This article reports a theory for superior configurations of a heat spreader between a high performance disk shaped heat sink and a high density heating device. We considered three cases: (a) perimeter weighted distribution of cooling resources, (b) uniform distribution of cooling resources, and (c) center weighted distribution of cooling resources. Then, the most preferable distribution of cooling resources with same amount of cooling resource is studied. The center weighted distribution shows the highest performance for this case. The cooling performance of the heat spreader per total thermal conductance decreases with the increase in the heat spreader radius. On the other hand, the cooling performance of the heat spreader increases with the increase in the heat spreader radius. The cooling performance under the same degree of cooling in the center area increases with the increase in the heat spreader radius for perimeter weighted distribution. Furthermore, the perimeter weighted distribution is most effective due to the significant cooling resource in perimeter region. This advantage diminishes rapidly with the increase in the temperature parameter m (which is a function of the product of Biot number and Svelteness number of the heat spreader).

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Although thermal insulation paper has attracted attention from various industrial fields, there are very few reports on its thermal conductivity at present. Especially, there are few examples of measuring the thermal conductivity with single sheet of thermal insulation paper, and there are no reports on the thermal conductivity in the in-plane direction where fibers are extremely strongly oriented. Therefore, a method for simultaneously measuring the thermal conductivity in the thickness and the in-plane directions using the heat flow separated method which have been developed in the preceding research was examined. The measurement apparatuses for large size (300 mm × 300 mm) and for small size (150 mm ×150 mm) have been developed based on our principle. And, the dependence of the size of the specimen and the measurement accuracy were examined by comparing the results of both. Furthermore, the obtained results were compared with those by Guarded Hot Plate (GHP) method. In addition, the uncertainty analysis of the proposed measurement method was carried out, and it was shown that both the measurement uncertainty of thickness and in-plane directions were about 6 % and 13 %, respectively.

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In this study, the spectral control of near-field radiation transfer between a metal-insulator-metal (MIM)-structured emitter and a metal-semiconductor-metal (MSM)-structured cell was studied for advanced nanogap thermophotovoltaic (TPV) power generation systems using the finite-difference time-domain method. Moreover, the mechanism of spectral control was investigated by the visualization of magnetic condition through the emitter/vacuum gap/cell. For the emitter side, an MIM emitter consisting of nickel and silicon dioxide was used for the spectral enhancement of near-field radiation. For the cell side, an MSM cell consisting of gold, as the electrode, and gallium antimonide, for the photovoltaic semiconductor, was proposed considering a thin-layered TPV cell. The simulation results demonstrated that by the adjustment of the size of the MIM and MSM structures, the near-field radiation can be transferred selectively aiming the target wavelength for the bandgap of GaSb, and those effects can be shown based on the comparison to the blackbody radiation transfer at the same temperatures of the emitter (1000 K). In addition, a unique magnetic resonance condition was appeared when sharper radiation spectral control with enhanced near-field radiation flux can be obtained by optimizing the surface electrode structure of the cell (300 K). Furthermore, the evaluation results show that the spectral efficiency and power ratio increase when the structured emitter and cell was applied. Consequently, using a thin semiconductor layer cell with a p-n junction, similar to conventional cells, an energy conversion system with higher power density can be developed through spectral-controlled radiation transfer between the MIM emitter and MSM cell. These results provide greater flexibility for the control and design of the emitter and cell for nano-gap TPV generation systems.

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