He II flow phenomena through fountain effect pump element

The He II flow through a porous medium for a fountain effect pump is investigated experimentally, in particular in superfluid turbulent flow situation, and a computer program is constructed for predicting the pump performance in these situations. Four porous elements are tested, two of which have small enough permeabilities to be regarded as ideal superleaks. It is found that, for small flow rates, the superfluid He II flows ideally through a porous element and that the London (1939) equation is valid. The He II velocity through a porous element reaches a maximum value with respect to the heater power; the maximum decreases nonlinearly with the decrease of the element thickness. In the superfluid turbulent region, the effective flow passage concept gives satisfactory estimates of the flow rate. 14 refs