Search

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: 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]

The circumferential film thickness distribution in an air-water horizontal annular two-phase flow was investigated in 26 mm pipe diameter by using the conductance probe. The superficial gas and liquid velocities were 10–40 m/s and 0.025–0.4 m/s, respectively. In general, the film thickness decreases as the liquid velocity decreases and the gas velocity increases. For low superficial gas velocity, high asymmetry of liquid film thickness distribution is generally found. In addition, the liquid film at the upper half of the pipe mostly consists of surge of waves with frequency lower than that of the bottom. At the lowest superficial liquid velocity of the present experimental range, the mean film thickness at the bottom ranges from 0.24 mm to 1.3 mm. Meanwhile, at the highest superficial liquid velocity, it ranges from 1.0 to 4.29 mm, depending on the superficial gas velocity. At the higher superficial gas velocity, a more uniform of liquid film thickness distribution is commonly found. Under this flow condition, the wave at the upper has a similar frequency to that of the lower half and a coherent liquid wave is normally found. To predict the film thickness at any circumferential position, an empirical correlation is proposed on the basis of the physics of the phenomena. In comparison to the available experimental data, the correlation has a good capability to predict the circumferential liquid film thickness distribution. [ABSTRACT FROM AUTHOR]

The bubble breakup pattern on a swirl-type bubble generator (MBG) with water and air fluids was experimentally studied. The bubble breakup pattern was analyzed visually and characterized using several parameters such as Pressure Drop (ΔP), Kolmogorov Entropy, Standard Deviation, and DWT (Discrete Wavelet Transform), which were taken from the extraction of pressure signals at the water inlet and outlet of the bubble generator. The wavelet spectrum of the measured signal was shown to identify the overall bubble breakup pattern, and the wavelet variance vector is proposed as a character vector to identify the bubble breakup pattern. The results show that there were three types of different flow breakup patterns: (1) static breakup, (2) dynamic breakup, and (3) tensile breakup. The observed bubble breakup sub-patterns can be categorized into tensile, moderate tensile, high tensile, dynamic, low dynamic, static, and high static sub-patterns. The static clustered breakup pattern has the highest wavelet energy compared to the tensile and dynamic clustered breakup. [ABSTRACT FROM AUTHOR]

The effects of fluid properties on the wave velocity and frequency of gas–liquid annular two-phase flow were investigated in 26 and 16-mm inner pipe diameters. The liquid viscosity was varied from 1.02 to 6.57 mPa s using water and glycerol solution and the surface tension was varied from 34.0 to 71.7 mN/m using water and butanol solution. The range of superficial liquid and gas velocities were set to 0.05–0.2 m/s and 12–40 m/s, respectively. In general, the wave frequency decreases with increasing liquid viscosity and decreasing surface tension. The wave velocity decreases with increasing liquid viscosity for all range of superficial gas and liquid velocities. The lower surface tension gives the lower wave velocity for low superficial liquid velocity. For high superficial liquid velocity, however, the wave velocity increases with decreasing surface tension. The wave frequency decreases with the increase of liquid viscosity and the decrease of surface tension, with more significant effects are found at the higher superficial gas and liquid velocities. Comparisons of experimental data with the existing correlations for wave velocity and wave frequency have been carried out and new correlations have been developed with a considerably good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

The aim of the present study was to identify the interfacial behavior of the sub-regime of gas-liquid stratified two phase flow by using the pressure differential signal data. Here, the probability distribution function (PDF), power spectral density (PSD), kolmogorov entropy and discrete wavelet transform (DWT) were used to analyze the differential pressure signals. The indicators of each flow sub regime were analyzed on the basis of the quantitative values of the statistical curves, which were also validated by visual observation of the video images. The results indicated that there are six identified sub-regimes of stratified flow namely stratified smooth (S), two-dimensional (2-D) wave, three-dimensional (3-D) wave, roll wave (RW), entrained droplet + disturbance wave (ED + DW) and pseudo slug (PS). Next, the increase of liquid viscosity will shift the transition line from the RW to ED + DW to a lower both of J L and J G. The increase of the liquid viscosity provides a stabilizing effect to reduce the chaos of the pressure gradient fluctuation. For the RW and the ED + DW sub-regime, the increase of the liquid viscosity shifts the wavelet energy to a larger scale and lower frequency. For the PS sub-regime, the increase of liquid viscosity shifts the wavelet energy to a smaller scale with a higher frequency. For the RW sub-regime, the increase of J G will increase the wavelet energy at the small-scale and high-frequency decomposition levels. • The sub-regimes of the stratified flow are stratified smooth, 2D wave, 3D wave, roll wave, entrained droplet + disturbance wave and pseudo slug. • Non linier statistics were implemented to analyze the differential pressure signals. • The increase of the liquid viscosity provides a stabilizing effect in reducing the chaos of the pressure gradient. • The wavelet energy shifts to a larger scale and lower frequency for the roll wave sub-regime as the increase of the viscosity. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to investigate the performance and flow structure of an airlift pump-bubble generator during the lifting of gas-water-solid particles three-phase flow experimentally. Here, a mechanistic model was also developed to predict the performance of an airlift pump bubble-generator on the basis of power balance. In the experimental part, the flow structure was analyzed visually, and taken from the extraction of the differential pressure signal at both the bottom and top test sections. Time series of differential pressure normalization was analyzed by using wavelet transform to determine the wavelet energy distribution. The wavelet energy was used as input the artificial neural network method to clustering the flow regime. The results indicate that under a constant of superficial gas velocity, the discharged both the water and particle increase with the submergence ratio (SR). SR is defined as the ratio of the distance from the injector to the water surface and the distance from the injector to the outlet side. Next, under a constant gas superficial velocity, the increase of SR will increase the solid fraction, but the fractions of both gas and water will decrease. The flow patterns were classified in the clustered bubble, homogeneous bubble, cap bubble, bubbly-stable slug, bubble unstable slug, and slug churn. Furthermore, the bubble flow is indicated by the peak wavelet energy on an eighth-level decomposition of approximation signal (a8), and the energy of the fourth-level decomposition of detail signal (d4) closes to the energy of the fifth-level decomposition (d5). The wavelet energy concentrated on the seventh and/or eighth level decomposition of detail signal (d7 and/or d8) is the indicator of slug flow in the riser pipe. The clustering flow patterns by using the ANN with input from wavelet energy gives a better approach than that of stochastic parameters of time series of the pressure differential. Moreover, the developed mechanistic model shows a good agreement with the experimental data. • The flow structure of air-water-solid particles in the airlift pump-bubble generator was identified. • The flow patterns are clustered bubble, homogeneous bubble, cap bubble, bubbly-stable slug, bubble unstable slug, and slug churn. • The submergence ratio has a significant effect on the fraction of solid, gas and water. • The clustering flow patterns by using the ANN with input from wavelet energy gives a better approach. • The developed mechanistic model shows a good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

This study investigates the flow dynamics of a non-Newtonian two-phase flow within a horizontal square microchannel. The experimental apparatus employed an acrylic channel with a side length of 8 × 10−4 m. Nitrogen served as the test gas, and the test liquids consisted of water and CMC (Carboxymethylcellulose) aqueous solutions at concentrations of 0.2 and 0.4 %wt. The superficial velocity of working gas and liquids spanned ranges of 0.26–20 m/s and 0.05–1.0 m/s, respectively. A differential pressure transducer was used to measure pressure gradients, while a high-speed video camera captured the flow behavior for analysis with a custom image processing technique. Nonlinear regression statistical analysis was applied to establish the criteria for flow pattern transition. Furthermore, signal processing techniques such as PSD (Power Spectral Density), DWT (Discrete Wavelet Transform), ANN (Artificial Neural Network), and Kolmogorov entropy were employed to analyze the flow behavior based on the pressure gradient signals from the differential pressure transducers. Our findings reveal the occurrence of bubbly, slug, slug-annular, and churn flow patterns. The nonlinear regression statistical analysis offered ambiguous results for determining flow pattern transitions. However, an empirical coefficient was obtained for the nondimensional liquid height. Moreover, the empirical nondimensional liquid height aligned well with the experimental values. The PSD and DWT analysis corroborated each other in clearly characterizing the flow pattern based on pressure gradient fluctuation and wavelet energy. The Kolmogorov entropy effectively captured the chaotic flow pattern. Furthermore, the ANN analysis demonstrated a solid agreement between the predicted and actual flow patterns. • The effect of rheological properties of non-Newtonian liquids on the flow pattern characteristics were investigated. • CMC (Carboxymethylcellulose) aqueous solutions as non-Newtonian liquids were used as the tested liquids. • The flow pattern characteristics were determined by using statistical analysis non-linear regression. • The flow pattern characteristics were identified by signal processing techniques including PSD (Power Spectral Density), DWT (Discrete Wavelet Transform), ANN (Artificial Neural Network), and Kolmogorov entropy. [ABSTRACT FROM AUTHOR]

Java-Bali is Indonesia's largest power system, with enormous CO 2 emissions. Therefore, the Government of Indonesia has committed to reducing CO 2 emissions by introducing two policies: (1) a new and renewable energy target and (2) coal phase-out planning. However, no study on the energy-carbon-economic nexus in Indonesia has analyzed the impact of reducing CO 2 emissions using these policies. Therefore, this research analyzes the economic impacts on the energy and carbon nexus in the Java-Bali system to obtain and review feasible strategies to support these policies. OSeMOSYS was used in this study to implement multiple scenarios of emission reduction. The results indicate that policies that clearly regulate carbon limits and taxes for power generation companies are required. A carbon limitation of 10,087 million tons with a carbon tax of 67 USD/ton and a carbon limitation of 8482 million tons with a carbon tax of 77 USD/ton are required to supporting the new and renewable energy target and coal phase-out plan. Nuclear energy and liquefied natural gas are crucial for supporting the new and renewable energy targets and coal phase-out policies. Therefore, the government must immediately decide to utilize nuclear energy and guarantee an adequate liquefied natural gas supply at an affordable price. Furthermore, it is crucial to seek alternatives to meet the demand projection through interconnection with other islands that have immense renewable energy sources to meet the new and renewable energy target and successfully implement the coal phase-out plan. [Display omitted] • A new and renewable energy (NRE) target and coal phase-out plan have been proposed • Carbon limits and taxes are required to support the NRE target and coal phase-out • The NRE target requires a carbon limitation of 10,087 million tons • The NRE target requires a carbon tax of 67 USD/ton • Coal phase-out requires a carbon limitation of 8482 million tons • Coal phase-out requires a carbon tax of 77 USD/ton [ABSTRACT FROM AUTHOR]

The Lattice Boltzmann Method (LBM) was implemented to simulate the two-dimensional (2-D) Rayleigh–Taylor instability (RTI) during the mixing of the immiscible fluids. Two important parameters of the density and the viscosity as represented respectively by the Atwood and the Reynolds numbers were considered. In the calculation the density of two immiscible fluids was calculated by using the equation of state (EOS). In the present simulations, both Atwood and Reynolds numbers were varied in order to investigate the time variations of the interfacial behavior during RTI, the position of bubbles and spikes, and the horizontal average density. The results indicate that the Atwood number has a higher effect than the Reynolds number in the mixing process during RTI. The bubbles and spikes positions go farther in the displacement with the increase of both Reynolds and Atwood numbers. Moreover, the increase of both Reynolds and Atwood numbers accelerate the mixing process during RTI. • Rayleigh–Taylor instability (RTI) was simulated using The Lattice Boltzmann Method. • Two important parameters such as density and viscosity were considered. • The density of two immiscible fluids was calculated by using the equation of state (EOS). • The Atwood number is more influential in the mixing process of RTI than the Reynolds number. • The increase of both Reynolds and Atwood numbers accelerate the mixing process during RTI. [ABSTRACT FROM AUTHOR]

Kelvin–Helmholtz instability (KHI) occurs at the interface of two fluids, in which the heavier fluid flows at the bottom. In the present numerical work, the KHI was analyzed by solving the modification of two-dimensional (2-D) incompressible Navier–Stokes equations. To capture the interface, the Cahn–Hilliard equation was implemented into the Navier–Stokes equations. The phenomena around the KHI of two and three-component fluids were investigated numerically by using radial basis function (RBF) combined with the domain decomposition method (DDM) in a primitive variable formulation. Here DDM is able to solve the large scale problem. On the other hand the calculation accuracy decreases with the increase of the number of the subdomains. For the above reason, in the present works, the domain was partitioned into 15 x 15 subdomains in order to reduce the decrease in accuracy due to the domain division. Next, fractional step method was used to solve the modification of the Navier–Stokes equations. The numerical results indicate that the procedure used in the present work can easily handle the KHI problem under the variations of the interface thickness, density ratios, and initial velocity differences. Moreover, the interface evolutions obtained from the present method agree well with those of the finite difference method. The effects of the interface thickness, density ratio and magnitude of velocity difference on the KHI were also investigated. The decrease of the interface thickness produces a non-smooth concentration profile, and the increase of the interface thickness produces too much surface diffusion. It was found also that the increase of the density ratio reduces the growth of KHI. The interface rolls up are strongly affected by the initial horizontal velocity difference. Finally, the present study also shows that the RBF method is a reliable method to solve the KHI on the complex domains. • Kelvin–Helmholtz instability (KHI) was simulated using meshless radial basis functions. • Fractional step method was used to solve the modified Navier–Stokes equations. • The numerical procedure can handle KHI problems under the various of fundamental parameters. • The density ratio and initial velocity difference play the important roles on the growth of KHI. [ABSTRACT FROM AUTHOR]

• A dual speaker thermoacoustic heat pump was constructed for frequency of 100 Hz. • Acoustic field was controlled by varying the magnitude and phase difference between speakers. • Thermoacoustic heat transport was improved when the values of impedances and impedance phase between the ends of the regenerator were matched. • Variation of phase featured acoustic power flow and thermoacoustic heat transport characteristics markedly different in comparison to higher frequency experiments due to differences in impedance and impedance phase matching between the ends of the regenerator. A dual acoustic driver thermoacoustic heat pump was constructed to investigate the effect of acoustic field control on travelling wave thermoacoustic heat transport at a frequency of 100 Hz. The acoustic field was controlled by varying the phase difference and magnitude between the two drivers. Variation of phase difference demonstrated the change of both acoustic power flow direction and standing-travelling wave characteristics. Maximum temperature differences obtained between the ends of the regenerator were 23 °C and 19 °C when the acoustic power was flowing in the negative and positive directions, respectively. It has been shown that matching impedances on the cold and hot side of the regenerator influence the thermoacoustic heat pumping characteristics. Where monodirectional acoustic flow was observed on both sides of the regenerator, the impedance angles also coincided well. Variation of magnitude displayed a trend in which activation of an opposing acoustic driver at weaker power enhanced acoustic power flow and heat transport. A maximum temperature difference between the hot and cold sections of 23 °C is obtained when the input electric power of the opposing acoustic driver was 17% of the power of the initial acoustic driver where the impedances and impedance angles on both ends of the regenerator are matched but the acoustic field travelling wave characteristics are still sufficient for travelling wave device operation. [ABSTRACT FROM AUTHOR]

Sulawesi is a strategic economic region in eastern Indonesia that is facing high growth in electricity demand. Two challenges need to be addressed to achieve its renewable energy (RE) target. The region comprises two unconnected electricity systems, and its RE resources are scattered geographically. It is therefore harnessing RE resources and interconnecting these two electricity systems can be an optimal scenario for generation expansion planning (GEP). This study aims to develop an open-source GEP model for the Sulawesi region as well as identify the optimal electricity development pathway while considering not only the need to achieve higher penetration of renewables and reduce CO 2 emissions but also the option and associated benefits and costs of interconnecting the two distinct electricity systems. The results show that the optimal RE development pathway is the interconnection scenario, which ensures a lower generation cost with reduced emissions. This scenario reduces the cost by USD 258.8 million compared with the total cost of the isolated scenario and ensures the RE target of 31% by 2050. This study recommends that investment in hydro and wind energy should be simultaneously encouraged, and robust policies are required to support investments in RE sources, such as geothermal, biomass, and solar energy. [Display omitted] • Renewable energy target set by the government of 31% of the energy mix by 2050 • Sulawesi region is dominated by coal at 44% of their energy mix • Interconnecting the systems is the cost-optimal solution to achieve the target • Interconnecting the systems produces a generation cost of 8.36 cents USD/kWh • Implementing the targets reduces emissions in 2050 by 35.8% compared to BAU [ABSTRACT FROM AUTHOR]

Highlights • The wave characteristics of gas-liquid stratified flow in horizontal pipe were investigated experimentally. • The wave characteristics were gathered by using the combination of the liquid hold-up and visualization data. • The experimental correlations to predict the flow parameters of the wave were proposed. • The ratio of Reynolds number and Martinelli parameter plays an important role in the proposed experimental correlation. Abstract The understanding of the interfacial wave structure and its effect to the interfacial friction factor is important to reveal the transition from stratified to the slug flows. However, the available theoretical of models, as well as the correlations to predict the wave interfacial characteristics, is quite rare. The discrepancy among researchers is often found. In the present work, the wave characteristics of air-water stratified flow were investigated experimentally. The inner diameter was 26 mm. The liquid superficial velocity (J L) raised from between 0.02 m/s and 0.075 m/s while the gas superficial velocity (J G) ranged from 4 m/s to 16 m/s. A high speed camera was used to capture high-quality visual data which was later processed with the image processing technique. As a result, the quantitative parameters of the stratified flow were successfully determined and analyzed. Next, the dimensional analysis was carried out to develop correlation to predict the flow parameters of the wave such as the wave frequency, the wave velocity, the wave amplitude, and the wavelength. Furthermore, it is found that the ratio of gas and liquid Reynolds number and Martinelli Parameter plays important role in almost all of the proposed correlation. [ABSTRACT FROM AUTHOR]

Highlights • Hydrodynamic characteristics of orifice type microbubble generator were investigated. • The bubbles diameter distribution is approached by the beta distribution function. • The liquid flow rate takes part an important role on the the volumetric mass transfer. • The empirical correlations of hydrodynamic parameters of the microbubbles were proposed. Abstract The aim of this work was to investigate the characteristics of oxygen dissolution into water in aeration using an orifice type microbubble generator (MBG). The analysis was conducted using dimensional analysis by taking into account bubble diameter distribution and oxygen mass transfer rate. The characteristics of microbubbles produced by MBG were affected by the combination of air and water flow rates through the MBG. In this study, the ranges of air and water flow rates were set at 0.1–1.0 l/min and 30.0–80.0 l/min, respectively. The microbubbles were captured by a high-speed camera using shadow photographic technique to obtain the bubbles size distribution as well as the average diameter of the bubbles. The volumetric mass transfer coefficient of oxygen was measured using dynamic physical absorption model. The results verified that the size of microbubble depend on air and water flow rates. The increase of the gas flow rate increased the average bubble diameter. On the other hand, the increase of the water flow rate decreased the average bubble diameter. Furthermore, the increase of water flow rate increased the oxygen volumetric mass transfer coefficient. Finally, by using dimensional analysis, the empirical correlation of volumetric mass transfer coefficient, average bubble diameter, and bubble diameter distribution, was proposed. The correlation showed that liquid Reynolds number played most important role in average bubble diameter and oxygen mass transfer rate obtained in MBG aeration. [ABSTRACT FROM AUTHOR]

The study on the interfacial phenomena of flooding during the counter-current flow of gas-liquid in a complex pipe was carried-out experimentally. It consists of a combination of the horizontal pipe, elbow and inclined pipes to simulate the hot leg pipe in a PWR. The inner diameter was 25.4 mm as scale down of real hot leg pipe of German Konvoi type reactor. The visual observations were performed using high-speed video cameras. The measured parameters were the liquid film thickness and the pressure difference between reactor pressure vessel (RPV) simulator and steam generator (SG) simulator. The film thickness inside the test pipe was determined by using the processed image of visual data. As a result, three different mechanisms at the onset of flooding in counter-current were clarified, and are strongly affected by liquid superficial velocity. At low liquid superficial velocity (J L ), the flooding mechanism is triggered by the presence of wavy interface along the horizontal pipes in the form of a liquid blockage on the elbow. At the medium J L , the slug was detected along the horizontal pipe. However, the slug collapses immediately since the water is insufficient to maintain the blockage. At high J L , the slug occurs and travels along the horizontal pipe until the elbow. Moreover, the effect of the length of horizontal pipe on the interfacial behavior of air water counter current flow also can be explained. As the length of the horizontal pipe decreases, the onset of flooding occurs at a higher gas liquid mass flow rate. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to propose an image processing technique in order to study the interfacial behavior of air-water slug two-phase flow in horizontal pipes. Here, the experiments were performed in two sets of transparent acrylic pipes with inner pipe diameters of 16 mm and 50 mm. To observe the interfacial behavior of slug flow, the liquid and gas superficial velocities were set to 0.2–0.77 m/s and 0.7–2.83 m/s, respectively. Visualization studies by using high speed video camera combined with image processing techniques were since it offered numerous advantages. Moreover, a sequential procedure was implemented for processing of each image. This technique has succeeded to enhance the image contrast and remove the uneven background. Next, a number of steps applied to binary image were also performed in order to remove the dispersed bubble attached on bubble tail which becomes one of the biggest challenges for the visualization studies of slug flow. As a result, the developed image processing technique was able to minimize the errors in order to produce the accurate measurement. Moreover, the processed image have been utilized to gather the quantitative information. It reveals the comprehensive characteristics of slug flow in horizontal pipes. Finally, a good agreement between the present and previous works proves the reliability of the developed technique. [ABSTRACT FROM AUTHOR]

The effects of the wettability of a droplet impacting onto a hot solid surface under medium Weber numbers were studied experimentally. The Weber numbers used in the present experiment were 52.1, 57.6, and 63.1. Three kinds of solid surfaces with different wettability were used. These were normal stainless steel (NSS), TiO coated NSS, and TiO coated NSS radiated with ultraviolet rays. The surface temperatures were varied from 60 to 200 °C. The image of side the view and 30° from horizontal were taken to explain the spreading and the interfacial behavior of a single droplet during impact the hot solid surfaces. It was found that under medium Weber numbers, the surface wettability plays an important role on the droplet spreading and evaporation time during the impact on the hot solid surfaces. The higher the wettability, the larger the droplet spreading on the hot surface, and the lower the evaporation time. [ABSTRACT FROM AUTHOR]

• The liquid hold-up fluctuations of gas-liquid counter-current flow in PWR hot leg was analyzed statistically. • The data were analyzed using non-linier statistics, discrete wavelet transforms, and the Kolmogorov entropy. • There were no significant differences between the flooding mechanisms for both air/water and steam/water flows. • The higher the system pressure, the higher the frequency occurrence of slugging during flooding. • Kolmogorov entropy enables to correlate the stabilizing effect due to the fluid resistance during flooding. This study addresses a statistical characterization of the interfacial behaviors during gas/liquid counter-current flow in a large scale of pressurized water reactor's hot leg typical geometry on the basis of both time and frequency domain analyses. Here, the visualizations were captured by high-speed cameras. Furthermore, the image processing algorithm on the basis of pixel identification was developed to identify the time-series interfacial dynamics of the liquid holdup fluctuations, comprising the wave growth and its movement. The obtained data were further analyzed by using various advanced statistical tools comprising the probability density function, power spectral density function, and also discrete wavelet transform. Additionally, chaotic levels of the flow were obtained through the Kolmogorov-entropy analysis. Particular results reveal that a typical mechanism of flooding begins with the appearance of a wavy interface which further develops into either a roll or large wave, and later blocks the entire cross-sectional area of the conduit around the bend region. This later stage indicates the inception of flooding which is characterized by the increase of the water level close to the bend region. Next, the higher the pressure of system, the higher the frequency occurrence of slugging, while the injected gas flow rate obtained a different trend. However, the Kolmogorov entropy enables to correlate the stabilizing effect due to the fluid resistance which corresponds to either the pressure of the system or the physical properties of the fluid. In addition, there were no significant differences between the flooding mechanisms for both the air/water and steam/water flows. [ABSTRACT FROM AUTHOR]

Slug flow is the most prevalent problem of two-phase fluid transportation in the petroleum industries. Here, large amplitude waves lead to the pipe blockage that possible to cause the damage of the mechanical structure. The experimental investigation of gas-liquid slug two-phase flow in a horizontal pipe was carried out to investigate the initiation and flow development mechanisms. Air and water were used as the working fluids. The inner pipe diameter was 26 mm. In the present experimental study, the slug initiation mechanisms were explained by visual observation and pressure fluctuations. Moreover, the initiation frequency of slug flow and the evolution of passing slug frequency along the pipeline were also observed by using two high video cameras. As a result, several basic mechanisms of slug flow initiation in a horizontal pipe were clarified. Those were the wave coalescences, the wave growth mechanism, and the large disturbance waves. A flow initiation map was proposed to address those mechanisms. Here, the slug initiation frequency and the passing slug frequency were obtained in relation to the pipe length position. The static pressure measurement was also used to verify the image processing results on the characteristics of slug initiation mechanisms. The obtained qualitative and quantitative results from the investigation can be used to evaluate the recent available models. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of liquid properties on counter-current flow limitation in 1/30 downscale PWR hot leg was investigated. • Five water-based solutions with different physical properties were utilized as the tested liquids. • The CCFL characteristics were examined by various existing correlations and models. • An empirical correlation was proposed to predict the flooding superficial velocity. To promote the safety of the nuclear reactors, numerous authors have carried out investigations of gas/liquid counter-current two-phase flow in order to understand the characteristics during the inception of flooding or CCFL. The present work covers an experimental and analytical study on the effect of liquid properties on CCFL characteristics in a complex geometry representing 1/30 scaled-down version of a German-Konvoi PWR hot leg. The obtained results reveal that the gas velocity to initiate the flooding monotonically decreases with the increase of the liquid velocity. At high liquid flow rates, it is noticed that with the increase of glycerol percentage, the gas flow rate needed to initiate the flooding significantly decrease due to either the increase in liquid viscosity or the decrease in corresponding surface tension. Here under the same flow condition, the flooding is initiated faster by the higher glycerol percentage. Moreover, instead of the well-known Wallis superficial velocity, the Kutateladze-type parameter or a combination of the Wallis parameter and liquid property numbers by Zapke & Kröger (1996) which were previously proposed by numerous authors to investigate the effects of liquid properties on CCFL characteristics, a modified non-dimensional Wallis parameter combined with the inverse viscosity number introduced by Ma et al. (2020) is found herein to more accurately correlate the present experimental data. Through a dimensional similarity analysis, a new empirical correlation reveals that the liquid Froude number is the greatest determinant of CCFL characteristics with respect to the effect of the liquid properties. [ABSTRACT FROM AUTHOR]

This paper presents a multi-objective optimization model for a long-term generation mix in Indonesia. The objective of this work is to assess the economic, environment, and adequacy of local energy sources. The model includes two competing objective functions to seek the lowest cost of generation and the lowest CO 2 emissions while considering technology diffusion. The scenarios include the use of fossil reserves with or without the constraints of the reserve to production ratio and exports. The results indicate that Indonesia should develop all renewable energy and requires imported coal and natural gas. If all fossil resources were upgraded to reserves, electricity demand in 2050 could be met by domestic energy sources. The maximum share of renewable energy that can be achieved in 2050 is 33% with and 80% without technology diffusion. The least cost optimization produces lower generation costs than the least CO 2 emissions, as well as the combined scenario. Total CO 2 emissions in 2050 are five to six times as large as current emissions. The least CO 2 emissions scenario can reduce almost half of the CO 2 emissions of the least cost scenario by 2050. The proposed multi-objective optimization model leads some optimal solutions for a more sustainable electricity system. [ABSTRACT FROM AUTHOR]

• The experiment was conducted during the liquid–gas counter-current two-phase flow in a 1/30 scaled-down of PWR hot leg. • The liquid thickening on the upper edge of the hydraulic jump triggers the liquid blockage to initiate the CCFL. • The statistical characterizations were investigated on the basis of both the locus and the flow parameters. • The time-domain and frequency-domain analyses implies a good agreement with the visual observations, while the wavelet analysis is able to differ the obtained flow regimes. The present work investigates the statistical characteristics of the fluctuations of the liquid film thickness obtained by resistive-conductance probe signals of a complex geometry representing a 1/30 down-scaled of a PWR hot leg. Here, four locations at the horizontal part of the test section were assessed, while the flow development was investigated through a close observation by using a high-speed video camera. Next, the normalized voltages, indicating the liquid film thickness fluctuations, are shown in the time-series. From the fluctuations, the amplitudes representing the film thickness were recorded. Hence, such statistical diagnostic tools were applied on the basis of time-domain, frequency-domain and also time–frequency domain analyses. From the probability density function, the distributions of the fluctuations were assessed, whereas the power spectral density function describes the dominant frequencies. In addition, the Kolmogorov entropy denotes the chaotic level of the signal, meanwhile the wavelet energy corresponds to several details on the wavy interfaces on the basis of its frequency scales. Next, those parameters were statistically employed to elaborate the interfacial behaviors due to the signal characteristics. The results indicate that the low dominant frequency corresponds to the occurrence of either liquid blockage or slugs during the acquisition, meanwhile the largest scale fluctuations reveal the wave movements. [ABSTRACT FROM AUTHOR]

An experimental study to assess the accuracy of wire-mesh sensors in dependence of bubble sizes and flow rates has been performed in a 50 mm × 50 mm transparent rectangular channel. The liquid superficial velocities were ranging from 0 m/s up to 0.62 m/s with the obtained bubble size ranging from 3 mm to 7 mm. A single wire-mesh sensor with 16 × 16 electrode wires was used with a temporal and spatial resolution of 10 kHz and 3.1 mm (lateral distance between two wires), respectively. Single bubbles with known bubble size, subsequently called reference bubble size, was injected into the test section via bubble injector approx. 25 cm upstream of the wire-mesh sensor. The bubble size measurement by using wire-mesh sensor cannot be obtained directly since it requires the information of bubble velocity which is not available only by installing a single sensor. Therefore, a stereoscopic observation was conducted to obtain the bubble velocity by tracking the successive frames as well as to study the intrusiveness of the sensor. This configuration gave an advantage that the registered bubble will be assigned with its real approach velocity and a better agreement is expected. As the result, a direct comparison of all individual bubbles with the reference bubble size showed an agreement within ±10%. However, a deceleration effect was found for low superficial and observed to disappear as the liquid superficial velocity increased then vanish at observed J L = 0.62 m/s. [ABSTRACT FROM AUTHOR]

• The LBM is used to investigate the complete behavior of RTI numerical model. • Good agreements with experiment and other numerical studies are obtained. • Instability rate is found to be greatly affected by Atwood numbers. • The equilibrium state of the instability is successfully simulated. The gravitational liquid-liquid two-phase flow was numerically investigated by using lattice Boltzmann method (LBM). The method was implemented for analyzing a model of Rayleigh-Taylor Instability (RTI). The feasibility of this present numerical approach was investigated by performing convergence test, and validating the obtained results with those obtained from experiments as well as other preceding numerical methods. Qualitative and quantitative comparisons were examined, whereby good agreements are noted for all cases. Parametric studies were also conducted by varying both of Reynolds and Atwood numbers to investigate the effects of viscosity and density ratio on the behavior of fluids interaction. Based on the obtained outcomes of this numerical approach, the present LBM was able to successfully simulate the complete phenomena during RTI, i.e.: the linear growth, secondary instability, bubble rising and coalescence, and liquid break-up, including turbulent mixing conditions as well as the equilibrium state. The finding obtained from this work might be beneficial in the investigation of parametric behavior in design of processes equipment such as for separator design. [ABSTRACT FROM AUTHOR]

The present work aimed to conduct the visualization study on the effect of the ethylene glycol concentration on the interfacial behavior of successive droplets during the impacting onto a horizontal hot solid surface. The tested liquid droplets were pure water and two ethylene glycol-water mixtures, which contain 10% and 20% of ethylene glycol. A polished cylindrical plate of stainless steel (SUS 304), with the surface roughness of 0.06 μm, was utilized as a solid surface. The surface varies for temperatures of about 110 °C–240 °C. The detailed phenomena during the droplet impact were recorded by using a high-speed video camera with the frame speed of 2000 fps and the resolution of the 1024 × 768. In addition, an own developed image processing technique was also implemented to obtain the quantitative parameters, such as the spreading ratio and the apex height during the droplet impacting onto a hot solid surface. As a result, the interfacial dynamics of the successive droplets were clarified. The addition of the concentration of ethylene glycol leads to the decrease of droplet oscillation during the spreading phase and delays both the bubble formation and the presence of secondary droplets. In addition, the research also reveals that the presence of the second droplet successfully improves the wetting area of the droplet. • The behaviors of successive droplets impact onto a horizontal hot solid surface were studied. • The tested liquid droplets were pure water and pure water that contain 10% and 20% ethylene glycol. • The tested solid material was polished stainless steel (SUS 304). • The effects of ethylene glycol on the droplet behavior were comprehensively presented. • The spreading velocity decreases with the increase of the ethylene glycol concentration. [ABSTRACT FROM AUTHOR]