ANALISIS EFISIENSI DAN PENURUNAN TEKANAN PADA SIKLON PERSEGI MENGGUNAKAN CFD

Artikel ini memaparkan hasil penelitian yang diperoleh melalui aplikasi komputasi dinamika fluida (Computational Fluida Dynamic,CFD) untuk mensimulasi medan alir di dalam siklon persegi. Perangkat lunak Gambit digunakan sebagai pre-processor untuk menggambar konfigurasi, diskritisasi, dan pendefinisian kondisi batas siklon. Geometri siklon silinder Lapple dan persegi ditinjau dari volume yang sama. Diameter siklon yang digunakan 0,2 m menyesuaikan dengan diameter siklon silinder Lapple yang digunakan Wang pada eksperimennya, dengan kondisi operasi  ditentukan pada laju alir gas sebesar 0,1m3/s sementara beban partikel dalam  laju alir gas sebesar 0,01kg/m3. Perangkat lunak CFD FLUENT 6.2.16 digunakan untuk simulasi medan alir dan dinamika partikel dalam siklon. Penelitian ini bertujuan untuk mengetahui pengaruh geometri siklon persegi terhadap medan alir, efisiensi dan penurunan tekanan. Prediksi yang dihasilkan memberikan informasi mengenai medan alir berupa kecepatan axial dan tangensial di dalam siklon serta informasi efisiensi dan penurunan tekanan. Hasil kajian menunjukkan bahwa kecepatan tangensial mendominasi medan alir di luar garis tengah siklon, sementara kecepatan aksial mendominasi medan alir di daerah garis tengah siklon. Penurunan tekanan yang terjadi pada siklon persegi lebih tinggi dari siklon silinder, namun efisiensi untuk siklon persegi lebih tinggi dibandingkan siklon Lapple

Women on the Steering Wheel: Identifying the Potentials of Women in Improving the Protection of Indonesian Women Migrant Workers

This paper is based on a research that looked into the potentials of women as stakeholders in improving the protection of Indonesian women migrant workers abroad. It was designed based on the assumptions that an identification of the potentials of women at various levels and in various institutions may positively contribute to the efforts of finding solutions for the problems faced by women migrant workers and that rather than being seen merely as victims, women should be seen as actors who can actively participate in addressing the problems. This paper analyzes efforts made by a number of Indonesian women who are publicly recognized for their works in promoting the protection of Indonesian women migrant workers, both as state and non-state actors in the context of policy making. The focus is on how these women perceive the extend to which their efforts have been able to influence the policy making process. The discussion also includes how the women responded to the challenges and opportunities that they encounter as part of their learning process. The data for this paper was gathered through interviews with six prominent woman figures who are known for their work on the issue of women migrant workers. While confirming that as actors outside the government these women have made efforts to influence the policy making process, this paper showcases that the actual impact of their efforts is highly determined by the policy environment

Women Refugees: An Imbalance of Protecting and Being Protected

The recent refugee crisis in Europe has become a prominent human security issues that continues to receive international attention. The main debate has been on the accommodation of refugees in European countries and the issues that arise from the sudden influx of people into those countries. Camps were established with limited time and information to prepare, leading to issues within these temporary living arrangements. Conditions are worse for women refugees, who suffer similarly to the men but have higher rates of insecurity. This paper attempts to argue for greater protection for women refugees. To do so, it will describe women refugees’ conditions and needs and relate them to an enforced moral responsibility. It argues for more attention to be given to women refugees with specific conditions, those who have been marginalized in most refugee policies. The main argument is that better protection for and empowerment of women refugees is urgently needed due to their own conditions and needs alongside the moral obligations to take care of children and the elderly. To do so, policies have to consult the specific needs of women. An important step towards this effort is to develop further and more detailed classification of women and their specific needs: women refugees’ needs are not merely determined by their own conditions but also the conditions of those they are responsible for

Labour Migration from Indonesia to South Korea: Challenges in Maximizing Potentials

Analisa tentang mengapa seseorang bermigrasi untuk bekerja di negara lain umumnya dilakukan melalui pencarian dan pendeskripsian faktor-faktor “push” dan “pull” , di mana pendapatan rendah dan pengangguran yang tinggi menjadi faktor pendorong dan pendapatan tinggi dan pengangguran yang rendah menjadi faktor penarik. Ini dapat digunakan untuk menjelaskan alasan umum bagi migrasi tenaga kerja yang bersifat sementara namun tidak cukup untuk menjelaskan lebih lanjut mengapa seseorang memutuskan bermigrasi ke suatu negara dan bukan ke negara lainnya. Inilah yang dihadapi Indonesia dan Korea Selatan. Walaupun masih banyak orang yang mencari pekerjaan di Indonesia dan Korea Selatan masih membutuhkan pekerja asing, jumlah orang Indonesia yang bekerja di kategorikan kecil bila dibandingkan dengan jumlah di negara penerima lainnya di kawasan seperti Malaysia, Singapura, Hong Kong dan Thailand. Asumsinya terdapat sejumlah faktor yang menghalangi terwujudnya dampak maksimum dari faktor pendorong dan penarik ini. Tulisan ini menganalisa faktor-faktor penghambat tersebut, terutama terkait dengan tingginya persyaratan yang ditetapkan oleh Korea Selatan dan keterbatasan kemampuan untuk memenuhi persyaratan ini dari sisi Indonesia. Pemahaman tentang faktor-faktor penghambat ini akan dapat berkontribusi bagi upaya meningkatkan jumlah pekerja Indonesia di Korea Selatan, yang dapat dianggap sebagai negara yang cukup aman untuk tempat bekerja. An analysis of why people migrate to work in another country is commonly conducted through a listing and description of the push and pull factors, with low income and high unemployment being the push factors and high income and low unemployment being the pull factors. It can be used to explain in general the reasons for temporary labour migration but not to explain why people choose to migrate to a certain country, instead of the others. This is the case of South Korea and Indonesia. There is still a number of Indonesian workers seeking for employment abroad, and there is also a high demand for foreign workers in South Korea. However, the number of Indonesians working in South Korea can still be considered small if compared to the numbers of Indonesians working in other countries in the region, such as Malaysia, Singapore, Hong Kong and Taiwan. The assumption is that there are factors that hinder maximum impacts of this push and pull factors. This paper looked into these hindering factors which are mainly related to the high requirements from the South Korea side and the inability to fulfill the requirements from the Indonesia side. An understanding of these hindering factors may contribute to the efforts of increasing the number of Indonesians working in South Korea, which is considered as a reasonably safe country to work in.</p

KAJIAN PENGARUH ANGIN SILANG TERHADAP KARAKTERISTIK NYALA HIDROKARBON

Artikel ini memaparkan hasil yang diperoleh dari kajian dinamika fluida komputasi (DFK) untuk mensimulasi nyala turbulen tak pra-campur akibat pengaruh angin silang. Konfigurasi, diskretisasi dan kondisi batas nyala digambarkan menggunakan perangkat lunak pra-prosessor Gambit.  Pengaruh angin silang terhadap nyala hidrokarbon (nyala dengan pengaruh angin silang) dilakukan pada kondisi kecepatan bahan bakar tetap 20 m/s dengan kecepatan angin berubah-rubah dan pada kondisi kecepatan angin silang tetap 1,1 m/s dengan kecepatan bahan bakar berubah - ubah . Hasil penelitian dengan kondisi bahan bakar tetap menunjukkan bahwa peningkatan kecepatan angin silang memberikan pengaruh yang signifikan terhadap medan alir dan temperatur. Pada kajian dengan kondisi bahan bakar berubah - ubah ketika kecepatan angin silang tetap, terlihat bahwa peningkatan kecepatan bahan bakar memberikan dampak positif pada nyala, karena nyala semakin mampu melawan pengaruh angin silang terhadap nyala

Comparative performance study of two simple soot models for the prediction of soot level in atmospheric turbulent non-premixed flames

The increase of current fossil fuel consumption has led to an increase of soot emission into atmosphere.  Accurate prediction of soot production and destruction in a combustion system is not only important for the purpose of the design of the system, but also vital for the operation of the combustor. Numerous soot models have been proposed to predict the soot production and destruction in a flame, categorized as empirical, semi-empirical and detailed soot models.  Although the detailed model represents the highest level of soot modelling, its use has been impaired by substantial requirement of resources of computer and time. Therefore, empirical and semi-empirical approaches still have their position in soot modelling of practical combustors. In this study, two soot models, single-step and two-step models are examined in the simulation of atmospheric turbulent non-premixed sooting flames. The soot models are compared and evaluated for their performance in predicting soot level in methane and ethylene non-premixed flames.  The commercial software Fluent 6.3 was used to perform the calculations of flow and mixing fields, combustion and soot. Standard k-ε and eddy dissipation models were selected as solvers for the representation of the turbulence and combustion, respectively.  The two soot models used in the study are available directly from the code for evaluation. The results show that the two-step model clearly performed far better than the single-step model in predicting the soot level in both methane and ethylene non-premixed flames. With a slight modification in the constant a of the soot formation equation, the two-step model was capable of producing prediction of soot level closer to experimental data.  In contrast, the single-soot model produced very poor results, leading to a significant under-prediction of soot levels in both flames

CFD analysis of efficiency and pressure drop in a gas-solid square cyclones separator

In this paper, two small cyclones with the same hydraulic diameter and volume, which one is square and the other one is round (Lapple cyclone), are numerically compared. A pre-processor software GAMBIT was employed to set up the configuration, discretisation, and boundary conditions of the cyclone. The characteristics of the cyclone being studied was 0.2 m in diameter, receiving a gas flow rate of 0.1 m3/s with a particle mass loading of 0.01 kg/s. A commercial CFD code FLUENT 6.2.16 was employed to simulate the flow field and particle dynamics in the cyclone. The Reynolds averaged Navier–Stokes equations with Reynolds Stress Turbulence Model (RSTM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The Eulerian–Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW).The results show that collection efficiency of square cyclone is the better with increasing flow rate than round cyclone. The pressure drop in square cyclone is higher than the pressure drop in small round one

Simulation of the crosswind and the steam addition effect on the flare flame

This paper presents the results obtained from the application of computational fluid dynamics (CFD) to modelling the crosswind and steam addition effect on a turbulent non-premixed flame. A pre-processor software GAMBIT was employed to set up the configuration, discretisation, and boundary conditions of the flame being investigated.  The commercial software Fluent 6.3 was used to perform the calculations of flow and mixing fields as well as combustion. Standard k-ε and eddy dissipation models were selected as solvers for the representation of the turbulence and combustion, respectively.  The results of all calculations are presented in the forms of contour profiles.  During the investigation, the treatment was performed by setting a  velocity of fuel at 20 m/s with varied cross-wind velocity at  3.77 m/s, 7.5 m/s and 10 m/s,  and steam/fuel ratio at 0.14, 0.25 and 2.35.  The results of the investigation showed that the standard k-ε turbulence model in conjunction with Eddy Dissipation Model representing the combustion was capable of producing reliable phenomena of the flow field and reactive scalars field in the turbulent non-premixed flame being investigated. Other results of the investigation showed that increasing the velocity of the crosswind, when the fuel velocity was kept constant, significantly affected the flow field, temperature and species concentrations in the flare flame. On the other hand, when the velocity of the fuel was varied at the constant crosswind velocity, the increasing velocity of the fuel gave positive impact as it enabled to counteract the effect of crosswind on the flare flame. The velocity of the crosswind very influence of combustion efficiency, from result of the investigation showed that increasing the velocity of the crosswind significantly affected the combustion efficiency, other result of the inverstigation showed that steam addition will very influencing combustion, excelsior the steam/fuel ratio results the combustion efficiency decreas