• Transactions of the Korean Society of Automotive Engineers
• /
• v.16 no.6
• /
• pp.10-18
• /
• 2008

Metal stamping is widely used in the mass-production process of the automobile industry. During the stamping process, air may be trapped between the draw die and the panel. The high pressure of trapped air induces imperfections on the panel surface and creates a situation where an extremely high tonnage of punch is required. To prevent these problems, many air ventilation holes are drilled through the draw die and the punch. The present work has developed a simplified mathematical formulation for computing the pressure of the air pocket based on the ideal gas law and isentropic relation. The pressure of the air pocket was compared to the results by the commercial CFD code, Fluent, and experiments. The present work also used the Bisection method to calculate the optimum cross-sectional area of the air ventilation holes, which did not make the pressure of the air pocket exceed the prescribed maximum value.

• Land and Housing Review
• /
• v.2 no.4
• /
• pp.463-469
• /
• 2011

LH has installed sashes to the balcony to save energy and increase residential space. Then, it is very difficult to protect a condensation of vapor on the walls in the winter time, because the space is closed and the wall surface temperature becomes very low in a balcony. We have tried to get the optimal thermal design methods to reduce the condensation on the walls. The one of the chosen method is to make holes on the walls, and then the condensation shall be reduce because the dew point temperature will be lower due to the effect of dehumidify. In this case, it is just necessary to find as like that how many holes should be perforated through the wall, what's their size, and where is their positions. In this study, a computational fluid dynamics was applied to analyze the temperature, the pressure and the velocity distribution for an incompressible flow in the balcony spaces. And field tests were also carried out to get the data to compare to the simulation results. Finally the design criteria of the ventilation holes in the balconies was suggested by analysis of the computer simulation models.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.5 s.98
• /
• pp.519-526
• /
• 2005

Recently, the interest on the comfortable dwelling environment is increasing and the effort to solve the problem of exterior noise was tried. The propose of this study is to suggest the design of balcony window in apartment and to evaluate the sound insulation of it. So, we designed five types of balcony window which were considered not only sound insulation but ventilation. The sound reduction index of window was evaluated by the measurement in mock-up room. The results showed that case 2 improved about 6 dB in the weighted apparent sound reduction index than case 1, and case 3 reduced about $39 \%$ in construction cost than case 4.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.923-924
• /
• 2007

due to the modification of ventilation system for variable speed high efficiency PMSM, the ventilation structure is analyzed in this part. First, a cooling structure was proposed for the variable speed PMSM. Through the contrast result of whole stress and speed distribution in the cooling channel by fluid field, the fans setting fashion is confirmed. By the studying of cooling structure for improved PMSM, the position of the cooling hole in the rotor is optimized by the finite element method. At last, the thermal field distribution of the motor is calculated by FEM. The calculated thermal rise is in accord with measured value, which provides effective basement for the design and safety operation of PMSM.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.11a
• /
• pp.445-450
• /
• 2004

Recently, the interest on the comfortable dwelling environment is increasing and the effort to solve the problem of exterior noise was tried. The propose of this study is to suggest the design of balcony window in apartment and to evaluate the sound insulation of it. So, we designed five types of balcony window which were considered not only sound insulation but ventilation. The sound reduction index of window was evaluated by the measurement in mock-up room. The results showed that case 2 improved about 6dB in the weighted apparent sound reduction index than case 1, and case 3 reduced about 39% in construction cost than case 4.

• Journal of Power System Engineering
• /
• v.10 no.3
• /
• pp.67-72
• /
• 2006

The effect of manufacturing parameters on wear and improve cooling of motorcycle break system was studied using a disk-on-pad type friction tester. Such parameters conditions have an effect on the wear and improve cooling factor such as applied load, sliding speed, frictional time and number of ventilated disk hole. However, it is difficult to know the mutual relation of these factor. In this study, the wear and cooling characteristics using design of experiment containing 4 elements were investigated for an optimal condition for the best motorcycle disk break system employing Taguchi robust experimental design. From this study, the result was shown that vents have an effect on convection area improving more cooling ability and reduced wear of the disk.

• Journal of Mushroom
• /
• v.10 no.2
• /
• pp.57-62
• /
• 2012

The plastic culture bottle cap types and accumulated concentration of carbon dioxide, media humidity in the process of medium culture, chitin content and yield were observed in Pleurotus ostreatus 850ml bottle in Iksan, Jeollabuk-do, Korea, during 2011. The concentration of carbon dioxide in the process of medium culture was the highest after 8~9 days cultivation irrespective of cap sizes and types. The accumulated concentration of carbon dioxide in size cap of 29~41mm was 6.5~4.0% in the upper-under perforation hole of cap and 9.0~6.5% in the under perforation hole of cap. The upper-under 23~33mm perforation hole and under 29mm perforation hole of caps in the 850ml bottle were best condition for cultivation of mushroom and increased fruit body, 15.8~21.2% and 20%, respectively. However, the upper-under & under 41mm perforation hole of fruit body were decreased 60.7% and 23.6%, respectively. Also it was weak, lose vitality and the lower of biologically activity substance because the upper medium humidity was too dry.

• Explosives and Blasting
• /
• v.39 no.3
• /
• pp.15-23
• /
• 2021

Ventilation shafts are pathways in mines and tunnels for the removal of dust or smoke during underground space construction and operation. In mines, blasting with long blast holes is preferred for the excavation of a ventilation shaft in the 10~20m long crown pillar section. In this case, the bottom part of the blast hole is completely drilled in order to determine the drilling error, and this causes a problem of lowering the explosive charge and blasting efficiency. It is possible to solve the problem of explosive loading and to increase the blast efficiency by covering the curb of the blasthole by using stemming material. In this study, simulations for the blasting of a ventilation shaft were performed with various stemming lengths and the blasthole diameters(45, 76mm) using AUTODYN 2D SPH(Smooth particle hydrodynamics) analysis technique. Also the optimal bottom stemming column was derived by checking the size of the boulder and burden line according to blasting. Analysis result, blasting efficiency is lessened in case of stemming length less than 30cm and the optimal length of the stemming material should be 30cm or higher to achieve high efficiency of blasting.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.26 no.1
• /
• pp.74-82
• /
• 2002

The present study is aimed to investigate the effect of the safety hat on the balance of body temperature by observation of the physiological response under hot working environment. The experiment was carried out in a climate chamber of 3$0^{\circ}C$, 50%RH for 70 minutes. To compare the two kinds of safety hat, 5 healthy male subjects worn safety hat without hole (called 'without hole') or safety hat with hole (called 'with hole') according to a randomized cross-over design. The main results of this study are as fellows: Rectal temperature and heart rate were significantly lower level in 'with hole'than in 'without hole'. The mean skin temperature was significantly higher in 'without hole'than in 'with hole'. Blood pressure were significantly low in 'with hole'. Sweat rate which was measured by weight loss before and after experiment was higher in 'without hole'. In subjective ratings, subjects replied more hot, more uncomfortable and more wet, they felt more fatigue in condition of 'without hole'. Work ability which was measured by a grip strength dynamometer was higher in 'with hole'. Safety hat which can be used for safety of the brain in work place is meaningful device of behavioral thermoregulatory response under the hot working environment. The safety hat which is designed for proper ventilation and hygiene can maintain the homeostasis of body temperature by releasing body temperature efficiently.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.2
• /
• pp.259-266
• /
• 2012

In this study, the temperature distributions are analyzed on the air flow according to the position of fan inside computer main frame by CFD simulation. In case that ventilation hole is existed at the side of computer frame, the air with lower temperature can be circulated near CPU radiant thermal panel. In case of installation with fan at the side panel, the temperature of air flow becomes lowest. The efficiency of thermal emission at personal computer and its durability can be improved by releasing a lot of heat at air flow effectively inside computer frame according to this simulation result.