

http://uf.catalog.fcla.edu/uf.jsp?st=UF021888922%26ix=pm%26I=0%26V=D%26pm=1

The purpose of this paper is to provide an error analysis for the p-version of the discontinuous Galerkin finite element method for heat transfer in built-up structures. As a special case of the results in this paper, a theoretical error estimate for the numerical experiments recently conducted by James Tomey is obtained.

It is noted that the application of finite element or finite difference techniques to the solution of transient heat transfer problems in structures often results in a stiff system of ordinary differential equations. Such systems are usually handled most efficiently by implicit integration techniques which require the solution of large and sparse systems of algebraic equations. The assembly and solution of these systems using the incomplete Cholesky conjugate gradient algorithm is examined. Several examples are used to demonstrate the advantage of the algorithm over other techniques.

Techniques for the computation of heat transfer and associated phenomena in complex structures are examined with an emphasis on reentry flight vehicle structures. Analysis methods, computer programs, thermal analysis of large space structures and high speed vehicles, and the impact of computer systems are addressed.