• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1053-1058
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• 2008

Porous medium was considered in the present study for the heat transfer enhancement. This was attributed to its high surface area to volume ratio as well as intensive flow mixing by tortuous flow passages. But when the air or water flow through in the porous medium, it is occurred the pressure drop between inlet and outlet. So in the present study investigated simulation result about the pressure drop in the porous medium before apply to heat exchanger. In this simulation, the thickness of the solid inside the porous medium region was varied 0.2 mm to 0.4 mm. And then the simulation result were compared the pressure drop in the same unit cell ($0.5\;mm{\times}0.5\;mm{\times}0.5\;mm$). To make the analysis model, it was assumed the 14-sided tetrakaidecahedron cell which has long been considered the optimal packing cell first proposed by the Lord Kelvin in 1887. And then the simulation is carried out using by STAR-CCM+ which is commercial software. The simulation result can be showed quantified pressure drop by solid effect in the porous medium.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.70-74
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• 2004

Pressure and temperature in the cavity of injection molding have been investigated. Special injection mold was designed to install pressure and temperature sensors. The sensors were supplied by KISTLER and the pressure and temperature were measured for various operational conditions, such as injection pressure, holding pressure, cooling time, mold temperature, and injection temperature. As injection pressure increased cavity pressure and temperature increase. There were no big differences in temperatures according to the holding pressures. As mold temperature increased pressure and temperature in the cavity increase. The flowability of resin increases as mold temperature increases subsequently the pressure in the cavity increases since the pressure loss is less in the low viscous medium than high ciscous medium. The cavity temperature highly depends upon mold temperature.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권1호
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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.

• 설비공학논문집
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• 제3권3호
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• pp.176-185
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• 1991

Pressure drop and flow characteristics through a filter medium have been investigated numerically. A basic model similar to the filter employed in a hard disk drive was established so that the inflow velocity was 0.1 m/s and the box size was $40mm{\times}50mm{\times}30mm$. The filter medium specifications were 0.38mm of thickness, $1{\mu}m$ of fiber diameter, 0.05 of packing density. And the filter medium was pleated by 10 within the filter box. Twenty-one sets of calculation were performed with different inlet velocities, pleated numbers, and packing densities from the basic model. As the result, it was found that the velocity after filter medium had maximum value at the rear of the upstream pleated line, but had minimum value at the rear of the downstream pleated line. This made the velocity distribution have sinusoidal form immediately after the filter medium. As the inlet velocity increased, the pressure drop increased linearly. But as the packing density increased the pressure drop increased quadratically.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2261-2266
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• 2007

In this study, the numerical analysis to estimate condensation heat and mass transfer of the condenser was carried out using the PMA (porous medium approach). In the PMA, the details of tube bundle in the condenser are replaced by the porous medium, and the flow resistance term is added in the momentum equation. In this regard, the PMA is quite helpful for the study of tube bundle in the large condenser. The pressure loss through tube bundle can be compensated by viscous and inertial momentum sink terms, which was validated numerically. Value of the pressure drop was compared to that of Butterworth correlation. Three dimensional analysis of condensation for McAllister condenser with the PMA was conducted using Fluent 6.2 and UDFs (use-defined functions). The result of condensation rate was analogous to previous results (experimental and numerical data).

• 한국전산유체공학회지
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• 제4권3호
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• pp.28-34
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• 1999

The objective of this study is to present a numerical treatment of the pressure gradient when control volumes are sharing the interface between a homogeneous fluid and a porous medium. Two possible approaches, e.g. linear interpolation and extrapolation, are considered, and they are applied to the case of a steady and two-dimensional curved channel flow which is partially filled with a porous medium. It was found that the linear extrapolation produces a continuous velocity-field at the interface and thus is recommended. On the contrary, the linear interpolation entails a discontinuous velocity field at the interface, thereby warning its use in connection with the Brinkman-Forchheimer-extended Darcy flow model.

• Journal of Power Electronics
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• 제9권4호
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• pp.544-552
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• 2009

This paper presents a novel spring pressure contact interconnect technique for medium power integrated power electronics modules (IPEMs). The key technology of this interconnection is a spring which is made from Be-Cu alloy. By means of the string pressure contact, sufficient press-contact force and good electrical interconnection can be achieved. Another important advantage is that the spring exhibits excellent performance in enduring thermo-mechanical stress. In terms of manufacture procedure, it is also comparatively simple. A 4 kW half-bridge power inverter module is fabricated to demonstrate the performance of the proposed pressure contact technique. Electrical, thermal and mechanical test results of the packaged device are reported. The results of both the simulation and experiment have proven that a good performance can be achieved by the proposed pressure contact technique for the medium power IPEMs.

• 전기의세계
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• 제29권8호
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• pp.519-523
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• 1980

The traditional mechanical manometer is improved to develop more convenient and precise manometer in continuous measurement of the gas pressure in medium-low vacuum range (1x10$^{-1}$ -10 Torr.) Glass (solid) is used as a detector material of the improved manometer. Using the strain gauge adhered to thin glass board, mechanical strain corresponding to variation of pressure in measurement system is converted into quantity of electricity, and the quantity of electricity is amplified. Experiments have also shown that the improved manometer have more advantages in reproducibility, measured sensibility, and responsible velocity than taditional one.

• Journal of Acupuncture Research
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• 제38권3호
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• pp.200-204
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• 2021

Background: Standardized procedures for the clinical application of fire cupping methods have not been established. In particular, the pressure parameters have not been fully characterized and described. Therefore, using various materials, this study investigated the pressure range exerted during fire cupping therapy. Methods: In this study, 3 differently sized (small, medium, large) glass and bamboo cups were used in the cotton ball fire cupping procedure to measure the pressure inside the cup applied to a human skin model. The pressure in each cup was measured 15 times for a total of 90 measurements. Results: A small bamboo cup had the minimum overall pressure (-305.4 mmHg), whereas the large glass cup exerted the maximum pressure (-401.3 mmHg), followed by the medium glass cup, large bamboo cup, small glass cup, and medium bamboo cup. The average pressure exerted by the cotton ball method for all cups ranged from -348.715 mmHg to -358.694 mmHg (95% confidence interval). Overall, the glass cups had a greater pressure than the bamboo cups in all groups (p < 0.001). Among the glass cups used, the larger the size of the cup, the higher the average pressure detected (-381.947 mmHg to -391.973 mmHg; p < 0.05). Conclusion: Large glass cups which are widely used in clinical practice, when used in the fire cupping method exerted pressure ranging from -381.947 mmHg to -391.973 mmHg (95% CI).

• Journal of Advanced Marine Engineering and Technology
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• 제24권4호
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• pp.526-534
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• 2000

In this study, the characteristics of exhaust emissions in medium speed diesel engine under various operating conditions were investigated through experiments to derive the optimum conditions for minimizing the exhaust emissions, especially, nitrogen oxides. The 355 KW$\times$1200 rpm medium speed diesel engine was intensively examined to investigate the trend of exhaust emissions in case that the parameters affecting combustion conditions such as fuel injection timing, intake air temperature and pressure, engine speed and load were changed. The exhaust emissions for 9 sets of medium speed diesel engine were analyzed in addition. From this study, NOx level could be reduced by 30~50% through the adjustment of retarded fuel injection timing, lowered intake air temperature and increased charging air pressure.