W. A. Van Hook

Membrane Distillation Employed for Separation of Water Isotopic Compounds

Abstract An attempt to apply membrane distillation (MD) for the enrichment of water isotopic compounds was made. The process was conducted as a direct-contact MD with flat-sheet microporous, hydrophobic polytetrafluoroethylene (PTFE) membranes in the temperature range 323–353K. The distillate condensation was carried out directly into a stream of cooling water. The comparison between calculated Rayleigh distillation curves and the results of permeation experiments demonstrated the MD process to be more efficient than simple distillation for enrichment of the heavy isotopes in water.

CASCADES FOR NATURAL WATER ENRICHMENT IN DEUTERIUM AND OXYGEN-18 USING MEMBRANE PERMEATION

Abstract Heavy isotope enrichment of water using a hydrophobic membrane permeation process is described. Simple and ordinary countercurrent cascades will not be of practical interest because of high energy demand. A better solution is to employ a double countercurrent cascade, reutilizing part of the heat of condensation.

Correlation of the volumetric properties of fluorinated ethers by the group-contribution volume-ratio method

Abstract(p, V, T) data obtained with simple volmnometers are usually restricted to a small range of temperatures below and above ambient temperature. The modified Tait equation has been very useful for extrapolating (p, V, T) data for individual liquids. The available volumetric data for fluorinated ethers is reviewed and is expressed as a correlation by using the Tait equation and the group-contribution volume-ratio method. Volume ratios obtained from this correlation used in combination with the densities of the liquid along the saturation boundary should provide the densities for a wide temperature and pressure range for the fluorinated ethers, including some which may be useful as longterm replacements for existing alternative refrigerants.

Comparison of SANS and DLS hydrodynamic correlation lengths for a polystyrene/methyl-cyclohexane solution in the vicinity of temperature- or pressure-induced critical demixing

Abstract Phase diagrams for polystyrene(PS)/deuteromethylcyclohexane have been determined over a wide range of temperature and pressure. In this work, we report hydrodynamic and SANS correlation lengths, ξDLS and ξSANS, and intensities, IDLS and ISANS, from dynamic light and small-angle neutron scattering, respectively, along various approaches to a near-critical demixing surface, ƒ(T ∗ , P ∗ ) cr . We examined isobaric, isothermal, and more complicated paths, sometimes in the hypercritical region. (At a lower hypercritical temperature ϖ(ƒ(T ∗ ,P ∗ )/ϖP = 0 and ϖ 2 (ƒ(T ∗ ,P ∗ )/ϖP 2 > 0 , and at a lower hypercritical pressure ϖ(ƒ(T ∗ ,P ∗ ) cr /ϖT = 0 and ϖ 2 (ƒ(T ∗ ,P ∗ ) cr /ϖT 2 > 0.) Both ξDLS and ξSANS diverge as ( T ∗ ,P ∗ ) is approached, but the strength of the divergence depends on the direction of approach to ( P ∗ ,T ∗ ) cr . We discuss a modified scaling expression which describes the observations.