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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]

As developing countries, Indonesia had their municipal solid waste (MSW) production increase due to population growth and its production reached 190,000 metric ton/day in 2014. Selection of appropriate technology is necessary to reduce the waste volume primarily and to utilize waste as the energy source because of the calorific value inside. Three thermal based technologies are available for waste to energy (WtE) which are incineration, conventional air gasification, and plasma gasification. Their feasibility was evaluated environmentally and economically. None of them was environmentally feasible due to greater CO 2 emission than the CO 2 emission standard of Environmental Protection Agency (EPA). However, two of which, conventional air gasification and plasma gasification, were economically feasible. [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]

Bio-syngas from gasification of sugarcane bagasse is one of the most promising sources for renewable energy. As an agriculture-based biomass, sugarcane bagasse has a high content of moisture (46-52%), fibrous (43-52%) and low bulk density (80-120 kg/m 3 ). This quality of bagasse will tend to initiate agglomeration and cause de-fluidization. It will disturb the gasification process and finally will decrease yield and quality of syn-gas. Its chracteristics in low quality can be improved by pretreatment, i.e. , torrefaction process, addressed by slow heating of biomass on wet or dry conditions on atmosphere pressure for 1 hour before it is used as feedstock gasification. This preliminary work features an experimental investigation of torrefaction process of Indonesian sugarcane cane bagasse. Temperature of torrefaction varies from 150, 175, 200, 225, 250 and 300 °C. For bagasse gasification process, the optimum temperature of dry torrefaction is 150 °C. At this temperature, yield of syngas will higher than other torrefaction temperature. Temperature of dry torrefaction will give energy saving opportunities than that's of wet torrefaction (180 °C, 1 hr). Analysis ultimate and proximate also indicate that sugarcane bagasse with temperature torrefaction 150 °C give better result than other torrefaction's temperature in high content of hydrogen and low content of carbon. [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 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 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]

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]

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]

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]