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"Sebuah experiment telah dilakukan untuk penggunaan refrigeran ramah lingkungan menjadi kebutuhan manusia. Dalam percobaan aliran mendidih R-22, diameter pipa konvensional 7,6 mm digunakan. Variasi fluks panas dari 5,9 kW / m2 hingga 25,04 kW / m2, fluks massa 282 kg / m2.s hingga 630 kg / m2.s, dan suhu saturasi dari -0,42 ° C hingga 11,97 ° C untuk hasil R- 22. Hasil tersebut dipengaruhi oleh penurunan tekanan di fluks massa, fluks panas dan temperature saturasi. Adapun perpindahan kalor dipengaruhi oleh fluks kalor dan temperatur, sedangkan fluks massa menunjukkan tidak ada perubahan dalam perpindahan kalor untuk nilai R-22. Dalam rangka untuk mencari dan membandingkan hasil, Computational Fluid Dynamics (CFD) telah menjadi pendekatan untuk desaindan evaluasi kinerja. Pada penelitian ini, simulasi numerik untuk internal pipa dilakukan dengan menggunakan model Eulerian dengan paket CFD, ANSYS Fluent 12.1. Turbulensi di fase cair dan gas dijelaskan menggunakan model k-ε. Parameter hidrodinamika global seperti fluks masa dan kecepatan cairan telah diteliti untuk berbagai dangkal uap dan kecepatan gas, dengan simulasi 3D. Selain itu, studi geometri dan skala pengaruh pada pipa horisontal telah dipertimbangkan. Hasil penelitian menunjukkan fluks massa dan fluks panas memiliki efek signifikan pada parameter hidrodinamik, yang dapat menyebabkan efek besar pada hasil penurunan tekanan. Perhitungan numerik dengan sistem aliran dua fase gas-cair telah dilakukan untuk mengetahui pengaruh penurunan tekanan, perbedaan suhu, dan massa penurunan fluks pada karakteristik hidrodinamika fluks massa yang berbeda dan fase atau jenis arus. Hasil ini diproduksi mengungkapkan bahwa CFD memiliki potensi yang sangat baik untuk mensimulasikan dua-fase sistem aliran.

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An experiment has been done previously to the use of environmentally friendly refrigerants into human needs. In the experiment of boiling flow conditions, R-22 is done in a conventional pipe diameter of 7.6 mm. Variation of heat flux of 5.9 kW / m2 to 25.04 kW / m2, the mass flux of 282 kg / m2.s up to 630 kg / m2.s, and the saturation temperature of -0.42 ° C to 11.97 ° C for R-22.The results are influenced by the pressure drop in the mass flux, heat flux and temperature saturation. As for the heat, transfer is affected by the heat flux and temperature saturation, whereas the mass flux showed no change in the heat transfer value for R-22. In order to find and compare results, Computational Fluid Dynamics (CFD) has become an approach for design, scale-up and performance evaluation. In the present work, numerical simulations for internal-pipe were performed using the Eulerian model with CFD package, ANSYS Fluent 12.1. The turbulence in the liquid and vapor phase are described using the k-ε model. Global hydrodynamic parameters like mass flux and liquid velocity have been investigated for a range of superficial vapor and gas velocities, only with 3D simulations. Moreover, the study of geometry and scale influence on the horizontal pipe have been considered. The results suggest mass flux and heat flux have significant effects on the hydrodynamic parameters, which may lead to substantial effects on the pressure drop results. Numerical calculations with gas-liquid two-phase flow system have been carried out to investigate the effect of mass flux and heat flux on the hydrodynamic characteristics of two-phase flows. These produced results reveal that CFD have excellent potential to simulate two-phase flow system."

"Pada paper ini void fraction dari R-290 di investigasi. Penggunaan R-290 ditujukan untuk menggantikan R-22, dikarenakan R-22 memiliki nilai ODP (Ozone Depletion Potential) sebesar 0.05 dan nilai GWP (Global Warming Potential) sebesar 1700. Nilai void fraction dibutuhkan karena berhubungan dengan prediksi nilai dari jatuh tekanan, yaitu pada jatuh tekanan akibat akselerasi. Sehingga, merupakan suatu kebutuhan untuk melakukan studi komprehensif mengenai void fraction pada aliran didih dua fase pada pipa konvensional berdiameter dalam 7.6 mm. Data primer didapatkan dengan melakukan eksperimen pada kondisi: Fluida kerja R-290, pipa horizontal berdiameter dalam 7.6 mm, temperatur saturasi pada rentang 5 hingga 15ºC, fluks kalor pada rentang 9 hingga 20 kW/m2 dan fluks massa pada rentang 300 hingga 420 kg/m2.s. Hasil jatuh tekanan eksperimen yang di dapatkan kemudian dibandingkan dengan jatuh tekanan prediksi.

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In this present paper the void fraction of R-290 was investigated. The use of R-290 is to replace R-22, since R-22 has 0.05 Ozone Depletion Potential (ODP) and 1700 Global Warming Potential (GWP). The relevancy to obtain the void fraction was related to predict the value of pressure drop, especially accelerational pressure drop. Therefore, it is a necessity to conduct a comprehensive study about void fraction in two-phase flow boiling in conventional pipe with 7.6 mm inner diameter. To obtain the primary data, the experiment was conducted with the experimental conditions of R-290 working fluid, 7.6 mm inner diameter horizontal tube, 5 to 15ºC saturation temperature, 9 to 20 kW/m2 heat flux, and 300 to 420 kg/m2.s mass flux. The recent results of pressure drop were compared to some existing method of pressure drop calculations"

"ABSTRAKDalam sistem perpindahan panas, Two-Phase Closed Thermosyphon (TPCT) sangat efektif dan efisien. Thermosyphon adalah sebuah pipa kapiler tertutup yang berisi fluida kerja yang berfungsi sebagai media untuk menghantarkan panas dari sisi panas ke sisi dingin dari pipa. Thermosyphon terdiri dari tiga bagian yaitu: evaporator, adiabatik, dan kondensor. Salah satu permasalahan yang sering muncul pada penggunaan thermosyphon adalah kekeringan atau "dry out". Kekeringan dapat menyebabkan melelehnya dinding evaporator karena laten panas yang berlebih sehingga menyebabkan fluida kerja di area evaporator berubah semua menjadi uap dan air kondensat hasil kondensasi tidak bisa kembali lagi ke area evaporator karena tertahan oleh uap. Tujuan dari penelitian ini adalah untuk membuat sistem yang dapat mencegah terjadinya kekeringan pada TPCT, simulasi CFD dilaksanakan untuk memahami karakteristik fenomena kekeringan pada TPCT dan sebagai bahan referensi dalam perancangan sistem kendali. Pengujian sistem dilaksanakan dengan menguji 3 jenis variasi filling ratio pada TPCT, yaitu 30%, 45% dan 60%. Bagian evaporator TPCT dipanaskan melalui kolam yang diberi pemanas dengan beban konstan sebesar 6000 watt. Dalam pengujian, filling ratio 30% mengalam 4 kali kekeringan pertama kali di suhu 336.05 K , 45% 1 kali di suhu 339.2 K, dan filling ratio 60% tidak mengalami kekeringan ditandai dengan nilai hambatan termal yang paling rendah sebesar 5.15446 K/W. Semakin sedikit volume fluida kerja yang ada pada TPCT menyebabkan semakin cepatnya terjadi kekeringan. Dalam pengujian, ketika kekeringan terjadi fluida kerja tambahan di injeksi ke TPCT untuk mencegah rusaknya dinding evaporator karena kekeringan yang terjadi, kemudian air hasil kondensasi kembali ke reservoar penampung fluida kerja tambahan sebelum kembali ke bagian evaporator.

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ABSTRACTIn a heat transfer system, a Two-Phase Closed Thermosyphon (TPCT) is highly effective and efficient. A thermosyphon is a closed tube that contains working fluid that serves to transfer heat from the hot section to the cooler section of the tube. A thermosyphon consists of three sections, namely: evaporator, adiabatic, and condenser. One of the problems that occur in thermosyphon applications is "dry out". Dry out can cause the evaporator wall to melt due to excessive heat latency, which causes the working fluid in the evaporator area to turn all into steam and condensate water resulting from condensation can not return to the evaporator area because it is blocked by steam. The purpose of this study is to create a system that can prevent dry out in TPCT, CFD simulations are carried out to understand the characteristics of dry out phenomena in TPCT and as a reference parameter in the design of control systems. System testing is carried out by experiment with 3 variation of filling ratio on TPCT, namely 30%, 45% and 60%. The TPCT evaporator section is heated through a pool that is heated with a constant load of 6000 watts. In experiment, 30% filling ratio occur 4 times dry out at first temperature 336.05 K, 45% 1 time at temperature 339.2 K, and 60% filling ratio did not occur dry out marked by the lowest thermal resistance value of 5.15446 K/W. The less volume of working fluid available in the TPCT causes more rapid dry out. In experiment, when dry out occurs additional work fluid is injected into the TPCT to prevent damage to the evaporator wall due to dry out, then the condensed water returns to the reservoir of additional working fluid before returning to the evaporator section."

"Nannochloropsis spp. adalah mikroalga yang menghasilkan asam omega-3 eicosapentaenoic (EPA) dan protein kasar bernilai tinggi, di mana keduanya bermanfaat bagi kesehatan dan diet manusia. Ekstraksi protein dari non-defatted, ethanol-defatted, dan isopropanol-defatted Nannochloropsis kering menggunakan Aqueous Two-Phase Systems (ATPS) dilakukan. Kurva binodal pertama kali ditentukan secara eksperimental dengan bahan yang digunakan: polietilen glikol (PEG) 400, 1000, dan 4000 terhadap buffer fosfat (K2HPO4-KH2PO4) dengan pH 9. Diketahui bahwa protein larut dalam PEG, menghasilkan total konsentrasi protein dalam fase atas. Memvariasikan berat molekul PEG memberikan efek yang dapat diamati pada kurva binodal; semakin tinggi berat molekul, semakin dekat kurva ke sumbu x dan y. Mengindikasikan bahwa berat molekul PEG yang lebih tinggi meningkatkan kemungkinan dua solusi terpisah menjadi beberapa lapisan. Selain itu, Tie Line Length (TLL) dengan nilai rata-rata 40% (w / w) dipilih untuk semua PEG untuk menstandarisasi komposisi akhir. Selain itu, protein di lapisan atas ditentukan menggunakan uji protein Lowry dengan spektrofotometer pada absorbansi 750 nm.Hasil menunjukkan bahwa biomassa yang tidak dihilangkan lemaknya dalam PEG400 menghasilkan pemulihan protein terbanyak pada 21,73%, diikuti oleh biomassa yang dihilangkan lemaknya oleh etanol di PEG400 dan biomassa yang dihilangkan lemaknya oleh isopropanol di PEG400 masing-masing dengan protein 12,67% dan 10,98% yang pulih. Diperkirakan bahwa mayoritas protein terdenaturasi selama proses penghilangan lemak menjadikannya tidak larut, dan  menghasilkan kadar protein yang rendah. Pemanfaatan biomassa mikroalga basah diduga dapat mengatasi masalah ini untuk penelitian di masa depan.

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Nannochloropsis spp. is a microalga which produces high-value omega-3 eicosapentaenoic acid (EPA) and crude protein, where both are beneficial for human health and diet. Protein extraction from non-defatted, ethanol-defatted, and isopropanol-defatted dried Nannochloropsis biomass using Aqueous Two-Phase Systems (ATPS) was performed. Binodal curves were first determined experimentally for the solutions used: polyethylene glycol (PEG) 400, 1000, and 4000 against phosphate (K2HPO4-KH2PO4) buffer with pH 9. It is known that proteins are soluble in PEG, yielding the total protein concentrates in the top phase. Varying molecular weights of PEG gave observable effects on the binodal curves; the higher the molecular weight, the closer the curve was to the x and y axis. Indicating that higher molecular weight of PEG increases the chance of the two solutions separating into layers. Furthermore, a Tie Line Length (TLL) with average value of 40% (w/w) was selected for all PEGs to standardize the final composition. Additionally, proteins in the top layers were determined using the Lowry protein assay with a spectrophotometer at 750 nm absorbance.

Results showed that non-defatted biomass in PEG400 yielded the most protein recovery at 21.73%, followed by ethanol-defatted biomass in PEG400 and isopropanol-defatted biomass in PEG400 with 12.67% and 10.98% protein recovered, respectively. It is suspected that the majority of the protein denatured during the defatting process making them insoluble, hence, the low protein yields. Utilization of wet microalga biomass might overcome this issue for future research."

"Gathering contributions by the most prominent researchers in a highly specialised field, this proceedings volume clarifies selected aspects of the physics of turbulent cascades and their statistical universalities under complex stationary and non-homogeneous conditions. Here, these conditions are induced by the presence of a gas/liquid interface, inertial particles, strong shear, rotation, MHD and stratification. By proposing different ways to model turbulence effects under these complex conditions, the book will be of considerable interest not only to academic researchers, but also to specialists and junior researchers in the domain of propulsion and power, as well as those whose work involves various applications related to atmospheric, oceanic and planetary physics."

"Slugging as a water hammer initiator is a fascinating topic because it has a strategic impact on equipment safety in industrial systems, i.e. pressurized water reactors (PWR), heat exchangers, etc. The present research’s objective was to investigate slugging as initiating the water hammer phenomenon through indirect contact steam condensing in a horizontal pipe heat exchanger. The experiment apparatus used in the present experimental study consisted of an inner annulus pipe made of copper (din = 17.2 mm, do = 19 mm) with a length of 1.8 m and an outer annulus pipe of galvanized iron (din = 108.3 mm, do = 114. 3 mm) with a length of 1.6 m. The tested liquid was water. The experiments were conducted at a static pressure of Ps = 108.825 kPa and the temperature of T = 119.7°C. The obtained experimental data of temperature and differential pressure fluctuations were analyzed using statistical analysis. The results were as follows: 1) the flow pattern area of non-slugging (stratified and wavy flow), transition (wavy-slug flow), and slugging (slug and large-slug) were determined, with the transition flow pattern of slug and large-slug defined as initiating water hammer; 2) transition area ranges for the wavy-slug flow pattern are from ?co=1´10-1 kg/s to ?co=6´10-1 kg/s for ?st=6´10-3 kg/s to ?st=7.5´10-3 kg/s, and ?co< 3´10-1 kg/s for ?st=8´10-3 kg/s to ?st=9´10-3 kg/s. These obtained data are very important in order to develop a database for the input of an early warning system design in a safe, two-phase flow installation piping system during steam condensation."

"An investigation into flow boiling void fraction was conducted to observe its characteristics and to develop a new correlation of void fraction based on the separated model. The study used a natural refrigerant of R-290, flowed in a horizontal tube of 7.6 mm inner diameter under experimental conditions of 3.7 to 9.6oC saturation temperature, 10 to 25 kW/m2 heat flux, and 185 to 445 kg/m2s mass flux. The void fraction, calculated by the present experimental data, was used for comparison with 31 existing correlations, including model types as follows: homogeneous, slip ratio, K?h correlation, drift flux, and a model based on the Lockhart-Martinelli correlation (Xtt). A new void fraction correlation, as a function of liquid and vapor Reynolds numbers, was proposed, based on the data. The measured pressure drop was compared with some pressure drop correlations that use the newly developed void fraction combination. The best prediction was shown by the homogeneous model."

"Due to certain advantages, natural refrigerants have recently become more popular. Environmental issues motivate this study, focused on the characteristics of propane (R-290) as a replacement for conventional refrigerants. The aim of the present research is to characterize the pressure drop of evaporative R-290 in a microchannel of 500µm diameter and 0.5 m length. The variables of the experimental conditions are mass flux between 155 and 1071 kg/m2s and vapor quality between 0 and unity. The results show a laminar flow for liquid R-290 and a turbulence flow for vapor. Some existing correlations of two-phase flow viscosity were used to predict the pressure drop. For homogeneous model, Dukler et al.’s (1964) prediction viscosity correlation best predicted the present experimental pressure drop."

"Teknologi pembuangan panas peluruhan secara pasif pada reaktor daya nuklir masih bergantung pada penggunaan penukar kalor yang memindahkan energi kalor ke dalam tangki atau kolam air dengan volume tertentu sebagai heat sink pamungkas dengan memanfaatkan konveksi alam atau gravitasi. Teknologi ini memiliki keterbatasan kapasitas dalam jangka waktu tertentu sehingga tetap mengandalkan sistem pendinginan secara aktif. Salah satu teknologi pendukung pengambil kalor peluruhan yang dapat digunakan adalah teknologi two-phased closed termosyphon (TPCT) yang telah digunakan sebagai objek penelitian dalam bentuk pemodelan maupun kegiatan eksperimen. Di sisi lain, sistem reaktor daya memiliki ukuran besar yang lebih praktis untuk dimodelkan dan disimulasikan. Salah satu program pemodelan adalah RELAP5/Mod3.4/SCDAP yang didesain untuk mensimulasikan proses pembangkitan dan pemindahan kalor pada reaktor daya nuklir berpendingin air saat kondisi operasi normal dan abnormal. Tujuan penelitian ini adalah melakukan simulasi kinerja termal TPCT yang telah dimodifikasi dengan menambahkan tangki air pendingin di sekeliling evaporator sebagai sumber kalor. Pemodelan RELAP5 yang diperoleh perlu divalidasi dengan hasil pemodelan lain seperti FLUENT dan hasil eksperimen yang telah dilakukan. Hasil validasi dengan memberikan beban kalor berbeda pada bagian evaporator menunjukkan tidak adanya fenomena dryout pada RELAP5 yang berbeda dengan hasil simulasi FLUENT. Hal ini disebabkan oleh perbedaan konsep pemodelan antara FLUENT dan RELAP5, namun demikian nilai tahanan termal TPCT memiliki kesamaan karakteristik di antara kedua metoda. Validasi simulasi dengan hasil eksperimen pada filling ratio (FR) 30 %, 45 %, 60 % menunjukkan karakterisasi perubahan temperatur dinding TPCT yang sama pada variabel FR 60 %. Pada FR lebih rendah, terdapat variasi perbedaan hasil simulasi dengan eksperimen terutama pada pencapaian temperatur pendidihan air tangki dan pola pengambilan kalor kondenser. Simulasi tambahan dengan FR 70 % dan 100 % menunjukkan kinerja termal TPCT yang lebih optimum pada FR 70 % dan menurun pada FR 100 %. Pemodelan TPCT dengan 2 volume radial menghasilkan simulasi yang lebih baik, namun demikian dibutuhkan pemahaman yang lebih tepat mengenai peranan parameter gas non-kondensibel pada nodalisasi model dengan kondisi vakum. Berdasarkan hasil validasi, simulasi TPCT dengan RELAP5 lebih tepat digunakan untuk tujuan prediksi kinerja termal TPCT berdasarkan FR yang optimum.

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The current technology in removing residual heat in passive way in nuclear power reactor still depends on the use of heat exchanger to transfer heat energy into a water tank or pool with certain volume as the ultimate heat sink utilizing natural circulation or gravitation. This technology still requires active cooling supply system in certain time period due to the limited capability. On of the proposed support technology to remove residual heat is two-phased closed thermosyphon (TPCT), which has been used as research object in form of modelling or experimental activity. In other side, power reactor system has big dimension, which is more practical to be modelled to simulate its performance and safety level. On of the modelling code is RELAP5/Mod3.4/SCDAP, designed to simulate the heat generation and removal process inside the water-cooled nuclear power reactor in normal and abnormal operation. Therefore, the research purposes are to model and simulate the TPCT, which has been modified by adding the external water tank around the evaporator. The generated model of TPCT using RELAP5 has to be validated using other modelling tool such as FLUENT and experimental results. The generated model of TPCT using RELAP5 has to be validated using other modelling tool such as FLUENT and experimental results. One of validation results by giving different heat load into the evaporator shows no indication of dry-out in the RELAP5 simulation as obtained otherwise in the FLUENT simulation. This is because the different modelling concept between FLUENT and RELAP5. However, the calculated thermal resistances had similar characteristics from both calculation tools. Simulation validation with experimental results using filling ratio (FR) of 30 %, 45 %, and 60 % shows a much more similar characteristics of the evaporator, adiabatic, and condenser wall temperature with higher FR of 60 %. In lower FR, there are several output variations in achieving the water tank boiling temperature and condenser heat transfer. Additional simulations with FR 70 % and 100 % indicated more optimum thermal performances of TPCT, especially in FR 70 %, which decreased in FR 100 %. TPCT modelling with 2 radial volumes results in a better simulation, however it requires a better understanding regarding the role of non-condensable gas in the model in the vacuum condition. Based on the validation results, TPCT simulation using RELAP5 is better conducted based on the optimum condition in term of filling ratio to predict the thermal performances of TPCT."