Inferring the Structure of Porous Materials Using Superfluid Helium
The operation of a phase separator for superfluid helium depends on the internal structure of the porous plug. We show how a phase separator apparatus can be used to study the flow through porous materials. This method appears to be better than conventional methods currently in use. Superfluid helium is a preferable test substance over ordinary fluids for two reasons. First, it has nearly zero contact angle for most substrates. Second, the superfluid film insulates the meniscus from surface contamination that causes variations of the contact angle. We present the theory of operation based on the governing equations. The largest term of the pressure balance equations is the jump across the meniscus. The jump is inversely proportional to the hydraulic diameter. We exploit this dependence to find the statistical properties of the hydraulic diameter that are helpful in predicting flows. We find the power spectrum of the hydraulic diameter from the measured data. All the useful probability distributions can be found from the power spectrum. We show how hysteresis loci arise due to the porous structure and discuss the probability distributions necessary to analyze hysteresis loci.
KeywordsContact Angle Phase Separator Hydraulic Diameter Pressure Jump Superfluid Helium
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