nan Indarto

Experimental investigation on the interfacial characteristics of stratified air-water two-phase flow in a horizontal pipe

The interfacial wave characteristics of stratified air-water two-phase flow in a horizontal pipe were experimentally investigated by using the flush-mounted constant electric current method (CECM) sensors. The experiments were conducted in a horizontal two-phase flow loop 9.5 m long (L) consisting of transparent acrylic pipe of 26 mm i.d. (D). To obtain the stratified flow pattern, the superficial gas and liquid velocities were set to 1.02 – 3.77 m/s and 0.016 – 0.92 m/s, respectively. Several interfacial wave patterns as described by several investigators were identified. The common parameters such as liquid hold-up, probability distribution function, wave velocity and wave frequency were investigated as the function of the liquid and gas flow rates. The interfacial curvature was calculated on the basis of the liquid hold-up data from the CECM sensors and the liquid film thickness data from the image processing technique in the previous work. As a result, it was found that the mean liquid hold-up decreas...

Image processing analysis on the air-water slug two-phase flow in a horizontal pipe

Slug flow is a part of intermittent flow which is avoided in industrial application because of its irregularity and high pressure fluctuation. Those characteristics cause some problems such as internal corrosion and the damage of the pipeline construction. In order to understand the slug characteristics, some of the measurement techniques can be applied such as wire-mesh sensors, CECM, and high speed camera. The present study was aimed to determine slug characteristics by using image processing techniques. Experiment has been carried out in 26 mm i.d. acrylic horizontal pipe with 9 m long. Air-water flow was recorded 5 m from the air-water mixer using high speed video camera. Each of image sequence was processed using MATLAB. There are some steps including image complement, background subtraction, and image filtering that used in this algorithm to produce binary images. Special treatments also were applied to reduce the disturbance effect of dispersed bubble around the bubble. Furthermore, binary images w...

Experimental investigation on the phenomena around the onset nucleate boiling during the impacting of a droplet on the hot surface

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 con...

Experimental investigation on liquid film asymmetry in air-water horizontal annular flow

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-to-bottom 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 sym...

Combination pulsed electric field with ethanol solvent for Nannochloropsis sp. extraction

Nowadays, energy is one of human basic needs. As the human population increased, energy consumption also increased. This condition causes energy depletion. In case of the situation, alternative energy is needed to replace existing energy. Microalgae is chosen to become one of renewable energy resource, especially biodiesel, because it contains high amount of lipid instead of other feedstock which usually used. Fortunately, Indonesia has large area of water and high intensity of sunlight so microalgae cultivation becomes easier. Nannochloropsis sp., one of microalgae species, becomes the main focus because of its high lipid content. Many ways to break the cell wall of microalgae so the lipid content inside the microalgae will be released, for example conventional extraction, ultrasonic wave extraction, pressing, and electrical method. The most effective way for extraction is electrical method such as pulsed electric field method (PEF). The principal work of this method is by draining the electrical current...

Determining Contact Angle and Spreading Velocity of a Droplet Impacted Hot Solid Surface

Spray cooling is a method to lower the solid surface temperature by splashing droplets. The evaporation of droplet will take the heat from solid surface. One of the factors that contributes to the evaporation rate and droplet spreads on the surface is the wettability of fluid on surface. Contact angle is a parameter in categorizing the wettability of fluid at a solid surface. Many methods have been developed to measure the contact angle on solid surface. This paper will explain how to measure the contact angle by analyzing the image taken when droplet fluid attached to a surface. The method use MATLAB codes as tools for processing image and compute the result. There are four steps in processing an image of droplet on a surface: convert image to binary image, detect the boundary of the surface, determine the correlation of x-y pixel, and take the tangent of a line at the outer point of contact between fluid and surface. Validation is taken by comparing the result with “standard image” with various resolutions. This method also explains droplet dynamics when impacting a hot surface.

Experimental study on the characteristics of flow pattern transitions of air-water two-phase flow in a horizontal pipe

The two-phase flow application was commonly found in industrial processes, such as oil and gas production in wells, gas and oil pipelines, etc. The characteristic of two-phase flow had various aspects depending on its interfacial behaviour. The interfacial structures of air-water two-phase flow in a horizontal pipe were experimentally investigated by using visualization method with high speed camera. The experiments were conducted in a horizontal two-phase flow facility, total length 10 m pipe made from acrylic with 26 mm ID. To obtain the flow pattern, a total of 132 flow condition were observed. The superficial gas and liquid velocities were set to 0.31 m/s – 20 m/s and 0.016 m/s – 0.77 m/s, respectively.High Speed Camera observation successfully characterized and demonstrated two-phase flow regime in a horizontal pipe. Its also developed flow regime maps. Air-water two-phase flow is characterized by bubble breakup and coalescence in the transition from plug to slug flow. Interfacial instabilities form in stratified to wavy flow, then small waves, larger waves and the droplet entrainment in transition to annular flow. High amplitude wave was required to form the slug flow. This flow pattern maps is a two-phase flow regime transition including stratified flow, plug flow, slug flow, annular flow and sub-regime of each patterns. The influence of superficial velocity of air and water has a significant effect on the flow patterns and sub-regime types.The two-phase flow application was commonly found in industrial processes, such as oil and gas production in wells, gas and oil pipelines, etc. The characteristic of two-phase flow had various aspects depending on its interfacial behaviour. The interfacial structures of air-water two-phase flow in a horizontal pipe were experimentally investigated by using visualization method with high speed camera. The experiments were conducted in a horizontal two-phase flow facility, total length 10 m pipe made from acrylic with 26 mm ID. To obtain the flow pattern, a total of 132 flow condition were observed. The superficial gas and liquid velocities were set to 0.31 m/s – 20 m/s and 0.016 m/s – 0.77 m/s, respectively.High Speed Camera observation successfully characterized and demonstrated two-phase flow regime in a horizontal pipe. Its also developed flow regime maps. Air-water two-phase flow is characterized by bubble breakup and coalescence in the transition from plug to slug flow. Interfacial instabilities form ...

The effect of liquid viscosity on the gas-liquid two-phase flow pattern in horizontal mini-channel

The experimental studies on flow pattern of adiabatic gas-liquid two-phase flow in horizontally oriented mini-channel were conducted. The test section was a 1.6 mm inner diameter glass pipe. The range of gas and liquid superficial velocities were 0.025 - 66.3 m/s and 0.033 - 4.935 m/s, respectively. The working fluids were air and glycerol aqua solution in various percentage, 0%, 20%, 40%, and 60% indexed by W, G20, G40, and G60, respectively. The flow pattern data were obtained by analyzing the video images, captured by using the high-speed camera. As a result, it was found that the flow patterns observed in the present study were bubbly, plug, slug-annular, annular, and churn, while the stratified flow was not appeared. In the flow pattern map, the change of liquid viscosity affects to the shift of the transition line between flow pattern, particularly slug-annular to annular and slug-annular and annular to churn flow.

The characteristics of the pressure gradient air-water stratified two-phase flow in horizontal pipes

The co-current air-water two-phase stratified flow is desired to occur in the application of pipelines system, such as natural gas gathering, long distance pipelines, and transmission pipelines, because this flow characteristics offers some advantages related to the safety factor of operational condition. The characteristics of pressure drop in stratified flow is considered as one of an important factor in the capital and operation costs for the simultaneous transportation of gas and liquid in various industries. The main objective of this study is to examine the effect of gas and liquid superficial velocities, and pipes diameter on the characteristics of pressure drop air-water two-phase stratified flow. Experiment has been conducted in 26 and 16 mm i.d. acrylic horizontal pipe with length 9.5 m. Air-water flow was recorded 190 D from the inlet using high speed video camera, and pressure difference was measured between 180 D and 210 D from the inlet using validyne pressure transducer. The common parameters such as visualization, pressure gradient signal in time series, probability density function (PDF), and mean of pressure gradient was analyzed. As a result the effect of gas and liquid superficial velocity, and pipes diameter on the characteristics of pressure gradient can be understood.

Experimental study on interfacial friction factor of the air-water stratified two-phase flow in a horizontal pipe

The Liquid hold-up and the Interfacial Friction Factor on the Air-Water Stratified Two-Phase Flow in a Horizontal Pipe have been experimentally investigated using superficial gas and liquid velocity of 4 – 16 m/s and 0.02 to 0.1 m/s, respectively. The stratified flow is observed on the horizontal acrylic pipe with 26 mm inner diameter and 9 m length. This present work has utilized the various methods of observation: visual observation through high speed video camera, hold up measurement by using CECM, and pressure gradient analysis which is gathered from the Validyne pressure transducer. The pressure gradient and liquid hold-up signal are sent through amplifier than converted into digital signal by Analog to Digital Converter (ADC). As a result, the characteristics of stratified flow is successfully revealed. Furthermore, a new correlation for hold-up which is based on the gas and liquid superficial velocity, and Froude number is proposed. The R2 which reaches 0.971 and the small value of error band (around 30 %) shows that the proposed correlation produce a good performance. Similarly, a new correlation for interfacial friction factor is also proposed which is arranged as a function of liquid hold-up, gas, and liquid Reynolds number. It produces a satisfying performance which is proven by the high value of R2, 0.999. Moreover, the error band between the proposed correlation and the experimental data is quite small, around 5 % on most of all data.