Academic literature on the topic 'Superficial air velocity'

The solid-liquid mass transfer rate at a stack of circular fin surfaces in a bubble column was investigated. A diffusion-controlled dissolution technique of copper in an acidified chromate solution was employed. Variables studied included the number of actively exposed fins ranging from 5 to 20, pertinent physical properties of the solution, and air superficial velocity. Experimental data showed that the rate of the diffusion-controlled mass transfer increases with increasing superficial air velocity and decreases with increasing chromate solution acid concentration. Moreover, at relatively low superficial air velocity, increasing the number of actively exposed fins results into a continuous increase in the mass transfer coefficient. At relatively higher superficial air velocity, however, the mass transfer coefficient decreases in the 5 to 10 range of actively exposed fins and then reverts to increase in the 15 to 20 range.

The flow characteristics in a ring-shaped microchannel with an inner diameter of 1 mm were studied in two-phase flow systems with air-water, air-glycerol aqueous solution and air-ethanol aqueous solution using the differential pressure method. The effects of liquid properties (surface tension and viscosity) and gas/liquid superficial velocity on frictional pressure drop were discussed. The experimental results show that the frictional pressure gradient increases with the increase of superficial gas velocity, superficial liquid velocity and liquid viscosity, and increases with the decrease of liquid surface tension, which has a good agreement with the literature values. The friction pressure drop data are compared with the classical models and correlations in literature, and a reliable correlation is proposed for prediction of two-phase friction coefficient in microchannels.

The experimental data for phase separation of the air-water mixture in a T-Junction with the expander section after the branch arm is presented in this work. The main and run arms of the T-junction are directed along the horizontal plane with the branch arm positioned in the vertical plane. The diameter of the main arm is 74 mm, with diameter ratio(s) of, 0.67, and 0.33 in relation to branch arm. At the inlet section of the T-junction, the flow regimes generated were stratified, stratified wavy and slug flow. At the inlet, the air and water superficial velocities are in the range of 0.25 - 0.140 m/s and 0.14-0.78 m/s respectively. The effect of the expander section after the branch arm, the air superficial velocity USA and water superficial velocity USw on liquid carryover (WL3/WL1)max in branch arm have been studied. Based on the experimental data obtained for T-junction with expander section, complete phase separation of air and water was observed in stratified and stratified wavy flow for all superficial velocities and improved phase separation for slug flow. In slug flow, increasing the liquid superficial velocity improves the phase separation but increasing the gas velocity decreases the phase separation. Finally, the volume weighted phase in this new T-junction design is compared with the phase separation data of a simple T-junction.

At the different elevation of the spouted bed riser pipe layout pressure measuring point, each point below is equipped with purge air, avoid the granular poly group on the pressure measuring point, by adjusting the frequency of the bandpass filter, guarantee the accuracy of pressure measurement. Through experimental study, under the low superficial air velocity, riser pipe pressure pulsation standard deviation has a linear relationship with the superficial air velocity and obey the chi-square distribution, based on the above found , rising pipe pressure pulsation standard deviation forecast the incidence of granular poly group is proposed in this paper. By comparing rising pipe pressure pulsation standard deviation forecast method with conventional average pressure drop forecast method found, rising pipe pressure pulsation standard deviation has higher superficial air velocity recognition rate and less response time when the granular poly group,achieves the spouted bed fast forecast the granular poly group phenomenon.

Experimental observations of particle capturing through the biological aerated filter bed indicated that air flow rate plays an important role in head loss development by influencing the suspended solids distribution along the depth of the bed as well as the morphology of the deposits. The active height for the SS removal prolonged with the increasing of the air velocity based on the mechanism of first-order kinetics. With the increasing of the superficial air velocity, the effluent SS concentration and the time need to reach the stead-states after backwash both increased. The value of the SS spike in the effluent after backwash at superficial air velocity of 27 m/hr was nearly twice as much as that of 5.4m/hr. Distribution of the deposits at higher air velocity was more uniform. Deposits at lower velocity with air flow rate produced higher head loss gradient. The headloss increased with the increasing of deposits and the increase rate was faster when the deposits exceeded higher value.

Bubbles coalescence frequency and the transition concentration in a dispersion column were studied experimentally by using ethanol-water mixture as a liquid phase and air as a gas phase. The study was devoted to express the effect of the liquid properties on the performance of the dispersion column, and the experimental work was designed for this purpose, where the range of weight percent of ethanol in water, (0.1-0.7) Wt%, and the range of superficial gas velocity of air, (2.5-30) mm/s. The experimental runs were planned using the central composite routable design method. The experimental data obtained agreed quite well with a polynomial type of correlations by using computer program. The experimental data shows that the values of bubble coalescence decrease with increasing superficial gas velocity of air, and ethanol transition concentration was successfully correlated as a function of the superficial gas velocity of air, ct= 0.158214 − 0.010849Ug + 0.00045Ug2 − 0.000008Ug3 . This equation gives mean deviation of 10.393%.

Aiming at the diameter range of boiler water wall tubes in practical engineering application, the air-water two phase flow pattern in horizontal tube was experimentally investigated in tubes with different inner diameters of 20mm and 8 mm under atmosphere condition. The stratified flow, wave flow, plug flow, slug flow, annular flow, bubbly flow and mist flow were observed in the tubes. Most of the experimental points agree well with the Baker flow pattern map when they appear in the map. With the experimental results, the range lines between the flow patterns were suggested for the tube of 20mm in inner diameter as well as 8mm. As the water superficial velocity increases, the annular flow transforms into mist flow at a decreasing air superficial velocity. The two phase flow patterns transition line is similar in tendency for different tubes. The slug flow transforms into annular flow at an increasing air superficial velocity as tube diameter decreases. The stratified flow transforms into slug flow at an increasing water superficial velocity as tube diameter decreases. The transition line between plug flow and slug flow is independent of tube diameter.

Experimental investigations on annular flow behaviour in two-phase (air/water) flow in horizontal pipe were conducted using 2-inch (0.0504m) with a total length of 28.68m closed loop system. The emphasis from the experiments were on pressure gradient, slip and interfacial friction factor in annular flow. For interfacial friction factor, the entrainment, gas quality, the droplets and slip mixture density values were obtained through the experimental results which were substituted to determine it. In all, effects of liquid velocity were felt, as increase in superficial liquid velocity, increases the interfacial friction factor and pressure gradient in annular flow in horizontal pipes. More so, increase in superficial gas velocity, reduces the interfacial friction factor. Thus, interfacial friction factor decreases with increases in superficial gas velocity, while the pressure gradient increases with increase in superficial liquid velocity. The lower the superficial liquid velocity, the higher the slip but the lower the pressure gradient. Likewise, the lower the superficial liquid velocity, the more ripple waves obtained while the higher the superficial liquid velocity, the more disturbance waves in annular flow in horizontal pipe from the experiments.

Experimental investigations on annular flow behaviour in two-phase (air/water) flow in horizontal pipe were conducted using 2-inch (0.0504m) with a total length of 28.68m closed loop system. The emphasis from the experiments were on pressure gradient, slip and interfacial friction factor in annular flow. For interfacial friction factor, the entrainment, gas quality, the droplets and slip mixture density values were obtained through the experimental results which were substituted to determine it. In all, effects of liquid velocity were felt, as increase in superficial liquid velocity, increases the interfacial friction factor and pressure gradient in annular flow in horizontal pipes. More so, increase in superficial gas velocity, reduces the interfacial friction factor. Thus, interfacial friction factor decreases with increases in superficial gas velocity, while the pressure gradient increases with increase in superficial liquid velocity. The lower the superficial liquid velocity, the higher the slip but the lower the pressure gradient. Likewise, the lower the superficial liquid velocity, the more ripple waves obtained while the higher the superficial liquid velocity, the more disturbance waves in annular flow in horizontal pipe from the experiments.

In this study we analyzed the effects of the hydrodynamic conditions and properties of the working fluid on the operation of external loop air lift bioreactors. In particular, the effects of design and operating parameters (e.g. reactor geometry, design of the gas sparger, superficial gas velocity, flow regime) as well as the fluid properties (liquid viscosity and addition of surfactants) on the liquid superficial velocity and gas hold-up were defined. Several correlations found in the literature based on theoretical models of fluid flow, as well as several semi-empirical and empirical correlations were tested and the applicability of all the proposed correlations was verified on the available experimental data. The most accurate correlations for the prediction of the gas hold up, liquid circulation velocity and slip velocity in each bioreactor operating regime were identified.

O reator de FAD deve propiciar condições adequadas para contato entre as micro-bolhas e os flocos formados no pré-tratamento e também condições para que o conjunto floco/bolha possa ser direcionado ao topo do reator, e assim ser removido. O projeto de pesquisa visou estudar condições hidrodinâmicas proporcionadas pela variação da Velocidade Cross-Flow (VCF) e assim verificar a influência na eficiência de uma estação piloto de flotação por ar dissolvido. A VCF é importante parâmetro para concepção de unidades de FAD e é função da vazão de entrada no tanque de flotação e da área entre o nível d\'água no tanque de flotação e o anteparo que separa a zona de contato da zona de separação. A velocidade cross-flow constitui um parâmetro de grande importância para projetos de unidades de flotação. Nesta região de transição entre a zona de contato e a zona de separação, ocorre a passagem do conjunto floco/bolha, e turbulência excessiva pode causar o rompimento do conjunto e assim comprometer a eficiência da flotação. Além disso, o padrão de escoamento observado na zona de separação dos flotadores, onde ocorre a separação dos aglomerados \"flocos + bolhas\", depende fortemente do valor médio da velocidade cross-flow, conforme comentado por Lundh et al. (2000 e 2002) e por Reali e Patrizzi (2007). Daí a necessidade de se investigar mais profundamente a influência da VCF na eficiência da clarificação por flotação. O projeto de pesquisa foi dividido em duas etapas. Para realização das etapas foi estudado um tipo de água preparada em laboratório, através da adição de substância húmica e caulinita, para obtenção de cor aparente e turbidez, respectivamente. A água estudada possui cor aparente e turbidez moderada (1 mg/L de substância húmica e 8,5 mg/L de caulinita) resultando em valores de turbidez por volta de 7 NTU e cor aparente por volta de 40 UH. A etapa 1 consistiu na determinação do par, pH de coagulação e dosagem de coagulante (sulfato de alumínio), gradiente médio de floculação e tempo médio de floculação adequado para a água de estudo. Para realização da etapa 1 foi utilizado equipamento de flotação de bancada de regime de batelada (Flotateste), que se encontra nas dependências do Laboratório de Tratamento Avançado e Reuso de Águas - LATAR/SHS/EESC/USP. Foram mantidos fixos os seguintes parâmetros: \'T IND.MR\', \'G IND.MR\', \'T IND.F\', \'G IND.F\', \'P IND.SAT\', \'T IND.REC\', \'V IND.FLOT\'. Conforme preconizado por Reali et al (2007), foi variada a dosagem de coagulante. Após determinado o melhor par pH e dosagem de coagulante foram realizados ensaios visando determinar o melhor \'G IND.F\' e \'T IND.F\' para a água em estudo. Para a água de estudo foram escolhidas duas condições de potencial Zeta, determinados na etapa 1 do projeto de pesquisa. A primeira condição o potencial Zeta permaneceria com valor próximo de 0 mV e na segunda condição o potencial Zeta seria positivo, por volta de +12 mV. A etapa 2 consistiu em variar a velocidade cross-flow, através da variação da altura do vertedor de saída da água flotada de uma unidade piloto de flotação, de forma a se obter diferentes valores de VCF (mantendo-se constantes os valores de tempo de contato e taxa de aplicação superficial na zona de contato), para dois valores de Taxas de Aplicação Superficial (TAS) (7,67 m/h e 15 m/h) na zona de separação e os dois valores de potencial Zeta (PZ), e com isto avaliar a sua influencia na eficiência de remoção de sólidos suspensos totais, cor e turbidez da instalação piloto retangular de FAD.
The reactor DAF should provide adequate conditions for contact between the micro-bubbles and the flakes formed in the pretreatment conditions and also for the aggregate flocs/bubble can be directed to the top of the reactor, and thus be removed. The research project aimed at studying hydrodynamic conditions provided by the variation of Cross-Flow Velocity (VCF) and thus checks the influence on the efficiency of a pilot plant of dissolved air flotation. The VCF is an important parameter to design units of DAF and is a function of input flow in the flotation tank and the area between the water level in the flotation tank and the bulkhead that separates the contact zone of the zone of separation. The cross-flow velocity is a parameter of great importance to projects of flotation units. In this region of the transition zone between the contact zone and the separation zone, occurs the passage of the aggregate flocs/bubble, and excessive turbulence can cause disruption of the aggregate and thereby harm the flotation efficiency. Moreover, the pattern of flow observed in the flotation separation zone, which occurs the separation of aggregates \"flakes + bubbles\", depends strongly on the average value of cross-flow velocity as described by Lundh et al. (2000 and 2002) and Reali and Patrizzi (2007). Hence the needs to investigate further the influence of VCF on the clarification efficiency by flotation. The research project was divided into two steps. To perform the steps has been studied a type of water prepared in the laboratory, through the addition of humic substances and kaolin, to obtain apparent color and turbidity, respectively. The study water has moderate turbidity and apparent color (1 mg/L of humic substance and 8.5 mg/L of kaolin) resulting in turbidity values around 7 NTU and color apparent by 40 HU. Step 1 consisted in the determination of the pair, coagulation pH and coagulant dosage (aluminum sulfate), flocculation gradient and time flocculation suitable for the study water. For the implementation of step 1 was used bench batch flotation system equipment (Flotatest), located on the Laboratory for Advanced Treatment and Reuse Water - LATAR / SHS / EESC / USP. Were kept fixed the following parameters: \'T IND.MR\', \'G IND.MR\', \'T IND.F\', \'G IND.F\', \'P IND.SAT\', \'T IND.REC\', \'V IND.FLOT\'. As predicted by Reali et al (2007), was varied the dosage of coagulant. After determined the best pair of coagulant dosage and pH coagulation the tests were performed to determine the best \'G IND.F\' and \'T IND.F\' for the study water. For the study water were chosen two conditions of Zeta potential values, determined in the step 1 of the research project, where the first condition the Zeta potential value kept near 0 mV and the second condition kept a positive value of Zeta potential, around +12 mV. The step 2 consisted of varying the cross-flow velocity, by varying the height of the outlet weir of the clarified water of the flotation pilot plant to obtain different values of VCF (keeping constant the values of time contact and application rate on the contact zone) for two values of superficial application rates (7.67 m/h and 15 m/h) in the zone of separation and the two values of Zeta potential (PZ) and then was availed the influence on removal efficiency of total suspended solids, colour and turbidity of the rectangular pilot plant of DAF.

O desempenho de unidades de flotação por ar dissolvido (FAD) depende significativamente do projeto da zona de contato (ZC) dessas unidades, situada na entrada das mesmas e responsável por promover condições adequadas para que ocorram taxas satisfatórias de colisão entre as microbolhas de ar e os flocos formados na etapa antecedente de floculação da água para abastecimento. Os dois principais parâmetros de projeto da ZC são o tempo de detenção hidráulico ou tempo de contato (Tzc) e o gradiente médio de velocidade na ZC (Gzc). A presente dissertação apresenta os resultados de estudo sobre a influência do Tzc e do Gzc na ZC de uma unidade piloto de flotação por ar dissolvido (UPFAD) com escoamento contínuo aplicada ao tratamento de água para abastecimento. Foram utilizados módulos contendo tela metálica em seu interior com malha de #25 mm com diferentes dimensões, de modo a se obterem diferentes valores de Gzc e Tzc. Foram investigadas duas configurações na unidade de FAD (Configurações A e B), nas quais o comprimento (Lzc) e a altura (Hzc) da ZC foram variados, permitindo a alteração do Tzc e mantendo-se controlados os valores de Gzc (com a introdução ou não de diferentes módulos de tela metálica na ZC) e vice versa. Os demais parâmetros do processo de FAD não sofreram variações, tais como taxa de aplicação superficial (TAS) na zona de separação, tempo de floculação, entre outros. Para a configuração A, foram estudadas três alturas diferentes na ZC e para a configuração B, quatro alturas diferentes na ZC, o que acarretou, para cada valor de Gzc variação do Tzc. Para cada configuração da ZC, também foram testados três valores de vazão de recirculação de água saturada com ar de modo a se obterem três diferentes concentrações de ar (A/V) no processo de flotação. Para todos os parâmetros analisados (Turbidez, Cor, Absorbância), as maiores eficiências de remoção foram obtidas nos ensaios realizados com o uso da tela #25 mm tanto na configuração A (TASzc = 136 m/h e G = 6,1 s-1) quanto na configuração B (TASzc = 87 m/h e G = 3,2 s-1). Os resultados permitem concluir que o par de valores (Tzc, Gzc) é mais apropriado para o projeto da zona de contato de unidades FAD do que o par (Tzc, TASzc) usualmente adotado pelos projetistas, sendo que, na faixa de valores investigados a UPFAD apresentou melhor desempenho para o par: Tzc de 41 s e Gzc de 6,1 s-1.
The performance of units dissolved air flotation (DAF) depend significantly of design on the contact zone (CZ) of these units, situated at the entrance thereof and responsible for promoting appropriate conditions to occur satisfactory collision rates between air microbubbles and the flocs formed in the step of flocculation of potable water. The two main design parameters of the CZ are the hydraulic detention time or contact time (Tcz) and the velocity gradient in the CZ (Gcz). This work presents the results of study of the effects of varying the Tcz and Gcz at the contact zone of pilot unit DAF with continuous flow applied to the treatment of potable water. Were used modules containing metal grille with mesh of #25 mm, with different dimensions in order to obtain different values of Gcz and Tcz. Were investigated two configurations in the unit FAD ( configurations A and B) where the length (Lcz) and height (Hcz) of contact zone were varied, allowing the variation of Tzc and keeping the values of Gcz controlled (with the introduction or not of different modules in the metal grille in CZ) and vice versa, without changes in other process variables FAD, such as rate of surface application (TAS) in the separation zone, flocculation time, among others. For the configuration A were studied three different heights in the CZ and in configuration B, four different heights in the CZ, which resulted, for each value of Gcz (relative to the chosen value of Lcz) the variation of Tzc. For each configuration of CZ were also tested three values of recirculation flow of air saturated in order to obtain three different values of concentration in air (A/V) in the flotation process. For all parameters analyzed (turbidity, color, absorbance), the highest efficiencies were obtained in assays performed using the grille #25 mm, both in configuration A (TAScz = 136 m/h and L = 6,1 s-1) and configuration B (TAScz = 87 m/h and G = 3,2 s-1). The results indicate that the pair of values (Tcz, Gcz) is more suitable for project of the CZ of units FAD than the pair (Tcz, TAScz) usually adopted by the designers, and values in the range investigated in UPFAD showed performed better for Tcz of 41 s and Gcz of 6,1 s-1.

Effects of superficial liquid velocity (Ul), superficial gas velocity (Ug), and fiber mass fraction (C) on gas holdup (ε) and flow regime transition are studied experimentally in well-mixed water-cellulose fiber suspensions in a cocurrent bubble column. Experimental results show that the gas holdup decreases with increasing Ul when C and Ug are constant. The gas holdup is not significantly affected by C in the range of C < 0.4%, but decreases with increasing C in the range of 0.4% ≤ C ≤ 1.5%. When C > 1.5%, a significant amount of gas is trapped in the fiber network and recirculates with the water-fiber slurry in the system; as a result, the measured gas holdup is higher than that at C = 1.5%. The axial gas holdup distribution is shown to be a complex function of superficial gas and liquid velocities and fiber mass fraction. The drift-flux model is used to analyze the flow regime transitions at different conditions. Three distinct flow regimes are observed when C ≤ 0.4%, but only two are identified when 0.6% ≤ C ≤ 1.5%. The superficial gas velocities at which flow transition occurs from one regime to another are not significantly affected by Ul and slightly decrease with increasing C.

The need for a revised methodology and uncertainty quantification for wire-mesh sensor void fraction measurements in horizontal low void fraction flow conditions was identified. Two-phase flow measurements were performed at a low-pressure, adiabatic and horizontal flow loop using wire-mesh sensors over a range of water superficial velocities from 3.5 to 5.5 m/s, air superficial velocities from 0.05 to 0.9 m/s and volumetric void fractions from 1 to 16% Using this proposed analysis, a corrected trend with average percent differences of 36, 21 and 6% was obtained for the low, medium and high gas flow rate cases, respectively, when comparing the wire-mesh sensor void fractions to two-phase pipe flow models. By combining these measurements of the void fraction with those of the interfacial velocity, the gas superficial velocity was calculated based on the physical theory, and compared to the superficial velocity measured by the flowmeters for validation purposes. An estimation of the uncertainty of these parameters showed that most of the measured parameters agreed reasonably with physical theory within 20%.

Air-water two-phase flow in a pipeline often occurs in petroleum industry. It is important to study behavior of such flows in order to characterize two-phase flow in upstream production pipelines. This paper presents pressure drop measurements of air-water two-phase flow in a horizontal and inclined 4 inch diameter stainless steel pipe at different flow conditions. Experiments were carried out for different inclination angles including; 0°, 15°, 30° (upward and downward flows) and for different water-to-air volume fractions. Inlet superficial water velocities were varied from 0.3 to 3 m/s and reference pressure was set at 1 and 2 bars. For a given superficial air velocity, pressure drop has been found to increase with increase in superficial water velocity. Pressure drop was also affected by the inclination of pipe. Upward flows were associated with high pressure drops as compared to downward flows. Measured pressure drops were compared with existing empirical relations and good agreement was found.

The effect of liquid properties on axial development of gas-volume-fraction profiles in bubble-column flows is investigated. Experiments are conducted in a cylindrical vessel with an inner diameter of 0.48 m and a height of 3 m. The liquids examined include water and two lightweight mineral oils. A cross sparger with 96 holes is used to inject air into the column with all the holes facing either upwards or downwards. The superficial gas velocity ranges from 5 to 30 cm/s, and the absolute column pressure ranges from 0.1 to 0.5 MPa. Gamma-densitometry tomography (GDT) is used to measure radial distributions of gas volume fraction at eight axial locations. The development length of the gas-volume-fraction profile is shown to increase with gas velocity and column pressure for all three liquids. The development of the cross-sectionally averaged gas-volume fraction for the air/water flow is remarkably different from that for the air/oil flows.

Abstract The fluctuating pressure drop for air-water two-phase flow was measured in the vertical upward section of U-type tube with 0.05m I.D. The feature of the fluctuations was extracted by means of statistical and chaotic theories. The influence of liquid superficial velocity on the features was also investigated. The results showed that the mean, root mean square, fractal dimension of pressure drop fluctuations is function of flow regimes. The fractal dimension can be larger than 1.5 in annular flow with great liquid superficial velocity which is reported for the first time. Furthermore, the present paper provided a feasible solution, which the gas-liquid two-phase flow regimes can be recognized automatically and objectively on basis of the combination of the Counter Propagation Network (CPN) and the FFT coefficients of the differential pressure fluctuations. The recognition possibility is determined by the clustering results of the Kohonen layer in the CPN. With the presented test cases, the possibility can be greater than 90 percent for different liquid phase velocity.

According to experiments and relational documents, slug regime, appeared in this experiment, can be divided into the following flow regimes: oil-based separated slug, oil-based dispersed slug, water-based separated and water-based dispersed slug. Experiments for oil-gas-water three-phase flow in a stainless steel pipe loop (25.7mm inner diameter, 52m long) are conducted. Compressed air, mineral oil and water are used as experiment medium. Mineral oil Viscosity is 64.5mPa.s at 20°C. Gas superficial velocity, liquid superficial velocity and water cut ranges are 0.5∼15 m/s, 0.05∼0.5 m/s and 0∼100% respectively. There are some strange observed in this experiment. At the very low gas superficial velocity less than 1m/s, the average liquid holdup of low liquid superficial velocity was larger than that of higher liquid superficial velocity especially in higher inlet water cut experiments. This is because at very low gas superficial velocity, the regime is separated slug flow which has water film below their liquid film zone, velocity difference between oil film and water film will affect the average liquid holdup greatly. With the increase of gas and liquid superficial velocity, the regime becomes dispersed slug flow which oil and water are homogeneous. It will be more obvious with the increasing of water cut for the thicker water film. A new liquid holdup model of oil-based and water-based separated slug has been developed. Based on statistical analysis, it is observed that the new model gives excellent results against the experimental data.

In this research the hydrodynamics of falling liquid film in a vertical downward two-phase flow (liquid-gas) is experimentally studied. The 4 inch clear PVC test section is 6.1 meters long, with a length to diameter ratio (L/D) of 64. The fluids utilized are compressed air, water, Conosol mineral oil (light oil) and Drake mineral oil (heavy oil). The superficial liquid velocities tested range from 12 to 72 cm/s while the superficial gas velocities range from 0.2 to 29 cm/s. The vertical facility is equipped with the state-of-the-art instrumentation for two-phase flow measurements, the capacitance Wire-Mesh Sensor (WMS), allowing two-phase flow measurements with conducting and non conducting fluids. Experimental results show that the liquid film thickness has a quasi-linear relationship with the superficial liquid velocity for the air-water case. For the air-oil cases, at superficial liquid velocities higher than 50 cm/s, the liquid film thickness trend is affected by the liquid droplet entrainment. Furthermore, it was found that the liquid droplet entrainment increases as the superficial liquid velocity increases or the surface tension decreases. Details of the liquid droplets traveling in the gas core, wave formation, wave breakup and film thickness evolution are observed in the WMS phase reconstruction.

The objective of this project is to investigate experimentally the phenomena of liquid entrainment in gas in horizontal pipes. This report contains the results of an experimental study on wave characterization. Entrainment in annular flow in horizontal pipes has been studied experimentally. It has been found out that wave characteristics and entrainment fraction are strongly interrelated and must be utilized together in any related analysis. Two experimental facilities, 2-inch and 6-inch diameter, have been designed, constructed and utilized for entrainment measurements in stratified and annular horizontal flow. For the 2-inch flow loop, the range of superficial liquids velocities are 0.35 cm/s to 10 cm/s, and from 2 m/s to 80 m/s for the superficial gas velocities. For the 6-inch flow loop, the ranges of the superficial liquid velocities and superficial gas velocities are from 0.35 cm/s to 10 cm/s and from 2 m/s to 20 m/s, respectively. Appropriate instrumentation for entrainment (adjustable liquid film extractor) and liquid film characteristics (conductance probes and multi-channel conductivity meter) measurements have been developed and implemented. The effects of fluid properties on entrainment and wave characteristics have been studied by utilizing air-water-Butanol solution (surface tension effects) and air-water-Glycerin solution (viscosity effects). Simultaneous measurements have been carried out for both wave characteristics and entrainment for a wide range of flow conditions. Closure relationships have been developed based on the data for wave celerity, frequency, amplitude and spacing. The entrainment fraction has been normalized with the maximum entrainment fraction and correlated with the ratio of the superficial gas velocity to the superficial gas velocity at the onset. The wave amplitude (Δhw) normalized by the film thickness (hL) tends to values of Δhw / hL = 0.2 to 0.3 for high gas rates. The wave spacing (Lw) for air-water normalized by the mean film thickness (hL) exhibits a clear linear behavior with gas velocity, almost independent of the liquid velocity.

An experimental investigation was conducted to study the two-phase flow distributions in a horizontal cylindrical manifold with two radial inlets and 11 parallel channels. The effects of the different inlet conditions on two-phase flow distribution of parallel channels in the manifold were investigated. The flow rates of air and water in 11 channels were measured under symmetrical and unsymmetrical inlet conditions. Experimental results show that the air and water flow distributions of manifold at channels keep a stable flow ratio when two radial inlet conditions keep symmetrical. Water flow distribution has a significant variation and air flow distribution has a small change when two radial inlet conditions keep unsymmetrical and water superficial velocity increases at right inlet. Water and air flow distribution has a significant variation when two radial inlet conditions keep unsymmetrical and air superficial velocity decreases.

Abstract This paper presents the experimental results and analyses of the structure velocity of air-water two-phase flow in a 3 × 3 rod bundle channel. A total of 56 flow conditions were tested and investigated for rod-gap, sub-channel, rod-wall and global regions of rod bundle geometry. The experimental tests were carried out under bubbly and cap-bubbly flow regimes with superficial gas and liquid velocities of 0–1 m/s and 1–1.7 m/s, respectively. The conductivity probes were set at different heights to measure the global and local void fractions. The structure velocity of air-water two-phase flow is the average bubble velocity calculated by the method in this study. The structure velocity were determined by utilizing the cross-correlation technique to analyze the time lags of the bubbles passing through the conductivity probes. The results of this study indicated that the structure velocity may increase with increasing superficial gas and liquid velocities. In low superficial gas velocity region, the structure velocity may first slightly increase and follow by a sudden jump which appear in most regions. After the sudden jump, the structure velocity may keep increasing mildly. The present structure velocities have been compared with the area-averaged gas velocities predicted by the drift flux model, and it appears that most structure velocities show a good agreement with the averaged gas velocities from the drift flux model after the jump.