It is well known that the seats in a parked vehicle become very hot and uncomfortable on warm days. A new self-powered thermoelectric car seat cooler is presented to solve this problem. This study details the design and optimization of such a device. The design relates to the high level layout of the major components and their relation to each other in typical operation. Optimization is achieved through the use of the ideal thermoelectric equations to determine the best compromise between power generation and cooling performance. This design is novel in that the same thermoelectric device is utilized for both power generation and for cooling. The first step is to construct a conceptual layout of the self-powered seat cooler. Using the ideal thermoelectric equations, an analytical model of the system is developed. The model is validated against experimental data and shows good correlation. Through a non-dimensional approach, the geometric sizing of the various components is optimized. With the optimal design found, the performance is evaluated using both the ideal equations and though use of the simulation software ANSYS. The final design consists of a flat absorber plate embedded into the car seat with a thermoelectric attached to the back. A finned heat sink is used to cool the thermoelectric. The device is shown to generate enough power to provide a reasonable temperature drop in the seat. / Master of Science

The thermal conductivity of thin Germanane (GeH) layers was measured using suspended micro-devices with integrated heaters and thermometers. The thermal contact resistance of the GeH samples suspended on the measurement devices was determined from the measured thermal resistance values of samples with different suspended lengths. The room-temperature thermal conductivity of the GeH samples was observed to be 0.6-1.0 Wm⁻¹K⁻¹. This low thermal conductivity is attributed to phonon scattering by defects and grain boundaries in the layered materials, including scattering caused by gangling bonds associated with missing Hydrogen atoms between adjacent layers. / text

No description available.

Since discovering the anomaly of the La-based cuprates (La2-xSrxCuO4) at x~ , researches of stripe phase have been prevailing recently. Related vast experiments, like neutron scattering, Raman and infrared ray (IR) spectra, Hall effect, and magnetic susceptibility etc. have performed on this subject. These results indicate that a crossover from one- to two-dimensional charge transport happens at x~ . In this thesis, we synthesize p-type superconductors La2-xSrxCu0.995Zn0.005O4 by solid-state reaction. It has been well know there is a marked drop in Tc- x phase diagram at x~ of La2-xSrxCuO4. It is possible that this phenomenon is related to the formation of a stripe phase. The experimental work on x-ray absorption near edge spectroscopy (XANES) in La2-xSrxCuO4 and La2-x-ySrxNdyCuO4 have been done during these years in our laboratory. The results show that the absorption-spectroscopy diagrams of two systems have apparent differences in the region of upper Hubbard Band (UHB). The differences are due to that the stripe is observed in La2-x-ySrxNdyCuO4, but not in La2-xSrxCuO4. No observation of stripe phase in La2-xSrxCuO4 may be attributed to that the drop at x~ in Tc-x phase diagram of La2-xSrxCuO4 is smaller than that in La2-x-ySrxNdyCuO4. Therefore, thesis reports the comparison of spectroscopic diagram between La2-x-ySrxNdyCuO4 and La2-xSrxCu0.995Zn0.005O4, which show more a pronounced Tc-x drop than the La2-xSrxCuO4 system. Meanwhile, the effect on the thermoelectric power by the formation of stripe phase is also investigated and discussed as well.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Sherif Michael. Includes bibliographical references (p. 105-109). Also available online.

Thesis (Ph. D.)--University of Oregon, 2000. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 91-93). Also available for download via the World Wide Web; free to University of Oregon users.

No description available.

Thermoelectric modules are an important alternative to heat engines in the harvesting of waste heat. Electrical-thermal analogues are often employed when studying heat conduction and this analogue can be extended to develop an equivalent circuit for thermoelectric effects. For the primarily one-dimensional problem of thermoelectricity, the equations can be discretized to create a simple mathematical model. In this document, such a model is developed from first principles and show that the electro-thermal coupling is properly in- corporated. The results of simulations using the model are then presented and validated experimentally. Furthermore, in one possible application of thermoelectric modules, a self-contained cooling unit with an integrated thermoelectric generator is designed. By performing fluid dynamics simulations on a fan and heat sink model, the geometry and operating conditions can be optimized and the start-up and transient characteristics are studied.

Thermoelectric modules are an important alternative to heat engines in the harvesting of waste heat. Electrical-thermal analogues are often employed when studying heat conduction and this analogue can be extended to develop an equivalent circuit for thermoelectric effects. For the primarily one-dimensional problem of thermoelectricity, the equations can be discretized to create a simple mathematical model. In this document, such a model is developed from first principles and show that the electro-thermal coupling is properly in- corporated. The results of simulations using the model are then presented and validated experimentally. Furthermore, in one possible application of thermoelectric modules, a self-contained cooling unit with an integrated thermoelectric generator is designed. By performing fluid dynamics simulations on a fan and heat sink model, the geometry and operating conditions can be optimized and the start-up and transient characteristics are studied.

Since the beginning of the industrial revolution in the late 18th century, there's an abrupt increase in need for energy and resources. Despite of advantages it offers, waste heat or energy generated by machines or vehicles exhaust is evolved into the surrounding atmosphere, resulting in the evolution of the Greenhouse effect. With rampant global warming, thermoelectricity - an environmentally benign technology that recovers waste heat and converts it directly into useful electricity or vice versa - has gradually become an interesting topic for researchers. Regardless, it has yet to be widely commercialised mainly due to its inferior energy conversion efficiency to the conventional power generators and cooling devices. The aim of this project was to explore ways of enhancing the efficiency of thermoelectric materials. NaC0204 is one of the state-of-the-art p-type thermoelectric materials to date due to its superior thermoelectric properties and stability at elevated temperatures. As a result of its layered structure, NaC0204 is highly anisotropic in thermoelectric properties. Literatures revealed that the thermoelectric properties along the in-plane direction are superior to that along the out-of-plane direction, which emphasise the significance of texture. In this work, the texturing mechanisms and the texturing process as a function of sintering duration were studied in detail and the synthesis procedure of highly textured NaC0204-; materials was optimized. The results indicate that the extent of texture increased with increasing process duration and then reached the maximum when the materials were sintered at 900??C for 12 hrs. The texturing kinetics obeys an exponential relationship, suggesting that the texturing processing is dominated by self-diffusion mechanism. The experimental evidence also shows that the extent of texture decreased when the annealing time exceeded 12 hrs. The mechanisms of such deterioration were highly due to the nature of grain growth in ceramics. Given that the Co ions in NaxC020 4-; have different valence between 3+ and 3.48+ depending on the Na content and have spins, it is expected that oxygen vacancies formed in the lattice would cause charge-spin interaction, which would have a profound effect on the thermoelectric properties. As part of current study, the oxygenation kinetics and possible mechanisms were investigated. Room temperature X-ray diffraction study shows a decrease in FWHM and a certain left shift of spectra for the oxygenated samples, suggesting an increase in d-spacing and lattice distortion as a result of oxygen deficiency. The extent of oxygen saturation increased with decreasing annealing temperature. The high oxygenation flux in the first three hours of annealing was possibly due to lower energy requirement for oxygen to occupy its vacant sites than that to interstitially occupy a site. These experimental results could be used to further study the oxygen dependence of thermoelectric performance. Moreover, the investigation of temperature effects on lattice structure of NaC02O4-; with/without oxygenation was carried out to understand oxygen contribution to the lattice structure and also thermal expansion behaviours. Refined high temperature XRD results revealed that lattice parameter a decreased and c increased over the temperature range investigated after oxygenation due to Coulomb interaction between the constituent ions. Linear thermal expansion coefficient along the a- b-axis direction is circa 1.105 x 10-5K-1 for the sample before oxygenation and 1.06 x 10-5K-1 after oxygenation. An almost three-fold increase was observed for the thermal expansion coefficient along the c-axis direction for the samples before and after oxygenation, suggesting that higher oxygen concentration suppresses the thermal expansion coefficient in all directions.