Abstract
The thermomechanical flow of He II through a porous element for a fountain effect pump was experimentally investigated to understand the general flow characteristics and to develop an evaluation formula for the flow rate. Two types of elements, compressed alumina powder elements and SUS fiber elements, were tested in a systematic way. The two flow states, the ideal and superfluid turbulent states, are found to exist according to the magnitude of heat input. It is a general conclusion that the flow rate through the former elements is always far smaller than the prediction from the straight forward application of the Corter-Mellink formula in the superfluid turbulent state. In order to resolve the inconsistency, the effective flow passage model is proposed, in which the tortuosity is introduced to take account of the winding of micro flow pas sages in an element. The model leads to firm understanding of general flow characteristics in both qualitative and quantitative senses, and to deriving the dynaical similarity law for the mass flow rate and the theoretical maximum flow rate. However, the tortuosity experimentally obtained with the alumina elements was considered to be too large, that is to say 4 to 5. On the other hand, those of SUS elements are found to be one or nearly one as expected from the interior structure. It is concluded that the flow rate degradation in the superfluid turbulent state is resulted mostly from the winding effect of passages, and that the model is confirmed to be quite valid.
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