In this study, an unsteady heat flux method is applied to determine thermophysical properties of water absorbent polymer. Effective thermal conductivity and diffusivity are measured both for dry and wet polymer. The moisture content is varied from 0 to 100 in mass ratio of water to dry polymer with temperature range 293K to 353K. No significant effect of the temperature dependency on the thermophysical properties is observed for dry polymer, but both the thermal conductivity and diffusivity increases with the mass ratio.
How much the thermal conductivity of a liquid can be altered by dispersing a small amount of ultra-fine particles into it has been studied. Fine powders of Al2O3, SiO2 and TiO2 were used as the ultra-fine particles, and water was selected as the base liquid. Three dispersed systems were made by applying the technique of electrostatic repulsion. For the systems of water-Al2O3 and water-TiO2, effective thermal conductivities were seen to increase much more as the particle concentration was increased, but that of water-SiO2 system almost never increased. Viscosities of their dispersed systems were also measured, and the characteristics were made clear.
The thermal conductivity measurement of fluid-saturated porous material by transient line source method must consider the effects of natural convection, if the measurement time becomes large. Since the occurrence of natural convection along the vertical needle probe generally enhances the heat transfer rate, the measured thermal conductivity may give a higher value than the true thermal conductivity of the medium. In the present paper the error associated with the convection in a saturated-porous material is studied using a mathematical model and a numerical technique. The variation of flow and temperature field due to different Rayleigh numbers is studied for four different values of slenderness ratio; 48, 96, 240 and 490. In general as the measurement time becomes larger, the effect of convection is more pronounced. For instance, the measurement at t=100 contains only a slightest error, if the Rayleigh number is less than 0.01, and the slenderness ratio of the probe is between 48 and 490. On the other hand, for a fixed value of the Rayleigh number, the convection is felt earlier as the slenderness ratio becomes smaller. For instance, for Ra=1 and h/a=490 the convection deteriorates the measurement only slightly at t=60, but it requires Ra=0.1 or even less for the same amount of error at t=60 if the slenderness ratio is decreased to h/a=48. The general criterion for the maximum allowable measurement time, within which the measurement may contain less than 10% error, is established as a function of Ra and h/a.
This paper dealt with physical properties of the oil (tetradecane, C14H30, melting point of 278.9K) water-emulsion as a latent heat storage material having a low melting point. The measured results on physical properties of the test emulsion, i.e., density and viscosity, were discussed in the temperature region of solid and liquid phases of the dispersion material (tetradecane). It was clarified that the emulsion density could be estimated by mixing ratio of the emulsion constituents. The useful correlation equations of the viscosity for the emulsion were proposed in terms of temperature and concentration ratio of the emulsion constituents.
This report is to present a method to measure air permeability under low flow rate where Darcy's law applies. The air permeability of polyester textile fabrics was measured and the conditions for the measurement was investigated. Test method by ASTM standard instructs to perform the test under a condition of relatively high flow rate. Consequently, the value obtained according to the standard depends upon the pressure difference between the two fabric surfaces. This conflicts with the real physical meaning of the air permeability. However, according to the method presented in this report, it is possible to obtain the value which is independent of the pressure difference.
Applying a choresteric liquid crystal, a temperature distribution on a surface, or in liquid, can be visualized qualitatively as a brilliantly colored map, and can be also determined quantitatively using a system of viedo-camera and image processor. This article reviews the art, forcusing on thermo-optical properties of microencapsulated liquid-crystal, which is the most common application mode, and the modern methods to determine a temperature map quantitatively.
This review describes, firstly, the outline of the mechanism of the global warming owing to the carbon dioxide increase in the atmosphere. Secondly, the present situation of the Earth's surface-atmosphere system is examined on the basis of the observed data. Finally, the obtained results from the numerical analysis using several climate models are mainly introduced on the prediction of the thermal environmental change on a global scale. Some points of the models are also picked up.