• International Journal of Air-Conditioning and Refrigeration
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• v.13 no.1
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• pp.11-21
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• 2005

The present paper investigates the heat transfer characteristics in a cylinder packed with porous medium of solid spheres for various parameters such as mass flow rate, sphere diameter, length of the porous medium, and gas temperatures. Pressures and temperatures at the inlet and outlet regions were measured by using static pressure gages and R-type thermocouples. The modified relationship based on the Ergun equation is suggested for the estimation of pressure drops. In addition, the useful empirical correlation for thermal efficiency is obtained in the current study. Thermal efficiency is expressed in terms of non-dimensional time, sphere diameter, porosity, and pressure drops. It is also found that the pressure drop through the cylinder becomes larger as the gas temperature does higher at the inlet region, whereas it substantially decreases when the inlet flow rate decreases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.766-773
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• 1999

A numerical analysis has been performed solidification problem using the fixed grid-enthalpy method with enthalpy-porosity relation. A modified standard $k-\varepsilon$ model was applied to describe the influence of turbulent flow. Computational procedures are based on the finite volume method and the non-staggered grid system. Comparisons with the different three experimental results show that applying a modified standard $k-\varepsilon$model in mushyzone is better than the previous computation results. This paper includes another EMBR's influences such as change of velocity field, Increasement of temperature and dispersion of flow out of nozzle into the flow field. These EMBR's influences are compared to case without EMBR.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.211-212
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• 2021

This study was conducted to derive quantitative air void volume calculation techniques in various complexes with porosity. Calculation of voids in a complex is an essential factor in improving mechanical properties, and quantitative measurement techniques are needed because the environment is not constant to apply the currently used ASTM criteria. Using the analysis technique obtained through 2D image analysis, it is believed that meaningful results can be derived through Micro CT analysis results and cross-check later.

• Journal of the East Asian Society of Dietary Life
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• v.11 no.6
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• pp.479-484
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• 2001

The absorption characteristics of persimmon powder related to different drying methods and various storage temperatures was investigated. The physical properties of persimmon powder by different drying methods displayed the largest amount of porosity in the freeze-dried sample, and the smallest in hot air dried sample. Equilibrium moisture was reached in 6 days. Monolayer moisture contents were predicted to 0.09687~0.19712(freeze drying), 0.07820~0.18617(vacuum drying) and 0.07715~0.18056(hot air drying) g H2O/g solid respectively using the BET equation. BET equation for isothermal absorption curve showed over 0.95 R-square for all dried methods. Monolayer moisture contents were increased as storage temperature was incremented because water molecular movement was more active and there was a greater chance to clash with the absorption surface area.

• Journal of Life Science
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• v.10 no.3
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• pp.229-235
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• 2000

The absorption characteristics of Korean yam powder according to different drying methods were investigated. The physical properties of yam powder by different drying methods were showed the biggest porosity in freeze drying sample, while the smallest in hot air drying sample. No difference was founded in proximate compositions of yam powder by various drying methods. The amount of total phenolic compound and Vit C were showed the bigger decrement in freeze dried sample than other drying methods. The time reaching to equilibrium moisture content were determined in 12 days. Monolayer moisture contents were predicted to 0.0508∼0.0588 by BET equation and 0.0705∼0.0811 g H2O/g solid by GAB equation. BET equation for isothermal absorption curve showed over 0.95 R-square for every drying methods. GAB equation showed over 0.99 in vacuum and freeze drying but a poor R-square in hot air drying.

• Membrane and Water Treatment
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• v.1 no.2
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• pp.121-137
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• 2010

This work presents inexpensive inorganic precursor formulations to yield submicron range symmetric ceramic microfiltration (MF) membranes whose average pore sizes were between 0.1 and $0.4{\mu}m$. Incidentally, the sintering temperature used in this work was about 800 to $950^{\circ}C$ instead of higher sintering temperatures ($1100^{\circ}C$) that are usually deployed for membrane fabrication. Thermogravimetric (TGA) and X-Ray diffraction (XRD) analysis were carried out to evaluate the effect of temperature on various phase transformations during sintering process. The effect of sintering temperature on structural integrity of the membrane as well as pore size distribution and average pore size were evaluated using scanning electron microscopy (SEM) analysis. The average pore sizes of the membranes were increased from 0.185 to $0.332{\mu}m$ with an increase in sintering temperature from 800 to $950^{\circ}C$. However, a subsequent reduction in membrane porosity (from 34.4 to 19.6%) was observed for these membranes. Permeation experiments with both water and air were carried out to evaluate various membrane morphological parameters such as hydraulic pore diameter, hydraulic permeability, air permeance and effective porosity. Later, the membrane prepared with a sintering temperature of $950^{\circ}C$ was tested for the treatment of synthetic oily waste water to verify its real time applicability. The membrane exhibited 98.8% oil rejection efficiency and $5.36{\times}10^{-6}\;m^3/m^2.s$ permeate flux after 60 minutes of experimental run at 68.95 kPa trans-membrane pressure and 250 mg/L oil concentration. Based on retail and bulk prices of the inorganic precursors, the membrane cost was estimated to be $220 /$m^2$ and $1.53 /$m^2$, respectively.

• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.715-721
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• 2004

Hydroxyapatite (HAp)/Gelatin (GEL) homogeneous composites of four different composition ratio were prepared by the co-precipitation process with synthetic HAp and GEL as a binder, HAP/GEL composites were molding by cold isostatic pressing and were sintering by various condition in air. Crystallinity and structure of sintered HAp/GEL composites were investigated by XRD and FTIR. Also, the compressive strength and the fracture surface of sintered specimens were measured by UTM and SEM. HAp/GEL composites showed a phase transformation to partially ${\alpha}$, ${\beta}$-tricalcium phosphate at the sintered condition of 1200$^{\circ}C$ for 3 h. The porosity of sintered body was in the range of 1.2-30.2％. The compressive strength of the sintered specimens was in the range of 16.2-60.1㎫, and its strength of sintered HAp/GEL comosites was higher than expected when the porosity was considered.

• Clean Technology
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• v.12 no.3
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• pp.175-181
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• 2006

The feasibility of the use of porous fossil diatoms for indoor air pollution control was investigated via the characterization of physical and chemical properties. The fossil diatoms were observed by SEM(Scanning Electron Microscope). Diatomite had well-distributed pores below 5 nm and relatively large surface area compare to sericite. However, no porosity in sericite was found. Results showed that diatomite had better performance than sericite in respect to porosity and large surface area. But diatomite which is thermally treated at $950^{\circ}C$ has no porosity and low surface area because of combustion of fossil diatoms or calcination of inorganic oxide at high temperature, and has poor adsorption capability of ammonia gas. In conclusion, porous diatomite has relatively high performance to adsorb noxious chemical compounds, such as ammonia gas and VOCs.

• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1177-1182
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• 2003

The porous sensing materials for BaTiO$_3$ gas sensors were fabricated by adding the graphite powders. The crystalline structure and microstructure of the porous BaTiO$_3$-based ceramics were studied. All the sintered bodies showed a tetragonal perovskite structure. The porosity increased with increasing graphite contents. This is mainly due to an enhanced evolution of CO and $CO_2$ gases resulting from the exothermic reactions of graphite and oxygen during the sintering. It was found that the discrepancy in the resistivities measured in air and CO atmospheres at high temperatures (>∼20$0^{\circ}C$) became remarkable with increasing temperature. The sensitivity of CO gas increased with porosity, since the reactions between CO gas and $O_2$$^{[-10]}$ and between CO gas and $O^{[-10]}$ are active due to the formation of many reaction sites. The porous BaTiO$_3$-based ceramics could be promising as a sensing material for CO gas sensors.

• Journal of Environmental Health Sciences
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• v.23 no.2
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• pp.35-43
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• 1997

A study on the effect of the biodegradability of the composting bulking agent in the swine manurecomposting was carried out in a batch system. The purpose of this study is to prove the effect of the biodegradability of the composting-bulking agent on the efficiency of the composting. In this study, it is the lignins: Klason-Lignin in the volatile solid that the index of the biodegradability of the composting-material mixes which are pig manure-rice straw pig manure-sawdusts pig manuremixture of rice and ricestraw (2:1) pig manure-mixture of rice and sawdust (1:1). It was carried out in the same condition (moisture contents, air supply rate, C/N ratio, initial input weight, porosity-structure) except the biodegradability of the raw material mixes. One of the results from this study is that the biodegradability of the bulking agent in the sense of the VS lignin content is not an insignificant factor in composting reaction. The less contents of the lignin in VS, the more efficiencies of the cornposting reaction in use of these parameters for the degree of the reaction: temperature, the trends of the ash contents, the change pattern of the C/N ratio. Under some assumptions, it is able to induce rough model on the relation of the VS lignin contents with the efficiency of the degradability. In this model, the biodegradability of the bulking agent is not an insignificant factor however, it is flexible within some degrees of range.