Flow Pattern Map Research Articles

Microgravity two-phase flow research in the context of vapor compression cycle experiments on parabolic flights

Research on two-phase channel flow in microgravity has extensively investigated flow regimes, pressure drop, and heat transfer during evaporation and condensation processes over several decades. This literature has been primarily motivated by the goal of enabling future space applications for two-phase thermal management systems, among them vapor compression refrigeration cycles. However, relative to the number of two-phase channel flow experiments, research on vapor compression cycles in microgravity has been almost non-existent. This paper reviews two-phase flow research and compares key outcomes with those from system-level measurements obtained from recent testing of a vapor compression cycle at varying inclination angles and on parabolic flights. Previous two-phase channel flow experiments have resulted in several microgravity-specific flow regime maps and have also generally found reduced condensation heat transfer coefficients in microgravity as compared to normal gravity. The flow pattern map of Jayawardena et al. (1997) and generally reduced condensation heat transfer are confirmed by the vapor compression cycle experiments. Regarding evaporation heat transfer coefficients and friction factors, there is not a consensus in the literature on the effects of microgravity in two-phase channel flows. Similarly, the system-level experiments do not show repeatable increases or decreases for those parameters. Lastly, the dependence of system-level behavior on orientation with respect to gravity was tested by performing dynamic inclination experiments, where the inclination angle was changed every 2 min by a 90-degree increment. These tests reveal an increased relative dependence of the vapor compression cycle to orientation with decreasing mass fluxes, in line with two-phase channel flow research that has generally shown that increasing the flow inertia acts to mitigate various flow instabilities and dependence on orientation. However, inclination testing with longer locking times per angle showed a constant relative dependence of the vapor compression cycle to orientation changes.

Unified Modeling of Pseudo-Slug and Churn Flows for Liquid Holdup and Pressure Gradient Predictions in Pipelines and Wellbores

Summary Pseudo-slug flow is a coherent flow pattern that occurs in horizontal or inclined pipes surrounded by segregated and conventional slug flows. Recent studies have demonstrated that this flow pattern can occupy a large area in the flow pattern map and cannot be simply ignored. Churn flow commonly occurs in upward vertical or slightly deviated wellbores characterized by a chaotic intermittent flow behavior. Pseudo-slug and churn flows are generally considered as two different flow patterns mainly because of their visual differences. However, some recent studies have shown that they share many similarities. There are several hydraulic models for churn flow, and the models for pseudo-slug flow have also emerged in recent years. However, these models only work for a certain inclination angle range, and none work for both flow patterns. This paper proposes a new unified hydraulic model that is applicable for both flow patterns. The liquid holdup prediction is based on the drift-flux model, while the pressure gradient is predicted using a two-fluid model that considers wall frictions from both gas and liquid phases. The new model better captures the effects of gas and liquid flow rates, gas density, liquid viscosity, inclination angle, and pipe diameter on the liquid holdup and pressure gradient compared with other models. Model evaluations show that the new model gives the best predictions compared with other available pseudo-slug or churn models. The new model reduces the total average absolute relative error to 14.0% for the liquid holdup prediction and 19.1% for the pressure gradient prediction.

Gas-liquid flow pattern identification and bubble characteristics analysis in a static mixer based HiPOxTM reactor

The multiphase flow in HiPOxTM reactor are the criteria for the mass transfer of ozone at the gas–liquid interface, determining the degradation rate of the refractory organic pollutant in industrial wastewater. In this work, the gas–liquid flow patterns and their transitions in a static mixer-based HiPOxTM reactor were investigated systematically by a high-speed camera. Six types of flow patterns were identified under the conditions of inlet liquid Re ranging from 8,000 to 160,000 and gas fraction from 3.23% to 86.96%. Three composite flow patterns are involved, and a flow pattern map was demonstrated. The effect of liquid inlet flow rate on the bubble groups is much more significant than that of gas phase in the bubble flow. If the liquid flow rate increases twice, the Sauter mean diameter is expected to fall to 65%, which was only reduced by 28% when the gas flow rate even drops 8 times.

Breakup dynamics and scaling laws of liquid metal droplets formed in a cross junction

The formation of liquid metal droplets in a microfluidic cross junction with different viscosities of the continuous phase is experimentally and theoretically investigated. The flow pattern is distinguished into squeezing and dripping by the presence of gaps. The differences in driving forces between the two patterns are analyzed theoretically and confirmed experimentally by Micro-PIV results. Roles of the squeezing force and the shear force in droplet formation are varying due to the dynamic evolutions of the gap width which reduces with time. Therefore, critical values of the initial gap width are obtained which are the outcome of the competition between neck thinning and tip growing. Compared to water–oil systems, gaps are more difficult to be formed due to the extremely high interfacial tension. Moreover, universal flow pattern maps are constructed using dimensionless parameters of Wed, Cac, and Rec, proving the important roles of both the squeezing force and the shear force. A scaling law of the droplet volume considering the influence of the viscosity ratio is proposed and a very good agreement between experimental data and theoretical predictions is obtained for different liquid systems.

Flow patterns of ionic liquid based aqueous biphasic systems in small channels

Ionic liquid based aqueous biphasic systems (IL-ABS) were formed by the addition in water of a hydrophilic ionic liquid (1-Butyl-3-methylimidazolium Chloride, C4mimCl) and a kosmotropic salt (tripotassium phosphate, K3PO4). The flow patterns of IL-ABS were studied in capillary channels with 0.2, 0.5 and 0.8 mm internal diameter; this is the first time such two-phase flows have been investigated. Three weight concentrations of the ionic liquid and the salt (18, 20 and 22 wt%) were chosen within the biphasic region. The main flow patterns included plug, dispersed and parallel flow. It was found that both channel diameter and weight concentrations would affect the flow patterns observed. Finally, a generalized flow pattern map was plotted using a combination of capillary and Reynolds numbers, where the transition boundaries of plug flow collapsed for all ionic liquid and salt concentrations studied.

Flow Boiling Heat Transfer of R134a in a Horizontal Smooth Tube: Experimental Results, Flow Patterns, and Assessment of Correlations

This study presents an extensive evaluation of heat transfer characteristics, flow patterns, and pressure drop for saturation pressures ranging from 460–660 kPa in a horizontal smooth tube of 5 mm internal diameter using R134a as the working fluid. The effect of saturation pressures for mass fluxes of 150–300 kg/m2s and heat fluxes of 8.26–23.3 kW/m2 which are typical of refrigeration and air conditioning applications are also investigated. Flow patterns observed during the study are predicted with a well-known flow pattern map of Wojtan et al. The experimental results are compared with seven (7) correlations developed based on different theories to find which correlation best predicts the experimental data. The results show that, at low mass flux, increasing saturation pressure results in an increased heat transfer coefficient. This effect is more pronounced in the low vapor quality region and the dominant mechanism is nucleate boiling. At high mass flux, increasing saturation pressure leads to an insignificant increase in the heat transfer coefficient. At this high mass flux but low heat flux, the heat transfer coefficient increases with vapor quality, indicating convective boiling dominance. However, for high heat flux, the heat transfer coefficient is linear over vapor quality, indicating nucleate boiling dominance. Pressure drop is observed to decrease with increasing saturation pressure. Increasing saturation pressure increases the vapor quality at which the flow pattern transitions from intermittent flow to annular flow. The flow patterns predicted are a mixture of slug and stratified wavy and purely stratified wavy for low mass fluxes. For increased mass fluxes, the flow patterns predicted are slug, intermittent, annular, and dryout. Cooper’s model was the best predictor of the experimental data and the trend of heat transfer coefficient.

Flow characteristics of heavy oil-water flow during high water-content cold transportation

As the water content in heavy oil gathering systems increases to 70–90% and large-scale popularization of cold transportation. Understanding the characteristics of heavy oil-water flow during high water-content cold transportation has greatly gained in importance. Here, a comprehensive flow loop experiment and microscopic observation was employed to investigate the flow characteristics of oil-water flow at low temperatures. The flow patterns of cold transportation were studied experimentally. The flow pattern maps were also created in detail, taking into account the temperatures (60–20 °C), mixture velocities (0.1–1.0 m/s), and water contents (70–90%). The relevant influencing factors of the pressure gradient were then investigated. The lubrication coefficient and viscosity models were used to modify the pressure gradient models, and average relative deviations were within ±25%. Moreover, the distinction between the oil-sticking layer and wax deposition formation mechanisms was highlighted. According to microscopic observation, the major elements impacting the strength of the oil-sticking layer were asphaltene aggregation and water droplet distribution. Finally, an evaluation method for predicting the minimum heavy oil-gathering temperature during high water-content cold transportation was presented. The findings of this study greatly contribute to understanding the mechanisms of cold transportation.

Numerical simulation on shell-side flow pattern transition and heat transfer of non-azeotropic refrigerant mixture

The non-azeotropic hydrocarbon refrigerant mixture flowing across shell-side of spiral wound heat exchanger is widely used in liquefied natural gas production industry. However, the phase-change heat transfer mechanism is still lack of thorough understanding. A numerical model is presented for simulating evaporation heat transfer of non-azeotropic hydrocarbon refrigerant mixture, CH4/C2H6, across multiple spiral wound tubes. Volume of Fluid model (VOF) was used to obtain liquid–vapor interface. The heat and mass transfer rates for each component were given as source terms. Thermophysical properties of the mixture were given using mixing laws in the literature. A flow pattern map was developed based on simulation results. The flow pattern transition and heat transfer were analyzed for the mixture with several component mixing ratios. With increasing vapor quality, pure ethane and methane-ethane mixture appear different flow patterns. The pure ethane has smoother liquid film on the tube wall than the methane-ethane mixture. The increasing of methane promotes the flow pattern transition. With vapor quality of 0.2–0.3, falling film flow transfers to shear flow. Shear flow transfers to spray flow for vapor quality of 0.7–0.8, where the heat transfer coefficient starts to decrease for methane-ethane mixture. For falling film flow, the heat transfer coefficient of pure ethane is higher than the methane-ethane mixture. The outcomes may help spiral wound heat exchanger design and evaluation for liquefied natural gas production.

Liquid-liquid colliding micro-dispersion and general scaling laws in novel T-junction microdevices

Colliding micro-dispersion has been extensively used to generate uniform droplets in liquid-liquid heterogeneous reactions. However, there are few reports on the colliding micro-dispersion. More importantly, only squeezing flow and big size droplets can be generated in the normal colliding micro-dispersion process, and even there exists no general scaling laws for droplet size. We have developed novel T-junction microdevices with new geometric structures to intensify the colliding micro-dispersion and proposed general scaling laws for droplet size in colliding T-junction microdevices. The droplet formation frequency was increased by more than 40 times, and a much wider operating range was allowed in the novel colliding T-junction microdevice. The flow regime distribution under high Weber number was explored for the first time and a complete liquid-liquid flow pattern map under colliding micro-dispersion has been also proposed. We also proved that jetting flow regime can be occurred under high Weber number and low capillary number.

Experimental study on boiling flow patterns of the zeotropic mixtures of R290/R600a in a horizontal smooth tube

The mixture of R290/R600a is a potential refrigerant alternative to R134a and the study of its flow pattern is the basis for designing heat exchangers in refrigeration systems. In the present study, the flow pattern and transition of the zeotropic R290/R600a two-phase mixtures are investigated experimentally using a 6 mm inner diameter horizontal smooth tube. Aiming at analyzing the influence of affecting parameters on the results, the variation range of the mass flux, heat flux, and saturation pressure were set to 63–190 kg m−2 s−1, 10.6–73.0 kW m−2, and 0.215–0.415 MPa, respectively. Three types of flow patterns were observed and recorded. The transitions between different flow patterns were compared with several flow pattern maps and none of them had enough accuracy. The reason can be attributed to the lack of consideration of the saturation pressure and the non-equilibrium characteristics in the boiling process of the zeotropic mixtures in the existing correlations. Consequently, a new model was proposed with a new dimensionless number F and Xtt. In the proposed dimensionless number F, the effects of inertia, gravity, shear tension, surface tension, heat flux, reduced pressure, and concentration were considered. The new flow pattern map showed satisfactory prediction accuracy and 94.9% of the experimental data could be accurately predicted.

Sub-Regimes of Air-Water Slug Flow Characteristics in Horizontal Pipes by Liquid Hold-up Model Correlated to Bubble Behaviours (LHmBb)

Sub-regimes of air-water slug flow in horizontal pipes have been characterized by a liquid hold-up model correlated to bubble behaviors (LHmBb). The LHmBB is composed of two sections which are the liquid hold-up model and bubble behavior investigations. The liquid hold-up model is developed based on the statistical analysis of the probability density function (PDF) to quantify the bubble distribution. The bubble behaviors are qualitatively investigated based on the high-speed camera and correlated to the quantified LH for the characterization of sub-regime of air-water slug flow. The LHmBB characterizes the sub-regime of air-water slug flow in a horizontal transparent acrylic pipe with an inner diameter of underwater and air superficial velocities of and, respectively. As a result, four sub-regimes are determined as Initially dispersed Bubbles (IdB), Low dispersed Bubbles (LdB), High dispersed Bubbles (HdB), and Dominantly dispersed Bubbles (DdB). The presence of bubbles determines the type of sub-regime by decreasing the number of bubbles and dispersing the bubbles mechanism. Moreover, the proposed LHmBb includes the correlation function to ease the prediction of the sub-regimes of air-water slug flow characteristics which leads to the enhancements of the two-phase flow pattern map in horizontal pipes.

Effect of Oil Viscosity on Flow Pattern Transition of Upward Gas-Oil Two-Phase Flow in Vertical Concentric Annulus

Summary Gas-oil two-phase flow usually occurs during gas influx into the wellbore annulus of deepwater drilling with oil-based drilling fluid or gas-oil production from the wellbore annulus. A flow pattern transition often is used in well control or in production parameter design. Related studies primarily have focused on gas-water two-phase flow, which is significantly different from gas-viscosity oil two-phase flow. We conducted experiments on a facility that included a flow section that was 13 000 mm long, with a 60-mm inner pipe and a 100-mm outer pipe in the annulus. A range of oil viscosities from 16 to 39 mPa∙s has been studied. The superficial gas and oil velocities varied from 0.55 to 17.077 m/s and from 0 to 0.414 m/s, respectively. A flow pattern was identified based on visualized analysis using electrical capacitance volume tomography (ECVT) and void faction wave analysis. Flow pattern maps of different viscosities were plotted based on measured data. Transition criteria based on Froude number and Archimedes number were established. The new model was compared with gas-water two-phase flow transition models and validated with experimental data. The effect of viscosity on flow pattern transition was revealed. The transition boundary of the bubble to slug flow and slug to churn flow both moved in the direction of smaller superficial gas velocity with an increase in oil viscosity. There may exist a critical viscosity value when churn flow transited to annular flow. When the viscosity was lower than this critical point, the above result was the same for churn to annular flow when the superficial oil velocity was low. With an increase in the superficial oil velocity, however, the boundary gradually changed to high superficial gas velocity as the oil viscosity increased. When the viscosity was larger than the critical point, the oil viscosity had a slight influence on the transition.

Experimental study on prediction model of wet gas pressure drop across single-orifice plate in horizontal pipes in the low gas phase Froude number region

The pressure drop prediction of wet gas across single-orifice plate in horizontal pipes had been solved satisfactorily under an annular-mist flow in the upstream of orifice plates. However, this pressure drop prediction is still not clearly determined when the upstream is in an intermittent flow or stratified flow, which is corresponding to a region of low Fr G (gas phase Froude number) in the flow pattern map of wet gases. In this study, the wet gas pressure drop across a single-orifice plate was experimentally investigated in the low Fr G region. By the experiment, the flow pattern transition in the downstream of single-orifice plates, as well as the effects of Fr G and Fr L (liquid phase Froude number) on Φ G (gas phase multiplier), were determined and compared when the upstream is in the flow pattern transition and the stratified flow region, respectively. Prediction performances were examined on the available pressure drop models. It was found that no model could be capable of jointly predicting the wet gas pressure drop in the low Fr G region with an acceptable accuracy. With a new method of correlating Fr G and Fr L simultaneously, new correlations were proposed for the low Fr G region. Among which the modified Chisholm model shows the best prediction accuracies, with the prediction deviations of Φ G being within 7% and 3% when the upstream is in flow pattern transition and stratified flow region, respectively.

Transition from plug/slug flow to annular flow in microchannel tube: A database and a model

A flow pattern map is a tool to predict flow patterns at a specific condition for a fluid. The map can also be used in heat transfer or pressure drop models when the detail of two-phase flow is important. In this work, a model for predicting flow patterns in microchannel tubes is proposed. Six fluids (R32, R1234yf, R134a, R1234ze(E), R1233zd(E), and R1336mzz(Z)) were measured in a 0.643 mm microchannel tube. The flow patterns are presented and reviewed. Comparison is made among the six fluids at 150 kg-m−2s−1. As saturation pressure is higher, the occurrence of transitional flow and annular flow delay to higher quality. In the model, the boundary from plug/slug flow to transitional flow is calculated based on the force balance of liquid shear, gravitation, and surface tension. It shows that when liquid velocity is large enough to counter the surface tension and gravitation, the liquid slug breaks down, and transitional flow occurs. The boundary from transitional flow to annular flow is calculated based on the kinetic energy ratio. It was suggested by Field and Hrnjak (2007), that when the ratio of vapor to liquid kinetic energy is between one to three, the annular flow starts. Five of the fluids except for R1336mzz(Z) in the database are used to build the flow pattern map. R1336mzz(Z) validates the flow pattern map.

Condensation Flow and Heat Transfer Characteristics of R410A in Micro-Fin Tubes and Three-Dimensional Surface Enhanced Tubes

Condensation heat transfer characteristics (using R410A as the working fluid) were studied experimentally to evaluate the heat transfer performance in copper and stainless-steel heat transfer tubes (smooth and enhanced). Experiments were carried out for a mass flux that varied from 250 to 450 kg m−2 s−1, at a saturation temperature of 318 K. Single-phase heat balance verification found that the heat loss is less than 6%, and the deviation between single-phase experimental results and various prediction correlations is less than 15%. Additionally, tube side condensation flow patterns were observed and recorded. Experimental results found that the enhancement ratio of the condensation heat transfer coefficient (enhanced tube/smooth tube) of the three-dimensional surface (1EHT) tube is in the range of 1.15~1.90, while the ratio of the micro-fin (HX) tube is in the range of 1.18~1.80. Heat transfer performance is affected by material conductivity, with the thermal conductivity of the smooth tube slightly affecting the heat transfer performance; larger heat transfer enhancements are produced in the enhanced tubes. At a low mass flow rates and vapor qualities, the flow pattern is a stratified wavy flow, while at higher mass flow rates and vapor qualities, the flow pattern is an annular flow (with the area in the enhanced tube being larger than the area of a smooth tube). Flow patterns in the smooth tube are consistent with the predicted values shown in previously reported flow pattern maps. A flow pattern diagram for condensation heat transfer in enhanced tubes is presented as part of this study. The condensation heat transfer coefficient increases with an increase in mass flow. When the mass flow rate increases, the turbulence of the liquid flow increases and the liquid film becomes thinner; thermal resistance is reduced and the heat transfer coefficient increases. Heat transfer values at lower mass velocities increase slightly with increasing mass flux values; however, at higher mass flux rates the heat transfer increase is larger than that at low mass flux values. Finally, tubes produced from high thermal conductivity materials produce larger heat transfer performance gains than the gains found in smooth tubes; small diameter tubes produce larger gains than larger diameter tubes.

Two-phase heat transfer correlations in three-dimensional hierarchical tube

Development of novel enhanced surface tubes is an important way to advance two-phase flow heat transfer. To make correlations of two-phase flow heat transfer in enhanced tubes with acceptable prediction has been a challenge for many years. The paper presents a method: two-phase heat transfer correlations in enhanced tubes are directly developed through existing two-phase heat transfer smooth-tube models by introducing several modifying factors and dimensionless numbers. An enhanced heat transfer tube containing staggered arrays of three-dimensional dimples and secondary petal-shaped protrusions (EHT) is one of the most complicated internal surface-tube configurations on the market. Visualizations of flow patterns and measurements of heat transfer coefficients of two-phase flow using refrigerant R410A in smooth and EHT tube are conducted. Detailed visualization experiments during two-phase flows show good agreements between flow regimes and flow-pattern maps in smooth and EHT tube. The equation of continuity is adopted to provide understanding of the mechanism of the agreements. Both theoretical analysis and experimental studies support the method. As a result of using it, new two-phase heat transfer correlations are developed in enhanced tubes as the EHT tube is an example. Flow boiling correlation can predict data points within +10% to -20% and flow condensation correlation can predict data points within ±10% in the EHT tube.

Machine Learning Algorithms for Flow Pattern Classification in Pulsating Heat Pipes

Owing to their simple construction, cost effectiveness, and high thermal efficiency, pulsating heat pipes (PHPs) are growing in popularity as cooling devices for electronic equipment. While PHPs can be very resilient as passive cooling systems, their operation relies on the establishment and persistence of slug/plug flow as the dominant flow regime. It is, therefore, paramount to predict the flow regime accurately as a function of various operating parameters and design geometry. Flow pattern maps that capture flow regimes as a function of nondimensional numbers (e.g., Froude, Weber, and Bond numbers) have been proposed in the literature. However, the prediction of flow patterns based on deterministic models is a challenging task that relies on the ability of explaining the very complex underlying phenomena or the ability to measure parameters, such as the bubble acceleration, which are very difficult to know beforehand. In contrast, machine learning algorithms require limited a priori knowledge of the system and offer an alternative approach for classifying flow regimes. In this work, experimental data collected for two working fluids (ethanol and FC-72) in a PHP at different gravity and power input levels, were used to train three different classification algorithms (namely K-nearest neighbors, random forest, and multilayer perceptron). The data were previously labeled via visual classification using the experimental results. A comparison of the resulting classification accuracy was carried out via confusion matrices and calculation of accuracy scores. The algorithm presenting the highest classification performance was selected for the development of a flow pattern map, which accurately indicated the flow pattern transition boundaries between slug/plug and annular flows. Results indicate that, once experimental data are available, the proposed machine learning approach could help in reducing the uncertainty in the classification of flow patterns and improve the predictions of the flow regimes.

Contamination assessment of soil and groundwater of a deactivated dumpsite in Brazil

The final disposal of solid waste in dumpsites can result in the migration of leachate components through the soil, contaminating it as well as the groundwater. The purpose of this manuscript was to analyze the contamination of a dumpsite along with three unlined leachate ponds that operated for approximately 25years. Soil, surface water from three leachate lagoons, and groundwater samples were collected. Chemical analyses such as chloride, ammonia nitrogen, and total organic carbon were performed. The present work also aimed at elaborating the local flow pattern map and the assessment of subsoil. The results showed local subsoil mostly clayey, also occurring a region of sandy predominance, and great variation of rocky outcrops depth. The groundwater flow occurs from the waste towards one of the leachate lagoons. The leachate lagoon located closer to deposited area presented the highest concentration of all contaminants measured. Groundwater and soil showed low ammonia nitrogen with a maximum value of 2mg.L-1. Elevated chloride levels were detected in all matrices studied. In soil depth, the concentration varied ​​between 17 and 1270mg.L-1 and in groundwater between 843 and 3,252mg.L-1. Results suggest the migration of leachate components through the local soil. The concentration of total organic carbon measured in soil was of 10-982mg.L-1, suggesting its natural presence.

Effect of surfactants on drop formation flow patterns in a flow-focusing microchannel

The formation of droplets in an immiscible liquid in the presence of different surfactants was studied experimentally using a flow-focusing microchannel. A low viscosity silicone oil (4.6 mPa s) was used as the continuous phase and a mixture of 48% w/w water and 52% w/w glycerol was the dispersed phase. A cationic (CMCDTAB = 20 mM), an anionic (CMCSDS = 11 mM), and a non-ionic (CMCTX100 = 3.5 mM) surfactant were added in the aqueous phase, at several concentrations. Five patterns of drop formation were identified, namely squeezing, dripping, jetting, threading and tip streaming/jetting, whose boundaries were affected by the surfactant type and concentration. Using dynamic interfacial tension values, it was possible to plot a universal flow pattern map with the capillary numbers of the two phases as coordinates, where the transition boundaries between the dripping and the jetting patterns collapsed for all fluid systems considered, including the solutions with and without surfactants.

Application of Flow Pattern Map for Solving Liquid Loading Problems in Well AA

About two-thirds of fields that exist in the world right now are classified as mature fields. Mature fields usually have a lot of problems that occurred during production. Mature field is classified as field which has produced as much as fifty percent of their established proved plus probable resources estimation or has produced for more than twenty-five years. Empowerment of mature well can be increasing the efficiency of well productivity. Productivity decline can be caused by low maintenance of flow pattern in a well. The other problems which commonly happen is decreasing of reservoir pressure of the well, liquid loading, slugging, and high water cut percentage. Several methods can be used to solve a lot of problems in mature well. The methods can be applied to get an optimum well productivity result. This study shows that Well AA has a slug flow pattern using matching method on a flow pattern diagram. Gas injection and velocity string are applied to solve the problems for Well AA. Gas rate of about 12 MMSCFD is obtained with gas injection method to get annular flow pattern and three different sizes of velocity string are used which are 1.25 inch, 1.5 inch, and 2.0625 inch with churn flow pattern. It is identified that the use of velocity string of 1.25 inch is the optimum method for Well AA.