He II phase separation with slits and porous plugs for space cryogenics

This paper compares and discusses the different research efforts for space cryogenics and tries to unify seemingly contradictory results within a simple theory deduced from the phase separating properties of single straight slits. According to the two-fluid model including Gorter-Mellink friction, the flow properties depend strongly on the internal geometry, which makes quantitative predictions for porous plugs difficult. Suggestions are made with regard to room temperature measurements of permeability, effective porosity and the like and with regard to a low temperature experimental programme. (author)