Judul: Studying rate of absorption steam by solutions Lithium Bromide (LiBr) as absorbant in absorption refrigeration
Abstrak: Absorption is the process of absorbing a fluid by another fluid to form a fluid solution. In absorption refrigeration system, LiBr as absorbent filters on components of the absorber will absorb water vapor with lower pressure than the evaporator pressure. The rate of absorption of water vapor is a function of concentration, temperature, humidity and pressure of water vapor. The goal of this research is to see the effect of concentration, temperature and vapor pressure of water at the rate of absorption of water vapor by aqueous absorbent filters (LiBr-H2O) in relation to the cooling system, to determine the equilibrium concentration absorption solution of LiBr-H2O, and to determine the sorption isotherm model. Equilibrium concentration is a function of temperature and humidity. Ce at 40oC and RH 60% was found 37%; at 40oC and RH 70% was 34%; at 40o and RH 80% was 29%; at 45oC and RH 60% was 37.5%; at 45oC and RH 70% was 36%; and at 45oC and RH 80% was 34.5%. The calculation results of Qe using Qe sorption isotherm model on temperature 40oC and 45oC were not too different. The calculation results of the percentage errors between Qe data and model from each of the humidity, obtained the lowest percentage of errors in model Freundlich was 0.4% in RH 60% and 70%; 0.3% in RH 80%.
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Judul: Uji Kinerja Pemanfaatan Membran Reverse Osmosis pada Mesin Pendingin Absorpsi LiBr-H20
Abstrak: Absorption refrigeration system LiBr-H2O is an alternative refrigeration system to substitute vapor-compression refrigeration system, which has negative impact to environment and using mechanical energy for its operation. However, the absoption refrigeration system still needs thermal energy to regenerate the refrigerant from its absorber. The purposes of this study is to study the performance of reverse osmosis membrane to regenerate refrigerant H2O from the LiBr-H2O in absorption refrigeration system and to calculate the COP of the system. The experiment was conducted intermittently, where regeneration and refrigeration process occured separately. The study uses 3 level of LiBr-H2O concentration, namely 30%, 25%, and 20% with a variety of pressure treatments. The result of this research shows that COP of the system at concentration of 30% was 0.130 – 0.270, at concentration of 25% was 0.035 – 0.055, and at concentration of 20% was 0.015 – 0.020
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf