Experimental verification of theoretical investigations into the behaviour of liquid metal convective flows is required to validate analytical models and numerical simulation codes. A real-time radioscopic density visualization system has been developed and is beginning to provide useful data. The X-ray facility for studying opaque low-Prandtl-number fluid flow is described. Density changes as low as 10−3 g cm−3 can be visualized by careful control of scatter radiation. The new capability is demonstrated with natural convection benchmark experiments in a narrow vertical layer of gallium melt of aspect ratio A=1.4. The density field in that cell is three-dimensional. Good agreement between calculations and experiments is obtained. Experiments with solidification are provided for further theoretical use.

For modern thermal applications, open cell porous metals provide interesting opportunities to increase performance. Several types of cellular metals show an anisotropic morphology. Thus, using different orientations of the structure can boost or destroy the performance in thermal applications. Examples of such cellular anisotropic structures are lotus-type structures, expanded sheet metal, and metal fiber structures. Lotus-type structures are made by casting and show unidirectional pores, whereas expanded sheet metal structures and metal fiber structures are made from loose semi-finished products that are joined by sintering and form a fully open porous structure. Depending on the type of structure and the manufacturing process, the value of the direction-dependent heat conductivity may differ by a factor of 2 to 25. The influence of the measurement direction is less pronounced for the pressure drop; here, the difference varies between a factor of 1.5 to 2.8, depending on the type of material and the flow velocity. Literature data as well as own measurement methods and results of these properties are presented and the reasons for this strongly anisotropic behavior are discussed. Examples of advantageous applications, for example a latent heat storage device and a heat exchanger, where the preferential orientations are exploited in order to gain the full capacity of the structure’s performance, are introduced.

No abstract

No abstract

No abstract