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This study investigates the statistical characteristics of liquid film thickness fluctuations during countercurrent flow limitation on a complex geometry containing a horizontal and inclined pipe which are connected by an elbow. The fluctuation data are obtained by image processing technique which was applied towards high-quality images captured by a high-speed video recording. The result indicates that the thickening of the liquid triggers the liquid blockage that initiates flooding at the upper edge of the hydraulic jump. Moreover, the stochastic analysis reveals that the obtained data imply consistence trends across whole water discharge. Furthermore, it also shows a good agreement to the visual observations. Meanwhile, the wavelet analysis can distinguish energy fluctuations under different water discharges. [ABSTRACT FROM AUTHOR]

T-junction geometry as a connection in a two-phase minichannel flow system is widely used, for both mixing and flow separation processes. When passing through the T-junction region, the uneven distribution of the two-phase flow can occur due to interfacial instability at the corner of the T-junction and affect the pressure drop characteristics in the downstream area. The purpose of this study is to identify the characteristics of pressure drop fluctuations measurement using statistical analysis, PDF, and PSD. This research was conducted on a horizontal rectangular minichannel T-junction test section with a hydraulic diameter of 1.6 mm. In the T-junction bend section, the bend radius is made with a size of half the hydraulic diameter (0.8 mm). The working fluids are water and air. To measure the pressure drop, a differential pressure transducer is used and installed between the T-junction and downstream areas. Statistical analysis of experimental data, such as the average of ΔP, standard deviation, PDF, kurtosis, skewnes and PDS are used to identify the characteristics of pressure drop fluctuations. The results of this study, it was found that both the superficial velocity of water and air have an effect on the pressure drop, but the effect of the superficial velocity of water has a more significant. Meanwhile, the effect of air superficial velocity is more significant on standard deviation, PDF and PSD than water superficial velocity. The comparison between the experimental data and the separated flow correlation model from Lockhart-Martenelli, Mishima-Hibiki, and Sudarja shows the value of conformity with an error margin of ± 30%. [ABSTRACT FROM AUTHOR]

Airlift pump-bubble generator is a development of the conventional airlift pump in the injector design. It uses a bubble generator to supply the bubble in the riser pipe. This method can be used to lift water and solid particles. In the current study, the airlift pump-bubble generator was operated only to lift water using a transparent acrylic riser pipe with 56 mm diameter and 2550 mm length. Water and air were the working fluid with the water level in the riser pipe was setted-up for a submergence ratio of 0.74, and the injected air flow rate was varied from 0.3 m3/h to 3 m3/h with the flow rate of injected water to the bubble generator being kept constant at 7.5 m3/h. Two bubble generator units with an angle of 45° to the horizontal and opposite directions were attached to the mouth bell-shaped suction head to form a swirl flow. A high-speed camera and a pressure tap were used to recording the video of flow pattern and pressure signals in the test section, respectively. The flow pattern was objectively classified by using wavelet analysis. As a result, it was found that the flow regimes were assigned into clustered bubbles, homogenous bubbles, cap bubbles, bubbly-stable slugs, bubbly-unstable slugs, and slug churn when the air flow rate was increased. The distribution of energy fluctuation will have a peak in the signal approximation section of the large scale when the bubble regime flows in the test section, while the peak of the energy fluctuation distribution will occur in the detailed signal when the slug regime is flowing. [ABSTRACT FROM AUTHOR]

Gas transmission system operator relies on a simulation model to predict unforeseen event caused by several gas flow scenarios. Absolute roughness is required to construct the simulation model based on the Colebrook friction factor equation. It is measured by comparing operation data with steady-state results of the model or best known as tuning activities. However, finding a steady-state condition is not easy on the long transmission pipeline. The difference between supply and demand behavior generates a transient effect, hence the steady-state model is obsolete. Absolute roughness determination under transient condition has been carried out on South Sumatera to West Java (SSWJ) gas transmission pipeline. The results show that the absolute roughness during five years of observation ranging between 0.0001 to 0.0005 inch. It increases by 0.0001 inch/year but decreases by 0.0002 inch after cleaning pig activities was conducted. The results indicate that change in absolute roughness of SSWJ pipeline is determined by fouling instead of corrosion mechanism. [ABSTRACT FROM AUTHOR]

Turbine meter is one of the measuring tools for natural gas which is commonly used in Indonesia. This is due to the ease of operation, wide measurement range and reliable measurement performance. However, in the operation of the piping network there are several technical things that makes the measurement anomalies. This study raises the case that occurred in the field, there was a decrease in the measurement performance of the meter due to damage to the blade rotor turbine meters in industry with usage ranging from 130-195 m3/hour. From the previous research, there have been similar studies in the case of crude oil. Modeling of the 16-blade rotor meter turbine G-400 was carried out using CFD of the steady-state simulation, isothermal, and realizable k-e turbulence models, varied for a flow rate of 65-650 m3/hour. The results showed that the decrease in the measurement performance of the turbine meter was 2.28% for a flow rate of 130 m3/hour on the damage to 1 turbine meter rotor blade, and decreased gradually as the number of damaged turbine meter rotor blades increased. A decrease in performance appears when 15 blades are broken by 32.52% for a flow rate of 130 m3/hour. [ABSTRACT FROM AUTHOR]

The effect of Weber number on the dynamic contact angle of single impacting droplet onto inclined hot surface has been studied experimentally. The Weber number variations are 10, 30 and 60. To adjust the Weber number variations, the droplet injector is modified at various height. In the present study, stainless steel is placed as heated material while the surface temperature is adjusted at the desired temperature, they are 100°C - 220°C controlled by the data logger. The droplet phenomena was recorded by high-speed video camera with frame rate 4000 fps and attached with the macro lens. The objectives of this studied are to understand the regime phenomenon, the time variations, and other important parameters of a droplet impacting onto an inclined surface. It was found that (1) the regime of droplet phenomena has specific models for each range of temperature, (2) The increase of Weber number decreases of contact time at temperature 200°C and 220°C, (3) The increase of Weber number increases the spreading ratio significantly at 200°C and 220°C, (4) The increase of Weber number will have significantly affected to result of advancing and receding contact angle are presented. [ABSTRACT FROM AUTHOR]

Airlift pump has a several flow pattern in lifting mixtures liquids and solid through a vertical pipe. The flow pattern in airlift pump have been investigated in previous studies, the study focus on two-phase flow and performance of air lift pump. For this reason, the purpose of experiment was to known the flow pattern of gas-solid-liquid three-phase flow in airlift pump during the solid particles lifting in the upriser. In the present experimental study, we have modified the conventional airlift pump system by used swirl injector in the system. Here, experimental study on the flow pattern of gas- solid-liquid three-phase flow in upriser airlift pump to lift the solid particles with the vertical pipe as the transporting medium was conducted. The upriser pipe was an acrylic pipe with an inner diameter at 56 mm, and the total height of 340 cm. The type of gas injector in the system was swirl with 2 injectors in suction head of air lift pump. The solid particle of the present experiment was sand with particle diameters 0.774 mm and 1.43 mm, and the supplied air flow rate ranged from (60-80 LPM). The solid lifting particles were capture by using a high speed camera of the frame speed of 3000 fps. As a result, it was obtained that (1) the optimum of solid lifting particle was found in the slug flow pattern, (2) the particle diameters and volumetric flow rate of the lifted particles affect the ability of the air lift pump. [ABSTRACT FROM AUTHOR]

Sediment from the environmental damage and erosion in the watershed will settle in the bottom of the reservoir. It can reduce the capacity of the reservoir. Airlift pump technology is one effective method for lifting the sediment from the reservoir. The airlift pump has a simple working principle, the pressurized air is injected into a riser pipe containing water, so those air bubbles are created. Air bubbles move upward and it will lift the around liquid due to interface friction. In this present experimental study, the airlift pump was designed by the transparent acrylic pipe with 3.4 m length, and 56 mm inner diameter. Air and water were the working fluid. The water column in the riser pipe was set-up corresponds to the submergence ratio from 0.5 to 0.68, and the superficial gas velocity was changed from 0.00677 to 0.677 m/s. The mouth bell suction head was placed on the lower end of the riser pipe to mounting the two injectors. It was placed on the lower end of the suction head with the 45° direction of the horizontal and opposite output direction to produce the swirl flow. A high-speed camera was used to record the flow pattern. As the results, we know that the higher the submergence ratio, the greater the superficial water velocity at the same of the superficial gas velocity. It is implying the greater the efficiency and effectiveness of the pump. The swirl flow at the suction head is generated when QG>2.8 m3/hr. The consecutive slug becomes the main factor in the existence of the pulsation effect when the pump is operated. The variation of superficial gas velocity is the dominant effect of change in the flow pattern than the variation of the submergence ratio. [ABSTRACT FROM AUTHOR]

This study aims to determine the mechanism of breaking bubbles into small size in a Swirl type microbubble generator (MBG) with variations in water discharge (QL) at the distance of the air nozzle to the MBG outlet of 1mm. Observations were made using a Phantom Miro M310 high speed video camera with a maximum resolution of 1200×800 to record the microbubble phenomenon. All measurements were taken at a frame rate of 3000 fps. The spatial resolution and frame rate used in this study allow the behavior of the microbubbles to be observed in detail. The focal length and lens aperture are 85 mm and 2.8 mm, respectively. The length between the lens and the viewing area is 350 mm. A wide measuring field and a narrow depth of field were obtained, which is about 2 mm. Its field of measurement is 40.3 mm x 85 mm, and it was found that the 1 pixel of the camera represents 89,55 µm. The results of the investigation showed that the mechanism of the bubbles breaking into smaller sizes starts with bubbly flow in the mixing chamber channel, then forming ligaments at the MBG outlet, before finally bursting into small bubbles. At higher QL and constant air flow (QG), more bubbles were produced and more uniform with smaller size. [ABSTRACT FROM AUTHOR]

The aim of the present study is to investigate the effect of the liquid viscosity on the liquid film thickness and the wave frequency of gas-liquid stratified co-current flow in a horizontal pipe. The inner diameter of the pipe is 26 mm. The superficial liquid velocity (JL) increased from 0.02 m/s to 0.1 m/s, while the gas superficial velocity (JG) increased from 4 m/s to 16 m/s. High speed video camera is used to take high quality visual data which is then processed using image processing techniques. From the results of this study, it is concluded that an increase in JG causes a decrease in the liquid film thickness, while an increase in liquid viscosity causes an increase in the liquid film thickness. From the entire JL range in this experiment, at JG > 8 m/s, the wave frequency tends to increase with increasing JG, while the wave frequency decrease with increasing liquid viscosity. In addition, the Reynold number ratio of gas and liquid and the Martinelli parameters affect the present proposed correlation to predict the frequency wave. The present proposed correlation to predict the frequency of the wave shows a satisfactory performance with the Mean Absolute Percentage Error values 27.1%. [ABSTRACT FROM AUTHOR]

The paper would report the aerodynamic CFD model characteristic studies of backward 3-D wind turbine blades in operation. It is found that the blade lip of the bottom section is suffered from strongly decelerated disturbance, while the upper section are accelerated. The region influenced by radial disturbance starts radially from the top toward the bottom part of the blade, from lightly disturbed to weakly disturbed region. Original radial source of disturbance, caused by centrifugal and Corriolis force, are still persist. Q-criterion was used to benchmark for the quality of computation to justify the most sensitive outcome, to determine the largest size for the smallest computational cell. Compare to structured grids, the unstructured grids gives significant results errors. [ABSTRACT FROM AUTHOR]

Onset of nucleate boiling of a droplet when impacted onto hot surface was investigated. Three kinds of surfaces, normal stainless steel (NSS), stainless steel with TiO2 coating (UVN), and stainless steel with TiO2 coating and radiated by ultraviolet ray were employed to examine the effect of wettability. The droplet size was 2.4 mm diameter, and dropped under different We number. The image is generated by high speed camera with the frame speed of 1000 fps. The boiling conditions are identified as natural convection, nucleate boiling, critical heat flux, transition, and film boiling. In the present report, the discussion will be focused on the beginning of nucleate boiling on the droplet. Nucleate boiling occurs when bubbles are generated. These bubbles are probably caused by nucleation on the impurities within the liquid rather than at nucleation sites on the heated surface because the bubbles appear to be in the bulk of the liquid instead of at the liquid-solid interface. In addition, the smaller the contact angle, the fastest the boiling. [ABSTRACT FROM AUTHOR]

The asymmetry of circumferential liquid film thickness distribution in an air-water horizontal annular flow has been experimentally investigated using superficial gas and liquid velocity of 10 - 40 m/s and 0.025 to 0.4 m/s, respectively. In general, the film at the bottom of the pipe will be thicker than that of the side and the top. The asymmetry parameter could be expressed in the ratio of average film thickness to the bottom film thickness or the ratio of the top-tobottom film thickness. Measurement using compact multiple probe instrument shows that the circumferential film thickness distribution is strongly affected by superficial gas velocity. The higher gas velocity results in the more uniform liquid film circumferential distribution. In comparison to the existing correlations, the asymmetry parameter resulted from the experiment shows a good agreement. It is also shown from the experiment that a less symmetry of film thickness distribution is resulted when the gravity force is dominant. A more symmetry distribution is resulted when the inertial force takes control. [ABSTRACT FROM AUTHOR]

A new design of automotive refrigeration system for a passenger car was proposed. To ensure less energy consumption and optimal thermal comfort, the performance of the system were evaluated. This current research was aimed to evaluate the refrigeration characteristics of the system for several types of cooling load. In this present study, a four-passenger wagon car with 1500 cc gasoline engine that equipped by a belt driven compressor (BDC) was used as the tested vehicle. To represent the tropical condition, a set of lamps and wind sources are installed around the vehicle. The blower capacity inside a car is varied from 0.015 m/s to 0.027 m/s and the compressor speed is varied at variable 820, 1400, and 2100 rpm at a set temperature of 22°C. A set of thermocouples that combined by data logger were used to measure the temperature distribution. The system uses R-134a as the refrigerant. In order to determine the cooling capacity of the vehicle, two conditions were presented: without passengers and full load conditions. As the results, cooling capacity from any possible heating sources and transient characteristics of temperature in both systems for the cabin, engine, compressor, and condenser are presented in this work. As the load increases, the outlet temperature of evaporator also increases due to the increase of condensed air. This phenomenon also causes the increase of compressor work and compression ratio which associated to the addition of specific volume in compressor inlet. [ABSTRACT FROM AUTHOR]

The lid driven cavity problem has been studied numerically. The present work is focused on reviewing the fluid flow patterns for the lid driven cavity problem. The left, right and bottom walls are maintained at no slip boundary condition and the top wall is moved in the right direction with uniform velocity (u = 1.0). The governing equations are processed by the mass and momentum equations and solved by using the radial basis function (RBF) method. The governing equations are expressed using a primitive variable formulation. The method was based on implicit Euler scheme for temporal discretization and RBF method for spatial discretization. The effects of the Reynolds number on the fluid flow in the square cavity are investigated. Stream functions and pressure contours are presented for various Reynolds numbers, such as 102, 4x102 and 103. Comparing the numerical results obtained using the present method with other numerical methods from the literatures shows very good agreement. [ABSTRACT FROM AUTHOR]

The demand for energy is increasing significantly over the past few decades. Mostly, the energy is coming from fossil fuels. It should be noted that fossil energy is not environmentally friendly and non-sustainable energy. Hence, it is necessary to replace fossil energy with renewable and sustainable energy such as solar PV energy. Solar energy is one of the renewable energies that can choose to replace fossil energy sources. Urban areas are areas with higher energy requirements than rural areas, but the availability of vacant land in urban areas is very minimal to the installation of solar power plants. Hence, rooftop solar PV energy can be a solution in dense areas such as urban areas. Before installing a rooftop solar PV plant, it is necessary to investigate how much energy can be provided to meet daily needs. Furthermore, it is also essential to optimize the installation so more daily energy can be supplied. This research focuses on investigating the solar energy potential to meet the daily demand from time to time. Modeling of solar energy potential in each house is essential to determine how much energy can be provided by solar PV plants in several years. In this research, the temporal analysis is used to model the energy demand from solar PV plants. This research will integrate statistical data and remote sensing data. The availability and the demand energy of each house will be investigated thoroughly in this research. Furthermore, how much electrical energy can be supplied by solar PV rooftop is also considered in this research. This research is expected to be used by policymakers in developing renewable energy in the city of Bandung and will increase community participation in switching to renewable energy. [ABSTRACT FROM AUTHOR]

Computational Fluid Dynamic (CFD) has an important assignment in fluid mechanics, including droplet cases. Finite-difference and front-tracking methods were used in numerical simulations of collisions of liquid droplets on horizontal solid surfaces. This study aims to model the dynamics of a single droplet impacting the horizontal surface with variations of density ratio and gravity. The numerical simulation of the droplet phenomena solution used finite difference method with an implicit scheme. The interface between different phases was tracked by using a front tracking method. The governing equations used continuity and momentum Navier-Stokes equation for incompressible 2-D unsteady flow immiscible fluid where the surface tension be discovered, and the viscosity fluid assumed constant. The Navier-Stokes equations were discretized using the implicit finite difference method on a staggered grid pattern with primitive variable formulation (u, v, p). The pressure term was solved by using the Poisson equation at Neumann boundary conditions. Initial conditions were conducted to the diameter of the droplet of 2.5 mm, and height fall of 0.125 cm with a static contact angle of 90°. The numerical results were validated with the research of Meten Muradog et al. (2010), and the spreading dynamics of the droplet was investigated. The studies show that gravity was dominant to the maximum deformation diameter, and the maximum spreading velocity will increase at a higher density ratio. The greater the density ratio, then droplet height decreases. [ABSTRACT FROM AUTHOR]

Photobioreactor is a system with light passing through a rectangular airlift reactor wall for Microalgae. Photobioreactors used to increase productivity of microalgae biomass. The purpose of this study is to determine the best form between modification of bubble column photobioreactors using horizontal baffles with triple segmental compared to bubble column configurations without using horizontal baffles and to know bubble velocity to maximize photobioreactor productivity. Bubbles velocity data was taken using a high-speed camera on each photobioreactors in the incoming discharge variable that processed with image processing by using the Fiji / imageJ application and PIVlab. Based on the results of the study, the best velocity results were 0.23 m / s at 1 LPM discharge with bubble size according to sauter mean diameter of 750 µm which was used in the photobioreactor with modified baffle. [ABSTRACT FROM AUTHOR]

Microalgae produce biomass used as one of the renewable energy sources. The utilization of photobioreactor is meant to control some parameters affecting microalgae growth and reduce the possibility of contamination. The optimal photobioreactor is required to obtain the best microalgae growth. This research is proposed by comparing two different photobioreactors (non-baffle and horizontal baffle) to get insights on the optimal configuration so that the mixing and good microalgae growth can be achieved. ANSYS Fluent is used to solve the CFD model. User-defined functions were used to integrate the microalgae kinetic equations into three-dimensional photobioreactor. Microalgae growth simulation results are obtained dependently over space and time within photobioreactor for several days. The simulation results showed that the microalgae growth in photobioreactor with horizontal baffle was better than the non-baffle photobioreactor. [ABSTRACT FROM AUTHOR]

Airlift pump can be used as an alternative to lift the sediment from the the water. The airlift pump employed in this study was a conventional type that used a compressor on the injector system. This study aimed to determine the characteristics of the airlift pump in a three-phase flow. In the experiments, the sludge used was solid spherical particles with 1.43 mm as the particle average diameters. The experiment operated upriser pipe with an inner diameter 56 mm and 3.4 m height. The submergence ratio of the upriser in water was: 0.5, 0.62, and 0.74, while the supplied air flow rate was 60 l/min, 70 l/min, and 80 l/min under atmospheric conditions. The research matrix was obtained by combined two variables, which were the submergence ratio and the airflow rate. Further, it was used to determine the effect on the flow rate of discharge solid particles, the flow rate of discharge water, and the pressure gradient. Visual observation was utilized to determine the behavior of the three-phase liquid-gas-solid flow in the pipe. The results were acquired from visual observations that depicted the flow regime occurrence, slug, churn, and annular. Moreover, the measurement results of the flow rate and pressure gradient discovered that in the submergence ratio and the injected air flow rate had a significant influence on the flow characteristics. [ABSTRACT FROM AUTHOR]

In lifting fluid and sediment by using upward force injected by gas through upriser, airlift pump has certain flow characteristics. The Airlift pump flow characteristics had been explored in the previous studies, yet those studies only focused on two phase airlift pump. For this reason, the recent study aimed at revealing the flow characteristics of three phase airlift pump. These characteristics was observed experimentally for different particle diameter by using liquid and gas as working fluid. When the airlift pump was operated by using solid material, the flow occurring in the upriser pipe was three phases. The current airlift pump experiment used a compressor to inject gas on the injector. The internal diameter of the upriser pipe of 56 mm and the total height of 3400 mm. This experiment was conducted on variable particle diameter mesh 24-20 and 16-12. The variation of air discharge given were 60 l/min, 70 l/min, and 80 l/min with atmospheric conditions. The research matrix was obtained by combining two variables. The experimental results indicated that (1) the velocity of air discharge has significant effects in lifting the particles as gas hold up occurring was greater, (2) the greater the air discharge was given, the greater gas hold up occurring in the flow, (3) the higher the air discharge was given, the higher upriser gradient, so the lifting capability became greater since the great pressure opposed the gravity, (4) the small particle diameter was used in the air lift pump system, the greater the lifting particle due to greater friction between particles and water. [ABSTRACT FROM AUTHOR]

Void fraction is an important parameter in two-phase flow. In the present work, the adiabatic two-phase airwater flow void fraction in a horizontal minichannel has been studied experimentally. A transparent circular channel with 1.6 mm inner diameter was employed as the test section. Superficial gas and liquid velocities were varied in the range of 0.025 - 66.3 m/s and 0.033 - 4.935 m/s, respectively. Void fraction data were obtained by analyzing the flow images being captured by using a high-speed camera. Here, the homogeneous (β) and the measured void fractions (ε), respectively, were compared to the existing correlations. It was found that: (1) for the bubbly and slug flows, the void fractions increases with the increase of JG, (2) for churn, slug-annular, and annular flow patterns, there is no specific correlation between JG and void fraction was observed due to effect of the slip between gas and liquid, and (3) whilst for bubbly and slug flows the void fractions are close to homogeneous line, for churn, annular, and slug-annular flows are far below the homogeneous line. It indicates that the slip ratios for the second group of flow patterns are higher than unity. [ABSTRACT FROM AUTHOR]

An experiment for investigating the flooding and deflooding phenomena in a complex system has been conducted. The liquid film behavior for the flooding and deflooding were studied under various superficial liquid velocities. The onset of flooding was observed at high superficial gas velocity when the superficial liquid velocity was low. On the other hand, for the high superficial liquid velocity, the flooding was initiated at the lower superficial gas velocity. In flooding experiment, it is obvious that the higher superficial gas velocity is needed than that of deflooding experiment. At the higher superficial liquid velocity, it is also found that the hysteresis is more significant than that of lower superficial liquid velocity. [ABSTRACT FROM AUTHOR]

Decreasing world reserve of fossil resources (i.e. petroleum oil, coal and natural gas) encourage discovery of renewable resources as subtitute for fossil resources. Biomass is one of the main natural renewable resources which is promising resource as alternate resources to meet the world's energy needs and raw material to produce chemical platform. Conversion of biomass, as source of energy, fuel and biochemical, is conducted using thermochemical process such as pyrolysis-gasification process. Pyrolysis step is an important step in the mechanism of pyrolysis - gasification of biomass. The objective of this study is to obtain the kinetic reaction of catalytic pyrolysis of dry torrified sugarcane bagasse which used Ca and Mg as catalysts. The model of kinetic reaction is interpreted using model n-order of single reaction equation of biomass. Rate of catalytic pyrolysis reaction depends on the weight of converted biomass into char and volatile matters. Based on TG/DTA analysis, rate of pyrolysis reaction is influenced by the composition of biomass (i.e. hemicellulose, cellulose and lignin) and inorganic component especially alkali and alkaline earth metallic (AAEM). From this study, it has found two equations rate of reaction of catalytic pyrolysis in sugarcane bagasse using catalysts Ca and Mg. First equation is equation of pyrolysis reaction in rapid zone of decomposition and the second equation is slow zone of decomposition. Value of order reaction for rapid decomposition is n > 1 and for slow decomposition is n<1. Constant and order of reactions for catalytic pyrolysis of dry-torrified sugarcane bagasse with presence of Ca tend to higher than that's of presence of Mg. [ABSTRACT FROM AUTHOR]

A nuclear power plant operation requires high safety system designs. Therefore, an accidental scenario such as the SBLOCA should be anticipated well. This particularly also relates to a flow phenomenon occurred during the primary circuit leakage called the counter current flow limitation (CCFL) which probably initiates a flooding regime. This work aims to investigate time-series pressure fluctuations of a flooding regime in a complex geometry representing 1/30 down-scaled of PWR hot leg. Statistical tools i.e. PDF and PSD were assessed to obtain the characteristics of time-series differential pressure fluctuations of the regime. The results obtained imply that the idea proposed are advisable to be assesed more. [ABSTRACT FROM AUTHOR]

Swirling Microbubble Generator (MBG) with a 1.2-millimeter diameter of gas nozzle and 1-millimeter distance to the outlet is a tool functioned as an aerator. MBG is capable of producing micrometer bubbles by using swirling flow. The swirling flow originates from the inlet channel with tangential direction leading to a swirling chamber. This experiment was conducted by giving variation toward air debit (QG) and water debit (QL) to figure out the characteristics of MBG. The MBG characteristics are influenced by the combination of air and water flow velocity through MBG. In this research, the range of air and water flow velocity are set 0.1-1.0 lpm and 20.0-50.0 lpm, respectively.MBG installed at a depth of 40 cm below the surface. After that, the bubbles' diameter was measured by capturing the image of bubbles with a high-speed Phantom video camera. This high-speed Phantom video camera has a maximum frame rate of 10.000 frames per second (fps) to observe the behavior of microbubbles produced. A sound lighting system is applied to gain better visualization. The microbubble recorded is then being analyzed by observing the interface behavior in two-phase flow with image processing. The result indicates that in microbubble distribution, the increase of water debit produces smaller bubbles. In contrast, the rise of gas debit results in the production of bigger microbubbles. Meanwhile, in the MBG working system, the increase in water debit causes the rise of pressure drop and hydraulic power. If the gas debit is raised, it results in the raise of pressure drops and hydraulic power. However, the change is not significant. According to PDF chart of microbubble distribution, microbubble diameter with the highest probability of being generated by MBG is 100 µm. [ABSTRACT FROM AUTHOR]

Computational study of flow and heat transfer characteristics from a rotating circular cylinder kept in cross-flow is performed. The interaction between inertial and thermal forces strongly affects the wake of the circular cylinder. To study this interaction, the cylinder is kept in a cross flow corresponding to Reynolds number in the range of 50 to 200, and is heated so that the Richardson number is 1. The rotation rate is varied between 0 to 2, and its effect on wake was studied. It was found that with increase in rotation rate the variation of average Nusselt along the cylinder surface becomes more uniform. This uniformity is achieved on behest of reduction in heat transfer which can be attributed to the negative vorticity generation due to rotation of the cylinder. [ABSTRACT FROM AUTHOR]

Most of geothermal power plants experience the deposition problems, mainly silica scaling that exhibits in the brine pipes and/ or the reinjection system. Many techniques have been introduced to overcome this problem, such as hot brine injection system, cold brine injection system and acidizing. Experiences showed that these techniques seemed not to be effective in handling the problems. This study proposes a technique of handling the scaling problem by separation process between liquid and solid using hydrocyclone separator where the solid phase is produced by adding a chemical into the brine. The reaction process between chemical and brine is not considered in this study. Before the manufacturing process, the numerical simulation on the separation process in the hydrocyclone separator is important to be carried out for the guidance in designing the appropriate separator geometry that meets the operating condition. The simulation was carried out using ANSYS Remote Solve Manager (RSM) and Discrete Phase Model (DPM). In this model, the fluid density was assumed to be constant and the inlet pressure was given for boundary condition. The mass flow rate of brines and the particles size were varied to evaluate the effects of these parameters on the cyclone efficiency. The simulation results showed that the values of particle size of 53 µm and the brine mass flow rate of 100 kg/s, respectively give the cyclone efficiency of 86 %. The cyclone efficiency increases as the fluid mass flow rate becomes larger. [ABSTRACT FROM AUTHOR]

The combined cycle power plant (CCPP) has higher thermal efficiency compared to steam power plant (SPP) and gas turbine power plant (GTPP). It combines gas turbine/ brayton cycle and steam/ rankine cycle. A study has been carried out to determine the effect of gas composition, air intake cooling and steam injection on the performance of the CCPP using Aspen Hysys V9 process simulator. The validity of simulation has been confirmed that shown by minor error of less than 10% in comparison with manufacturer data. The results showed that changes in gas composition caused a decrease in power of 0.23 - 3.92 MW. The inlet air temperature and steam injection configurations were found to have a positive effect in increasing the efficiency of 1.97% - 8.03% and 4.24% - 4.59%, respectively. [ABSTRACT FROM AUTHOR]