• Journal of Energy Engineering
• /
• v.11 no.3
• /
• pp.276-282
• /
• 2002

The process of energy separation in a low Pressure vortex tube with compressed air as a work-ing medium is studied in detail. Experimental data of the temperature of the cold and hot air leaving the vortex tube are presented. The variation of the maximum wall temperature along the inner surface of the vortex tube and the temperature distribution in a vortex tube provide useful information about the location of the stagnation point of the flow field at the axis of the vortex tube. Analysis of the results enabled to find the optimum length of the vortex tube, the optimum shape of the Throttle and the usefulness of the Sleeve. In this study Outer tube is used for the exhaust application. The hot gas flow is turned 180$^{\circ}$and passes the out-side of the vortex tube a second time heating it. From this geometric setup of a vortex tube He effects of energy separation and the prediction of the ignition of Diesel Soot is presented by experimental data.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.4
• /
• pp.269-275
• /
• 2020

An explosive bolt is one of many representative pyrotechnic release devices that separates two joined structures using explosives inside the bolt. In this study, a 1/2 inch ridge-cut explosive bolt with an EBW detonator was developed for usage in sled tests. The initial shape design was carried out based on the design method, and the performance test showed that the separation performance was outstanding but fragments occurred. Therefore, numerical analysis was performed to reduce the amount of debris by minimizing the amount of explosives. From the numerical analysis, the separation mechanism and characteristics of the ridge-cut explosive bolts were identified, and the minimum amount of explosives that does not generate debris was proposed. Verification tests revealed that the ridge-cut explosive bolts with the proposed explosive weight minimized fragments while maintaining the separation performance.

• Wind and Structures
• /
• v.34 no.5
• /
• pp.437-450
• /
• 2022

Vortex-induced vibration (VIV) is a significant concern when designing slender structures with square cross sections. VIV strongly depends on structural dynamics and flow states, which depend on the conditions of the approaching flow and shape of a structure. Therefore, the effects of the angle of attack on the coupling effects of VIV for a square cylinder are expected to be significant in practice. In this study, the aerodynamic forces for a fixed and elastically mounted square cylinder were measured using wind pressure tests. Aerodynamic forces on the stationary cylinder are firstly discussed by comparisons of variation of statistical aerodynamic force and wind pressure coefficient with wind angle of attack. The coupling effect between the aerodynamic forces and the motion of the oscillating square cylinder by VIV is subsequently investigated in detail at typical wind angels of attack with occurrence of three typical flow regimes, i.e., leading-edge separation, separation bubble (reattachment), and attached flow. The coupling effect are illustrated by discussing the onset of VIV, characteristics of aerodynamic forces during VIV, and interaction between motion and aerodynamic forces. The results demonstrate that flow states can be classified based on final separation points or the occurrence of reattachment. These states significantly influence coupling effects of the oscillating cylinder. Vibration enhances vortex shedding, which creates strong fluctuations in aerodynamic forces. However, differences in the lock-in range, aerodynamic force, and interaction process for angles of attack smaller and larger than the critical angle of attack revealed noteworthy characteristics in the VIV of a square cylinder.

• Journal of Korean Society for Atmospheric Environment
• /
• v.24 no.4
• /
• pp.483-491
• /
• 2008

The filtration characteristics of $CYBAGFILTER^{(R)}$ unit with pleated filter bags were evaluated by comparing the performance of the unit with the lower part of cyclone shape with that of the unit with conventional lower part. Results from the test were also compared with those from the previous research with the $CYBAGFILTER^{(R)}$ in which round filter bags were installed. $CYBAGFILTER^{(R)}$ is the unit which combines the centrifugal separation mechanism and the fabric filtration mechanism in a single unit for efficient removal of particulate matters. The pleated filter bags are made of pleated fabric with an extension of the filtration area about 3 times compared with the conventional round filter bags. The results from the test using pleated filter bags showed an overall collection efficiency of over 99.9% regardless of the shape of lower part installed. When the lower part of cyclone shape was installed, the filter cleaning interval was over 2 times longer compared with that when the conventional lower part was installed. At the same conditions of filtration velocity and filter pressure drop, the $CYBAGFILTER^{(R)}$ with the lower part of cyclone shape, in which the pleated filter bags are installed, can be operated with a flow rate of round 3 times higher than that with conventional round filter bags.

• Fashion & Textile Research Journal
• /
• v.16 no.4
• /
• pp.635-644
• /
• 2014

This study provides basic reference data for brassiere wearing conditions, design preferences of new silver women (50s-60s) and development of brassiere products. We compiled and compared 163 pieces of brassiere (considering of 105 domestic general brassieres and 58 foreign silver brassieres) analyzed using SPSS Statistics 21 program. A survey was then conducted on the actual wearing, purchasing conditions, design preferences for 176 females (50s-60s). The result of this study are as follows: First, comparing actual product conditions (domestic general products and foreign silver products), the ratio of full cup in cup height, V-shape type in neckline shape, long type in front-end length, wide type in wing width, U-shape type in shoulder strap form, wide type in shoulder strap width, no-wire brassieres in breast wire type, all-in-one type in shoulder strap separation, back type in closure type appeared higher than other types of brassiere in domestic general product. Second, a study also showed that 60s women's wearing time is lower than 50s women's; however, 60s women expressed a higher figure and preference for the purchasing ratio in the department store, full cup in cup height, short type in length of brassieres, wide type in wing width, U-shape in shoulder strap form, small type in shoulder strap width, back type in closure type and no-wire brassieres than those in their 50s. It was found they prefer fabric with a high natural content, nude tone color without decoration & pattern and camisole brassieres.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.5
• /
• pp.571-577
• /
• 2012

In this study, a small movable batch treatment system for dredging soil deposited in a rain water tube is proposed; further, a vacuum silo sorting separation device with a vacuum silo, first-stage sorting separator, and conveyor is designed. The vacuum silo sorting separation device also consists of a storage tank, transferring screw, vacuum gate, screen bar, screen bar cleaner, and vacuum discharging device. In view of the fact that the flow of drawn air in the storage tank is a major factor influencing the sorting separation performance, the optimum shape of the tank is determined by CFD flow analysis. In addition, by using CAE structure analysis, the safety of a storage tank made of boards is examined. The specifications of the vacuum silo sorting separation device are determined by conducting mechanical and dynamic simulations of the driving mechanism of the vacuum silo sorting separation device through 3D-CAD modeling. Following this study, we will design a drum-screen-type second sorter, a decanter-type dehydration device, and waste water tank and pump as a secondary device. Further, on the basis of this design, we will construct a prototype model and carry out a field test.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.2
• /
• pp.109-117
• /
• 2015

Aircraft needs an inlet duct to supply the airflow to engine face. A fighter aircraft that requires low radar observability has to hide the engine face in the fuselage to reduce the Radar Cross Section(RCS). Therefore, the flow path of the inlet duct is changed into S-shape. The performance of the aircraft engine is known to be influenced by the shape and the centerline curvature of the S-Duct. In this study, CFD analysis of the RAE M 2129 S-Duct has been performed to investigate the influence of aspect ratio of inlet geometry. The performance of the S-Duct is evaluated in terms of the distortion coefficient. To simulate the flow under adverse pressure gradient better, $k-{\omega}SST$ turbulence model is employed. The computational results are validated with the ARA experimental data. The secondary flow and the flow separation are observed for all computational cases, while the semi-circular geometry has been found to produce the best results.

• Solar Energy
• /
• v.17 no.2
• /
• pp.67-74
• /
• 1997

Spherical shape of phase change material(PCM) has been prepared by using sodium acetate trihydrate as a latent heat storage medium. Gelatin was used as an effective thickener to prevent undesirable phase separation. Sodium pyrophosphate decahydrate was used as nucleator to decrease the degree of supercooling in the thickened phase change material. Spherical PCM particles of 3-3.5 mm in diameter continuously manufactured with molten PCM with those conditions. The particle size of PCM was not affected by the effluent velocity of molten PCM in range of 1.3-1.8 ml/min. DSC, SEM and XRD were also used to characterize the properties of PCM particles.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.8
• /
• pp.99-106
• /
• 2003

Geometrical design variables are numerically investigated to improve aerodynamic performance of the supersonic impulse turbine of a turbopump in a liquid rocket engine. Aerodynamic redesign was performed for maximization of the blade power. Four design variables considered are blade angle, blade thickness and radii of upper and lower arc blade with appropriate constraints. A fast Navier-Stokes solver was developed and Chien's k-$\varepsilon$ turbulence modelling was used for turbulence closure. In initial shape, a flow separation was found in the middle of blade chord. However, it disappeared in final shape via its geometrical design variable change. About 3.2 percent of blade power was increased from this research.

• Journal of architectural history
• /
• v.26 no.2
• /
• pp.31-42
• /
• 2017

This study investigates how the spatial recognition structure is emerging through the case of rectangular plan combined with a combination of Dang-Sil(堂室) and Gong(工) shape roof, and identifies a type of architecture in the early Joseon Dynasty that has never been revealed. The conclusion of this study is as follows. First, the Dang and the Sil are connected to each other, but the architectural elements such as pillars, frame, and windows are distinguished and appear as separate buildings. Second, the distinction between Dang and Sil is evident by the difference in the number of ridges and the shape of the roof. In addition, the roof and roof framework of the independent rooms and the rooms were common in the right angled architecture where the direction and the expandability of each structure were maintained. Third, the construction of the Dang-Sil combined structure, in which two or more structure frameworks were combined with the rectangular combined flat roof structure, gradually changed into a single structure with a single ridge. Fourth, this change means that people of the early Joseon Dynasty recognized the Dang and Sil as separate architecture, but the strict sense of spatial separation has disappeared over time.