• Fire Science and Engineering
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• v.32 no.1
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• pp.7-15
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• 2018

The prediction performance of combustion models in the Fire Dynamics Simulator (FDS) were evaluated by comparing with experiment for compartment propane gas fires. The mixture fraction model in the FDS v5.5.3 and Eddy Dissipation Concept (EDC) model in the FDS v6.6.3 were adopted in the simulations. Four chemical reaction mechanisms, such as 1-step Mixing Controlled, 2-step Mixing Controlled, 3-step Mixing Controlled and 3-step Mixed (Mixing Controlled + finite chemical reactions) reactions, were implemented in the EDC model. The simulation results with each combustion model showed similar level for the temperature inside the compartment. The prediction performance of FDS with each combustion model showed significant differences for the CO concentration while no distinguished differences were identified for the $O_2$ and $CO_2$ concentrations. The EDC 3-step Mixing Controlled largely over-predicted the CO concentration obtained by experiment and the mixture fraction model under-predicted the experiment slightly. The EDC 3-step Mixed showed the best prediction performance for the CO concentration and the EDC 2-step Mixing Controlled also predicted the CO concentration reasonably. The EDC 1-step Mixing Controlled significantly under-predict the experimental CO concentration when the previously suggested CO yield was adopted. The FDS simulation with the EDC 1-step Mixing Controlled showed difficulties in predicting the $CO_2$ concentration when the CO yield was modified to predict the CO concentration reasonably.

• Elastomers and Composites
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• v.37 no.1
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• pp.14-20
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• 2002

Silica-filled rubber compound needs longer mixing time compared to carbon black-filled one since it has poor dispersion or the filler. Influence of the mixing procedure on the properties of natural rubber compound filled with both silica and carbon black was studied. The discharge temperature of the master batch (MB) mixing was $150^{\circ}C$. The mixing time was longer when silica and carbon black were loaded separately than when loaded simultaneously. The mixing time was longer when silica was loaded first than when carbon black is loaded first. The compounds prepared by one MB step (conventional mixing) were compared with the compounds prepared by two MB steps (two-step mixing). Scorch times of the two-step mixing compounds were longer than those by the conventional mixing ones. Bound rubber contents of the formers were lower than those of the tatters. The two-step mixing vulcanizates had longer elongation at break, higher tensile strength, and better fatigue life.

• Elastomers and Composites
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• v.51 no.2
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• pp.81-92
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• 2016

1,3-Diphenylguanidine (DPG) is commonly used as a secondary accelerator which not only acts as booster of cure but also activating silanization reaction. The aim of this study is to increase the interaction between silica and rubber by using DPG. In this study, mixing was proceeded in two steps. The T-1 compound is mixed DPG with silica and silane coupling agent in the kneader at high temperature which is named as $1^{st}$ mixing step. T-3 compound is mixed DPG with curatives in the two-roll mill at low temperature which is named as $2^{nd}$ mixing step. The T-2 compound is mixed a half of DPG in $1^{st}$ mixing step and the remainder is mixed in $2^{nd}$ mixing step. Total DPG content was equal for all compounds. When DPG is mixed with silica, silane coupling agent during the $1^{st}$ mixing step, a decrease in cure rate and an increase in scorch time can be seen. This indicates that DPG is adsorbed on the surface of silica. during rubber processing. However, bound rubber content is increased and dynamic properties are improved. These results are due to the highly accelerated silanization reaction. However, there are no significant difference in 100%, 300% modulus.

• Journal of ILASS-Korea
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• v.15 no.4
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• pp.177-181
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• 2010

This paper has designed a mixing enhancement apparatus called Lobed-plate and Step-plate and comparatively calculated desulfurization efficiency of when its shape was changed. The parameters used at this time were the shape, SR ratio and the number of nozzles of the mixing enhancement apparatus and comparatively analyzed desulfurization efficiency according to these parameters. As a result, the Step-plate appeared as more highly by around 4% than Lobed-plate in desulfurization efficiency according to the shape of the mixing promotion apparatus, and when the desulfurization efficiency as a SR ratio is considered, it appeared highly by an average of 5% when the SR ratio is 3 rather than 2. As a result of comparing desulfurization efficiency by fixing the SR ratio and setting the number of nozzles as 4 pieces and 6 pieces, there was no big change in desulfurization efficiency when the SR ratio is 2, but it could be confirmed to improve by around 5% when the SR ratio is 3 when time passed 8 seconds.

• Journal of Food Hygiene and Safety
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• v.12 no.4
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• pp.346-353
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• 1997

This study was undertaken to find out distribution and contamination sources of hazardous microbes through microbial hazard analysis on the processing steps of surimi-based imitation crab (SBIC). As a results of ananlysis of 9 hazardous microbes for 16 raw materials and 8 processing steps, no Samonella spp. and Escherichia coli were detected in all samples. Level and distribution of hazardous microbes in mixed color were similar to those of surimi. Changes of aerobic plate counts (APC), psychrotropic bacteria, coliforms, Staphylococcus aureus and Vibrio parahaemolyticus showed similar trends at different processing steps. Thermotrophic bacteria and aerobic sporeformers were not detected until mixing step and feeding step, respectively and not reduced after cooking step. According to the comparison of APC at each step, it was suggested that surimi, workers and silent cutter at mixing step, and mixed color, workers and bundler at packaging step were the major contamination sources of bacteria.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.263-268
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• 2000

Recently, the recycling of the by-products was attempted to various fields. One of the major industry, the copper manufacturing industry produced a lot slags. in this study, the copper smelting slag was used to use practically application for the aggregate of concrete. To find the optimum mixing ratio of mortar with the copper smelting slag as substitution for sand, the mixing ratio was increased 1:2 to 1:5 step by step and every mixture was contained 5 steps sand substitutive ratio. The substitutive ratio of sand was increased 25% st대 by step from 0% to 100%. The result of this study was shown as follows. 1. In the every mixture, as the substitutive ratio was increased, the flow was decrease 3.64% from 18cm, and the unit content weigth was increased 5.5% in average. 2. The property of the strength was judged that it was more affected W/C and mixing ratio than the copper smelting slag.

• Fire Science and Engineering
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• v.33 no.5
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• pp.48-54
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• 2019

A Large Eddy Simulation (LES), adopting the Eddy Dissipation Concept (EDC) 1-step model, was successfully performed for backdraft phenomena. The activation energy of the finite chemistry reaction in the EDC 1-step model was adjusted to simulate the backdraft. The prediction of the EDC 1-step model was similar to that of the Mixing-Controlled Fast Chemistry (MCFC) model, except when the backdraft occurred. The EDC 1-step model could be used to simulate the experimental peak pressure, but not the first peak pressure of the backdraft.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.7
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• pp.527-534
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• 2009

Flame stabilization characteristics were experimentally investigated in a fuel-air cross flowing mixing layer. A combustor consists of a narrow channel of air steam and a cross flowing fuel. Depending on the flow rates of methane and air, flame can be stabilized in two modes. First is an attached flame which is formulated at the backward step where the methane and air streams meet. Second is a lifted-flame which is formulated within the mixing layer far down steam from backward step. The heights and flame widths of the lifted flames were measured. Flame shapes of the lifted flames were similar to an ordinary edge flame or a tribrachial flame, and their behavior could be explained with the theories of an edge flame. With the increase of the mixing time between fuel and air, the fuel concentration gradient decreases and the flame propagation velocity increases. Thus the flame is stabilized where the flow velocity is matched to the flame propagation velocity in spite of a significant disturbance in the fuel mixing and heat loss within the channel. This study provides many experimental results for a higher fuel concentration gradient, and it can also be helpful for the development and application of a smaller combustor.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.7
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• pp.736-743
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• 2005

In this study, three different types of mechanical ventilation systems are compared based on their ventilation characteristics: tracer gas concentration decay characteristics, and ventilation effectiveness by calculating actual ventilation air flow rate. The experiments are performed by using a step-down method for measuring tracer gas. $CO_{2}$ gas, concentration in the model chamber. Application of a mixing factor, k, was used and measured values ranged from 0.68 to 0.77. The Type 2 ventilation system was found to have the highest ventilation effectiveness rather than the Types 1 and 3.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.94-99
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• 2001

The numerical simulation of the particle dispersion in the vortical flows provides insight into the mechanism of particle-fluid interaction. The simulation results show that the mixing layers are characterized by the large-scale vortical structures undergoing pairing process. The particle dispersion is strongly influenced by the large-scale structures and the particle sizes. The analysis shows that the mixing layers grows like a step-function.