• International journal of advanced smart convergence
• /
• v.10 no.1
• /
• pp.159-165
• /
• 2021

Electronic devices used in the mobile environments fabricated under the plasma conditions in high vacuum system. Especially for the development of advanced electronic devices, high quality plasma as the process conditions are required. For this purpose, the variable conductance throttle valves for controllable plasma employed to the high vacuum system. In this study, we analyzed the effects of throttle valve applications on vacuum characteristics simulated to obtain the optimum design modelling for plasma conditions of high vacuum system. We used commercial simulator of vacuum system, VacSim(multi) on this study. Reliability of simulator verified by simulation of the commercially available models of high vacuum system. Simulated vacuum characteristics of the proposed modelling agreed with the observed experimental behaviour of real systems. Pressure limit valve and normally on-off control valve schematized as the modelling of throttle valve for the constant process-pressure of below 10-3 torr. Simulation results plotted as pump down curve of chamber, variable valve conductance and conductance logic of throttle valve. Simulated behaviors showed the applications of throttle valve sustained the process-pressure constantly, stably, and reliably in plasma process.

• International Journal of Fluid Machinery and Systems
• /
• v.2 no.1
• /
• pp.1-12
• /
• 2009

Surrogate modeling is applied to a compressor blade shape optimization to modify its stacking line and thickness to enhance adiabatic efficiency and total pressure ratio. Six design variables are defined by parametric curves and three objectives; efficiency, total pressure and a combined objective of efficiency and total pressure are considered to enhance the performance of compressor blade. Latin hypercube sampling of design of experiments is used to generate 55 designs within design space constituted by the lower and upper limits of variables. Optimum designs are found by formulating a PRESS (predicted error sum of squares) based averaging (PBA) surrogate model with the help of a gradient based optimization algorithm. The optimum designs using the current variables show that, to optimize the performance of turbomachinery blade, the adiabatic efficiency objective is improved substantially while total pressure ratio objective is increased a very small amount. The multi-objective optimization shows that the efficiency can be increased with the less compensation of total pressure reduction or both objectives can be increased simultaneously.

• Journal of Korean Society of Water and Wastewater
• /
• v.32 no.2
• /
• pp.115-122
• /
• 2018

Direct spring loaded pressure relief valve(DSLPRV) is a safety valve to relax surge pressure of the pipeline system. DSLPRV is one of widely used safety valves for its simplicity and efficiency. However, instability of the DSLPRV can caused by various reasons such as insufficient valve volume, natural vibration of the spring, etc. In order to improve reliability of DSLPRV, proper selection of design factors of DSLPRV is important. In this study, methodology for selecting design factors for DSLPRV was proposed. Dynamics of the DSLPRV disk was integrated into conventional 1D surge pressure analysis. Multi-objective genetic algorithm was also used to search optimum design factors for DSLPRV.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.335-340
• /
• 2000

A 3 valve-type pulse tube refrigerator optains its cooling effect from pressure drop by releasing the part of the charged gas through hot end nozzle. The objective of this study is to analyze the performance and to find an optimal expansion pressure of the 3 valve-type pulse tube refrigerator. It is assumed that gas lumps are not mixed and periodically repeat the adiabatic compression and expansion processes. And the nodal model is applied for the analysis of the regenerator. As the result of analysis, the optimum pressure at the end of expansion process was about 80-90% of the maximum pressure.

• 한국태양에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.409-414
• /
• 2009

Since cryogens are stored at very low temperatures, the cryogenic storage systems are quite sensitive to heat leaks. Even though the vessel operated under sealed condition with vacuum insulation and reflective coatings are used, the heat leakage into the vessel is still unavoidable. Therefore, this paper concerns with numerical study of self-pressurization used to analysis the optimum design with the variation volume fraction, effect of heat flux and storage pressure of liquid nitrogen. The result shows that as the volume fraction increases, the pressure rise reduces and the relatively at atmosphere pressure is better than the higher one. In addition, higher heat flux leads the pressure rise increases faster than low one. The additional of heat pipe system to reduce the pressure rise rate also has been done. By this comparison, the optimum design for storage umbilical cord blood can be selected.

• Journal of Biosystems Engineering
• /
• v.28 no.6
• /
• pp.525-530
• /
• 2003

This study was carried out to develop a vacuum nozzle seeder for the automation of large seeds sowing of fruit vegetables and rootstocks. Moreover, the seeding efficiency was examined to find the optimum operating condition considering high precision seeding. The important operating factors for high seeding rate were typically nozzle diameter and absorbing vacuum pressure. The optimum nozzle diameters were found 1.5, 1.5 and 2.0 mm for Chambak, Tuktozwa and Hukjong while the optimum vacuum pressures were 8.0㎪, 10.6㎪ and 5.3㎪, respectively. Under the optimum operating condition, the results indicated that the maximum seeding rates were 97.6％, 98.8％ and 97.6％ respectively for Chambak Tuktozwa and Hukjong. The vibrating acceleration of the hopper did not make any significant effects on the seeding rate when the vacuum pressure reached 8.0㎪ and the sowing rate became higher with lighter seed. As the seed became heavier, the larger diameter of nozzle was recommended 1.5mm of the nozzle diameter was found to be applied for the experimental seeds. The vacuum pressure was also found 8.0㎪ - 13.3㎪ at that time.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2642-2647
• /
• 2008

Starting characteristics of the axi-symmetric supersonic exhaust diffuser(SED) with a second throat are numerically investigated. Main purpose of this study is to predict theoretical starting pressure of STED using 1-D normal shock theory and to present the range of optimum starting pressure through parametric study with essential design parameters of STED influencing on starting performance. Renolds-Average Navier-Stokes equations with a standard ${\kappa}-{\varepsilon}$ turbulence model incorporated with standard wall function are solved to simulate the diffusing evolutions of the nozzle plume. Minimum(optimum) starting pressure difference of $20{\sim}25%$ between 1-D theory and experimental evidences validated from previous results[5] is also applied to predict those in this system. The analysis results indicate that dominant parameters for diffuser starting in this system is diffuser expansion ratio($A_d/A_t$), which has optimum value 120 and second throat area ratio($A_d/A_{st}$), which has optimum range $3.3{\sim}3.5$.

• Geomechanics and Engineering
• /
• v.1 no.3
• /
• pp.179-191
• /
• 2009

For a two-way drainage deposit under a surcharge load, it is possible to leave a layer adjacent to the bottom drainage boundary without prefabricated vertical drain (PVD) improvement and achieve approximately the same degree of consolidation as a fully penetrated case. This depth is designated as an optimum PVD installation depth. Further, for a two-way drainage deposit under vacuum pressure, if the PVDs are fully penetrated through the deposit, the vacuum pressure will leak through the bottom drainage boundary. In this case, the PVDs have to be partially penetrated, and there is an optimum installation depth. The equations for calculating these optimum installation depths are presented, and the usefulness of the equations is studied by using finite element analysis as well as laboratory model test results.

• Journal of Energy Engineering
• /
• v.13 no.1
• /
• pp.34-39
• /
• 2004

The process of energy separation in a low pressure vortex tube with compressed air as a working 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 a 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 ratio of nozzle area and the optimum shape of an orifice. From this optimum geometric setup of a low pressure and big vortex tube the effectiveness of energy separation was better than a high pressure and small vortex tube.

• Composites Research
• /
• v.23 no.5
• /
• pp.1-7
• /
• 2010

To increase the adhesive strength of acrylonitrile butadiene rubber(NBR) and steel plate, the atmospheric pressure flame plasma(APFP) treatment device is applied. The effect of various conditions(processing velocity and distance) is experimentally investigated to ascertain the optimum conditions to yield the best adhesive properties. It is found that the optimum distance between burner port and steel plate is 40mm and the optimum processing velocity is 50m/min at given condition. When the surface is coated twice with the bonding agent, the adhesion strength of APFP treated steel plate is increased to about 20.5%. It suggests that the surface modification of steel by flame plasma treatment at atmospheric pressure is a proper and applicable method to improve the adhesion strength between steel and rubber.