• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1165-1166
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• 2006

An experiment was carried out to investigate the effect of Ba Stearate as a reducing agent on the magnetic and physical properties of anisotropic $BaFe_2-W$ type ferrite magnets. It was found that the magnetic properties of $BaO{\cdot}8.5Fe_2O_3$ were improved by adding 0.3 wt% of Ba Stearate, 0.5 wt% of $SiO_2$, and 0.5 wt% of CaO together. The optimum conditions for making magnets were as follows; semisintering condition: $1350^{\circ}C{\times}4.0$ h in nitrogen gas atmosphere, drying condition: $180^{\circ}C{\times}2.0$ h in air, sintering condition: $1160^{\circ}C{\times}1.5$ h in nitrogen gas atmosphere. Magnetic and physical properties of a typical sample were $J_m$ = 0.46 T, $J_r$ = 0.43 T, $H_{cJ}$ = 182.3 kA/m, $H_{cB}$ = 177.2 kA/m, $(BH)_{max}$ = 33.8 kJ/$m^3$, $T_C$ = $495^{\circ}C$ and $K_A$ = $2.65{\times}10^5\;J/m^3$ and $H_A$ = 1332 kA/m.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.440-445
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• 2008

The present study was investigated the effect of the driving condition on the performance of a louver fin and tube type heat exchanger under frosting condition. Heat transfer rate and pressure drop by frost were experimentally investigated. Effects of the wet blub temperature and the shape of a fin on heat transfer performances has been also investigated. The key parameters were fin type(louver and corrugate fin) and the wet blub temperature of air (0.5, 1.0, $1.5^{\circ}C$). The heat transfer performance of the louver fin and tube type heat exchanger was higher by 0.89% than the corrugate fin type. As the wet blub temperature of air were increased, the heat transfer rate, pressure drop and mass of frost of three test models(Type A, B, C) were increased. Especially, the maximum heat transfer rate and maximum pressure drop were shown for the louver fin and tube type heat exchanger. As a experimental result, the enhancement factor(EF) of louver fin and tube type heat exchanger was $0.2{\sim}0.4$ due to the high pressure drop.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.906-911
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• 2008

Because the perimeter of buildings is strongly influenced by solar and the outdoor air temperature, the area has different environmental properties compared to the interior of a building, as in summer heat gain, and in winter heat loss. In particular, if the external wall is glass, the characteristics of the glass material make it pervious to outside conditions, thereby making big changes to the thermal environment. By combining shading device and the efficient exhaust system, an energy saving can be achieved compared to no air barrier systems. The simplified air barrier system is developed with the idea that energy could be conserved by carefully and effectively blowing out the air caught between the glass surface and the roller blind. The way it is configured is therefore by making the roller blind's air-path, and by placing the air output ducts in the most optimum positions. This simplified air barrier system will give improvement in the thermal environment of the parameter area that is strongly affected by solar and the outdoor condition.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.1
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• pp.40-49
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• 2000

The capillary tube performance for R-407C is experimentally investigated. The experimental setup is a real vapor-compression refrigerating system. Mass flow rate is measured for various diameter and length while inlet pressure and degree of subcooling are changed. These data are compared with the results of a numerical model. The mass flow rate of the numerical model is about 14% less than the measured mass flow rate. It is found that mass flow rate and length for R-407C are less than those for R-22 under the same condition. Based on this experimental study and the numerical model, a set of design charts for capillary tube of R-407C is proposed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5430-5437
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• 2011

The objective of this study is to investigate the cooling performances of the electrical air-conditioning system using electric driven scroll compressor for zero emission passenger vehicles. This air conditioner with air source was used R-134a as a refrigerant and installed in a real zero emission passenger vehicle for tests under various driving conditions. The cooling performance of the electrical air conditioner was affected by driving velocities and conditions of the tested vehicle. The condensing rate of the condenser during driving is better than that of the idle condition. The average cool down temperature in the cabin room decreased on average $5.2^{\circ}C$ with the increase of the outdoor temperature from $20.0^{\circ}C$ to $30.0^{\circ}C$. In addition, the cooling performances were sufficient for cooling loads of the tested passenger car under tested conditions.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1062-1067
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• 2003

In this study, corrosion fatigue characteristics of CF8M and CF8A steel were investigated on the simulated PWR condition(Temp.:$316^{\circ}C$, Pres.: 15:MPa). To make the simulated PWR condition. the special test machine consisted of INSTRON, Autoclave, LOOP and Measurement system was developed. As ${\Delta}K$ is ranged from 11 to $20MPa{\sqrt{m}}$, Crack growth rate of PWR condition is faster than air condition. Above $20MPa{\sqrt{m}}$, the crack growth rate of PWR and air condition is similar. Corrosion fatigue characteristics regardless of the ferrite contents($10{\sim}25wt.%$) is not different. After the test, the fracture surface of specimens was examined. It was difficult to verify the fracture modes such as striation, intergranular crack and cleavage and so on. As the ferrite content of CF8M is increased, the more particles covered fracture surface were peeled.

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.2
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• pp.185-190
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• 1995

Recently, because of the worse of the air pollution, the excessive airtught of building and the inferiority of air conditioning system, the development of high efficiency air purification technology was enlarged to the environmental improvement of an indoor or a harmful working condition. The air purification technology has used chemical filters or charcoal filters or charcoal to remove hazardouse gaseous pollutants (SO$_{x}$, NO$_{x}$, NH$_{3}$, etc.) by air pollutant control technology, but they have many problems of high pressure loss, short life, wide space possession, and treatment of secondary wastes. For these reason, the object of reasearch shall be hazardous gaseous pollutants removal by the surface discharge induced plasma chemical process that is A.C. discharge of multistreams applied A.C. voltage and frequency between plane induced eletrode and line discharge eletrode of tungsten, platinum or titanium with a high purified alumina sheet having a film-like plane. As a result, the control performance for hazardous gaseous pollutants showed very high efficiency in the normal temperature and pressure. Also, after comtact oxidation decomposition of harmful gaseous pollutants, the remainded ozone concentration was found much lower than that of ACGIH or air pollution criteria in Korea.rea.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.621-626
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• 2006

Regenerative evaporative cooling is known as an environment-friendly and energy efficient cooling method. A regenerative evaporative cooler (REC) consisting of dry and wet channels is able to cool down the air stream below the inlet wet-bulb temperature. In the regenerative evaporative cooler, the cooling effect is achieved by redirecting a portion of the air flown out of the dry channel into the wet channel and spraying water onto the redirected air. In this study, a horizontal regenerative cooler is considered. In the horizontal regenerative cooler, the flow direction of evaporating water has a right angle to the flow direction of supply air. This difference was investigated with visualization technique and simplified 2-module performance test was done in a thermo-environment chamber. Optimum design configuration is changed due to the wet channel which are easily fully covered with evaporating water and block the air flow inside the channel. Applying the optimized fin configuration design with the highly wetting surface treatment, a regenerative evaporative cooler was fabricated and tested to Identify the cooling performance improvement and operation characteristics. From the experimental results at the intake condition of $32^{\circ}C$ and 50% RH, the supply temperature was measured to be around $23.4^{\circ}C$. The cooling effectiveness based on the inlet dewpoint temperature was evaluated 73% which is almost close to the design expectation.

• KIEAE Journal
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• v.6 no.2
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• pp.43-50
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• 2006

A Double Facade System(DFS) is well known as an innovative solution of ecological facade in the west european countries. There are more than 200 various realized DFS in Germany. At the same time, the korean engineers have researched to find out the physical advantages of DFS in the moderate korean climate, which has a very humid summer with high temperature and a dry winter with low temperature. For example, the monthly mean temperature in Korea comes up to 28K, while that in Germany comes up to only 19K. That is, why a other solution of DFS is needed in Korea. This study has experimented the physical performance of the natural ventilation in the heating period. The preheating function of the cold air by DFS can improve no doubt the performance of the natural ventilation at the cold season as well as spring and autumn. The physical difference between single and double facade on natural ventilation has been tested at the newly constructed laboratory, which can turn $360^{\circ}$ to confirm the characteristic of a facade with the various directions. The results show the natural ventilation of the DFS has definitely much more comfortable than that of the single facade system. The air velocity of the inflow as well as the air temperature in the DFS provide a more stable condition than in the SFS. The theoretical limit(air velocity max 0.2m/s, air temperature min. $18^{\circ}C$, temperature difference between 100mm and 1700mm height max. 3K) on the indoor comfortableness doesn't go over in the DFS. On the other hand, the SFS showed an unstable condition with an excess of comfortableness limit on air velocity as well as temperature. In view of the researching results so far achieved, the research came to a conclusion, that the DFS can provide a more comfortable indoor condition by the preheating in the heating period than a SFS, and the period of natural ventilation in winter time could be definitely increased at the DFS.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.8
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• pp.1423-1428
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• 2010

The results of off-line and on-line diagnostic tests performed on the stator winding of an air-cooled gas turbine(G/T) generator are reported in this paper. Off-line diagnostic tests included measurements of the ac current, dissipation factor(tan${\delta}$), and partial discharge(PD). Six epoxy-mica capacitors were installed in the three phases of G/T generator for performing on-line diagnostic testing with the turbine generator analyzer(TGA). The TGA showed that the normalized quantity number(NQN) and the PD magnitude($Q_m$) were high in phase A of the stator winding. Internal discharges were generated in phases B and C, and slot discharge occurred in phase A. According to the trend analyses of the NQN and $Q_m$ values available for insulation condition assessment for G/T generator stator windings, it was concluded that phases B and C were in good condition, whereas phase A has been significantly deteriorated.