E. Rhodes

Viscosity/Concentration Relationships for Emulsions

Empirical and theoretical relationships are developed to describe the viscosity/concentration behavior of Newtonian and non‐Newtonian emulsions having dispersed‐phase concentrations less than 74% by volume. The developed equations are valid for both oil in water and water in oil types of emulsions. Emulsions exhibiting electroviscous effect (increase in viscosity due to presence of electric charge on the surface of droplets) could also be described adequately by these equations. The proposed equations have the ability to predict the emulsion viscosity as a function of dispersed‐phase concentration and shear rate if the flow curve (shear stress versus shear rate plot) is known experimentally at a single value of the dispersed‐phase concentration.

A novel viscosity correlation for non-newtonian concentrated emulsions

Abstract The flow properties of concentrated oil-in-water and water-in-oil emulsions have been determined by using the Fann coaxial cylinder viscometer, the Weissenberg Rheogoniometer, and the Brookfield viscometer. Based on the extensive amount of experimental data collected, an empirical equation which correlates the relative viscosities of emulsions (both oil-in-water and water-in-oil) as a function of normalized dispersed phase concentration is proposed. According to the equation, if the viscosity of emulsion at any single dispersed phase concentration is known, the viscosity at other concentrations of dispersed phase can be predicted. A comparison of the correlation has been made with those proposed for solid-in-liquid suspensions.

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.

Mass transfer in upwards co-current gas-liquid annular flow

Abstract The absorption of carbon dioxide in water has been studied in gas-liquid annular flow in a vertical tube. New types of probes have been developed to al

Pyrometric Measurement of Dust-Laden Gas Temperature

Continuous measurement using radiation pyrometry under industrial conditions has often met with difficulties whose causes have been obscure. In this paper, the experience gained in utility boilers, with temperatures in the range of 800 °C to 1400 °C, is reported. It is shown that the inherent problems are best resolved by using a spectral pyrometer not sensitive to gas radiation. The radiation from the suspended particles thus provides the signal. A theoretical analysis is given. Heat fluxes originating from surrounding surfaces and reflected by the particles to the pyrometer play a major role. Several examples are given how problems may be resolved using process information and/or additional measurements, fed to and processed by an on-line microcomputer.

TWO-PHASE FLOW HEAT TRANSFER IN A HORIZONTAL STEAM WATER SYSTEM

Abstract There are various correlations available for predicting heat transfer coefficients during forced convective two-phase flow. The present work was undertaken to gather heat transfer rate data for the steam-water system and to evaluate (and if necessary, to modify) the available correlations in light of those data. A boiling water loop, capable of being operated at pressures up to 1300 kPa, was used. The test section was in the form of a U-tube with two straight horizontal sections connected by a 180° return bend. Using this loop, accurate pressure drop and heat transfer data were gathered over a wide range of mass and heat fluxes. The data obtained were used to arrive at an improved correlation for the two-phase convective heat transfer coefficient hpfor steam-water systems at relatively low pressures (800 kPa). The proposed correlation shows hpis a much stronger function of Lockhart-Martinelli parameter than is indicated by most of the other correlations. Among the existing correlations evaluated,...

EFFECT OF MASS FLUX AND SYSTEM PRESSURE ON TWO-PHASE FRICTION MULTIPLIER

A horizontal boiling water loop was used to obtain pressure drop and heat transfer data for two-phase steam-water flow for pressures of up to 825 kPa. The data were used to examine the predictions of the separated flow model using the Lockhart-Martinelli method of estimating the two-phase friction multiplier. The influence of mass flux on the two-phase friction multiplier has been reported for high pressure systems by many workers. The present work confirms the existence of this influence at low pressures as well. System pressure is also found to be a parameter. A correlation for the two-phase friction multiplier, incorporating the effects of mass flux and pressure, is presented here. The correlation has been tested against data from two independent sources. The predictions have been found to be in very good agreement with the data.

BOILING TWO-PHASE FLOW HEAT TRANSFER IN A HORIZONTAL BEND

Abstract A paucity of heat transfer rate data for boiling two-phase flow through bends was noted after an extensive literature survey, The present work was undertaken to redress this shortcoming. A boiling water loop, capable of being operated at pressures up to 1300 kpa, was used. The lest section was in the form of a U-tube with two straight horizontal sections connected by a 180° return bend. Using this loop, pressure drop and heat transfer data were gathered over a wide range of mass and heat fluxes. steam qualities and system pressures. The data obtained were used to investigate the variation in heal transfer coefficients around the radial positions of the bend. Correlations for heat transfer coefficients for four different radial positions (top. bollom, inside and outside of the bend) have been presented for the first time. A possible explanation for the observed variations in heat transfer coefficients has also been suggested.