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SummaryIntermittent flow is one of the most complex flow regimes in horizontal pipes. Various studies have classified this regime as two distinct subregimes: plug and slug flow. This classification has been made based on flow observations. In this work, the behavior of several flow parameters that characterize plug and slug flow are presented. Data from eight published works in the open literature were collected and studied to explain the behavior of both regimes. These data include pressure drop, void fraction, and slug frequency, as well as the lengths of liquid slugs and elongated bubbles for slug and plug regimes.It is observed from the evolution and analysis of these parameters that plug and slug flows have several different distinct features and should be considered as two separate regimes for the empirical modelization of the hydrodynamic parameters. The mixture Froude number, and to a lesser extent the liquid superficial velocity to gas superficial velocity ratio, seem to have significant impacts on the plug-to-slug flow transition.

Gas-liquid flows are affected strongly by both the liquid and gas properties and the pipe diameter, which control features and the stability of flow patterns and their transitions. For this reason, empirical models describing the flow dynamics can be applied only to limited range of conditions. Experiments were carried out to study the behaviour of air passing through silicone oil (360 Pa.s) in 240 mm diameter bubble column using Electrical Capacitance Tomography and pressure transducers mounted on the wall. These experiments are aimed at reproducing expected conditions for flows including (but not limited to) crude oils, bitumen, and magmatic flows in volcanic conduits. The paper presents observation and quantification of the flow patterns present. It particularly provides the characteristics of gas-liquid slug flows such as: void fraction; Taylor bubble velocity; frequency of periodic structures; lengths of liquid slugs and Taylor bubbles. An additional flow pattern, churn flow, has been identified. The transition between slug and churn has been quantified and the mechanism causing it are elucidated with the assistance of a model for the draining of the liquid film surrounding the Taylor bubble once this has burst through the top surface of the aerated column of gas-liquid mixture. It is noted that the transition from slug to churn is gradual.

A two-phase flow predictive model with the integration of conservative level-set method (LSM) and Carreau-Yasuda constitutive equation was developed herein. The LSM was chosen as a potential interface capturing scheme for elucidating the interfacial phenomena including insight into the mechanism of shear-thinning droplets. In present paper, the dynamics of shear-dependent droplet emergence, growth, detachment and translocation in a Newtonian microsystem were examined via computational fluid dynamics (CFD) analysis. Dilute sodium carboxymethylcellulose (Na-CMC) solution was treated as dispersed phase (70 mPa.s η o C*˜0.40 wt%). This striking behaviour highlights the importance of rheological effects in flows with a shear-dependent fluid under various flow conditions. The viscous effect of Na-CMC fluids substantially affects the manipulation over the droplet pinch-off time and production rate. Thus, it necessitate the control of the shear rate by adjusting the flow conditions and aspect ratio of microchannels.

T-junctions are often used in offshore platforms to partially separate gas from produced fluids. Poorly designed T-junctions frequently produce very high liquid (oil and/or water) carryovers, causing major issues to the downstream equipment train which is not designed to handle excessive liquid. This paper reports the liquid carryover experiments in T-junctions using five different side to main arm diameter ratios under slug flow regime. The obtained phase separation curves can be divided into two component variables; liquid-carryover threshold and peak liquid carryover. The experiments demonstrate that with a decrease in diameter ratio both of these variables decrease. Yet, for superior multiphase flow separation, a high liquid carryover threshold and a low peak liquid carryover are required. Hence, the generally accepted rule that a reduction in diameter ratio improves the phase separation is revealed to be an over-extrapolated statement. The novel findings of this work are: 1) for optimum flow splitting under slug flow conditions, the diameter ratio should be kept between 1 and 0.67, while the diameter ratio 0.67 was found to be most suitable; 2) two correlations were developed for predicting two-phase slug flow separation in different diameter ratio T-junctions. These correlations offer beneficial guidance and clarifications for a number of oil and gas flowline and pipeline applications.

A conservative level-set method (LSM) embedded in a computational fluid dynamics (CFD) simulation provides a useful approach for the studying the physics and underlying mechanism in two-phase flow. Detailed two-dimensional (2D) computational microfluidics flow simulations have been carried out to examine systematically the influence of different controlling parameters such as flow rates, viscosities, surface wettability, and interfacial tensions between two immiscible fluids on the non-Newtonian shear-thinning microdroplets generation process. For the two-phase flow system that neglects the Marangoni effect, the breakup process of shear-thinning microdroplets in cross-flowing immiscible liquids in a microfluidic device with a T-shaped geometry was predicted. Data for the rheological and physical properties of fluids obeying Carreau-Yasuda stress model were empirically obtained to support the computational work. The simulation results show that the relevant control parameters mentioned above have a strong impact on the size of shear-thinning droplets generated. Present computational studies on the role and relative importance of controlling parameters can be established as a conceptual framework of the non-Newtonian droplet generation process and relevant phenomena for future studies.

In this paper, the phase behaviour of a cellulose nanocrystal (CNCs) dispersion in sulphuric acid solutions was investigated, aimed at the development of an energy efficient separation method for this mixture. The system in consideration was a mixture of 30 wt% aqueous sulphuric acid (ρl = 1219 kg/m3) containing 12.6 mg/ml of cellulose nanocrystals (CNCs) (ρs = 1590 kg/m3, volume fraction of CNCs less than 1%). This volume filling mixture was obtained directly from a CNC extraction process, as obtained after the hydrolysis of cotton using 64 wt% sulphuric acid at ca. 45 ̊C for 45 minutes (this condition was required for the extraction of CNCs from cotton) followed by quenching the hydrolysis with water. The CNCs form the desired product and need to be separated from the acid that can then be recycled. Conventionally this separation has been difficult and requires a large input of energy. This work addresses this problem by investigating into the phase behaviour and physicochemical and hydrodynamic character of this mixture. This understanding led to the development of a very energy efficient separation mechanism for this mixture, which is 5 orders of magnitude more energy efficient than the most widely used centrifugation systems.

The electric power generation and oil/gas production industries have a strong interest in the physical characterization of conducting and non-conducting liquid films that are formed during the flow of liquids in pipes. Conducting and non-conducting liquid films do not lend themselves to the same characterization techniques due to the different requirements originating from their electrical properties. Techniques based on the use of ultrasound are extremely attractive for that purpose as they do not depend on the electrical properties of the liquid and are also non-invasive. This paper presents the application of ultrasonic techniques for measuring the thickness of wavy thin liquid films ( 0.5 mm a time of flight method was utilized whereas for a film thicknesses

A linear dynamic model of water droplet deformation in the presence of an electric field has been developed. Analytical solutions of the differential equation of motion are provided with different waveforms as forcing terms, namely in the case of half-sinusoidal, square and sawtooth waves. The main dimensionless groups are identified as a result of this analysis. The predictions of the model are compared with some data of droplet deformation available in the literature. The calculations based on this model show that the waveform affects the response of the droplet to the electric field stimulus. Resonance is possible only when the droplets are sufficiently large (i.e. for Ohnesorge number less than 1). The oscillation amplitude decreases rapidly with the electric field frequency. A qualitative comparison with some experiments of droplet-interface coalescence available in the literature has also been addressed, suggesting a correlation between the formation of secondary droplets and the amplitude of oscillation of the mother droplet. The outcomes of this analysis can be useful for the selection of the best operating conditions to improve the electrocoalescence process efficiency, as they can provide guidelines to the choice of the most suitable electric field parameters. 2016 Institution of Chemical Engineers This work was made possible by NPRP grant #5-366-2-143 from the Qatar National Research Fund (A Member of The Qatar Foundation). The statements made herein are solely the responsibility of the authors. Scopus

Distillation and chemical processing under vacuum is of immense interest to petroleum and chemical industries due to lower energy costs and improved safety. To tap into these benefits, energy efficient reboilers with lower maintenance costs are required. Here, a horizontal thermosyphon reboiler is investigated at subatmospheric pressures and low heat fluxes. This paper presents detailed experimental data obtained using Wire Mesh Sensor in a gas-liquid flow with heat transfer as well as temperatures, pressures and recirculation rates around the loop. Flow regimes which have been previously identified in other systems were detected. The nature of the instability which underpins the mechanisms involved and conditions aiding instability are reported. Churn flow pattern is persistently detected during instability. The nature of the instability and existence of oscillatory churn flow are interconnected

Intermittent flows in vertical pipes occur in many industrial settings including power generation and downstream oil-and gas production. This type of flows include cap bubble, slug and churn flow regimes. These regimes are of interest as downstream processes and control may heavily depend on the intermittency of the inflow. There are a number of correlations that predicts the features in such flows in vertical pipes. Most of the correlations were developed for air and water fluid pair for slug flow regime in vertical pipes with 25 to 50 mm inner diameter. In this paper, an attempt has been made to assess the suitability of several of these correlations specific to slug flow regime for a fluid pair that is different to air-water system. In this work, air-silicone oil flow development was experimentally investigated in a vertical pipe with an inner diameter of 68mm. A Wire Mesh Sensor (WMS) and an Electrical Capacitance Tomography (ECT) sensor were installed in series at four locations (15D, 30D, 45D and 65D) downstream of the mixing section. The flow was visually observed using a high speed camera. The void fraction time series obtained from the WMS and the ECT were used to establish the flow characteristics such as slug length, slug frequency, void fraction in liquid slugs and Taylor bubble velocity. A comparison showed that the void fraction measurements using ECT and WMS are in good agreement. Axial measurements shows that the flow development beyond 45D is minimal. Change in physical properties of the liquid phase is responsible for the deviation associated with the existing slug flow models, particularly those developed to predict the gas holdup in liquid slugs.

The focus of this work is to examine the effect of flow rate ratio (quotient of the dispersed phase flow rate over the continuous phase flow rate) on a regime transition from squeezing to dripping at constant capillary numbers. The effect of the flow rate ratio on the volume of droplets generated in a microfluidic T-junction is discussed, and a new scaling law to estimate their volume is proposed. Existing work on a regime transition reported by several researchers focuses on the effect of the capillary number on regime transition, and the results that are presented in this paper advance the current understanding by indicating that the flow rate ratio is another parameter that dictates regime transition. In this paper, the transition between squeezing and dripping regimes is reported at constant capillary numbers, with a transition region identified between squeezing and dripping regimes. Dripping is observed at lower flow rate ratios and squeezing at higher flow rate ratios, with a transition region between the two regimes at flow rate ratios between 1 and 2. This is presented in a flow regime map that is constructed based on the observed mechanism. A scaling model is proposed to characterise droplet volume in terms of flow rate ratio and capillary number. The effect of flow rate ratio on the non-dimensional droplet volume is presented, and lastly, the droplet volume is expressed in terms of a range of parameters, such as the viscosity ratio between the dispersed and the continuous phase, capillary number, and the geometrical characteristics of the channels.

In this paper, the separation of sulphuric acid from a suspension of cellulose nanocrystal by manual shaking is described. Cellulose nanocrystals are prepared from acid hydrolysis of cotton using 64 wt% sulphuric acid at ca. 45 °C for 45 minutes. After the hydrolysis was complete, water was added to dilute the mixture to a resulting concentration of 30 wt% of the acid. This mixture was shaken rigorously in a closed container and after 48 hours, separation occurs such that cellulose nanocrystals float, with the bubbles introduced by the shaking, to give clear acid solution at the bottom. This shaking-floating process is repeatable for several cycles after the acid was removed from the bottom and more water was added. Using this simple process, the total acid recovery of > 90% has been achieved, and the concentration of all the acid recovered combined was 17.5 wt%. This work demonstrates a method that allows energy efficient and up-scalable separation of cellulose nanocrystals from the acidic suspension from which it was extracted.

This article investigates impact of substituting fumed silica with a cellulosic-crystal innovation in a commercial Vacuum Insulated Panel (VIP) core. High building performance demands have attracted VIP technology investment to increase production capacity and reduce cost. In building retrofit VIPs resolve practical problems on space saving that conventional insulations are unsuitable for. Three challenges exists in fumed silica: cost, low sustainability properties, and manufacture technical maturity. Cellulosic nano-crystal (CNC) technology is in its infancy and was identified as a possible alternative due to a similar physical nano-structure, and biodegradability. The study aim was to determine a performance starting point and establish how this compares with the current benchmarks. Laboratory cellulosic-crystal samples were produced and supplied for incorporation into commercial VIP manufacture. A selection of cellulosic-panels with core densities ranging 127–170 kg/m3 were produced. Thermal conductivities were tested at a pressure of 1 Pa (0.01 mBar), with the results compared against a selection of fumed silica-VIPs with core densities ranging 144–180 kg/m3. Conductivity tests were then done on a cellulosic-VIP with 140 kg/m3 density, under variable pressures ranging 1–100,000 Pa (0.01–1000 mBar). This investigated panel lifespan performance, with comparisons made to a fumed silica-VIP of similar core density. Manufactured cellulosic-samples were found unsuitable as a commercial substitute, with performance below current standards. Areas for cellulosic nano-material technology development were identified that show large scope for improvement. Pursuit could create a new generation of insulation materials that resolve problems associated with current commercial versions. This is most applicable in building retrofit where large ranges of domestic and commercial cases are marginalised from their construction markets due to impracticalities and high upgrade costs. This being a problem in multiple economies globally.

Measurements of the composition of multiphase flows, especially water-cut in oil-water flow, is a frequently encountered problem in the petroleum industry. New techniques that can offer improvements towards that are continuously sought and the use of microwave sensors is considered very promising. The current paper reports on the performance of a microwave cylindrical resonator, integrated into a multiphase flow experimental facility, used to determine water-cut in an upward flowing oil-water mixture. The performance and suitability of two microwave resonant modes (TM010 and TM110) was studied. The TM110 mode was found to be less dependent on the spatial phase distribution of the oil-water flowing mixture and provided more consistent results across a broader flow regime. The relative errors between the predicted and actual water-cut were from −6.53% to 9.16% and relative errors of 78% of the total data points were inside −5% to 5%. The results suggest that appropriate sensor design and careful selection of the operating frequency/resonant pattern can offer a powerful technique for real time, on-line and non-destructive determination of water-cut in multiphase flow systems.

Ionic liquids are liquid salts at low temperatures (normally less than 100°C). They are powerful solvents with very low vapour pressure. They have great potentials in many applications such as gas absorption and chemical synthesis. However, they are expensive. This limits extensive studies towards establishing phenomenological models. To address this limitation, an analogue liquid, with properties similar to an ionic liquid, has been identified which on the grounds of cost and safety appears to be suitable. In this paper, the hydrodynamic behaviour of an ionic liquid in a bubble column is compared with those of water and other liquids with similar physical properties. Average gas holdup, bubble coalescence, bubble size and specific interfacial area with different liquids are examined. Gas hold-up was determined by monitoring the change of conductivity between two flush mounted rings. The differences in bubble size and coalescence are revealed by analysing the stills taken from a high speed video camera. The dominant flow pattern in a small diameter column with ionic liquids or other fluids having similar viscosity is slug flow. The small bubbles in the liquid slugs make a smaller contribution to the specific interfacial area than Taylor bubbles. It is observed that Taylor bubbles can coalesce. The hydrodynamics of an ionic liquid in a bubble column can be estimated from that of a fluid with similar physical properties.

Thermosyphon systems have been the subject of several studies due to instability issues negating their attractive high heat fluxes, low temperature gradients requirement, reduced weight and simple, pump-less system. There is a dearth of design data for horizontal thermosyphons hence the transient behaviour of a horizontal thermosyphon reboiler loop has been studied experimentally here. Most studies here have explored and defined geysering instability in single and parallel vertical columns with closed bottom end. This study presents geysering detected in 51 mm riser of a horizontal thermosyphon reboiler. Experiments were undertaken with water as the process fluid and steam as the heating medium, using 6 – 20 kW/m2 heat flux, 1.165 – 1.265 m static head and a range of recycle flow restrictions. Pressure, temperature and flow rate data were continuously logged at 100Hz. Flow rate was examined as a significant indicator of instability since it is the parameter with highest and varied amplitude of oscillation. Heat flux is most significant for stability: above 20 kW/m2, the system is stable; between 11 – 20 kW/m2 there are varying degrees of sustained oscillations and below 11 kW/m2 flow rate is low. Reboiler inlet flow restriction also stabilises the system by reducing the flow rate to such a level that heat transfer rate can maintain a consistent vapour product rate. Static head influences the recirculation rate and subcooling at the reboiler inlet, but has a secondary effect on stability. Churn flow pattern is detected in the riser as a characteristic aftereffect of the cyclic instability.

The coalescence of a water drop in a dieletric oil phase at a water layer interface in the presence of an electric field is simulated by solving the Navier-Stokes and charge conservation equations with the finite element method. The proprietary software Comsol Multiphysics is used for this purpose. The interface between the oil and water phases is tracked by implementing a level-set approach. Preliminary simulations to assess the sensitivity of the model with respect to some input parameters are reported. In particular, the calculations are very sensitive to the size of the computational grid elements and the interface thickness parameter. Nevertheless, the model is able to reproduce the occurrence of partial coalescence for the experimental case examined. Good quantitative agreement can be obtained if the parameters are suitably tuned.IntroductionThe application of an external electric field is a technique currently used in the oil industry to promote migration and enhance coalescence of droplets in the water-in-oil emulsions formed during the oil extraction process [1, 2]. It is generally acknowledged that the effect of the electric field is to increase film drainage and hence the thinning rate between two coalescing droplets [1]. However, an excessive value of the field strength can reduce the quality of coalescence, as secondary droplets form [3-6] as a result of an incomplete coalescence process. The efficiency of the process would be significantly improved if the operating conditions to prevent partial coalescence from occurring were known. In this regard, it has been shown [5] that the ratio between the volume of the secondary droplet formed and the initial drop volume can be described as a function of a dimensionless number which is the product of the Weber and Onhesorge numbers. The same authors have recently addressed the effect of the electric field type on the coalescence quality. Their experimental results have revealed that the volume of the secondary droplet decreases if pulse-DC fields are applied, leading to the transition from partial to complete coalescence under certain conditions [6]. These findings can have an important impact on the development of compact electrocoalescer designs. The aim of this work is to provide a mathematical description of the phenomenon. For this purpose, a finite element approach combined with the level-set method [7] is adopted in this work to analyse the process of partial coalescence. To the authors' knowledge, there are no attempts at predicting numerically the occurrence of incomplete coalescence in the presence of an electric field. The proprietary software Comsol Multiphysics (Comsol, Sweden) software has been used for this purpose, in an attempt to assess the capability of the proposed approach to reproduce and analyses the phenomenon.Model EquationsA level-set approach is employed to track the boundaries between different phases. The evolution of the boundary is described by the equation: where is a smooth step function which varies from 0 to 1 across different phase domains, is a reinitialization parameter which gives stability to the solution and is related to the thickness of the interface. The fluid velocity is denoted by u (bold letters denote vectors). It should be noted that Eq. (1) is the non-conservative formulation of the level-set equation, which attains convergence more easily but introduces some errors in the calculations. However, the non-conservative formulation is more suitable for a rapid test of the model capabilities. Navier-Stokes and continuity equations are solved using average physical properties for the two phases: where and are the volume fraction weighted density and viscosity, which differ from the pure liquids properties only at the interface. In eq. (2), forces due to surface tension and induced by the electric field are included. The force due to surface tension is calculated as: where is the surface tension coefficient, the local surface curvature, n the outward pointing interface normal vector and d is a smooth approximation of the Dirac function which is non-zero only at the interface. The electric force is calculated from the divergence of the Maxwell tensor: where is the average permittivity. The electric field E is computed by satisfying the charge conservation equation: where is the average conductivity. With reference to the computational domain depicted in Fig. 1, the following boundary conditions have been applied in order to solve this set of equations: the upper boundary is kept at a fixed electric potential while the opposite one is earthed and no-slip conditions are prescribed for both boundaries; the domain is axisymmetric; slip conditions are considered on the right boundary, as this allows significant reduction of the simulation domain. The properties of the two liquids correspond to the sunflower oil/water system investigated experimentally by Mousavichoubeh et al. [5] and are reported in Table 1. The interfacial tension is equal to 25 mN mm–1, as measure experimentally. In order to assess the effect of and the mesh element size, the following case is analysed. The initial drop size is 1.196 mm and the electric field strength is 373 V mm–1. Under these conditions, partial coalescence occurs and the ratio between the volume of the secondary droplets formed and the initial drop volume is equal to about 0.088, as measured by Mousavichoubeh et al. [3].ResultsThe calculated values of this ratio are reported in Table 2. For all cases, the reinitialization parameter is set equal to 1 m/s, which is comparable to the maximum fluid velocity in the system. The results shown in Table 2 reveal that the tuning of the interface thickness, is strictly connected to the level of mesh refinement (hmax/D is the maximum element size in the computational grid). With, the calculated volume of secondary droplets becomes invariant with the grid element size when this is sufficiently small. In this case the volume ratio of the secondary droplet to that of the initial drop is very close to the experimental value. However, the phenomenology described in the two simulations is different, and the results are compared in Figs. 2 and 3. The value of does not produce realistic results and convergence fails in a number of cases of the behaviour observed experimentally is also reported in Fig. 4. The numerical results obtained with reproduce the experimental observations exactly, whereas with a jet-like behavior is reproduced. This may be due to the larger interface thickness, which makes the droplet more deformable and the break-up process more difficult, although the predicted volume ratio is very close to the experimental value. problems, and a solution is obtained only for, which, however, provides a higher value of the secondary droplet volume formed as compared to the experiments. Decreasing further the grid element size to 0.02 causes non-convergence again, as should usually be smaller than the maximum grid size. This requirement becomes more critical when is small.ConclusionsA model to describe partial coalescence in the presence of an electric field has been proposed. It has proved to be capable of reproducing the phenomenon observed in experimental work previously reported in the literature. A satisfactory quantitative agreement can be achieved by the right selection of the interface thickness parameter and computational grid size. This study constitutes the basis for the development of a reliable mathematical description which can be used for the design of a compact and efficient electrocoalescer.AcknowledgementThis work was made possible by NPRP grant #5-366-2-1435-366-2-143 from the Qatar National Research Fund (A Member of The Qatar Foundation). The statements made herein are solely the responsibility of the authors.References[1] Mhatre, S., Vivacqua, V., Ghadiri, M., Abdullah, A.M., Al-Marri, M.J., Hassanpour, A., Hewakandamby, B., Azzopardi, B., Kermani B., 2015. Electrostatic phase separation: A review. Chem Eng Res Des, 96, 177-195.[2] Vivacqua V., Mhatre S., Ghadiri M., Abdullah A. M., Hassanpour A., Al-Marri M. J., Azzopardi B., Hewakandamby B., Kermani B. (2015). Electrocoalescence of water drop trains in oil under constant and pulsatile electric fields Chem Eng Res Des, doi:10.1016/j.cherd.2015.10.006.[3] Aryafar H., Kavehpour H.P. (2009). Electrocoalescence: Effects of DC electric fields on coalescence of drops at planar interfaces, Langmuir 25 (21), 12460-12465.[4] Mousavichoubeh M., Ghadiri M. and Shariaty-Niassar M., 2011a. Electro-coalescence of an aqueous droplet at an oil–water interface, Chem Eng Process, 50, 338-344.[5] Mousavichoubeh M., Shariaty-Niassar M. and Ghadiri M., 2011b. The effect of interfacial tension on secondary drop formation in electrocoalescence of water droplets in oil, Chem Eng Sci, 66, 5330-5337.[6] Mousavi, S.H., Ghadiri, M. and Buckley, M., 2014. Electro-coalescence of water drops in oils under pulsatile electric fields. Chem Eng Sci, 120, 130-142.[7] Sethian, James A. (1999). Level Set Methods and Fast Marching Methods: Evolving Interfaces in Computational Geometry, Fluid Mechanics, Computer Vision, and Materials Science. Cambridge University Press. ISBN 0-521-64557-3.

The results of an experimental study on droplet impactions in the flow of a gas-sheared liquid film are presented. In contrast to most similar studies, the impacting droplets were entrained from film surface by the gas stream. The measurements provide film thickness data, resolved in both longitudinal and transverse coordinates and in time together with the images of droplets above the interface and images of gas bubbles entrapped by liquid film. The parameters of impacting droplets were measured together with the local liquid film thickness. Two main scenarios of droplet-film interaction, based on type of film perturbation, are identified; the parameter identifying which scenario occurs is identified as the angle of impingement. At large angles an asymmetric crater appears on film surface; at shallow angles a long, narrow furrow appears. The most significant difference between the two scenarios is related to possible impact outcome: craters may lead to creation secondary droplets, whereas furrows are accompanied by entrapment of gas bubbles into the liquid film. In addition, occurrence of partial survival of impacting droplet is reported.

Multiphase flows are common in industrial settings and bends in pipe lines cannot be avoided due to space limitations. Gas-liquid two phase flows could form material discontinuities that could have adverse effect on productivity and the pipe network due to sudden variations resulting due to the rapid momentum flux variations at fittings such as bends. Research into gas-liquid flow and bends can be motivated by the effect of the bend on the flow downstream of it which could alter the flow pattern occurring and the performance of downstream equipment. Alternatively, the interest might come from what occurs in the bend itself, there could be dryout of the film on the walls and consequent damage to the heat transfer equipment. Here we present measurements made with a number of accurate and fast responding sensors on three cases, two on the effect of the bend and one considering effects in the bend. The results show that the flow transformations occur in two phase flows depending on the orientation of the bend and the change could be captured using fast sweeping measurement techniques. We present the evidence of effectiveness of several types of measurement techniques that could fit into various combinations of phases. The results, point to how to achieve certain flow patterns. Also recommendations are provided regarding the position of any sensor installed to determine flow pattern.