Judul: Rancang bangun alat pengering dengan memanfaatkan panas kondensor AC ruangan (kasus pengeringan chips kentang
Abstrak: Drying process is a method to decrease moisture content of the food products. The objectives of the research were to design and evaluate the performance of drying chamber using rejected heat of AC condenser for potatoes chips drying, determine potatoes moisture content and drying efficiency, and to investigate the influence of condenser fan velocity on cooling capacity. The drying chamber had 50.2 × 50.2 × 150.2 cm volume dimension, which contained seven aluminium trays. The chamber was connected to the condensing unit of an air conditioner. Potatoes were peeled, and cut sliced into 2.5 mm thickness of slices and then blanced using hot water. Then the slices were dried by using drying chambers for 6 h at high velocity fan, low velocity fan and substitution fan. The result showed that rejected heat of a room AC could be used for potatoes chips drying with temperature ranged from 33.88 to 44.05oC. The drying process with substitution fan was combined with reverse tray treatment produced relatively uniform moisture content of dried chips (8.20 ± 1.04% wb). The drying process resulted 20.42 – 23.32% of drying efficiency to AC condenser heat and 67.17 – 78.77% to AC electric energy consumtion. The velocity of condenser fan did not significantly influence on the cooling capacity. It can be concluded that the drying chamber using rejected heat of AC condenser can be used for the drying of agricultural products e.g. the potatoes drying.
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Judul: Strategi Pengendalian pada Pengeringan Jagung Pipilan yang Memanfaatkan Udara lingkungan
Abstrak: In artificial drying, consumption of thermal energy is about 90%-95% of requirement total energy (Manalu, 1999; Nelwan, 1997). Ambient air drying is a drying method that use unheated air, thus its thermal energy consumption is very low. Indonesia is a tropical country that ambient air condition generally has high relative humidity, however the mean temperature is more than 30oC and the relative humidity is lower than 70%. This condition is potential to dry the corn up to it’s equilibrium moisture content (Me) i.e. 14%. Because of the fluctuative condition, the ambient air doesn’t have potential ability to dry at all. In deep bed dryer, there are various moistures in layers. Therefore, control system based on differences of moisture content in corn layers is needed to flow the potential ambient air -high of air temperature and low relative humidity- and to control the velocity of ambient air flow. The control system consists of detector of temperature and RH by SHT11 and SHT75 sensor, LCD, power supply and zero crossing circuits. The controlling system program was written ‘C language’, and written by Uc51 software 3.48 version, and also has function as compiler to convert ‘C language’’ to file.hex. The controlling strategy compare equilibrium moisture content in layer with the ambient as a hint of round of blower. If ambient Me < Me of the lower layer, the blower flows the maximum flow rate (0.455 m2/s). Contraryly, if Me >Me of the upper layer, the blower won’t flows . And if Me of the lower layer < ambient Me < Me of the upper layer, the blower flows the ambient air with five different levels of flow rate ( 0.398m2/s, 0.347 m2/s, 0.272 m2/s, 0.169 m2/s ,and 0.136 m2/s ) based on the comparation of the third Me. The experiment without control system showed that when the ambient temperature is about 25.7oC - 36oC and average ambient RH is about 55.25% - 97.65%, can dry the corn from average moisture content 20.48% b.k to 16.08% bk in 46.5 hours and consumed electrical energy as much as 4.288 MJ/kg of water evaporated. But, In the experiment with control system with average ambient temperature is about 27.9oC – 40.6oC, and average ambient RH is about 39.47% - 93.43%, the drying process start from average moisture content 20.89% b.k to 16.20% b.k due 10.517 hours and consume electric energy as much as 1.553 MJ/kg of water evaporated. Control Strategy Program worked properly and consumed less electrical energy and drying time process than the experiment without control system.
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Judul: Persamaan Geodesik Black Hole dengan Metrik Kerr 4+1 Dimensi dalam Koordinat Waktu Kosmik
Abstrak: Persamaan geodesik black hole dengan metrik Kerr 4+1 dimensi dalam koordinat waktu kosmik merupakan interpretasi lain dari persamaan geodesik black hole dengan metrik Kerr 4+1 dimensi, dimana acuan waktu yang digunakan diubah dari koordinat waktu wajar (proper time) ke dalam koordinat waktu kosmik (cosmic time). Waktu kosmik merupakan koordinat waktu yang dimana pengamat bergerak mengikuti ekspansi dari alam semesta. Penelitian ini merekonstruksi persamaan geodesik black hole dengan metrik Kerr 4+1 dimensi yang telah ditemukan pada penelitian sebelumnya menjadi persamaan geodesik yang memiliki fungsi terhadap dimensi waktu (t). Hasil akhir dari transformasi persamaan dapat digunakan sebagai bahan studi pustaka untuk penelitian lebih lanjut mengenai persamaan geodesik black hole dalam koordinat waktu kosmik.
Keyword: Dimensi ekstra, Metrik Kerr, Persamaan geodesik, Waktu kosmik