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Abstrak :
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.

Abstrak :
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.

Abstrak :
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.

Abstrak :
Kebutuhan terhadap refrigeran alternatif untuk sistem refrigerasi semakin meningkat. Salah satu refrigerant alternatif yang umum digunakan terutama dalam keperluan sistem tata udara pemukiman adalah propana. Propana atau R290 memiliki keunggulan karena selain mudah didapatkan, juga memiliki sifat properti termodinamika dan perpindahan kalor yang cukup baik antara lain viskositas dinamik serta rapat massa jenis yang kecil dan stabil sehingga memiliki kemampuan penyerapan kalor yang baik meskipun membutuhkan perhatian terutama di dalam penannganan potensi bahaya ledakan. Salah satu metode yang umum digunakan di dalam analisis performa sistem refrigerasi adalah aliran dua fasa. Perhitungan korelasi perhitungan tekanan dilakukan dengan menggunakan basis data yang berasal dari penelitian Pamitran, et. al (2011) yang terdiri dari fluks kalor q = 5-20 kW/m2, G = 50-180 kg/m2. s; temperatur saturasi 0-11 oC, dan fraksi massa atau kualitas uap 0-1. Hasil menunjukkan bahwa fluks laju aliran massa, fluks kalor, dan bilangan Reynolds fasa campuran berbanding lurus terhadap penurunan tekanan aktual, persamaan korelasi Friedel (1979) memberikan nilai yang lebih akurat untuk memprediksi penurunan tekanan dengan nilai MAE (Mean Absolute Error) sebesar 59,12 % dan regim aliran yang terbentuk adalah regim aliran plug (kantong udara), slug, dan transition menuju wavy-annular menurut peta pola aliran Zhuang, et.al (2016). ......The need for alternative refrigerants for refrigeration system is increasing. One of the alternative refrigerants that commonly used, especially in residential air conditioning systems, is propane. Propane or R290 has the advantage because in addition to being easy to obtain, it also has good thermodynamic properties and heat transfer, including small and stable dynamic viscosity and density so that it has good heat absorption ability although it requires attention, especially in potential explosion hazards. One of the methods that commonly used in refrigeration system performance analysis is two-phase flow. Calculation of the correlation of pressure drop is carried out using a database derived from Pamitran, et. al (2011) which consists of parameters range such as heat flux q = 5-20 kW/m2, G = 50-180 kg/m2. S, saturation temperature 0-11 oC, and mass fraction or vapor quality 0-1. The results show that the mass flow rate flux and heat flux are directly proportional to the actual pressure drop with a greater effect of mass flow rate flux and Friedel's (1979) correlation equation provides a more accurate value for predicting pressure drop with MAE (Mean Absolute Error) value of 59,12 %. On the flow pattern map of Zhuang, et.al (2016) a plug-slug and transition flow condition to wavy-annular is formed.

Abstrak :
Berbagai percobaan pressure drop aliran dua fasa pada pipa minichannel telah dilakukan. Selain mendapatkan data eksperimental, banyak peneliti juga membandingkan data eksperimen mereka, bahkan menambahkan data peneliti lain ke korelasi yang ada. Tujuan pada eksperimen ini untuk mengenal karakteristik pressure drop pada aliran dua fasa dengan menggunakan pipa horizontal minichannel dan refrijeran propane (R290), eksperimen ini menggunakan 18 korelasi yang ada dimana terbagi menjadi dua metode untuk mencari nilai pressure drop, yaitu metode separated dan homogeneous. Kondisi eksperimen ini menggunakan pipa horizontal dengan diameter dalam 3 mm, untuk mass flux divariasikan dari 50 hingga 180 kg/m2s, sedangkan untuk heat flux divariasikan 5 hingga 20 kW/m2, temperature saturasi divariasikan 10 hingga 11 oC dan vapor quality 0 hingga 1. Hasil pada eksperimen ini berhasil mendapatkan korelasi terbaik dalam memprediksikan data eksperimen, yaitu korelasi milik Sun dan Mishima (2008) dengan mean absolute error sebesar 27,64 % ......Various experiments on the pressure drop of the two-phase flow boiling in the mini channel tube has been carried out. In addition to obtaining data on experimental pressure drop, many researchers have also compared their experimental data, and even added the data of other researchers to existing correlations. The purpose of this experiment is to identify the characteristics of the pressure drop in a two-phase flow using a horizontal minichannel pipe and a propane refrigerant (R290), this experiment uses 18 existing correlations which are divided into two experiments using a horizontal pipe with an inner diameter of 3 mm, for mass flux. varied from 50 to 180 kg / m2s, while for heat flux it was varied from 5 to 20 kW/m2, saturation temperature was varied from 10 to 11 oC and vapor quality was 0 to 1. This experiment managed to get the best correlation in predicting experimental data,the correlation of Sun and Mishima (2008) with a mean absolute error of 27.64%

Abstrak :
ABSTRAK
Drag reducing polymer DRP merupakan salah satu jenis drag reducer yang banyak digunakan pada industri-industri sebagai aditif untuk meningkatkan efisiensi aliran fluida dalam pipa. Penelitian ini dilakukan untuk menganalisis parameter yang berpengaruh terhadap efisiensi DRP, yaitu melalui penurunan model persamaan, serta untuk melihat fenomena yang terjadi pada aliran fluida melalui simulasi CFD. Data yang digunakan berasal dari eksperimen oleh Vancko 1997 untuk aliran satu fasa. Sementara untuk aliran annular dua fasa digunakan data eksperimen Vancko 1997, Al-Sarkhi dan Hanratty 2001 a,b, dan Fernandez et al. 2004. Masing-masing parameter berupa konsentrasi DRP, kecepatan fluida, dan besar diameter pipa dianalisis berdasarkan persamaan model yang ada. Hasil penelitian menunjukan model persamaan aliran satu fasa dengana nilai = 4,0 menghasilkan error hingga 18. Sementara persamaan aliran annular yang diajukan hanya sesuai untuk kondisi distribusi film cairan uniform dan simetris menghasilakn error sekitar 20, untuk pipa dengan diameter yang lebih kecil. Untuk simulasi CFD terdapat perubahan profil kecepatan fluida menjadi lebih parabolik, menunjukan bertambahnya rata-rata kecepatan keluaran fluida hingga 0.43 sebagai efek penggunaan DRP.

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ABSTRACT
Drag reducing polymer DRP is one of drag reducers types that is widely used in industry as an additive to improve fluid flow efficiency in pipes. This study is conducted to analyze the parameters that influence the efficiency of DRP through developing equation model, and to see the phenomenon that occurs in fluid flow through CFD simulation. The data used are obtained from experiments by Vancko 1997 for a single phase flow. As for two phase annular flow, the experimental data of Vancko 1997, Al Sarkhi and Hanratty 2001 a,b, and Fernandez et al. 2004 are used. Each parameter such DRP concentration, fluid velocity, and pipe diameter were analyzed based on the proposed model equations. The results showed the proposed equation model of single phase flow with 4,0 gives an error up to 18. While the proposed annular flow equation is only suitable for flow under condition such fluid film distribution is uniform and symmetrical with the error around 20 , i.e. for smaller diameter pipes. The CFD simulation results shows a change in the fluid velocity profile becoming more parabolic, indicating an increase in the mean output fluid velocity up to 0.43, as the effect of DRP.

Abstrak :
Penelitian ini membahas tentang Bilangan Reynolds pada dua fasa dari hasil percobaan dengan refrigeran berbeda. Percobaan dilakukan pada kondisi perpindahan panas konveksi didih pada kanal mini horizontal dengan refrigeran R-290 dan R-600a. Test section terbuat dari pipa stainless steel dengan diameter dalam 3 mm, panjang 1000 mm dan dipanaskan secara merata di sepanjang pipa tersebut dengan heat flux divariasikan antara 5 kW/m2 sampai dengan 8 kW/m2. Dari penelitian didapat perubahan temperatur yang terjadi pada dinding dalam test section dengan metoda konduksi dan Nilai Reynolds number dibandingkan dengan kualitas Massa Uap. Fluktuasi Nilai Reynolds number menggambarkan kondisi aliran tiap fasa didalam test section. Dari hasil perbandingan dua Reynolds number untuk masing-masing refrigeran, Isobutana memiliki nilai Reynolds number lebih rendah dibandingkan dengan Propana pada kondisi mass flux dan heat flux yang relatif sama. Nilai Reynolds number ini selanjutnya akan digunakan untuk menentukan Chisolm Number dalam menghitung friction multiplayer. ......This study discusses the Reynolds Number of two phase flow in Horizontal Mini Channel. Experiments were performed on the convective boiling in Horizontal minichannel with R-290 and R600a. The test section was made of stainless steel tube with inner diameter of 3 mm, length of 1000 mm and it is uniformly heated along the tube with heat flux was varied from 5 kW/m2 up to 8 kW/m2. From the experiments, taken data was results the temperature of test section inner diameter and Reynolds Number of liquid phase and gas phase. The Reynolds Number represent flow of the two phases in test section. Comparison of Reynolds Number from the two refrigerant shows that Isobutana have better value than Propana since its Reynolds Numbers is lower than Propana in similar mass flux and heat flux condition. Based on the Reynolds Number, Chisolm Number will concluded to determine two phase friction multiplayer.

Abstrak :
Penelitian ini membahas tentang karakteristik perpindahan kalor aliran dua fasa yang didapat berdasarkan pengujian dan dibandingkan dengan prediksi korelasi yang terdapat pada literatur. Percobaan ini dilakukan dengan menggunakan refrijeran R-22 dan R-290 yang dilakukan dalam pipa konvesional berdiameter 7,6 mm dengan bahan stainless steel (SS 316) dan panjang 1,07 m. Pengujian dilakukan dengan variasi fluks kalor (q), fluks massa (G), dan temperatur saturasi. Hasil yang didapat pada penelitian ini adalah nilai fluks massa yang tinggi cenderung memiliki nilai koefisien perpindahan kalor yang tinggi pada awal evaporasi dan jika diberikan fluks kalor yang tinggi maka nilai koefisien perpindahan kalor juga akan naik, dan sistem dengan nilai temperatur saturasi yang tinggi maka akan dipengaruhi oleh koefisien perpindahan panas nucleat boiling. Perbandingan refrijeran mengindikasikan bahwa nilai koefisien perpindahan kalor R-290 lebih tinggi daripada R-22. ...... This study discusses about the characteristics of two-phase flow which obtained by experiment and the data is compared with predictions data of correlations in the literature. This experiment was conducted using refrijeran R-22 and R-290 in a conventional 7,6 mm pipe with stainless steel (SS 316) material and length of 1,07 m. Tests carried out with variations of heat flux (q), mass flux (G), and the saturation temperature. The result of this study is high value of the mass flux values tend to have a high coefficient of heat transfer at the beginning of evaporation and high heat flux will increase the heat transfer coefficient value. Systems with a high value of the saturation temperature will be influenced by nucleat boiling heat transfer coefficient. Refrijeran comparison indicates that the value of heat transfer coefficient of R-290 is higher than R-22.