Law of Micro-Liquid-Layer Formation between a Growing Bubble and a Solid Surface with a Special Refrence to Nucleate Boiling

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Spreading velocity of a bubble front and thickness of a micro-liquid layer are measured experimentally for two cases-a flattened bubble in a narrow space between a pair of parallel disks, and a bubble in normal boiling at low pressures. In the former case, the thickness of liquid-layer is determined by optical means for a bubble made by spurting air into water and alcohol. In the latter case, the thickness of liquid-layer is determined from the evaporating velocity of the liquid-layer for a bubble in saturated boilling of water at the pressure of 0.11kg/cm^2 abs. The following empirical formulae are derived from the experimental results : dh/dr=1.4(μU_0/σ)^2/3 H1/r(U_0r/ν)^1/2 for a flattened bubble in a narrow space between a pair of parallel disks, and dh/dr=0.65(μU_0/σ)^1/6 1/(U_0r/ν)1/2 for a bubble in normal boiling at low pressures, where h : thickness of a micro-liquid-layer, r : radial coordinate (distance measured from a nucleation center), μ : viscosity of liquid, U_0 : local velocity of a bubble front at the positon of r, σ : surface tension, H : half of normal distance between a pair of parallel disks, and ν : kinematic viscosity of liquid.
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