Evaluating the effects of surface tension and viscosity on two-phase flow in horizontal pipes

Two-phase gas/liquid flow in pipes is a common occurrence in the petroleum, chemical, nuclear and geothermal industry. In the petroleum industry, it is encountered in the production, transportation, and processing of hydrocarbon from oil and gas field. In designing these systems, accurate prediction of pressure drop is imperative which is determined from flow regime map. Unfortunately, most of the flow regime maps were developed for the air-water system and widely used for the gas/oil system. In spite of the practical importance the general applicability of these maps is not addressed. In order to improve the generality of flow regime maps it is necessary to evaluate the effect of fluid properties such as surface tension which differ by great magnitude (air/water = 72 dyne/cm and gas/oil = 35 dyne/cm) and viscosity (viscosity of water 1 centipoise and for oil 10 centipoises at standard condition) on the flow regimes. Thus, this study aims to evaluate the effects of surface tension and viscosity on the flow regimes in horizontal pipes. The most flow regime maps are generated using the air-water system and widely applied to the oil-gas system. In addition, the empirical equations based on flow regime maps are not accurate with relatively high error (20-30%).So that the applicability of these maps is limited due to the lacking knowledge of fluid properties effect. Evaluation of these properties will address the applicability of these maps for other systems. The objective of this study is to evaluate the effects of surface tension and viscosity on flow regimes in horizontal pipes and investigate its effects on boundary transition. The experiments were conducted on horizontal pipe flow-loop (length 30' and diameter 1”) with two-phase air/ water. The range of superficial gas velocity is 0-60ft/s and superficial liquid velocity is 0-10ft/s. The effect of surface tension has been introduced by reducing the surface tension with the aid of a surfactant, and the effect of viscosity has been introduced by increasing the viscosity with aid of glycerin. Four different surfactant concentrations (0.02, 0.05 0.1, 0.5%) and four different glycerin concentrations (5,10,20,30%) have been selected to evaluate the effects of the surface tension and viscosity. The experimental data were utilized to generate flow pattern map and the effect of surface tension and viscosity were evaluated based on the variation in the boundaries of different flow patterns.