This study reports the results of comparative evaluation of the measured and theoretical values of the thermal conductivity of a carbon nanotube-dispersed fluid in which multi-walled carbon nanotubes, MWCNT, with extremely high thermal conductivity are dispersed in distilled water. The thermal conductivity of MWCNT dispersed water was measured by the wire heating method with the mass composition ratio and temperature as parameters. The ratio of thermal conductivity of the dispersoid to the continuous phase of this test sample is unprecedentedly large, which is a range that has never been evaluated in other study. The test MWCNT has a very thin and long shape, and is considered to be dispersed in the continuous phase in a deformed and interlaced state. Therefore, a model suitable for estimating the thermal conductivity of MWCNT dispersed water was examined by comparing the experimentally measured values with the theoretically calculated values. The thermal conductivity of the MWCNT dispersed water was measured to be higher than that of the single-phase water, and the results were in good agreement with the values estimated by the Rayleigh model with a cylindrical arrangement or Hamilton model equation.

Silica aerogels are low density silica gel with nanoporous structure and are famous as materials with the lowest thermal conductivity (below 0.02 W/(m∙K)) except for vacuum insulation panels. Silica aerogel-composite insulation materials with polymer sheets or nonwoven fabrics have been developed and commercially available. The standard method of thermal conductivity measurement has not yet been established for these materials, due to limited applicable methods for this low conductivity region and requirement of large sample size. We developed a silica aerogel composite sheet and compared its thermal conductivity measured by different methods. Heat flow meter (HFM) method showed almost the same value (0.016 W/((m∙K)) with guarded hot plate (GHP) method. Sandwiching thin sample (1.8 mm) with silicone sponge provided a thermal conductivity close to that obtained by stacking the samples. Effect of sample size on HFM method and comparison with hot wire method were also investigated.

In this study, to understand the thermal behavior of structural materials molded from powdered vanadium dioxide, sintered moldings and binder moldings were actually made. And their thermal properties were investigated by heating experiments and simulations using the thermal network method. The results show that it was found that the phase transition temperature of vanadium dioxide has the effect of maintaining the temperature due to the latent heat and that the temperature change can be predicted by the thermal network method. Furthermore, when the type of binder was changed, the thermal behavior of the molded object itself changed significantly depending on the thermophysical properties of the binder.

Insulation materials for spacecraft are required to have high radiation resistance, high heat insulation, high heat resistance, and light weight. Therefore, we focus on polyimide foam that has these characteristics. Since a simple and compact evaluation device is desired in the development stage of a new thermal insulation, we are trying to measure the effective thermal conductivity of a small sample with a diameter of 52 mm. In general, the effective thermal conductivity of a thermal insulation is measured by the guarded hot plate method, but in this paper we aimed to downsize the device by using a simple design that does not use a guarded hot plate. However, since the sample to be measured is high insulation and small, the effect of heat leak is relatively large and the reliability of the measured value degrades. Therefore, we applied the heat flow separation method using the temperature difference between the samples. In addition, analysis of heat transfer using Monte Carlo method was introduced.

For the thermal diffusivity analysis in Laplace space, it is necessary to set the Laplace variable. When using the theoretical formula obtained under the same conditions as the measurement data, there are no restrictions for Laplace variables setting, but if they are different, the Laplace variables are restricted. In this paper, the finiteness and the time origin deviation of the measurement data are taken up as different conditions from the theoretical formula and the appropriate region of the Laplace variable was confirmed. The appropriate region of the Laplace variable was confirmed by the product of the Laplace variable p and the measurement time t_m (p×t_m). The finiteness of the measurement data determines the lower limit of the Laplace variable appropriate region, and the time origin deviation determines the upper limit of the Laplace variable appropriate region. It is necessary to set the Laplace variable in the range between the upper and lower limits. It was found that the longer the measurement time, the wider the region of the appropriate Laplace variable, and the larger the deviation of the time origin, the narrower the appropriate Laplace variable region. It was also found that the proper region of the Laplace variable for thermal diffusivity is wider than for the Biot number.