Paraffin melting experienced in the nozzle-and-shell, tube-and-shell, and reducer-and-shell models in thermal storage with 3D numerical and experimental approach has been studied. The numerical study aims to evaluate the melting process and discover temperature distribution, liquid-solid interface, liquid fraction, and the average surface Nusselt number, while the aim of this experimental study is to determine the distribution of melting temperature. The comparison of temperature distribution between the numerical approach and experimental one indicates a good agreement. The comparison result between the three models shows that the melting process of the nozzle-and-shell model is the best, followed by tube-and-shell and reducer-and-shell models, successively. To finish the melting process, the time required is 6130 s for the nozzle-and-shell model, while tube-and-shell model requires 8210 s and reducer-and-shell model requires 12280 s.
The melting of paraffin in thermal storage tube-and-shell and combine-and-shell models was conducted with the numerical research aim of decreasing the charge time through changing the shape of the tube into combining form. The results discussed are temperature contour, liquid-solid interface contour, temperature distribution, liquid fraction, and the average Nusselt number. The results show that the charge time in the tube-and-shell model is 2000 s, while the combine-and-shell model is 1200 s, meaning an overall decrease in charge time in the combine-and-shell model by 40% when compared to that of the tube-and-shell model.
Paraffin as a heat storage material has many advantages but also has drawbacks, namely low thermal conductivity so that the melting time becomes long. Efforts have been made to accelerate the melting time, including by increasing a surface area of the hot wall, or also by changing the geometry. In this study was carried out by changing the temperature of the hot wall from uniform to increase gradually, uniform hot wall temperature was 330 K, increased gradually hot wall temperature was 324 K, 327 K, 330 K, 333 K, dan 336 K. Paraffin used has specifications according to reference. They have performed numerically used ANSYS software. They are using three models, namely modelA, model-B, and model-C. The study aimed to obtain liquid-solid interface contours, changes in temperature at measurement points, and changes in the liquid fraction. The results of model validation show similarities to previous studies. The results show that the melting time in the model-A is the fastest, followed by model-B and model-C.
An air lift pump is a type of pump that works by injecting air into the bottom of the channel containing water, the position of the channel is vertical, because air has a specific gravity smaller than water, the air will move upwards to form bubbles, the bubbles lift the water. so the water flows with it. This study uses an air lift pump unit, the injector diameters used are 6 mm, 8 mm, and 10 mm. Variations in the diameter of the channel used are 21 mm, 31 mm, and 41 mm. The length of the channel is 500 mm, the submerged channel is 150 mm. the air flow rate is 5 lt/min. The research time for each variation is 1 minute. The media in the research are water and air. The results show that the greater the value of d/D, the greater the volume of water produced. The flow pattern that occurs is the bubble flow pattern and the slug flow pattern, with the increase in the value of d/D. The flow pattern that occurs changes from a bubble flow pattern to a slug flow pattern.
Karena tekanan pembakaran pada silinder mesin diesel harus mampu menghasilkan pembakara tanpa nyala api, maka hal ini mengakibatkan getaran yang tinggi, getaran ini bisa dikonversi menjadi energi listrik dengan menggunakan piezoelektrik, dengan cara memasang salah satu sisi piezelektrik pada bodi mobil dan sisi yang lain pada mesin mobil, pada penelitian ini menggunakan 4 buah piezoelektrik yang dirangkaii secara seri dan parallel, variasi putaran mesin adalah 1500, 2000, 2500, dan 3000 rpm. Hasilnya menunjukkan bahwa semakin besar putaran mesin maka semakin kecil tegangan listrik yang dihasilkan
Hardening pada baja AISI-4120 dilakukan dengan tahapan berupa pemanasan sampai temperatur tertentu, holding time pada temperatur konstan sampai beberapa saat, dan pendinginan menggunakan media cair agar terjadi penurunan temperatur secara cepat. Pada penelitian ini variasi yang dilakukan adalah holding time, yaitu selama 10 menit, 20 menit, dan 30 menit. Uji yang dilakukan berupa uji kekerasan dan struktur mikro. Temperatur tungku pemanas adalah 8500C, media pendingin adalah air, pengujian kekerasan menggunakan Vickers, dan pengujian struktur mikro menggunakan mikroskop optik metalografi dengan perbesaran 1000X. Hasil penelitian menunjukkan nilai kekerasan paling tinggi terdapat pada benda uji dengan variasi holding time 30 menit sebesar 623 HVN. Untuk hasil pengujian mikrostruktur terdapat struktur berupa martensit dan bainit, persentase martensit pada benda uji dengan variasi waktu penahanan 30 menit yaitu 97%. Semakin lama holding time maka nilai kekerasan dan persentase mikrostruktur martensit yang terbentuk akan semakin meningkat.
Storing heat in the form of latent heat is a good method, because it is able to store a large amount of heat energy with a small volume of storage media. The use of paraffin as a heat storage medium has many advantages, including thermal stability, non-toxicity, no degradation, and high latent heat storage capacity. This study uses a parabolic mirror dish as a collector of solar thermal energy, equipped with a hinged holder that can be adjusted so that it points to the sun's position from morning to evening, the collected energy is stored in thermal storage using paraffin as a storage medium. The research was conducted from 09.00 WIB to 24.00 WIB, the research location was on the Ronggolawe College of Technology campus. The results showed that the highest temperature obtained in paraffin as a heat storage was 112 oC, while the duration of storing until 24.00 WIB was still able to maintain the temperature at 36 oC.
Penyulingan minyak bumi secara tradisional hanya menggunakan sebuah drum berisi minyak mentah, drum tersebut dipanaskan oleh api yang berasal dari kayu, pada proses ini semua produk keluar melalui satu saluran, ketika keluar pertama berupa minyak bening, selanjutnya keluar minyak yang berwarna lebih gelap. Penggunaan minyak produk ini secara terus menerus berakibat tidak baik pada komponen permesinan. Maka dari itu perlu ditingkatkan kualitasnya, dilakukan dengan mengganti sistem penyulingan tradisional dengan penyulingan menggunakan distilator bertingkat. Pada penggunaan distilator bertingkat ini menghasilkan 3 produk. Yaitu produk A, produk B, dan produk C. Berdasarkan hasil uji laboratorium, kemudian dibandingkan dengan standar dan mutu bahan bakar minyak, dapat dikategorikan bahwa produk A dan produk B adalah solar, sedangkan produk C adalah bensin.
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