Helium II flow through narrow pore filters

Abstract

Studies of helium II flow through the narrow pore filters of cylindrical shapes, fabricated by compacting under pressure fine powders of aluminium oxide (0·05 μm), nickel and chromium (1 μm), have been made by measuring the volume flow rates in a two bath arrangement. The “easy” direction mass flow rates are in general agreement with the Gorter Mellink description, but for large temperature gradients where the observed mass flow rates are lower than predicted by the theory and tend to saturation. However; if one can treat the cross-sectional area as a fit parameter, our results show that this parameter decreases with increasing chemical potential gradient, very similar to the case of non-cylindrical geometries. Can then one conclude that irrespective of the geometrical shape of the filter the superfluid flow behaves analogously to the classical flow especially for large pressure differences? The breakthrough studies confirm the occurrence of “choking effect” in the filter made from very fine size aluminium oxide powder. Our studies point to the limitations in using these filters for practical applications such as fountain effect pumps and helium II transfer devices.