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Fracture mechanical properties of hard cellular solids (porous materials) with the Young modulus E larger than 3000 MPa have been well understood; scaling relations between fracture mechanical quantities and porosity are established, which can be explained by a theory based on the geometrical parameters of a cellular solid. In this study, we obtain experimentally the fracture energy of a very soft polyethylene foam with E around 1 MPa. We find scaling laws different from those for hard foams, which can be understood by considerations independent of the structural parameters of foams.

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Water cooling panels have been adopted as the vessel cooling system of the High Temperature Engineering Test Reactor (HTTR) to cool the reactor core indirectly by natural convection and thermal radiation. In order to investigate the heat transfer characteristics of high temperature gas in a vertical annular space between the reactor pressure vessel and cooling panels of the HTTR, we carried out experiments and numerical analyses on natural convection heat transfer coupled with thermal radiation heat transfer in an annulus between two vertical concentric cylinders with the inner cylinder heated and the outer cylinder cooled. In the present experiments, Rayleigh number based on the height of the annulus ranged from 2.0 × 10 7 to 5.4 × 10 7 for helium gas and from 1.2 × 10 9 to 3.5 × 10 9 for nitrogen gas. The numerical results were in good agreement with the experimental ones regarding the surface temperatures of the heating and cooling walls. As a result of the experiments and the numerical analyses, the heat transfer coefficient of natural convection coupled with thermal radiation was obtained as functions of Rayleigh number, radius ratio, and the temperatures and emissivities of the heating and cooling wall surfaces.

Effects of walls on shedding vortex in developed channel flow were investigated putting a cylinder a t the center of channels or on a wall for the value of wld from 2 to 4. Results were compared with the uniform flow result.When a cylinder was put at the center of the channels, non-dimensional frequency plotted against Reynolds number agreed with the uniform flow result a t low Reynolds number. However, i t increased rapidly with Reynolds number, then it lay considerably above the uniform flow results a t high Reynolds number. When a cylinder was put on a wall, nondimensional frequency was considerably lower than the uniform flow result in the cases Of wld=3 and 4. In the case of w J d = 2 , however, frequency was higher than the uniform flow result a t high Reynolds number. In all cases in the present study, the transition Reynolds number increased with decrease in the value of wld.These results indicate that the increase in shedding frequency was due to the shift in velocity distribution from Poiseuille parabora in the wake region, which obviously increased with Reynolds number and with decrease in channel width.

The natural convection flow phenomena that occur inside an enclosed space are very interesting examples of complex fluid systems that may yield to analytical, empirical and numerical solutions, and many reports have looked into this basic problem. In the present study, heat transfer and fluid flow for natural convection in a horizontal rectangular container with a free surface are investigated using infrared thermography. The temperature field was measured and visualized at a gas-liquid (air -silicon oil) interface using infrared thermography. The heat transfer phenomena were also investigated by statistically analyzing the temperature data. The applicability of the infrared thermography to quantitative heat transfer measurement at the gas-liquid interface was evaluated. It is revealed that infrared thermography is effective not only in visualization of a gas-liquid interface but also in heat transfer measurement. A new heat transfer correlation is proposed for the gas-liquid interface of this flow system. The coefficient of heat transfer can be summarized by a specific heat transfer correlation formula regardless of several conditions, including container aspect ratio, fluid viscosity and fluid layer depth.

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