Abdelsalam Al-Sarkhi

Drift-Velocity Closure Relationships for Slug Two-Phase High-Viscosity Oil Flow in Pipes

The drift velocity of a gas bubble penetrating into a stagnant liquid is investigated experimentally in this paper. It is part of the translational slug velocity. The existing equations for the drift velocity are either developed by using the results of Benjamin (1968) analysis assuming inviscid fluid flow or correlated using air-water data. Effects of surface tension and viscosity usually are neglected. However, the drift velocity is expected to be affected with high oil viscosity. In this study, the work of Gokcal et al. (2009) has been extended for different pipe diameters and viscosity range. The effects of high oil viscosity and pipe diameter on drift velocity for horizontal and upward inclined pipes are investigated. The experiments are performed on a flow loop with a test section 50.8, 76.2 and 152.4 mm ID for inclination angles of 0o to 90o. Water and viscous oil are used as test fluids. New correlation for drift velocity in horizontal pipes of different diameters and liquid viscosities is developed based on experimental data. A new drift velocity model/ approach are proposed for high oil viscosity valid for inclined pipes inclined from horizontal to vertical. The proposed comprehensive closure relationships are expected to improve the performance of two-phase flow models for high viscosity oils in the slug flow regime.

Experimental Study on the Flow Regimes and Pressure Gradients of Air-Oil-Water Three-Phase Flow in Horizontal Pipes

An experimental investigation has been carried out to study the flow regimes and pressure gradients of air-oil-water three-phase flows in 2.25 ID horizontal pipe at different flow conditions. The effects of water cuts, liquid and gas velocities on flow patterns and pressure gradients have been studied. The experiments have been conducted at 20°C using low viscosity Safrasol D80 oil, tap water and air. Superficial water and oil velocities were varied from 0.3u2009m/s to 3u2009m/s and air velocity varied from 0.29u2009m/s to 52.5u2009m/s to cover wide range of flow patterns. The experiments were performed for 10% to 90% water cuts. The flow patterns were observed and recorded using high speed video camera while the pressure drops were measured using pressure transducers and U-tube manometers. The flow patterns show strong dependence on water fraction, gas velocities, and liquid velocities. The observed flow patterns are stratified (smooth and wavy), elongated bubble, slug, dispersed bubble, and annular flow patterns. The pressure gradients have been found to increase with the increase in gas flow rates. Also, for a given superficial gas velocity, the pressure gradients increased with the increase in the superficial liquid velocity. The pressure gradient first increases and then decreases with increasing water cut. In general, phase inversion was observed with increase in the water cut. The experimental results have been compared with the existing unified Model and a good agreement has been noticed.

Power-Law Correlation for Two-Phase Pressure Drop of Gas/Liquid Flows in Horizontal Pipelines

Original SPE manuscript received for review 6 October 2009. Revised manuscript received for review 22 January 2010. Paper (SPE 138516) peer approved 13 April 10. Summary New dimensionless parameters and a simplified power-law correlation to predict pressure drop during the gas/liquid flow in horizontal pipes are proposed. The new equation fits the published data very well. The proposed power-law equation can correlate the stratified-smooth, stratified-wavy, stratified-atomization, stratified-annular-transition and annular flow patterns. The proposed simplified dimensionless formula can be used for flowline-design purposes and flow-assurance predictions in pipelines.

Water Droplet Dynamics on a Hydrophobic Surface in Relation to the Self-Cleaning of Environmental Dust

The dynamic motion of a water droplet on an inclined hydrophobic surface is analyzed with and without environmental dust particles on the surface. Solution crystallization of a polycarbonate surface is carried out to generate a hydrophobic surface with hierarchical texture composed of micro/nanosize spheroids and fibrils. Functionalized nanosize silica particles are deposited on the textured surface to reduce contact angle hysteresis. Environmental dust particles are collected and characterized using analytical tools prior to the experiments. The droplet motion on the hydrophobic surface is assessed using high-speed camera data, and then, the motion characteristics are compared with the corresponding analytical results. The influence of dust particles on the water droplet motion and the amount of dust particles picked up from the hydrophobic surface by the moving droplet is evaluated experimentally. A 40 μL droplet was observed to roll on the hydrophobic surface with and without dust particles, and the droplet slip velocity was lower than the rotational velocity. The rolling droplet removes almost all dust particles from the surface, and the mechanism for the removal of dust particles from the surface was determined to be water cloaking of the dust particles.

Low complexity RF sensor for multiphase oil flow estimation in pipelines

We propose a radio frequency (RF) sensor that is flexible and capable of measuring the volume fraction of the individual phase in a two or three phase combinations of oil, water and gas. The 28-port RF sensor is designed and optimized to operate at 250 MHz with an input power of 1 mW. By applying the least square method, an equation was obtained for dielectric constant estimation using the transmission coefficient of each RF sensor port. Static two phase combination of oil-water and three phase combination of oil-water-gas are experimentally validated with an average measured error percentages of 5.5% and 5% respectively.

A Radio Frequency Sensor Array for Dielectric Constant Estimation of Multiphase Oil Flow in Pipelines

The measurement of the single phase portion in a multiphase flow is very important to oil and petrochemical industries. This paper presents a radio frequency (RF) sensor for dielectric constant estimation of two or three phase combinations of oil, water, and gas. The 28-port RF sensor was designed and optimized to operate at 250 MHz. Using the transmission coefficient of each RF sensor port, an equation was obtained for dielectric constant estimation by applying the least squares method. Three different static two phase combinations including oil–water, gas–water, gas–oil and three phase combination of oil–water–gas are experimentally validated with an average measured error percentages of 5.5%, 17.3%, 16% and 6.2%, respectively. A shake test for the three phase combination was performed to resemble an actual three phase flow and the average measured error was 9.3%. The proposed sensor can estimate two or three phase combinations of oil, water, and gas with an average error less than 10%. The proposed sensor is low cost, with low complexity and is the first to provide low error estimations to 2 or 3-phase static or dynamic flows.

Application of the Critical Heat Flux Look-Up Table to Large Diameter Tubes

The critical heat flux look-up table was applied to a large diameter tube, namely 67u2009mm inside diameter tube, to predict the occurrence of the phenomenon for both vertical and horizontal uniformly heated tubes. Water was considered as coolant. For the vertical tube, a diameter correction factor was directly applied to the 1995 critical heat flux look-up table. To predict the occurrence of critical heat flux in horizontal tube, an extra correction factor to account for flow stratification was applied. Both derived tables were used to predict the effect of high heat flux and tube blockage on critical heat flux occurrence in boiler tubes. Moreover, the horizontal tube look-up table was used to predict the safety limits of the operation of boiler for 50% allowable heat flux.

Effect of Carbon Nanotube Additive on the Thermal Performance of a Horizontal V-Grooved Heat Pipe

An experimental facility to examine the effect of carbon nanotubes (CNT) on the performance of a horizontal V-grooved heat pipe was build. The circular heat pipe was made of copper with an inner diameter of 10 mm and equipped with 10 axial V-grooves with 1 mm depth and 1 mm mouth. The experiment was performed using water as working fluid with mass percentage of CNT of 0%, 1%, 3% and 5%. The optimum fill ratio of the heat pipe was first determined by examining the fill ratio effect on the total resistance. This optimum fill ratio was then used throughout the whole experiment. The evaporator of the heat pipe was heated using a copper heater block equipped with 6 cartridge heaters. The power input to the evaporator was varied from 60 W to 240 W in steps of 60 W with maintaining steady-state operation at each power level. The condenser was cooled by a water jacket fed by a chiller. The surface temperature of the heat pipe was measured by 7 K-type self-adhesive thermocouples connected to data acquisition system. The experimental results showed that the performance of the heat pipe improved with the use of CNT-water mixture in terms of a reduction in the thermal resistance. The results also showed that this enhancement is a function of the amount of CNT additive.