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The effects of submergence ratio and gas flow rate on the performance and hydrodynamic behavior of air–liquid two-phase flow have been investigated during liquid lifting in the developed bubble-generator-type airlift pump system. Here, a mechanistic model was also developed to predict the performance of the bubble-generator-type airlift pump system on the basis of pressure balance with considering the intake angle of the injector, and the suction pipe length. A developed image processing technique was implemented to determine the hydrodynamic behaviors including gas slug velocity, water slug velocity, slug length, and gas hold up under the various submergence ratio and gas flow rate. The submergence ratio is the ratio between the static lift and the sum of static lift and static head. The experimental result was found that the minimum air flow rate for removing water is reduced by 19.17% when the airlift pump is combined with an orifice-type bubble generator. The decrease in submergence ratio causes the lower the efficiency at the critical point of airlift pump-bubble generator. Under the same submergence ratio, an increase in the supplied air superficial velocity increased the hydrodynamic parameter. A mechanistic model from pressure balance and dimensional analysis have a maximum error of 11.97% and 3.33%, respectively. [ABSTRACT FROM AUTHOR]

In this study, we numerically investigated the effects of CO2 gas in geothermal water and the scale deposition formed in the wellbore on the flow characteristics. Geothermal water that contains CO2 gas has the potential to produce calcite scale deposits in the wellbore. To prevent scale formation, scale inhibitor is injected below the flash point in the wellbore, which is a challenging job. Therefore, using a wellbore simulator to predict the depth of flash commencement and the effects of scale deposition above the flash point on flow characteristics is important. In our numerical simulations, we changed the values of the CO2 gas concentration to study its effect on the flow characteristics. The simulation results show that the presence of CO2 increases the flash pressure relative to that of pure water. A higher CO2 gas concentration in the water will initiate flashing at a lower depth than a lower CO2 concentration. However, when the presence of scale deposits in the wellbore is taken into account, the calculated wellhead pressure is lower than that in a wellbore without scale deposition. [ABSTRACT FROM AUTHOR]

The choice for using a fighter fuselage in a fighter jet design affects a vortex generation advantageous in maneuverability. To study the effect of straight-body-type-fuselage (SBTF) on the vortex dynamic, a computational fluid dynamics (CFD) method is used, in order to simulate a model of SBTF fighter. The simulation uses Q-criterion to probe vortices, and a logarithmic grid to emphasize the micro-gridding effect of the turbulent boundary layer. The results show detailed quantitative velocity, pressure, trajectory of the vortex core, and wing negative surface pressure distribution (SPD), providing clear pictures of opportunity for performance improvement, better lift, agility, and maneuverability of a fighter if a model requires a new design. [ABSTRACT FROM AUTHOR]

An experimental study on the contact angle dynamic during the impact of single water droplet onto a hot flat practical stainless steel surface under medium weber number was performed. The tested solid material was practical stainless steel of SUS 304. The surface roughness of the hot surface, the static contact angle at ambient pressure, and the diameter of the solid materials were respectively Ra = 0.2 µm, 85.7o, and 30 mm. The surface temperatures were varied from (60–200) oC. The liquid droplet diameter was 2.4 mm. The Weber numbers were 52.1, 57.6, and 63.1. The dynamic contact angles of single droplet during the impact were determined by implementing the developed image processing technique of the obtained video images from experiments. As a result, it was found that (1) the time needed to reach a maximum diameter of single droplet on a flat hot solid surface decreases with the increase of surface temperature, (2) the increase of the Weber number will postpone the spreading of the droplet from its receding, (3) there are three regions of the dynamic contact angle during the liquid evaporation, those are transient spreading region (region 1), a quasi-mechanical equilibrium region (region 2), and transient evaporation region (region 3), and (4) The contact angle in quasi-mechanical equilibrium region the under the nucleate boiling is insensitive to the surface temperature. [ABSTRACT FROM AUTHOR]

Due to increasing concern of the Indonesian government towards the ever increasing national level of carbon emissions and the increasing demand of oil, in 2014 the Indonesian National Energy Council released the National Energy Policy which set the target of an increased renewable energy portion to become 23% of the total national energy consumption while setting a limit to oil consumption to be at most 25%. As the road transportation sector consumes more than 60% of the national oil consumption, measures targeting this sector will be important in fulfilling the target. A model has been set up to evaluate the impact of the measures on oil consumption via two main avenues: the substitution of oil based fuels with alternative fuels (e.g. biofuel, compressed natural gas/CNG), the reduction of oil consumption via vehicle retirement and the acceleration of fuel economy improvement for vehicles. Results have shown that it is important that policies consider the presence of older vehicles in the population since there is presently no vehicle retirement policy or penalty for older vehicles resulting in a large number of old vehicles still being operational. Thus, introduction of new vehicles will have a limited effect on the average fuel efficiency. Implementation of a vehicle retirement policy to reduce the amount of older vehicles is shown to be very effective in stemming the increase of oil consumption. In regards to fuel substitution, oil substitution with ethanol is most impactful, as most motor vehicles in Indonesia rely on gasoline including the rapidly increasing motorcycle population. While oil consumption is also reduced by biodiesel substitution, impact is more limited due to a smaller diesel vehicle population with a lower annual increase of vehicle population. In addition, financial, social and regulatory barriers exist that impend implementation of alternative fuels and vehicle limitation schemes. We also evaluated possible barriers and avenues that can further promote these measures to meet the national energy policy target. • The impact of fuel substitution of Indonesian road transportation energy was simulated. • The avenues in order to meet the national energy policy target were evaluated. • Fuel substitution with ethanol is the most impactful for the Indonesian transportation energy sector. • Oil consumption can be also reduced by biodiesel substitution. • Regulatory barriers exist in the implementation of alternative fuels and vehicle limitation schemes. [ABSTRACT FROM AUTHOR]

Highlights • The liquid film behavior at the transition to slug flow in horizontal pipes were studied experimentally. • It was obtained from the visualization studies, the pressure gradient and the liquid hold-up measurements. • The wave growth and the wave coalescence are the responsible mechanisms for slug formation. • The wave growth exists at low J L and J G , meanwhile the wave coalescence exists at a higher J G. Abstract The knowledge of the slug flow is essential the design safety of hydrocarbon transportation in the pipeline system of petroleum industries. However, the suitable models to predict the transition condition to slug flow are limited due to insufficient availability of experimental data. In the present study, the hydrodynamic characteristics of the near the transition to slug flow of air-water two-phase flow in horizontal pipes were investigated experimentally for inner pipe diameters of 16 mm, 26 mm, and 50 mm. The superficial velocities of water and air ranged from J L = 0.03 to 0.30 m/s and J G = 0.7 to 10.0 m/s. The hydrodynamic behavior was obtained from the combination of the visualization detected by using a high-speed video camera, the pressure gradient, and instantaneous volumetric liquid fraction measurements. The experimental results indicate that the wave growth and the wave coalescence are involved in the mechanism of the slug flow formation. Both gas and liquid superficial velocities have a significant effect also of those mechanisms. The average volumetric liquid fraction near the transition to slug flow is not affected by superficial gas velocities. Next, under a constant superficial gas velocity, an increase in the inner pipe diameter requires a larger superficial liquid velocity to change the flow patterns from stratified smooth to slug flow, and from pseudo-slug to slug flow. [ABSTRACT FROM AUTHOR]

The interfacial dynamics of the micrometric size liquid droplets during impact onto inclined hot surfaces have been experimentally studied. The inclination angles were varied at 15°, 30°, and 45° from horizontal for surface temperatures were decreasing from 500 °C to 100 °C. The droplet diameters tested were 500 μm and 700 μm. The tested material was stainless steel-grade 304 (SUS 304) with varying surface roughness ranging from Ra 0.04 up to Ra 10. The interfacial dynamics during the impact onto inclined hot surfaces were investigated by using a high-speed video camera with the frame speed of 15,000 fps. The objectives of this study are to provide insight into the dynamic behaviors of contact angles and dependence of importance parameters at various surface temperatures. It was found that depending on the surface temperature the droplet evaporation and its bouncing process play an important role on the droplet detachment mechanisms from the inclined surface. Three transient regions of the interfacial evolution during the micrometric droplets impacting onto oblique hot surface were identified. Moreover, the contribution of the important physical parameters, such as, advancing and receding contact angles on the interfacial dynamics are presented. [ABSTRACT FROM AUTHOR]

The design of future transportation energy mix has become an important issue in Indonesia. Oil-based fuels such as gasoline and diesel seems to be infeasible options in the future due to limited availability, high subsidy, and environmental issues. This paper presents energy mix model for transportation sector in Indonesia. The model considers a variety of feasible technology options and includes three competing objectives, i.e., energy consumption, fuel subsidy, and CO 2 emission. Scenarios were developed to include business as usual (BAU), the introduction of compress natural gas (CNG) technology, vehicle retirement program, the implementation of hybrid vehicles energy mix which considers future behavioral factors. The result indicates that the most effective strategy to reduce energy consumption and eventually fuel subsidy is through retirement program of old vehicles. The introduction of the CNG vehicle on public transportation appears to give little significance in reducing the annual subsidy costs, fuel consumption and CO 2 emissions. [ABSTRACT FROM AUTHOR]

• The effect of the liquid properties on the fundamental parameters of stratified two-phase flow have been studied. • The non-linier statistics and discrete wavelet transform were used to analyze the time wise of the liquid film thickness data. • The liquid viscosity shifts the wavelet energy to a lower frequency in roll wave & entrained droplet sub-regimes. • The correlations to predict the frequency and velocity of the interfacial waves in stratified two-phase flow were proposed. The aim of the present study was to investigate the effect of the liquid physical properties on the liquid film thickness, wave frequency, and wave velocity in co-current gas-liquid stratified two-phase flow in a horizontal pipe. The present experimental study was conducted using an acrylic pipe with an inner diameter of 26 mm and a length of 9500 mm. The superficial velocity of liquid (J L) and gas (J G) were 0.02 m/s to 0.1 m/s and 4 m/s to 16 m/s, respectively. A highspeed video camera was used to take the visual data which is then processed by the developed image processing techniques to obtain the time series data of the liquid film thickness. The probability distribution function (PDF) and discrete wavelet transform (DWT) were used to analyze the time series of the liquid film thickness. In addition, the data were also analyzed using the power spectral density (PSD) in order to obtain the wave frequency and the wave velocity. Next, the experimental correlations to predict the wave frequency and the wave velocity were developed using the dimensional analysis. From the time series of the liquid film thickness, the effect of the viscosity and surface tension on the shifting of scale and frequency of the wavelet decomposition level, as well as the frequency and velocity of the waves were clarified. In addition, a correlation to predict the frequency and velocity of waves has been successfully developed, in which the Martinelli parameter, the ratio of gas and liquid Reynold numbers, and the Weber number play the important roles in the correlation. [ABSTRACT FROM AUTHOR]

In order to improve the understanding of transient behavior of gas-liquid plug two-phase flow in a horizontal pipe, CFD simulations and experimental studies on the relevant phenomena were carried-out. The pipe diameter and pipe length were 26 and 9.5 m respectively. The transient calculations were carried out using a Volume of Fluid (VoF) multiphase flow model of the commercial CFD code of FLUENT 6.3. The corresponding CFD solution has been obtained by using the Best Practice Guidelines of CFD for thermal engineering purposes. In the present works, the series of high quality experimental data was used to validate the CFD calculations in terms of time and space. A comparison with the high-speed video observations shows a good qualitative agreement. The results indicate also a quantitative agreement between calculations and experimental data for the elongated bubble length and the time variation of the liquid hold-up. [ABSTRACT FROM AUTHOR]

The effect of surface roughness on the dynamic behavior and the heat transfer phenomena of multiple successive micrometric water droplets impacting onto inclined heated solid surfaces has been studied experimentally. The inclination angles were 15°, 30°, and 45° from horizontal. The droplet diameters were 500 μm and 700 μm. The solid surface temperatures were decreased from 500 °C to 100 °C. The test material was stainless steel-grade 304 (SUS 304) with different surface roughness ranged from Ra 0.04 up to Ra 10. The droplet dynamics during the impacting onto inclined hot surfaces were investigated by using high-speed video camera. It was found that the surface roughness significantly affects quenching behavior. The higher the surface roughness, the lower the quenching time during the spray cooling. The solid-droplet contact time and the droplet spread diameter increase with the increase of surface roughness. Thus causing the decrease of the quenching time of inclined hot walls. Meanwhile, the critical heat flux and Leidenfrost temperatures are shown to be insensitive to the surface roughness. [ABSTRACT FROM AUTHOR]

The studies on the hydrocracking process to obtain the fuel by cracking of the carbon chain from the hydrocarbon compound both in the form of gas and liquid fuels have been carried-out massively by researchers over three decade. In the present experimental study, heavy hydrocarbon represented by asphaltic base materials (named as Extracted Asbuton) and paraffinic (waxy residue from Cepu oil refinery) were used as the object of the study; by observing the differences of the reaction mechanisms and the results that can be obtained. Here the operational conditions such as pressure, temperature, and time as well as the kinds of catalyst were considered as the main parameters. The experiments were carried-out under the similar operating condition such as temperature around 350 - 500°C, pressure around 5 up to 15 atmospheres, and evaporation time was (1 - 3) hours. As a result, it was obtained (a) the higher the temperature, pressure, and heating time, the higher hydrocracking conversion both of hydrocarbons, (b) reaction mechanism of hydrocracking by using asphalt extract as the material follows the Model 3 of the present work, in which asphalt vapor was trapped in catalyst surface, meanwhile the waxy residue followed the Model 1, (c) under the same condition, the conversion of asphalt extract was smaller than waxy residue, and (d) the conversion of asphalt extract using Pt/Pd catalyst was higher than γ-Alumina catalyst. [ABSTRACT FROM AUTHOR]

Abstract: The effect of surface wettability on the collision dynamics and heat transfer phenomena of a single water droplet impacting upon a heated solid surface has been studied experimentally. To modify the surface wettability, two modules of stainless steel coated by TiO2 were employed. The first module was induced by ultraviolet irradiation to produce the hydrophilic surface, while the second one was not. The diameter and the depth of coating surface were 30mm and 200nm, respectively. The droplet size was varied from 1.90 to 2.90mm and substrate temperature raised up to 340°C. The interaction of an impact water droplet with a heated solid surface was investigated using a high-speed video camera. As a result, it was found that; (1) in the lower surface temperature region the evaporation time decreases as the static contact angle decreases, (2) the wetting limit temperature decreases with the increase of static contact angle, (3) the ultraviolet irradiation on the TiO2 surface does not change the qualitative behavior of the evolution of wetting diameters, and (4) the maximum wetting diameter increases with the decrease of static contact angle below the wetting limit temperatures. [Copyright &y& Elsevier]

In order to improve the understanding of counter-current two-phase flows and to validate new physical models, CFD simulations of 1/3rd scale model of the hot leg of a German Konvoi PWR with rectangular cross section was performed. Selected counter-current flow limitation (CCFL) experiments at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) were calculated with ANSYS CFX 12.1 using the multi-fluid Euler-Euler modeling approach. The transient calculations were carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a SST turbulence model for each phase. In the simulation, the surface drag was approached by a new correlation inside the Algebraic Interfacial Area Density (AIAD) model. The AIAD model allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows a good qualitative agreement. The results indicated that quantitative agreement of the CCFL characteristics between calculation and experimental data was obtained. To validate the model and to study scaling effects CFD simulations of the CCFL phenomenon in a full scale PWR hot leg of the UPTF test facility were performed. Also these results indicated a good agreement between the calculation and experimental data. The final goal is to provide an easy usable AIAD framework for all ANSYS CFX users, with the possibility of the implementation of their own correlations. [ABSTRACT FROM AUTHOR]

Abstract: Research into gas–liquid countercurrent two-phase flow in a model of pressurized water reactor (PWR) hot leg has been carried out over the last several decades. An extensive experimental data base has been accumulated from these studies, leading to the development of phenomenological correlations and scaling parameters of the countercurrent flow limitation (CCFL). However, most of the proposed correlations apply under a relatively narrow range of conditions, generally limited to the test section conditions and/or geometry. Moreover the development of mechanistic models based on the underlying physical processes has been limited. In contrast to this mechanistic form of modelling, the implementation of computational fluid dynamics (CFD) techniques has also been pursued, but the considerable robust three-dimensional (3D) closure relations for this application remain an unachieved goal due to lack of detailed phenomenological knowledge and consequent application of empirical one-dimensional experimental correlations to the multidimensional problem. This paper presents a comprehensive review of research work on countercurrent gas–liquid two-phase flow in a PWR hot leg and provides direction regarding future research on this topic. In the introductory section, the problems facing current research are described. In the following sections, recent experimental as well as theoretical research achievements are overviewed. In the last section, the problems that remain unsolved are discussed, along with some concluding remarks. It was found that only limited theoretical developments exist in the literature, however highly reliable experimental data are needed to support this effort. Additional work, both analytical and experimental, needs to be carried out on the effects of mass transfer on countercurrent flow limitation to improve the existing correlations and analytical models. [Copyright &y& Elsevier]

Abstract: This paper presents different CFD-simulations on flows which are relevant for nuclear reactor safety using a new modeling approach for the interfacial drag at free surfaces. The developed drag coefficient model was implemented together with the Algebraic Interfacial Area Density (AIAD) model () into the three-dimensional (3-D) computational fluid dynamics (CFD) code ANSYS-CFX. The applications considered include the prediction of counter-current flow limitations (CCFL) in a PWR hot leg, the development of hydraulic jump during the air–water co-current flow in a horizontal channel, and pressurized thermal shock (PTS) phenomena in a PWR cold leg and downcomer. For the modeling of these tasks, an Euler–Euler approach was used. This approach allows the use of different models depending on the local morphology. In the frame of an Euler–Euler simulation, the local morphology of the phases has to be considered in the drag model. To demonstrate the feasibility of the present approach, the computed main parameters of each case were compared with experimental data. It is shown that the CFD calculations agree well with the experimental data. This indicates that the AIAD model combined with new drag force modeling is a promising way to simulate the phenomena in frame of the Euler–Euler approach. Moreover the further validation of the model by including mass transfer effects should be carried out. [Copyright &y& Elsevier]

Abstract: In order to improve the understanding of counter-current two-phase flow and to validate new physical models, CFD simulations of a 1/3rd scale model of the hot leg of a German Konvoi pressurized water reactor (PWR) with rectangular cross section were performed. Selected counter-current flow limitation (CCFL) experiments conducted at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) were calculated with ANSYS CFX using the multi-fluid Euler–Euler modelling approach. The transient calculations were carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a shear stress transport (SST) turbulence model. In the simulation, the drag law was approached by a newly developed correlation of the drag coefficient () in the Algebraic Interfacial Area Density (AIAD) model. The model can distinguish the bubbles, droplets and the free surface using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows a good qualitative agreement. The results indicate also a quantitative agreement between calculations and experimental data for the CCFL characteristics and the water level inside the hot leg channel. [Copyright &y& Elsevier]

Abstract: In order to improve the understanding of counter-current two-phase flows and to validate new physical models, CFD simulations of 1/3rd scale model of the hot leg of a German Konvoi PWR with rectangular cross section was performed. Selected counter-current flow limitation (CCFL) experiments at the Helmholtz–Zentrum Dresden–Rossendorf (HZDR) were calculated with ANSYS CFX 12.1 using the multi-fluid Euler–Euler modeling approach. The transient calculations were carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a k-ω turbulence model for each phase. In the simulation, the surface drag was approached by a new correlation inside the Algebraic Interfacial Area Density (AIAD) model. The AIAD model allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows a good qualitative agreement. The results indicated that quantitative agreement of the CCFL characteristics between calculation and experimental data was obtained. The goal is to provide an easy usable AIAD framework for all Code users, with the possibility of the implementation of their own correlations. [Copyright &y& Elsevier]

Abstract: This paper replaces the paper published in the journal by . Because of an error in the implementation of the air flow meter some of the data given by are wrong. They are corrected within the present paper. The general results and conclusions remain unchanged. An experimental investigation on the air/water counter-current two-phase flow in a horizontal rectangular channel connected to an inclined riser has been conducted. This test-section representing a model of the hot leg of a pressurized water reactor is mounted between two separators in a pressurized experimental vessel. The cross-section and length of the horizontal part of the test-section are (0.25m×0.05m) and 2.59m, respectively, whereas the inclination angle of the riser is 50°. The flow was captured by a high speed camera in the bended region of the hot leg, delivering a detailed view of the stratified interface as well as of dispersed structures like bubbles and droplets. Counter-current flow limitation (CCFL), or the onset of flooding, was found by analyzing the water levels measured in the separators. The counter-current flow limitation is defined as the maximum air mass flow rate at which the discharged water mass flow rate is equal to the inlet water mass flow rate. From the high-speed observations it was found that the initiation of flooding coincides with the formation of slug flow. Furthermore, a slight hysteresis was noticed between flooding and deflooding. The CCFL data was compared with similar experiments and empirical correlations available in the literature. Therefore, the Wallis-parameter was calculated for the rectangular cross-sections by using the channel height as length, instead of the diameter. The agreement of the CCFL curve is good, but the zero liquid penetration was found at lower values of the Wallis parameter than in most of the previous work. This deviation can be attributed to the special rectangular geometry of the hot leg model of HZDR, since the other investigations were done for pipes. [Copyright &y& Elsevier]

Abstract: The purpose of the present study is to investigate the effects of surface tension on flooding phenomena in counter-current two-phase flow in an inclined tube. Previous studies by other researchers have shown that surface tension has a stabilizing effect on the falling liquid film under certain conditions and a destabilizing or unclear trend under other conditions. Experimental results are reported herein for air–water systems in which a surfactant has been added to vary the liquid surface tension without altering other liquid properties. The flooding section is a tube of 16mm in inner diameter and 1.1m length, inclined at 30–60° from horizontal. The flooding mechanisms were observed by using two high-speed video cameras and by measuring the time variation of liquid hold-up along the test tube. The results show that effects of surface tension are significant. The gas velocity needed to induce flooding is lower for a lower surface tension. There was no upward motion of the air–water interfacial waves upon flooding occurrence, even for lower a surface tension. Observations on the liquid film behavior after flooding occurred suggest that the entrainment of liquid droplets plays an important role in the upward transport of liquid. Finally, an empirical correlation for flooding velocities is proposed that includes functional dependencies on surface tension and tube inclination. [Copyright &y& Elsevier]

Abstract: An experimental investigation on the air/water counter-current two-phase flow in a horizontal rectangular channel connected to an inclined riser has been conducted. This test-section representing a model of the hot leg of a pressurized water reactor is mounted between two separators in a pressurized experimental vessel. The cross-section and length of the horizontal part of the test-section are (0.25m×0.05m) and 2.59m, respectively, whereas the inclination angle of the riser is 50°. The flow was captured by a high-speed camera in the bended region of the hot leg, delivering a detailed view of the stratified interface as well as of dispersed structures like bubbles and droplets. Countercurrent flow limitation (CCFL), or the onset of flooding, was found by analyzing the water levels measured in the separators. The counter-current flow limitation is defined as the maximum air mass flow rate at which the discharged water mass flow rate is equal to the inlet water mass flow rate. From the high-speed observations it was found that the initiation of flooding coincides with the formation of slug flow. Furthermore, a hysteresis was noticed between flooding and deflooding. The CCFL data was compared with similar experiments and empirical correlations available in the literature. Therefore, the Wallis-parameter was calculated for the rectangular cross-sections by using the channel height as length, instead of the diameter. The agreement of the CCFL curve is good, but the zero liquid penetration was found at lower values of the Wallis parameter than in most of the previous work. This deviation can be attributed to the special rectangular geometry of the hot leg model of FZD, since the other investigations were done for pipes. [Copyright &y& Elsevier]

Abstract: The purpose of the experimental study is to investigate the effects of pipe inclination, pipe length, pipe diameter and surface tension of the working liquid on the onset of flooding of gas–liquid adiabatic counter-current two-phase flow in inclined pipes. Flooding in inclined pipes were observed by using the combination of visual observation, measurement of discharged liquid flow rate and time variation of liquid hold-up. And it was defined as the maximum air flow rate at which the discharged liquid flow rate is equal to the inlet liquid flow rate. As a result we proposed a correlation to predict the flooding gas velocity in inclined pipes under a given liquid flow rate, and the predictions agreed well with the experimental observations. [Copyright &y& Elsevier]

Abstract: The liquid film characteristics at the onset of flooding in an inclined pipe (16mm i.d. and 2.2m in length) have been investigated experimentally. A constant electric current method and visual observation were utilized to elucidate the flow mechanisms at the onset of flooding. Two mechanisms are clarified to control the flooding in lower flooding and upper flooding, respectively. The lower flooding occurred at lower liquid flow rate and high pipe inclination angle. In this mechanism, the liquid film does not block the pipe cross-section. On the other hand, the upper flooding occurred at higher liquid flow rate and low pipe inclination angle. In this case, blocking of the pipe cross-section by large wave and entrainment plays an important role. The experimental data indicated that there was no reversal motion of liquid film at the onset of flooding during the operation of both lower flooding and upper flooding. The effects of pipe inclination angle on the onset of flooding are also discussed. [Copyright &y& Elsevier]

• The flow structure in the airlift pump-bubble generator was identified. • The chaotic and wavelet transform were used to analyze the diferential pressure signals • The chaotic level increases as the increase of both air volumetric flow rate & submergence ratio. • The observed flow patterns are bubbly-stable slug, bubbly-unstable slug, and slug-churn. The aim of this study is to identify the flow structure in an airlift pump–bubble generator system by using experimentally obtained differential pressure signals. Differential pressure measurements were applied at both the bottom and top test sections. The normalized time variation of the differential pressure data was analyzed using the probability density function (PDF), power spectral density function (PSDF), Kolmogorov entropy, and discrete wavelet transform (DWT). The results indicate that the water movement mechanism in the riser pipe could be divided into three regions, namely fixed liquid, locally moving liquid, and fully moving liquid, depending on the supplied superficial air velocity. Moreover, the chaotic in riser pipe increases with the increase of the submergence ratio at high supplied superficial air velocity. The chaotic level at the bottom of the test section was higher than that at the top of the test section at low supplied superficial air velocity. Finally, the observed flow patterns closely conformed to the previous definition and flow pattern maps. The bubbly flow was classified into clustered, homogeneous, and cap bubble regimes. The slug flow regime was classified into bubbly stable slug, bubbly unstable slug, and slug-churn, wherein the frequencies of both the liquid and air slugs increased with an increase in the air superficial velocity and submergence ratio. [ABSTRACT FROM AUTHOR]

A two-phase flow measuring device whose measurement system does not disturb the flow pattern, real-time measurement, and non-destructive measurement or non-intrusive model is a typical tool for an ideal situation. One measuring instrument that meets these criteria is an ultrasonic flow meter. Ultrasonic sensors can measure the velocity of fluid flow in pipelines. It has the advantage of high accuracy and reproducibility and does not make direct physical contact with the fluid in the pipe. Low fabrication costs and fast response make ultrasonic flowmeters widely used for two-phase flow measurements in both horizontal and vertical orientations. The void fraction or liquid holdup and velocity are the two most essential parameters for flow monitoring. The Time of Flight (ToF) method is mainly used for measurements in several ultrasonic flowmeter methods. In the present manuscript, the introductory section of this review explains the advantages of using the Time of Flight (ToF) method and its basic principles. This review also discusses research on measuring velocity and flow rate, differences in intrusive and non-intrusive measurement methods, parameters that affect ultrasonic measurements, and finally, measuring film thickness using non-intrusive methods. • The mass flow rate of two-phase flow is measured using a non-intrusive ultrasonic flowmeter. • The velocity of each phase and the void fraction or the liquid hold-up are two important parameters to be determined for two-phase flow mass flow rate measurement. • The Time of Flight (ToF) method and its basic principles, advantages are discussed in detail. • The comparison of flow patterns characterization using echo amplitude ratio method and other existing methods such as PDF (Probability Distribution Function), PSD (Power Spectral Density) and DWT (Discrete Wavelet Transform) is proposed. [ABSTRACT FROM AUTHOR]

The micro-bubble generator (MBG) is a novel aeration technology utilizing the concept of fluid flow through an orifice, where air is sucked into the internal chamber of the MBG by the pressure difference created by the orifice and immediately pushed by the high-velocity flow of the fluid. This mechanism creates micro-size bubbles with a high dissolution rate. This study focused on studying the effect on the oxygen dissolution rate of the two most important operating parameters, i.e. the volumetric flow rate of the liquid (QL) and the volumetric flow rate of the air (QG). Various combinations of values for QL and QG were systematically compared by means of the oxygen mass transfer coefficient (kLa). The experiment was carried out in a transparent container of 2.8 m x 0.6 m x 0.4 m filled with tap water that was aerated using an orifice/porous-pipe type MBG. The dissolved oxygen (DO) values were measured at distances of 60 cm, 120 cm, and 180 cm from the MBG outlet. The experiment was designed with five different values for QL and QG respectively. The results showed that the value of kLa, which is proportional to the oxygen dissolution rate, increased asymptotically with increasing QL value, while the QG values did not significantly affect the kLa value. [ABSTRACT FROM AUTHOR]

Oil and Gas is natural resources in Indonesia which is the business related to is regulated in Law Number 22 of 2001 about Oil and Gas. There are two kinds of business related to oil and gas that are upstream and downstream. In upstream oil and gas business, there still a lot problem faced by the government and the enterprises. Thus, it is needed simplification license for upstream oil and gas in order to increase investment which will lead into effective and efficient public services. Normative law here is applied as method to analyse the regulations related to oil and gas industry license. Furthermore, the approach used here are statute approach and conceptual approach. The results reveal that the Licensing for Utilization of Resources and/or Infrastructure of Upstream Oil and Gas Business does not yet have a synchronization of authority in the issuance of these licenses. In order to obtain effective and efficient upstream oil and gas business licensing services, it is necessary to synchronize and harmonize regulations and it is need a one-stop licensing service as referred to the Presidential Regulation Number 97 of 2014 concerning Implementation of One Stop Integrated Services. [ABSTRACT FROM AUTHOR]