• Journal of computational fluids engineering
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• v.21 no.1
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• pp.50-57
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• 2016

In various industries related with construction and military machinery, a large amount of power is normally required because such machinery operations, such as digging or breaking, take place under difficult working conditions in a rough environment. Thus, a hydraulic system needs to be applied as the major power transfer system. To produce and supply hydraulic power depending on the various load conditions, a hydraulic piston pump is utilized as a typical power source for a hydraulic system. In the present study, numerical simulations were conducted using the commercial program, Ansys CFX 14.5. To lubricate the moving parts as the pump starts to operate, a small amount of oil leaks out through the clearance between the orifice in the piston-shoe and the recess at the swash-plate. Taking this into consideration, a cylindrically shaped computational domain was modeled to maintain the same equivalent leakage area. To validate the numerical method applied herein, the numerical results of the flow rate at the discharge port were compared with the experimental data, and a good agreement between them was shown. Using the verified method, the effects of the discharge pressure and the angle of the swash-plate were also evaluated under several load conditions. The results of the present study can be useful information for a hydraulic piston pump used in many different manufacturing industries.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.883-890
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• 2011

A numerical study was conducted to determine the optimal design for a vehicle vacuum pump. The degree of vacuum was examined for different design factors such as the angle of vanes, number of vanes, angle and position of the pump inlet-outlet pipe, and angular rotational speed of vanes. The results show that there is a little difference in the degree of vacuum when the angle of vanes are changed, but an angular change in the outlet pipe reduces the pump loss. As the rotational speed is increased, the mass flow rate increases, but a high rotational speed does not result in the maximum degree of vacuum. In addition, when the number of vanes is increased, the scattering range of mass flow rate decreases and pressure drop is abated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.9
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• pp.468-474
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• 2015

When oil is used for cooking in detached or apartment houses, large amounts of oil-mist, smoke, and particulate substances are generated and dispersed into the indoor-air environment. These pollutants diffuse into the surroundings and spread their odor while rising fast at a high temperature due to the heat energy from the gas range. Although the exhaust gas is discharged from the exhaust hood, which is installed on the top of a gas range to remove the diffuse pollutants, the exhaust conditions can vary greatly because they depend on the shape of the exhaust hood and the discharge rate. In this paper, the air that is required for the gas-exhaustion process is supplied by an air curtain that surrounds the kitchen hood, and the pollutant-capturing efficiency varies depending on the angle of the discharge grills; the pollutant-capturing efficiency was studied using a numerical-analysis method. The results indicate that the pollutant-capturing efficiency is not significantly changed by a change of the discharge-grill angle at a low air-discharge rate; however, at a high air-discharge rate, the efficiency value increases with an increase of the discharge-grill angle, whereby the best value occurs at 30 degrees and the efficiency decreases above this angle. Below 30 degrees, the effect of the discharge rate on the capturing efficiency is more than that of the discharge-grill angle.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.5
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• pp.304-313
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• 2008

This paper investigates the indoor-air-quality (IAQ) characteristics of the interior space equipped with system air-conditioner. The behaviors of individual variables such as temperature, humidity and concentration of carbon dioxide ($CO_2$) that influence on IAQ of the interior space were characterized under various cooling conditions by numerical and experimental studies. The numerical analysis predicting the temperature behavior of the interior space was conducted, and its results showed a good agreement with the experimental ones. The $CO_2$ concentration and humidity were measured and their time dependent behaviors were monitored and analyzed. From the results, it was found that there existed the differences of the time-dependent behaviors of IAQ variables according to the locations. In addition, it is demonstrated that the large discharge angle of $45^{\circ}$ made the temperature profile more irregular and the high discharge flow of 5.34 m/s produced similar temperature profiles at three different sensing locations. Finally, the humidity of interior space was less sensitive to the changes of the air cooling conditions than the case of temperature and the $CO_2$ concentration increase mainly depended on the number of individuals inside the space.

• Fire Science and Engineering
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• v.27 no.6
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• pp.1-7
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• 2013

In this study, the effects of various disk shapes of hydrant on the pressure drop are experimentally and numerically analyzed. The test methods for measuring pressure drop of hydrant are comply with standard of Underwriters Laboratory (UL). The hydrant as used in this study has one inlet, diameter 150 mm, and three outlet, 114.3 mm diameter for one outlet and 63.5 mm diameter for the others. The pressure of the hydrant are measured in the range 760 L/min~2,270 L/min for 63.5 mm outlet and 3,030 L/min~6,060 L/min for 114.3 mm outlet. Also, the numerical results of pressure drop are compared with the experiments to verify the accuracy and to analyze the of various valve shape of hydrant on the pressure drop. The engineering parameters, flow coefficients, are reduced from 181.57 to 136.35 ($L/min/kPa^{0.5}$) with inclined angle of disk from $0^{\circ}$ to $45^{\circ}$. These results are able to practical use for design hydrant to minimize pressure drop.

• Journal of Aerospace System Engineering
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• v.13 no.1
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• pp.29-37
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• 2019

The objective of this study was to investigate the influence of the blade shape on the impeller performance, for design optimizing of the high airflow impeller. First, the quantity, angle, and length of blades, which are considered to have a large influence on the impeller performance, were selected as design variables. Then, 27 cases of impeller shapes were selected according to the design of experiment (DOE). To predict the conduct of the blower based on the selected impeller shape, flow analysis was performed using the immersed solid method of ANSYS CFX. In the CFD results, the highest airflow was expected in the impeller having a combination of 50 EA, $6^{\circ}$ and 5 mm. Finally, a blower with the original impeller shape and the optimized impeller shape was fabricated using a 3D printer, and the analysis tendency and experimental tendency were verified through experiments.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.1
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• pp.59-65
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• 2013

In recent years, the crisis of energy is growing seriously and also the contamination of ecology has been reverberated as international problem. The social concerns on energy crisis have been growing for the last several years and also the interests in new and renewable energy have been increased. Therefore, in order to solving these problems, as solution of one, this paper is investigated using the aeration system at the fish farm, etc from nature energy such as wind power. This study suggests the fundamental data of designing for these similar apparatus and examines the parameters of wind velocity and wind receiving area. Especially, the water outlet position was mainly investigated with optimum outlet angle of wind pump.

• Journal of Bio-Environment Control
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• v.29 no.1
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• pp.73-79
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• 2020

The objective of this study is to analyze the heat transfer loss of covering materials in a single-span plastic greenhouse under the steady-state wind environment. To achieve this objective, the following were conducted: (1) design of a small-scaled wind tunnel (SCWT) to analyze heat losses of the greenhouse and its performance; (2) determination of the overall heat transfer coefficient (OHTC) for the covering materials using a small-scaled greenhouse model. The SCWT consists of the blowing, dispersion, steady flow, reduction and testing areas. Each part of the SCWT was customized and designed to maintain air flow at steady state and to minimize the variances in the SCWT test. In this study, the OHTCs of the covering materials were calculated by separating each with the roof, side wall, front and back of the small-scaled greenhouse model. The results of this study show that the OHTC of the roof increases as wind speed increases but the zones in which the increase rate of the OHTC decreased, were distinguished by wind tunnel wing speed of 2 ms^-1. For the side wall, the increase rate of the OHTC was particularly higher in the 0-1 ms^-1 zone.