Nucleation in small capillary tubes

In this paper, the classical theory of nucleation is extended to describe heterogeneous nucleation in small capillary tubes, of diameters of less than 100 μm. The effect of confinement within progressively finer capillary tubes is to increase the required superheat or applied tension before nucleation is observed and is particularly pronounced when the liquid has been pre-compressed under high pressure. Thus, by reducing the tube diameter, the nucleation thresholds or concentrations of gases which remain dissolved in carrier liquids transported along capillaries can be raised. The extended theory requires a pair of experimentally-determined coefficients which account for physico-chemical effects on nucleation at the tube surface. It then yields results for capillary tubes of a range of diameters in good agreement with: (i) experimental measurements of the degree of supersaturation of water with oxygen which can be achieved without nucleation during decompression; and (ii) measurements of the temperature at which nucleation of pure water is observed.