• Title/Summary/Keyword: arrhenius equation

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A Study on the Life Time Prediction and Acid-Heat aging Property of NBR Rubber for Fuel Cell Gasket (연료전지 카스켓용 NBR 고무의 산-열 노화 특성과 수명예측에 관한 연구)

  • Kim, Mi-Suk;Kim, Jin-Hak;Kim, Seok-Jin;Kim, Jin-Kuk
    • Elastomers and Composites
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    • v.42 no.1
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    • pp.20-31
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    • 2007
  • Material characteristics and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the NBR compound was prepared by sulfur-cure system, and was used in predicting the lifetime of rubber gasket made by the compound. The accelerated material aging was investigated at different temperatures at 120, 140 and $160^{\circ}C$ and aging time from 3 hours to 600 hours at 5, 6, 7 vol %. of $H_2SO_4$ concentrations The rubber strips were placed in acid solution using pyrex g1ass tube. Both ends of pyrex g1ass tube were sealed to avoid evaporation of solution during heating at given time. The material test and accelerated acid-heat aging test were carried out to predict the useful life of NBR rubber gasket for a fuel cell stack. In order to investigate the effects of acid-heat aging on the properties of the NBR, tensile strength, elongation at break, hardness and crosslink-density were measured. The tensile strength decreases as the $H_2SO_4$ concentrations and temperature increase. Results were evaluated using Arrhenius equation.

Qualitative Characteristics and Determining Shelf-Life of Milk Beverage Product Supplemented with Coffee Extracts

  • Yoon, Ji-Woo;Ahn, Sung-Il;Kim, Ha-Na;Park, Jun-Hong;Park, Sun-Young;Kim, Jae-Hoon;Oh, Duk-Geun;Jhoo, Jin-Woo;Kim, Gur-Yoo
    • Food Science of Animal Resources
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    • v.37 no.2
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    • pp.305-312
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    • 2017
  • This study was conducted to establish the shelf-life of a milk beverage product supplemented with coffee extracts. Qualitative changes including peroxide value (PV), microorganism content, caffeine content, and sensory evaluation were measured periodically in beverages kept at 10, 20, and $30^{\circ}C$ for 8 wk. Lipid oxidation of the product was measured by peroxide value analysis, and apparent changes were observed during a 4 wk storage period. Caffeine analysis revealed that the changes in caffeine content were negligible during the storage period. Total aerobic bacteria, Escherichia coli, yeast, and mold were not detected in the products during an 8 wk storage period. Sensory evaluation revealed that after 4 wk of storage overall acceptance was less than 3 points on a 5-point scale. In this study, PV was used as an indicator of the shelf-life of the milk beverage product. PV analysis revealed that a value of 20 meq/kg was the end of the shelf-life using the Arrhenius equation and the accelerated shelf-life test (ASLT). Assuming that the beverages are kept at $4^{\circ}C$ during distribution, calculation of when the PV reached the quality limit point (20 meq/kg) was done with the equation ln(PV) = 0.3644X - 2.21834 and, using that equation, $PV=e^{0.3644X-2.21834}$ was calculated. Therefore, 14.3086 wk was determined to be the shelf-life of the milk beverage supplemented with coffee when stored at $4^{\circ}C$.

Estimation of Effective Moisture Diffusivity of Rapeseed (Brassica napus L.) (유채 종자의 수본확산계수에 관한 연구)

  • Duc, Le Ahn;Hong, Sang-Jin;Han, Jae-Woong;Keum, Dong-Hyuk
    • Journal of Biosystems Engineering
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    • v.33 no.5
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    • pp.296-302
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    • 2008
  • The effective moisture diffusivity and its dependence on drying temperature during drying of rapeseed were experimentally investigated. The data were recorded from thin layer drying experiments at nine different combinations of drying air temperatures of 40, 50, and $60^{\circ}C$ and the relative humidities of 30, 45, and 60%. The moisture diffusion equation was analyzed using stepwise multiple regression analysis. Effective moisture diffusivities were calculated based on the moisture diffusion equation for a spherical shape using Fick's second law. The effective diffusivities during the drying of rapeseed were $l.72{\times}10^{-11}$, $2.41{\times}10^{-11}$ and $3.31{\times}10^{-11}\;m^2{\cdot}s^{-1}$ at 40, 50 and $60^{\circ}C$, respectively. The activation energy for moisture diffusion during drying was $28.47\;kJ{\cdot}mol^{-1}$. The dependence of moisture diffusivity on temperature was described by an Arrhenius-type equation. Drying occurred in the falling rate period and the internal moisture diffusion phenomenon is the governing physical mechanism of the moisture movement in the particles.

Influence of Dynamic Strain Aging on Tensile Deformation Behavior of Alloy 617

  • Ekaputra, I.M.W.;Kim, Woo-Gon;Park, Jae-Young;Kim, Seon-Jin;Kim, Eung-Seon
    • Nuclear Engineering and Technology
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    • v.48 no.6
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    • pp.1387-1395
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    • 2016
  • To investigate the dynamic strain aging (DSA) behavior of Alloy 617, high-temperature tensile tests were carried out with strain rates variations of $10^{-3}/s$, $10^{-4}/s$, and $10^{-5}/s$ from $24^{\circ}C$ to $950^{\circ}C$. Five flow relationships, Hollomon, Ludwik, Swift, Ludwigson, and Voce, were applied to describe the tensile true stress-strain curves, and the DSA region was defined. In describing the tensile curves, Ludwigson's equation was superior to the other equations, and the DSA region was adequately defined by this equation as plateaus at intermediate temperatures from $200^{\circ}C$ to $700^{\circ}C$. It was identified that Alloy 617 is dominated by three types of serrations, known as Types D, A+B, and C. The activation energy values for each serration type were obtained by the Arrhenius equation. By using the obtained activation energy values, the serrated yielding map and the DSA mechanism were drawn and manifested. In addition, the relationship between the tensile strength and strain rate at higher temperatures above $700^{\circ}C$ was found to be closely related to the amounts of slip lines. In the scanning electron microscope (SEM) fractographs, there was a significant difference at the low, intermediate, and high temperatures, but almost the same to the three strain rates.

Production and Characterization of Phenylalanine Ammonia-lyase from Rhodotorula aurantiaca K-505

  • Cho, Dae-Haeng;Chae, Hee-Jeong;Kim, Eui-Yong
    • Preventive Nutrition and Food Science
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    • v.2 no.4
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    • pp.354-359
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    • 1997
  • Optimal cultivation conditions for the production of phenylalanine ammonia-lyase(PAL) from Rhodotorula aurantiaca K-505 were selected, and the kinetic parameters of the produced PAL were determined. The most suitable carbon and nitrogen sources were glucose and tryptone, respectively. The strain expressed PAL constituttively when using the optimized semi-complex media. High cell density culture could be critical for maximal production of PAl since the PAL ynthesis was growth associated. maximum PAL activity was observed at initial pH 6.0. although the ll growth was not markedly affected by temperature between 22 and 28$^{\circ}C$, the cells yielded the maximum PAL activity when cultivated at 22$^{\circ}C$. The maximum activity for deamination of L-phenylalnine to trans-cinnamic acid was observed around pH 8.8. The PAL activity gave the maximum at 45$^{\circ}C$, and greatly decreased at higher than 5$0^{\circ}C$. Activation energy({TEX}$E_{a}${/TEX}) calculated from Arrhenius equation was 6.28 kcal/mol in the range of 22$^{\circ}C$ to 4$0^{\circ}C$. A oolf plot showed that the enzyme reaction follows Michaelis-Menten equation, whose {TEX}$K_{M}${/TEX} and {TEX}$V_{max}${/TEX} values were 4.65$\times${TEX}$10^{-3}${/TEX} M and 0.89$\mu$ mol/mg-min respectively.

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Characteristics of PET Microfiber Fabrics Decomposed by Sodium glycerolate/Glycerol Solution (Sodium glycerolate/Glycerol 용액에 의한 PET 신합섬직물의 분해특성)

  • Yoon, Jong Ho;Huh, Man Woo;Bae, Jeong Sook;Cho, Yong Suk
    • Textile Coloration and Finishing
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    • v.8 no.2
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    • pp.16-24
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    • 1996
  • Polyester microfiber fabrics were alcoholysed at 120, 140, and 16$0^{\circ}C$ in 0.5, 1.0, and 1.5% of sodiumglycerolate/glycerol solutions(NaGR) up to 80% and the characteristic decomposition features were compared and discussed with the results of the hydrolysis done by 5% sodium hydroxide solution(NaOH) at 80, 90, and 10$0^{\circ}C$. The resulting activation thermodynamic parameters calculated by the combined use of the Arrhenius equation and the Eyring equation were in NaOH case ${\Delta}H^*$=- 13.89 kcal/mol, ${\Delta}S^*$/=-38.12 cal/mol K, and ${\Delta}G^*$=25.25 kcal/mol and in NaGR case ${\Delta}H^*$=29.81 kcal/mol, ${\Delta}S^*$=-2.29 cal/mol K and ${\Delta}G^*$=30.49 kcal/mol. Since in all cases NaGR-PET system has higher activation thermodynamic parameters, it was concluded that NaGR-PET reaction system is more favorable at high temperatures and occurs in a less selective fashion, in comparison to the NaOH-PET reaction system.

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A Study on the Combustion and Smoke Emission Characteristics of the Natural Aspiration Type Diesel Engine (자연흡기식 디젤 기관의 연소와 매연 배출 특성에 관한 실험적 연구)

  • 정우인;박찬국
    • Transactions of the Korean Society of Automotive Engineers
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    • v.5 no.4
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    • pp.70-83
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    • 1997
  • We made a selection of engine operating conditions in the natural aspiration type diesel engine as load and speed. The effects on the power, smoke emission and cylinder pressure characteristics of these variations in operating conditions were observed experimentally. Also, the smoke emission was predicted by using the Arrhenius equation and empirical equation of the smoke emission was made. At the same time, the correlations, between the combustion and smoke emission characteristic were examined. From the above results, it is clear that to prevent power dropping and to decrease exhaust fume whin the conditions are changed, one should improve the intake system. To do this, the best way is to lower the air-fuel mixing ratio. We found that the parameters of the indicated mean effective pressure, maximum pressure and its location and combustion duration, etc. change the motion in accordance with the conditions described above. Also, we found that the variation of the pressure cycle comes from an amplified variation of the early part of process. From the analysis of comparing combustion and exhaust fume, the exhaust fume is produced at the latter time of combustion and decreased when the combustion ratio is higher. Also, we developed a special formula which can predict the exhaust fume value according to the engine load and speed.

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Analysis for Filling Stage of Injection Molding Considering Compressibility and Phase Change (압축성과 상변화를 고려한 사출성형의 충전과정 해석)

  • Lee, Sang-Chan;Park, Chang-Eon;Yang, Dong-Yeol
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.12
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    • pp.60-65
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    • 2001
  • To simulate the real molding conditions, the effects of phase change and compressibility of the resin were considered in the present investigation. A modified Cross model with either an Arrhenius-type or WLF-type functional form was used for modeling viscosity of the resin. A double-domain Tait equation of state was employed to describe the compressibility of the resin during molding. The energy balance equation including latent-heat dissipation fur semi-crystalline materials was solved in order to predict the solidified layer and temperature profile. Injection molding experiments were carried out using polypropylene(PP) in the present study. Based on the comparison between experiments and simulations, it was found out the predicted pressure distributions and melt front propagations were accurate. Thus it was concluded that the program developed in this study was proved to be useful in simulations of injection molding process.

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A Kinetic Study on the Hydration Process of Barley Kernels with Various Polishing Yields (도정수율별 보리의 수화공정(水和工程)에 관(關)한 속도론적(速度論的) 연구(硏究))

  • Mok, Chul-Kyoon;Lee, Hyun-Yu;Nam, Young-Jung;Min, Byong-Yong
    • Korean Journal of Food Science and Technology
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    • v.15 no.2
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    • pp.136-140
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    • 1983
  • The hydration characteristics of barley kernels with various polishing yields were investigated at temperatures of $20-60^{\circ}C$ and their sorption kinetics were studied. The moisture gain in initial stage of hydration was directly proportional to square root of hydration time and there was a break point at the moisture gain of 0.45-0.55g $H_2O/g$ solid. The hydration rate was great in order of polishing yield of 50, 70, 95, 90 and 100%, and increased with increasing hydration temperature. The diffusivity of water into barley kernels followed Arrhenius equation, and the activation energies in hydration reaction of polished barley were ranged from 6.9 to 9.5 Kcal/mole and that of non-polished one was 11.6Kcal/mole.

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Accelerated Life Test Using Structural Analysis of a Helicopter Accumulator (헬기용 축압기의 구조해석에 의한 가속 수명시험)

  • Lee, Geon-Hui;Hur, Jang-Wook
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.19 no.6
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    • pp.67-72
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    • 2020
  • Life tests are essential in reducing the catastrophic damage caused by the accidents of large machinery such as aircraft and ships. However, life tests are challenging to implement due to the high costs and time required to test the life of large machinery parts. Therefore, it is advantageous and convenient to apply accelerated life test techniques for key components to reduce costs and time. In fact, extensive research has already been conducted on these techniques. However, recently, there have been cases in which an experimental value was applied to the shape parameter of the Weibull distribution used in the reliability test, but the test time was not significantly reduced. Therefore, in this paper, the shape parameters are estimated from the probability density function of the Weibull distribution for the analysis of an accelerated life test for bladder accumulators, which are core components of military helicopters. The test time was derived based on the number of samples and confidence level by substituting it into the test time equation. Next, the accelerated life test time was calculated using the steady-state test time with an acceleration factor obtained from the Arrhenius model. The steady-state life test required approximately 15,000 H, whereas the accelerated life test time for one sample at 100 ℃ was 34% shorter than that of the steady-state life test.