• Elastomers and Composites
• /
• v.34 no.4
• /
• pp.321-331
• /
• 1999

The curing process is the final step in tire manufacturing whereby a green tire built from layers of rubber compounds is formed to the desired shape and the compounds are converted to a strong, elastic materials to meet tire performance needs under elevated pressure and temperature in a press. A numerical optimization procedure was developed to improve product quality in a tire curing process. First, a dynamic constrained optimization problem was formulated to determine the optimal condition of the supplied cure media during a curing process. The objective function is subject to an equality constraint representing the process model that describes the heat transfer and cures kinetic phenomena in a cure press and is subject to inequality constraints representing temperature limits imposed on cure media. Then, the optimization problem was solved to determine optimal condition of the supplied cure media for a tire using the complex algorithm along with a finite element model solver.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.4
• /
• pp.368-373
• /
• 2015

As a preliminary study for the development of the gas fueled marine engine, prediction of indicated performances was carried out for a spark-ignition engine using commercial software, GT-POWER. The optimized models through a previous study were applied for the simulation of the intake and exhaust systems in a SI engine. The Spark-Ignition Wiebe model was used to calculate the burn rate in the cylinders and the modified Woschni model was used to calculate the heat transfer to the walls. The predicted performances, such as air delivery, cylinder pressures and indicated mean effective pressures under a range of operating conditions showed good agreement with the experiments.

• Journal of the Korean Solar Energy Society
• /
• v.33 no.6
• /
• pp.12-18
• /
• 2013

Domestic solar hot water system can be divided into a passive type and an active type. In a passive type the storage tank is horizontally mounted immediately above the solar collectors. No pumping is required as the hot water naturally rises into the storage tank from the collectors through thermo-siphon flow. While, in an active type the storage tank is ground- or floor-mounted and is below the level of the collectors; a circulating pump moves water or heat transfer fluid between the storage tank and the collectors. We installed two types solar hot water systems consisting of the same storage tank and collectors at the same place, and were measured and compared typical operating characteristics under the same external conditions. In particular, the daily system performance was presented through the stirring test after the sunset. The results show that the amount of solar radiation obtained for an active type were less than a passive type on a cloudy day, because the operation of the circulation pump stops frequently took place on that day. However, on a sunny day, depending on the stable operation of the circulation pump, the amount of solar radiation obtained for an active type were increased than a passive type.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.9
• /
• pp.505-512
• /
• 2009

A thermosiphon is utilized as a thermal shunt to reduce the cool-down time of a cryogenic system cooled by a two stage cryocooler. The cool-down time reduction by the thermosiphon is determined by the type of working fluid which is directly related to the operating temperature range of the thermosiphon. A mixed working fluid has a potential to widen the operation temperature range of the thermosipohon. In this study, the thermosiphon using N$_2$ and CF$_4$ mixture as the working fluid is fabricated and tested to verify its transient heat transfer performance. The thermosiphon with the mixed working fluid has no noticeable reduction of cool-down time compared with that of the thermosiphon with pure working fluid in this experiment. However, it seems that the thermosiphon with mixed working fluid may have an advantage according to the cooling capacity of a cryocooler, the cooling target temperature and the size of a cooling object.

• Journal of the Korean Solar Energy Society
• /
• v.29 no.1
• /
• pp.44-49
• /
• 2009

Steam reforming of methane in the high temperature solar chemical reactor bas advantage in its heating method. Using concentrated solar energy as a heating source of the reforming reaction can reduce the $CO_2$ emission by 20% compared to hydrocarbon fuel. In this paper, the simulation result of methane-steam reforming on a high temperature solar chemical reactor(SCR) using Fluent 6.3.26 is presented. The high temperature SCR is designed for the Inha Dish-1, a Dish type solar concentrator installed in Songdo city. Basic SCR performance factors are referred to the former researches of the same laboratory. Inside the SCR porous metal is used for a receiver/reactor. The porous metal is carved like a dome shape on the incident side to increase the heat transfer. Also, ring-disc set of baffle is inserted in the porous metal region to increase the path length. Numerical and physical models are also used from the former researches. Methane and steam is mixed with the same mole fraction and injected into the SCR. The simulation is performed for a various inlet mass flow rate of the methane-steam mixture gas. The result shows that the average reactor temperature and the conversion rate change appreciably by the inlet mass flow rate of 0.0005 kg/s.

• Food Science and Biotechnology
• /
• v.16 no.1
• /
• pp.127-132
• /
• 2007

[ ${\alpha},\;{\alpha}$ ]-Trehalose was efficiently modified by a transgalactosylation reaction of Escherichia coli ${\beta}-galactosidase$ using lactose as a donor to yield two galactosyl trehalose trisaccharides. The reaction products of trehalose by the enzyme were observed by thin layer chromatography (TLC) and high performance anion exchange chromatography (HPAEC) and were purified by BioGel P2 gel permeation chromatography and recycling preparative HPLC. Liquid chromatography-mass spectrometry (LC-MS) and ^{13}C$ nuclear magnetic resonance (NMR) analyses revealed that the structures of the main products were $6^2-{\beta}-D-galactosyl$ trehalose (1) and $4^2-{\beta}-D-galactosyl$ trehalose (2). A reaction of 30%(w/v) trehalose and 15%(w/v) lactose at pH 7.5 and $45^{\circ}C$ resulted in a total yield of approximately 27-30% based on the amount of trehalose used. The galactosyl trehalose products were not hydrolyzed by trehalose. In addition the mixture of transfer products (9:1 ratio of 1 to 2) showed higher thermal stability than glucose, lactose, and maltose, but less than trehalose, against heat treatment over $100^{\circ}C$ at pH 4 and 7. It also exhibited better thermal stability than sucrose at pH 4 alone.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.11
• /
• pp.7773-7780
• /
• 2015

Analysis of existing kettle and its heating system has been the topic for localization technology development. Test pieces are made, polished and etched for existing kettle analysis. Surface of test pieces is observed using SEM, the kettle is verified to be made by deep drawing process from Ferrite-Perlite material. The kettle is also identified to be plated $16{\sim}49{\mu}m$ of thickness with Nickel(16%). Also heat transfer characteristics based on hot wire arrangement is investigated and optimal hot wire system is developed. Developed control system detects overheating and stops the whole system on the long operating time. Developed kettle takes the performance evaluation test for volume expansion and satisfied for standard 'KS G3602'.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.5
• /
• pp.1197-1205
• /
• 1988

An analytical method to predict qualitative performance characteristics of the Stirling Engines in the preliminary design stages is investigated. Both the expansion and the compression cylinder are treated as adiabatic and piston motions are approximated as saw-toothed waves. Basic equations which were originally proposed by Finkelstein consist of mass conservation and energy balances for each adiabatic cylinder. The approximation on piston motions and physical conditions make it possible to divide an engine cycle into four fundamental processes. In each process, first, pressure can be expressed as a function of the crank angle by solving a nonlinear first order ordinary differential equation and other thermodynamic variables are determined in turn. Application of the cyclic steady condition to the whole processes can complete a cycle. Also, further analysis results in analytic expressions for cyclic work and heat transfer in terms of the engine parameters and thermodynamic variables at boundary points. The results are expected useful as a quick reference for the engine performances. Finally, the present method can be applied to the other adiabatic analyses on the Stirling Engines with piece wise linear piston motions, if mass variations are predictable.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.2
• /
• pp.157-166
• /
• 2014

A light water reactor (LWR) fuel rod consists of zirconium alloy cladding tube and uranium dioxide pellets with a slight gap between them. The modeling of heat transfer across the gap between fuel pellets and the protective cladding is essential to understanding fuel behavior under irradiated conditions. Many researchers have been developing fuel performance codes based on finite element method (FE) to calculate temperature, stress and strain for multidimensional analysis. The gap conductance model for multi-dimension is difficult issue in terms of convergence and nonlinearity because gap conductance is function of gap thickness which depends on mechanical analysis at each iteration step. In this paper, virtual link gap element (VLG) has been proposed to resolve convergence issue and nonlinear characteristic of multidimensional gap conductance. In terms of calculation accuracy and convergence efficiency, the proposed VLG model has been evaluated for variable cases.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.11 no.2
• /
• pp.45-52
• /
• 2011

To improve fire-resistance of a high strength concrete against spalling under elevated temperature, fibers can be mixed to provide flow paths of evaporated water to the surface of concrete when heated. In this study, the experiment of a column under fire and mechanical loads is conducted and the material model for predicting temperature of reinforcement steel bar and mechanical behavior of fiber-mixed high strength concrete is suggested. The material model in previous studies is modified by incorporating physical behavior of internal concrete and thermal characteristics of concrete at the elevated temperature. Thermo-mechanical analysis of the fiber-mixed high strength concrete column is conducted using the calibrated material model. The performance of the proposed material model is confirmed by comparing thermo-mechanical analysis results with the experiment of a column under fire and mechanical loads.