Studies of gas→liquid (non-Newtonian) slug flow: void fraction meter, void fraction and slug characteristics

Abstract

Measurements are reported of the void fraction, slug velocity and slug frequency for the cocurrent slug flow of highly viscous non-Newtonian fluids and air. The experimental work was performed in a horizontal tubular test section 2.54 cm in internal diameter and 10.67 m long. Three different polymer solutions were used over wide concentration ranges. The void fraction and slug characterization measurements were carried out with a specially constructed coil void fraction meter operating in a capacitive mode. This system allowed not only the measurement of the instantaneous void fraction but also a recording of the slug voidage trace. Correlations are presented for void fraction, slug velocity and slug frequency, noting in all cases the effects of fluid rheology and apparent viscosity. (1) An investigation of the effects of non-Newtonian liquids on the behaviour of cocurrent gas-liquid slug flow has been undertaken. (2) To allow experimentation with viscous fluids, a new electrically resonating void fraction meter was devised which worked satisfactorily for a wide variety of polymer solutions when it was carefully tuned. (3) Empirical rheological constants were obtained for a wide range of polymer solutions. (4) Slug frequencies, velocities and average void fractions were measured. (5) Liquid slugs travel at approximately the maximum gas velocity even when the liquid becomes quite viscous. (6) The method of Gregory and Scott 16 correlates slug frequency data for each individual polymer system. No generalized correlation has been obtained. (7) The void fraction data can be expressed according to the method of Zuber and Findlay. However, the straight line curves are peculiar to each individual polymer system. (8) Most importantly, the void fraction data are correlated according to the method of Lockhart and Martinelli provided that the liquid phase pressure drop in the parameter X is calculated by allowing for the non-Newtonian characteristics of the liquid phase. This is the most general and useful result of the work.