A Journal of the ASEAN Committee on Science & Technology Vol. 30, No.1&2, 2013

 

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Vol. 30, No. 1&2, 2013 ISSN 0217-5460 J STd Science & Technology V A Journal of the ASEAN Committee on ASEAN Journal on Science & Technology for Development

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ABOUT THE ASEAN JOURNAL ON SCIENCE AND TECHNOLOGY FOR DEVELOPMENT The ASEAN Journal on Science and Technology for Development is a refereed Journal of the ASEAN Committee on Science and Technology (ASEAN COST). It reports on science and technology policies and programmes, and research activities undertaken by COST in support of social and economic development of the ASEAN member countries. The coverage is focused but not limited to, the main areas of activity of ASEAN COST, namely, Biotechnology, Non-Conventional Energy Research, Materials Science and Technology, Marine Sciences, Meteorology and Geophysics, Food Science and Technology, Microelectronics and Information Technology, Space Applications, and Science and Technology Policy, Infrastructure and Resources Development. ABOUT THE ASEAN COMMITTEE ON SCIENCE AND TECHNOLOGY The ASEAN Committee on Science and Technology was established to strengthen and enhance the capability of ASEAN in science and technology so that it can promote economic development and help achieve a high quality of life for its people. Its terms and reference are: ●● To generate and promote development of scientific and technological expertise and manpower in the ASEAN region; ●● To facilite and accelerate the transfer of scientific and technological development among ASEAN countries and from more advanced regions of the world to the ASEAN region; ●● To provide support and assistance in the development and application of research discoveries and technological practices of endogenous origin for the common good, and in the more effective use of natural resources available in the ASEAN region and in general; and ●● To provide scientific and technological support towards the implementation of existing and future ASEAN projects. Information on the activities of ASEAN COST can be obtained at its website http://www.asnet.org DISCLAIMER While every effort is made to see that no inaccurate or misleading data, opinion or statement appears in the Journal, articles and advertisements in the Journal are the sole responsibility of the contributor or advertiser concerned. They do not necessarily represent the views of the Editors, the Editorial Board nor the Editorial Advisory Committee. The Editors, the Editorial Board and the Editorial Advisory Committee and their respective employees, officers and agents accept no responsibility or liability whatsoever for the consequences of any inaccurate or misleading data, opinion or statement. © Copyright 2013: ASEAN Committee on Science and Technology No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form of by any means, without permission in writing from the copyright holder.

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Editorial Board Editor-in-Chief School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia Emeritus Prof Md Ikram Mohd Said Editorial Board Members Malaysia Dr Ahmad Ibrahim Assoc. Prof Tan Tin Wee Chief Executive Officer, Academy of Sciences Malaysia Prof Abdul Halim Shaari Prof Thong Kwai Lin Department of Biochemistry, National University of Singapore Thailand Prof Narongrit Sombatsompop Faculty of Science, Universiti Putra Malaysia Institute of Biological Science, Faculty of Science/UMBIO Cluster, Institute of Graduate Studies, University of Malaya Assoc. Prof Mohd Fadzil Mohd Idris School of Energy, Environment and Materials, King Mongkut’s University of Technology, Thonburi Prof Prida Wibulswas Cambodia Pal Des President, Shinawatra University Higher Education Leadership Academy, Malaysia Brunei Darussalam Rosita Abdullah Vice-Rector, Royal University of Phnom Penh Indonesia Dr Warsito Purwo Taruno Senior Special Duties Officer, Ministry of Development Assoc. Prof Zohrah Sulaiman Minister, Special Advisor for Research and Cooperation Lao PDR Kongsaysy Phommaxay Deputy Vice-Chancellor, Universiti Brunei Darussalam Myanmar Dr Zaw Min Aung Acting Director General, Cabinet Office of the Ministry of Science and Technology Keonakhone Saysuliane Director General, Department of Technical and Vocational Education, Ministry of Science and Technology Philippines Dr Carol M. Yorobe Acting Director General, Department of Information Technology Vietnam Dr Mai Ha Undersecretary for Regional Operations, Department of Science and Technology Singapore Assoc. Prof Ong Sim Heng Director General, Ministry of Science and Technology Department of Electrical and Computer Engineering, National University of Singapore

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Editorial Advisory Panel Brunei Darussalam Eddie Sunny Lao PDR Dr Maydom Chanthanasinh Deputy Permanent Secretary, Ministry of Development Myanmar Dr Ko Ko Oo Deputy Minister, Ministry of Science and Technology, National COST Chairman Singapore Prof Low Teck Seng National COST Chairman, Deputy Minister, Ministry of Science and Technology Cambodia Dr Om Romny National COST Chairman, Managing Director, Agency for Science, Technology and Research Thailand Assoc. Prof Weerapong Pairsuwan Director, Institute of Technology of Cambodia Philippines Dr Graciano P. Yumul Deputy Permanent Secretary, Ministry of Science and Technology Malaysia Dr Madinah Mohamad Undersecretary for R&D, Department of Science and Technology Indonesia Prof Syamsa Ardisasmita, DEA National COST Chairman, Secretary General, Ministry of Science, Technology and Innovation Vietnam Dr Le Dinh Tien Deputy Minister for Science and Technology Network, National COST Chairman Deputy Minister for Science and Technology, National COST Chairman Editor/Technical Editor/Executive Editor Academy of Sciences Malaysia Higher Education Leadership Academy, Malaysia Dr Mohaida Mohin Kanesan Solomalai Production Manager Universiti Putra Malaysia Kamariah Mohd Saidin Publisher Universiti Putra Malaysia Press

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Contents ASEAN J. Sc. Technol. Dev. Volume 30(1&2), 2013 Computational Fluid Dynamics Simulations of Gas-liquid Two-phase Flow Characteristics through a Vertical to Horizontal Right Angled Elbow N. Z. Aung and T. Yuwono Performance Appraisal of Non-governmental Organizations: A Discussion on Pakistan 2010 Floods Response and Recovery A. Ali, N. Baig and A. Khan Toughening of Bisphenol-A Diglycidyl Ether-based Epoxy by Modification with Hydroxyl-terminated Liquid Natural Rubber H. L. Pham, B. T. Do, T. S. Pham and D. G. Le Synthesis and Characterisation of Hydroxyl-terminated Liquid Natural Rubber by Photo-Fenton Reaction H. L. Pham, B. T. Do, T. S. Pham and D. G. Le Physical Fitness and Metabolic Profile among Malay Undergraduates of a Public University in Selangor Malaysia M. Emad, M. Kandiah, W. K. Lim, M. Y. Barakatun-Nisak, A. Rahmat, S. Norasruddin and M. Appukutty A Preliminary Study: Comparative Toxicity of Extracts from Tinospora tuberculata Beumee and Lumnitzera racemosa Willd on Aedes aegypti Linnaeus Larvae (Diptera: Culicidae) A. A. Wahizatul and R. Shasita Biodegradation of NR Latex-based Materials via a Carbon Dioxide Evolution Method F. M. S. Shabinah and M. Y. A. Hashim Effects of Chocolates Using Low Calorie Cocoa Butter Substitutes on Rat’s Plasma Profile and Determination of Sn-1,3 Position B. Ros-Haniza and S. Mamot 1 17 22 29 37 44 50 63

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ASEAN J. Sci. Technol. Dev.,  30(1&2): 1 – 16 Computational Fluid Dynamics Simulations of Gas-liquid Two-phase Flow Characteristics through a Vertical to Horizontal Right Angled Elbow N. Z. AUNG1 * AND T. YUWONO2 Having a clear understanding on the phase distribution of gas-liquid two-phase flow through elbow bends is vital in mixing and separation system designs. This paper presents the computational fluid dynamics (CFD) simulations and experimental observations of gas-liquid two-phase flow pattern characteristic through a vertical to horizontal right angled (90°) elbow. Experimental observations were conducted in a transparent test section that consisted of a vertical pipe, elbow bend and horizontal pipe with an inside diameter of 0.036 m. The CFD simulations were performed by using a computer software package, FLUENT 6.2. Bubbly flow conditions were created in the vertical test section with the variation of superficial liquid Reynolds number from 13 497 to 49 488 and volumetric gas quality from 0.05 to 0.2. The CFD results showed a good agreement with experimental results in the following observations. The results showed that gas-liquid flow pattern inside and downstream of the elbow bend mainly depended on liquid velocity and it is also influenced by gas quality at high liquid velocities. At lower liquid velocities, gas-liquid separation began early in the elbow bend and gas-phase migrated to outer bend. Then, it smoothly transformed to stratified flow at elbow outlet. When the liquid velocity was further increased, the liquid phase occupied the outer bend rubbing the gas phase to the inner bend and delayed the formation of gas layer in the horizontal pipe. The increase of gas quality in higher liquid velocities promoted gas core formation at the elbow exit and caused wavy gas layers at the downstream of the elbow. Key words: Gas-liquid; two-phase; flow pattern characteristic; vertical to horizontal; 90° elbow The understanding of transport phenomena in multiphase flows plays a vital role in improving the performance of operating systems in boiling and condensing processes, hydrocarbon production and refining, minerals transport as well as power generation. Such transport phenomena are quite sensitive to the phase distribution in the flow termed as ‘flow pattern’. In turn, the flow pattern also mainly depends on the flow velocity and physical properties of each phase and pipe geometry (Akilli et al. 2001) In the case of pipe geometry, the correct usage of pipe bends is very critical in 1 2 multi-phase flow piping system designs, since these can give strongly interference in phase distribution and consequently promote the vibration of the system (Abdulkadir et al. 2001) Hence, increasingly, attempts are being made to observe the effect of pipe bends (especially 90° elbows) on phase distribution and other flow related characteristics in multiphase flows. Akilli (2001) conducted experimental measurements and CFD simulations of gassolid concentration and velocity profile in horizontal pipe after vertical-to-horizontal 90° Department of Mechanical Engineering, Mandalay Technology University, Myanmar Laboratory of Fluid Mechanics, Department of Mechanical Engineering, Institute Technology Sepuluh Nopember, Campus ITS, Sukolilo, Surabaya * Corresponding author (e-mail: nay1572@gmail.com; triyogi@me.its.ac.id)

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ASEAN Journal on Science and Technology for Development, 30(1&2), 2013 elbow bend. His distinct observation was that a strong rope was formed in the elbow bend and it disintegrated within 10D of the pipe after elbow exit. Huseyin (2004) has also performed investigations on gas–solid flow characteristics after a 90° vertical-to-horizontal elbow. Yang and Kuan (2006) have measured the velocity fluctuation level of gas-solid flow inside a 90° elbow by using Laser Doppler Anemometer (LDA). They found that the level of velocity fluctuations in the solid phase was higher than that of the gas phase at the bend entrance because of particle-wall collisions. Kim et al. (2007) investigated the effect of 90 ° elbow on local void fraction distribution. According to their results, the elbow had more significant effect on phase distribution at further downstream ( L/D = 43.9 after elbow) than immediate downstream ( L/D = 18.1 after elbow). At the same time, Spedding and Benard (2007) performed pressured drop measurements through a vertical to horizontal 90 ° elbow bend. They proposed a general correlation for prediction of gas-liquid two-phase pressure drop for elbow bends. The same authors (2008) also reported the pressure drop characteristics of water-oil-air three-phase flow through a vertical to horizontal 90 ° elbow bend. Concerning the air-water two-phase flow pressure drop in vertical to horizontal internal wavy 90° elbow bends, Benbella et al . (2009) carried out a research. Their results demonstrated that wavy 90 ° wavy elbows had total pressure about 2 −5 times greater than smooth bends. In the work of Abdulkadir et al. (2011), the effect of 90° bends on air-oil (silicon) flow pattern were observed using advanced instruments such as Electrical Capacitance Tomography (ECT), Wire Mesh Sensor Tomography (WMS) and high-speed video. Changing the flow velocities, they had discovered transitions of flow pattern before and after elbow bends. They concluded that horizontal bend has less effect on the flow patterns compared with the vertical bend. 2 Zhang et al . (2012) performed CFD simulations to observe erosive ware damages (puncture point locations) in elbow bends by varying slurry velocity, bend orientation and bend angle. They discovered that the location of the maximum erosive location moved to downstream (elbow exit) when slurry velocity increased. Liu et al. (2012) also experimentally studied air-water flow induced fluctuating force on a 90° elbow. They discussed force fluctuation phenomenon matching with the observations of flow pattern such as bubbly flow, slug flow and churn flow. For forgoing review, a summary of information of previous researches that focused on 90° elbow bend is shown in Table 1. From the entire review, it is very obvious that multiphase flow phenomena before, inside and after elbow bend are very violent and the effects are undesirable. However, the existence of bended pipes is very common in conveying process of oil and gas mixture from downhole to separator because they are absolutely necessary for flow directional changes. Thus, in designing such bended pipes, a clear understanding of phase distribution (or flow pattern) before, inside and after the bend is very critical since these can negatively affect the performance of operating system. However, available information in literature is mostly based on probe measurement. Indeed, experiences in visual observations of multiphase flow phenomena without any intrusive measuring tool are still lack and needed to obtain a better understanding on the phase distribution through bended pipes. Even though some visual observations can be found in Abdulkadir (2011), the focus point was only inside the elbow bend. Without having visual information at the downstream of the elbow bend, a sharp imagination still cannot be made in designing a bend pipe. Moreover, long elbow bends are also becoming attractive in industrial applications and related information is in demand.

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N. Z. Aung & T. Yuwono: Gas-liquid Two-phase Flow—through a Vertical to Horizontal 90° Elbow Table 1. Summary of previous researches that focused on effect of elbow. Research (Reference no.) Huseyin et al. 2004 Kim et al. 2007 Liu at al. 2012 Mahvash & Ross 2008 Mahmoud et al. 2012 Margot et al. 2012 Riverina et al. 2006 Singhal et al. 2002 Spedding & Benard 2007 Spedding et al. 2008 Multiple-phase classification Gas-solid (Two-phase) Gas-solid (Two-phase) Gas-solid (Two-phase) Gas-liquid (Two-phase) Gas-liquid (Two-phase) Gas-liquid-liquid (Three-phase) Gas-liquid (Two-phase) Gas-liquid (Two-phase) Gas-solid (Two-phase) Gas-liquid (Two-phase) Elbow geometry R/D = 1.5,3 (vertical to horizontal upward flow) R/D = 1.5,3 (vertical to horizontal upward flow) R/D = 1.5 (horizontal to vertical upward flow R/D = 1.515 (horizontal to horizontal, the same plane flow) R/D = 0.654 (vertical to horizontal upward flow R/D = 0.654 (vertical to horizontal upward flow R/D = 4,6,8,10 (vertical to horizontal upward flow R/D = 2.3 (vertical to horizontal upward flow) R/D = 3.255 (various orientations) R/D = 1.451 (vertical to horizontal upward flow) Methodology Experiment, CFD simulation Experiment Experiment Experiment Experiment Experiment Experiment and correlations Experiment CFD simulation Experiment In this regard, the aim of this work is to experimentally and numerically observe phase distribution (the flow pattern) characteristic of gas-liquid two-phase bubbly flow through a vertical to horizontal right angled (90°) long elbow bend with a wide focusing view and to provide more descriptive information. Numerical Simulation Advanced computational methods in fluid dynamics are becoming powerful and capable of modeling multiphase flows and the acceptable simulated results are at proven stage in many researches (Akilli 2001; Zhang 2012; Singhal 2002). Thus, the CFD simulations of gas-liquid two-phase flow through a vertical to horizontal elbow bend are also performed to confirm the experimental observations in this work. 3 Governing Equations Flow governing equations for a two-phase mixture are obtained from the ensemble averaging of the Navier–Stokes equations and the following mass and momentum continuity equations are solved in computation. Continuity equation: 2 ^t mh v 2t + d: ^t m umh = 0 (1) Momentum transfer equation: 2 ^t m fh v v 2t + d : ^t m um umh = vm + u vT v - dp + d : 6n m ^du m h@ + t m g + v + d: c / a t u v v F k k dr, k udr, k m n k=1 (2)

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ASEAN Journal on Science and Technology for Development, 30(1&2), 2013 where, the subscript m , k , dr describe the mixture, secondary phase and drift respectively, v is ρ is density, t is time, µ is viscosity, u v velocity, p is pressure, F is body force vector, α is volume fraction. For having reasonable accuracy (Singhal 2002; Margot 2002; Mahmoud 2012) the standard k-ε model is adopted to solve the set of turbulent kinetic energy and dissipation rate equations. The equations for mixture turbulent kinetic energy and its dissipation rate are obtained by the summation of mixture as a single phase. Turbulent kinetic energy equation: 2 ^t m k h n c t, m m v 2t + d : ^t m um k h = d: v k dk + (3) G k, m - t m f The mesh has 240 000 hexahedral elements. The base of vertical pipe is set as velocity inlet condition and the end of horizontal as outflow condition. No slip condition is considered at the walls. Solving Strategies A commercial CFD package FLUENT 6.2 is used to solve the set of governing equations; continuity, momentum, and turbulent k-ε equations. Velocities of phases and gas phase fraction are set as known inlet boundary condition for every run. The SIMPLEC algorithm is used for coupling between velocity and pressure. The second-order upwind discretization scheme is used for the momentum equations while first-order upwind discretization is used for volume fraction and k-ε equations. The convergence criteria are third order residual value of each parameter and deviation of 10–5 between the inlet and outlet mass flow rates to satisfy the continuity law. Experimental Setup and Procedure The schematic diagram of constructed air-water two-phase flow loop is shown in Figure 1. The test section consists of 2.1 m long vertical pipe, elbow bend and a horizontal pipe that runs 1 m after the elbow exit. The vertical and horizontal pipes are acrylic pipes which have inside diameter of 0.036 m. The elbow bend is also made of acrylic material and has the same inside diameter. The detail structure of the elbow bend is shown in Figure 2. Aiming to create bubbly flow in vertical test section, the air is injected at the base of vertical test section by using radial injectors. There are 32 ports of 710 µm diameter along the periphery of the injector. The liquid flow rate is measured by using “Doppler” flow meter and the gas flow rate is measured by using float type (Dwyer Rate-Master) gas flow meter. Two high speed digital cameras are used to capture the visual observation of flow patterns in vertical pipe, inside elbow bend and at its downstream. Experiments are conducted 4 Turbulent dissipation equation: 2 ^t m fh n c t, m m v 2t + d : ^t m um fh = d : v k df + (4) f t f C G C ^ h 1 k m 2 m , f f k The turbulent viscosity of the mixture was calculated by: k n t, m = C n t m ! 2 (5) where the subscript t represents for turbulent, k is turbulent kinetic energy, ε is turbulent dissipation rate, C1ε, C2ε, Cµ, σk and σε are the standard k– ε model constants and G is the turbulence production term. This standard model is used without any further modifications taking C1ε =1.44, C2ε =1.92, Cµ =0.09, σk =1 and σε =1.3 since they have been accepted in a wide range of wall-bounded air and water turbulent flows. Computational Domain The whole test section is considered as the computational domain and constructed in GAMBIT 2.2. It is shown in Figure 3a–3b.

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N. Z. Aung & T. Yuwono: Gas-liquid Two-phase Flow—through a Vertical to Horizontal 90° Elbow 1. Water tank 2. Pump 3. Regulation system (Bypass) 4. Accumulator 5. Doppler flow meter 6. Annular air injector 7. Pressure gauge 8. Thermocouple 9. Rotameter 10. Compressor 11. Digital camera 1 12. Photo editing system 1 13. Test section 14. Digital camera 2 15. Photo editing system 2 16. Gas-liquid separator Figure 1. Schematic diagram of experimental test loop. Curvature radius, R = 0.09 m Inside diameter, ID = 0.036 m Outside diameter, ID = 0.04 m Figure 2. Detail structure of elbow bend. 5

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ASEAN Journal on Science and Technology for Development, 30(1&2), 2013 (a) (b) Figure 3. Computational grid structure of test section: (a) Side view (x-y plane) (b) Cross-sectional view (x-z plane and y-z plane). by varying superficial liquid velocity and volumetric gas quality. The liquid superficial velocity (in terms of Reynolds number) is varied in the range of ReSL=13497 to 49488 and the gas volumetric quality (β) is varied in the range of 0.05−0.2. These initial parameters are calculated from measureable parameters by using equations expressed in Appendix. RESULTS AND DISCUSSION Flow Pattern in Vertical Test Section In this work, for all flow conditions, bubbly flow regimes are created in the vertical test section at the upstream of elbow bend. The visual observations of bubbly flow are captured with a high speed digital camera at a height of 0.35 m above the air injector. Some sample observations of the bubbly flows in vertical test section are shown in Figures 4a–4c. The observed bubbly flows can be classified into three categories. Clustered bubbly flow. This kind of flow occurs at high superficial liquid velocities ( Re SL = 40490, Re SL = 49488) with low volumetric gas qualities (β = 0.05, β = 0.07) as shown in Figure 4a. The gas phase (bubbles) are cluttered in liquid medium forming bubbleclusters. In other word, the bubble distribution is not symmetric to the vertical axis of the pipe at any elevation and a series of bubble-clusters is formed along the pipe. Homogeneous bubbly flow . This flow condition is observed at every flow condition with medium range of volumetric gas qualities (β = 0.09−0.13) as shown in Figure 4b. The bubble size becomes larger and it seems that the bubbles occupy homogeneously over the entire cross-section of the pipe at any elevation. Dense bubbly flow. Figure 4c shows dense bubbly flow condition. It is clear that this kind of bubbly flow occurs at high gas qualities. 6

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N. Z. Aung & T. Yuwono: Gas-liquid Two-phase Flow—through a Vertical to Horizontal 90° Elbow (a) (b) (c) Figure 4. Visual observations of bubbly flow in vertical test section: (a) ReSL = 49488; β = 0.05; (b) ReSL = 31492; β = 0.11; (c) ReSL= 40490; β =0.2. The entire cross sectional area of the pipe is filled with bubbles, but formation of elongated bubbles is not yet observed. Flow Pattern in Elbow Bend and Downstream Figures 5–9 show the experimental observations and numerically simulated results of gas-liquid two-phase flow patterns through the elbow bend for flow conditions of ReSL = 13497−49488 with constant volumetric gas quality β = 0.2. The numerical results are taken from both longitudinal mid-plane and transverse crosssectional plane at various distances inside and after elbow bend. The experimental results clearly state that the two-phase flow pattern is mainly governed by liquid velocity. For flow conditions with low liquid velocities (Figures 5−6), the gas phase starts to separate from inner wall about bend angle (Θ) of 30°−45° and flows up to the outer wall. It can be explained that the momentum and buoyancy force attained by bubbles overcomes the pressure at the outer surface of the elbow and the bubbles try to migrate to the outer surface. Then, gas-liquid stratification begins before the exit of the elbow bend. Further increase of liquid velocity (ReSL = 31492) delays the gas phase separation from inner surface of elbow bend showing uniformly distribution in the elbow bend. At the outlet of elbow bend, the gas phase moves up to upper surface of horizontal pipe. Formation of gas layer initiates about 2D−3D after elbow exit. Figures 8−9 depict comparisons of recorded and computed results for flow conditions of ReSL = 40490 and Re SL = 49488 with constant gas quality. In contrast to the former observations, the gas phase leaves away from the outer surface of the elbow and totally concentrates on inner bend. The whole outer surface of the elbow bend is free from migration of gas bubbles and the entire inner surface is apparently covered by gas layer. This phenomenon is related to the increasing of pressure at the outer bend. When the mixture enters into the elbow bend with a high velocity, the liquid phase with higher 7

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(a) (b) Figure 5 (a)–(b). Experimental and numerical observation of two-phase flow pattern through elbow bend at ReSL = 13497, β =0.2. 8

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(a) (b) Figure 6 (a)–(b). Experimental and numerical observation of two-phase flow pattern through elbow bend at ReSL = 22494, β =0.2. 9

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