A new method to measure local heat flux distribution from capsule surface in packed bed of ice thermal storage capsule using magnetic resonance imaging (MRI) was developed to investigate nonuniform heat transfer phenomena in porous media. In this method, local heat flux distribution from a capsule was calculated from freezing rate of water in the capsule cooled by brine below 0°C in a time interval. The mean heat flux of single capsule surface under uniform flow obtained by this method agrees with one by the conventional method. By applying this method to packed bed, heat flux distributions on capsule surfaces in packed bed were measured, and axial velocity distributions of brine through packed bed were obtained by the phase method in MRI techniques. Based on these results, it was found that heat exchange effectiveness of brine through channel was lower than that through the region where channel flow was not induced. In addition, time-variations of overall heat transfer coefficient of packed bed at different flow rates were obtained.

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Bubble plume is known as one of transport phenomena which drive a large scale natural convection due to buoyancy of bubbles. Surface flow generated by the bubble plume is utilized for protecting naval systems, rivers, and lakes. In the past, however, the detailed mechanism of the surface flow generation process has not been measured experimentally. This paper reports the characteristics of the surface flow which depends on the gas flow rate, the bubble size, and the internal two-phase flow structure of the bubble plume. The data are obtained by applying particle imaging velocimetry (PIV) to three kinds of visualized images; the first is visualization of the whole field around the bubble plume, the second that of the upper view of the surface flow, and the third that of the surface flow generation region under the free surface. As an additional function of the surface flow, the wave-damping effects are also discussed.

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Measurement accuracy of a fast-scanning X-ray CT, designed to measure the unsteady void fraction and the interface area in multi-phase flow, was evaluated with spherical and cylindrical acrylic phantoms of known dimensions. Limitations of the spatial resolution and the object velocity were examined from the velocity and dimensions of the phantoms, X-ray fan beam thickness, and the scanning speed. Measurement errors less than 5% can be achieved by appropriate selection of the threshold level in binary images for stationary objects. However, the errors exceed over 20% for spherical objects moving at 1.0m/s. Another phantom simulating a unit of slug bubble frequently seen in multi-phase flow was scanned with the fast X-ray CT and its profile was compared with the phantom's actual dimensions. The results showed the system's successfull capability to reproduce the cylindrical part, while a further improvement is required to resolve detailed interface structure at the rear end of the phantom moving at large velocities.

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To understand the dynamic mechanics of a droplet in the still water, two-phase CFD simulations are carried out together with flow visualization and PIV measurements. Our CFD method incorporates a MAC-type NS solver and a front capturing technique by using the maker density function. The CFD method indicates the defomation, zigzag trajectory and the vortex shedding from it, each of which is compared well with the measurements. The method also presents the mass transfer at the interface of a droplet and the resultant Sherwood number agrees well with the solution of an experimental equation.

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