Koichi Araga

Simultaneous determination of micellar structure and drag reduction in a surfactant solution flow using the fluorescence probe method

As widely known, the addition of a specific type of surfactant to water reduces drag in a pipe flow. This effect is considered to be a result of the suppression of turbulent transition caused by the ordered structure of rod-like micelles that is referred to as a shear-induced structure (SIS). However, it is typically difficult to determine the SIS since it is necessary to noninvasively detect the SIS with several hundred nanometers in the actual moving flow. In this study, we used the fluorescence probe method to locally determine the SIS in a pipe flow. When hydrophobic fluorescence molecules are added to the surfactant solution, the fluorescence molecules are trapped in micelles. Thus, fluorescence intensity varies based on the change in the micellar structure. We verified the applicability of the fluorescence probe method to the SIS detection and determined the relationship between the micellar structure and the drag reduction in the pipe flow by simultaneously measuring the fluorescence intensity and ...

G226 Thermal Control of a Layer of Corroding Iron Powder

This paper presents an experimental investigation of the thermal characteristics in a layer of an exothermic powder mixture that is utilized in body warmers, hot compresses, etc. The research objective is to develop a manufacturing method that enables the exothermic temperature to be controlled in order to prevent cases of low-temperature burns. This powder mixture is composed of iron powder, activated carbon powder, vermiculite and NaCl.百levariation over tIIne of the temperature distribution and the generated heat in a layer of the exothermic powder mixture is measured. Absorbent polymer and nonwoven fabric are used to control the water and oxygen volume supplied into the layer, and their effects are examined. Keyword Iron Powder, Corrosion, Exothermic powder, Chemical reaction, Temperature con仕01,Absorbent polymer, N onwoven fabric

Forced Convective Boiling of Refrigerant HCFC123 in a Mini-Tube

This paper presents an experimental investigation of the forced convective boiling of refrigerant HCFC123 in a mini-tube. The inner diameters of the test tubes, D, were 0.51 mm and 0.30 mm. First, two-phase frictional pressure drops were measured under adiabatic conditions and compared with the correlations for conventional tubes. The frictional pressure drop data were lower than the correlation for conventional tubes. However, the data were qualitatively in accord with those for conventional tubes and were correlated in the form φL 2 −1/Xtt . Next, heat transfer coefficients were measured under the conditions of constant heat flux and compared with those for conventional tubes and for pool boiling. The heat transfer characteristics for mini-tubes were different from those for conventional tubes and quite complicated. The heat transfer coefficients for D = 0.51 mm increased with heat flux but were almost independent of mass flux. Although the heat transfer coefficients were higher than those for a conventional tube with D = 10.3 mm and for pool boiling in the low quality region, they decreased gradually with increasing quality. The heat transfer coefficients for D = 0.30 mm were higher than those for D = 0.51 mm and were almost independent of both mass flux and heat flux.Copyright