• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.113-122
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• 2010

A two-dimensional thermal response and ablation analysis code for predicting charring material ablation and shape change on solid rocket nozzle is presented. For closing the problem of thermal analysis, Arrhenius' equation and Zvyagin's ablation model are used. The moving boundary problem are solved by remeshing-rezoning method. For simulation of complicated thermal protection systems, this method is integrated with a three-dimensional finite-element thermal and structure analysis code through continuity of temperature and heat flux.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.746-754
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• 2015

In this study, we investigated the effects of the temperature on the coal/biomass $char-CO_2$ gasification reaction under isothermal conditions of $700{\sim}900^{\circ}C$ using the lignite(Indonesia Eco coal) with biomass (korea cypress). Ni catalysts were impregnated on the coal by the ion-exchange method. Four kinetic models which are shrinking core model (SCM), volumetric reaction model (VRM), random pore model (RPM) and modified volumetric reaction model (MVRM) for gas-solid reaction were applied to the experimental data against the measured kinetic data. The Activation energy of Ni-coal/biomass, non-catalyst coal/biomass $Char-CO_2$ gasification was calculated from the Arrhenius equation.

• Journal of Applied Reliability
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• v.4 no.2
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• pp.73-90
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• 2004

We performed the heat aging test to predict the useful lifetime of Elastomeric Bearing Chloroprene Rubber (CR) used for supporting bridge. During the test, we measured elongation that are influenced by temperature and aging time. The failure of a test piece is defined as the point at which the elongation reaches to 75% of the initial value. This failure criterion is based on KS F 4420: 1998 (Elastomeric Bearing for bridge). Through the accelerated heat aging test, we found that the Arrhenius relationship and the Weibull lifetime distribution are appropriate as the life-temperature relationship and lifetime distribution of the CR, respectively. Using the Arrhenius -Weibull model, the parameters of the model are estimated and the lifetime of the CR at use condition is predicted.

• Food Science and Biotechnology
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• v.15 no.2
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• pp.264-269
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• 2006

Basic rheological data of dandelion leaf concentrates were determined to predict processing aptitude and usefulness of dandelion leaf concentrates as functional food materials. Hot water and 70% ethanol extracts of dandelion leaves were concentrated at 5, 20, and 50 Brix, and their static and dynamic viscosities, and Arrhenius plots were investigated. Most concentrated dandelion leaves extracted with hot water and 70% ethanol showed flow behaviors close to Newtonian fluid based on power law model evaluation. Apparent viscosity of concentrated dandelion leaves extracted with hot water and 70% ethanol decreased with increasing temperature. Yield stresses of concentrated dandelion leaves extracted with hot water and 70% ethanol by Herschel-Bulkley model application were 0.020-0.641 and 0.017-0.079 Pa, respectively. Activation energies of concentrated dandelion leaves extracted with hot water and 70% ethanol were $2.102-32.669{\times}10^3$ and $1.657-5.382{\times}10^3\;J/mol{\cdot}kg$ with increasing concentration, respectively. Loss modulus (G") predominated over storage modulus (G') at all applied frequencies, showing typical flow behavior of low molecular solution. G' and G" of concentrated dandelion leaves extracted with hot water slowly increased with increasing frequency compared to those of concentrated dandelion leaves extracted with 70% ethanol.

• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.8-13
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• 2019

Weight and elongation changes of IV and HIV insulations were measured simultaneously at several given temperature of $80^{\circ}C$, $90^{\circ}C$ and $100^{\circ}C$. And the lifetime was predicted using the Arrhenius model. Based on the initial weight values, a 50% elongation reduction was seen at 6.96% for the IV insulation and 10.29% for the HIV insulation. The activation energy from the slope of the lifetime regression equation was calculated as 92.895 kJ/mol(0.9632 eV) for the IV insulation and 95.213 kJ/mol(0.9873 eV) for the HIV insulation. Also, the expected lifetime at the operating temperature of $30^{\circ}C$ to $90^{\circ}C$ is 2.02 to 94.32 years, and longer lifetime was predicted on HIV insulated wires than on IV insulated wires. As a result, it was found that the thermal characteristics of the HIV insulated wires were about 12.44% better than those of IV insulated wires under the same conditions of use.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.243-245
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• 2000

In general, aluminum electrolytic capacitors are used in the DC link of PWM inverters fur ac motor drives. The capacitor usually has the shortest lifetime in the system and then determines the lifetime of the inverter system. In this paper, a method of capacitor lifetime estimation is proposed by using an ESR(equivalent series resistance) model and a heat transfer model of capacitor, from which internal operating temperature is estimated. Then, the lifetime is predicted by Arrhenius's equation. A practical example is presented.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.1
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• pp.66-74
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• 1991

A multidimensional numerical simulation of turbulent combustion in a constant volume bomb is implemented to clarify the effects of swirl on combustion. This simulation includes the ICED-ALE numerical technique, the skew-upwind differencing scheme, the modified .Kappa.-.epsilon. turbulence model, and the combustion model of the Arrhenius type and the turbulence-mixing-control type. The calculations of the turbulent combustion with swirl are carried out. It shows that the results agree with the measurements allowably. Therefore, the effects of swirl on turbulent combustion are examined through the parametric study of swirl.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.424-429
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• 2018

In this study, an expansion joint that is susceptible to waterhammer was tested for its vibration durability. The operation data for the hydraulic actuator was the expansion length of the expansion joint when the waterhammer occurred. In the case of the vibration durability test, the internal temperature status of the expansion joint was assumed to be a stress factor and a lifespan prediction model was assumed to follow the Arrhenius model. A test was carried out by increasing the internal temperature status at $30^{\circ}C$, $50^{\circ}C$, and $65^{\circ}C$. By a linear transformation of the lifespan data for each temperature, a constant value and activation energy coefficient was induced for the Arrhenius equation and verified by comparing the value of a lifetime prediction model with the experimental value at $85^{\circ}C$. The failure modes of the ongoing or finished test were leakage, bellows separation, and internal deformation. In the future, a composite lifespan prediction model, including two more stress factors, will be developed.

• Journal of the Korean Society of Safety
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• v.31 no.1
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• pp.19-24
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• 2016

Rubber parts are widely used in many applications such as dampers, shock absorbers, and seals used in railway and automotive industries. Much research has thus far been conducted on property estimation and life prediction of rubber parts. To predict the service life of rubber parts at room temperature, most prior work adopts the well-known Arrhenius model that needs the accelerated life test in high-temperature conditions. However, they may not reflect the actual conditions of use that rubber parts are usually used under a specific strain condition during long period of time. In this context, we propose a method for the life prediction of rubber parts in actual conditions of use. The proposed method is based on the accelerated life test using stress relaxation during which three relatively high elongation percentages (100%, 200%, and 300%) are applied to the rubber specimens. Rubber specimens were prepared in accordance with KS M 6518 standard and three stress relaxation testers were fabricated for actual experiments. Finally, a inverse power model for life prediction was derived from experimental results. The predicted life was compared with the actual test life for validation.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.5
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• pp.907-918
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• 2000

The pyrolysis characteristics of celluloses and plastics, which are the principal materials contributing to the municipal solid wastes(MSWs), was investigated with a thermal gravimetric analysis reaction system. The experiments were carried out in a nitrogen atmosphere in the temperature range of 400~900K at various experimental conditions. Also, a modified pyrolysis model for compressed MSWs has been proposed. Varing the heating rate to 20, 30, 40K/min, reaction orders of MSWs' main component were around 1.1~1.9, activation energies were 117~166kJ/mol for celluloses and 187~239kJ/mol for plastics. Char yield was proportional to the heating rate, particle size, and compressed ratio. The model proposed in this study, which is applying Arrhenius equation and thermodynamics, is closer to the experimental results than the conventional model.