Hasil Pencarian  ::  Simpan CSV :: Kembali

"Predictive theories of phenomena involving phase change with applications in engineering are investigated in this volume, e.g. solid-liquid phase change, volume and surface damage, and phase change involving temperature discontinuities. Many other phase change phenomena such as solid-solid phase change in shape memory alloys and vapor-liquid phase change are also explored. Modeling is based on continuum thermo-mechanics. This involves a renewed principle of virtual power introducing the power of the microscopic motions responsible for phase change. This improvement yields a new equation of motion related to microscopic motions, beyond the classical equation of motion for macroscopic motions. The new theory sensibly improves the phase change modeling. For example, when warm rain falls on frozen soil, the dangerous black ice phenomenon can be comprehensively predicted. In addition, novel equations predict the evolution of clouds, which are themselves a mixture of air, liquid water and vapor."

"A state-of-the-art description of metastability observed in chalcogenide alloys is presented with the accent on the underlying physics. A comparison is made between sulphur(selenium)-based chalcogenide glasses, where numerous photo-induced phenomena take place entirely within the amorphous phase, and tellurides where a reversible crystal-to-amorphous phase-change transformation is a major effect. Applications of metastability in devices optical memories and nonvolatile electronic phase-change random-access memories among others are discussed, including the latest trends. Background material essential for understanding current research in the field is also provided."

"The objective of the present study is to investigate numerically the problem of melting phase change material (PCM) containing paraffin where one of the area interfaces moves with time and wherein the result of the fusion between the coupling in the solid phase conduction and convection in the liquid phase, then processes the effect of integration of the material in the walls of the building in order to increase its thermal inertia to validate the result ,we will study the numerically transient and performance of a fixed bed filled with uniform spheres, randomly arranged and each containing a (PCM). So we use a two-dimensional theoretical model applied in two separate phases; it was used to predict the temperature distribution of the fluid and the fusible material along the bed in the energy storage method."

"ABSTRAKTingginya angka kelahiran bayi prematur di Indonesia menyebabkan inkubator sangat diperlukan. Seiring dengan kemajuan teknologi, inkubator bayi menjadi semakin canggih yang mana membuat harganya semakin mahal. Distribusi listrik yang belum merata di Indonesia, menjadikan inkubator elektrik tidak efektif. Salah satu solusi yang aplikatif adalah penggunaan Phase Change Materials (PCM) sebagai elemen pemanas. Karena besarnya nilai kalor laten yang dimilikinya, PCM dapat menyuplai energi panas dalam waktu yang cukup lama. Penelitian ini bertujuan untuk mengetahui efektifitas dua jenis PCM sebagai elemen pemanas pada inkubator bayi, yaitu paraffin wax dan beeswax.Variasi yang dilakukan dalam pengujian ini adalah waktu, jenis PCM, dan wadah PCM. Pengujian dilakukan dengan memanfaatkan prototipe Inkubator Grashof Seri-F dan fenomena konveksi natural. Pengukuran temperatur dilakukan menggunakan termokopel di dalam ruang inkubator, pada PCM, dan pada dinding wadah PCM. Melalui pengujian ini dapat disimpulkan bahwa paraffin wax dan beeswax mampu bekerja sebagai elemen pemanas pada inkubator bayi, yang mampu menjaga kondisi pada ruang inkubator pada rentang 32°C – 36°C. Beeswax memiliki performa yang lebih handal dibandingkan dengan paraffin wax, karena beeswax memiliki efisiensi volumetris sebagai reservoir panas yang lebih baik. Hal ini ditunjukkan melalui percobaan dimana dengan volume yang sama, beeswax dapat mempertahankan suhu pada ruang bayi selama 2-3 jam lebih lama pada siang hari dan 1-2 jam lebih lama pada malam hari.

---

ABSTRACTIndonesia’s high mortality rate of preterm birth causes the presence of infant incubator is very important. As the technology develops, infant incubator also becomes more developed which makes its price even higher. Furthermore, the electricity distribution issue in Indonesia makes electric incubator becoming less effective. One of the applicable solutions is the usage of Phase Change Materials (PCM) as heating element. Its high amount of latent heat makes it is capable of mantaining heat supply for a long time. The goal of this experiment is to find out the effectiveness of paraffin wax and beeswax as heating element for infant incubator.Time, kind of PCM, and placement method is three variations that is tested in this experiment. The experiment uses Grashof Incubator F-Series prototype and natural convenction phenomenon. Data gathering is completed by measuring the temperatures of incubator, PCM, and container’s surfaces using thermocouple. Based on this experiment, can be concluded that both paraffin wax and beeswax are capable for being used as incubator’s heating element, because they can maintain incubator’s temperature in range of 32°C-36°C. Beeswax has a better performance than paraffin wax because it has higher volumetric efficiency. This is showed by the result section which states that beeswax lasts 2-3 hours longer than paraffin wax during the day and 1-2 hour longer during the night."