Measurement of drop size in horizontal annular flow with the immersion method

A modified version of the oil immersion sampling system developed by Okada was exploited to obtain measurements of drop diameter in a horizontal annular flow of air and water in a 9.53-cm pipe. Drop samples were captured in a high-viscosity oil and photographic images of the samples were used to measure the distribution of diameters. Advantages of the immersion method are that the drops are spherical when photographed and that the measurement does not require removal of the film from the wall. Drop size distributions are found to be similar to distributions measured using a photographic technique for vertical annular flow in a 4.2-cm pipe. Drop size distributions show some differences from measurements that used a laser diffraction system in the same horizontal pipeline. In particular, the diffraction method indicates the existence of larger maximal drop sizes than are determined with the immersion technique.