• Journal of Advanced Marine Engineering and Technology
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• 제31권8호
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• pp.954-960
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• 2007

The purpose of this paper is to obtain design method of air-distribution system. Air-distribution system is composed of blower, duct, diffusers and measuring equipment. The air-flow rate from each diffuser is not equal. The air-flow rate is calculated with the combined equations which are Bernoulli's equation, continuity equation and minor loss equations. Inlet condition and outlet condition are adapted in each duct system. Then square difference between function of maximum air-flow rate and minimum air-flow rate is used as an object function. Area of diffuser and velocity are established as constraints. To minimize the object function, the optimization method is used. After optimization the design variables are selected under satisfaction of constraints. The air-distribution system is calculated again with the result of optimized design variable. It is shown that the air-distribution system has the equal air-flow rate from diffusers.

• 대한기계학회논문집A
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• 제29권12권
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• pp.1615-1620
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• 2005

We present a novel flow-rate independent cell counter using a fixed control volume between double electrical sensing zones. The previous device based on the single electrical cell sensing in a given flow-rate requires an accurate fluid volume measurement or precision flow rate control. The present cell counter, however, offers the flow-rate independent method for the cell concentration measurement with counting cells in a fixed control volume of $22.9{\pm}0.98{\mu}{\ell}$. In the experimental study, using the RBC (Red Blood Cell), we have compared the measured RBC concentrations from the fabricated devices with those from Hemacytometer. The previous and present devices show the maximum errors of $20.3\%\;and\;16.1\%$, which are in the measurement error range of Hemacytometer (about $20\%$). The present device also shows the flow-rate independent performance at the constant flow-rates ($5{\mu}{\ell}/min$ and $10{\mu}{\ell}/min$) and the varying flow-rate (4, 2, and $4{\mu}{\ell}/min$). Therefore, we demonstrate that the present cell counter is a simple and automated method for the cell concentration measurement without requiring an accurate fluid measurement and precision flow-rate control.

• Tribology and Lubricants
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• 제39권2호
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• pp.76-80
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• 2023

This paper describes an experimental investigation of the effect of cooling flow rate on gas foil thrust bearing (GFTB) performance. In a newly developed GFTB test rig, a non-contact type pneumatic cylinder provides static loads to the test GFTB and a high-speed motor rotates a thrust runner up to the maximum speed of 80 krpm. Force sensor, torque arm connected to another force sensor, and thermocouples measures the applied static load, drag torque, and bearing temperature, respectively, for cooling flow rates of 0, 25, and 50 LPM at static loads of 50, 100, and 150 N. The test GFTB with the outer radius of 31.5 mm has six top foils supported on bump foil structures. During the series of tests, the transient responses of the bearing drag torque and bearing temperature are recorded until the bearing temperature converges with time for each cooling flow rate and static load. The test data show that the converged temperature decreases with increasing cooling flow rate and increases with increasing static load. The drag torque and friction coefficient decrease with increasing cooling flow rate, which may be attributed to the decrease in viscosity and lubricant (air) temperature. These test results suggest that an increase in cooling flow rate improves GFTB performance.

• 한국안전학회지
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• 제13권3호
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• pp.51-59
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• 1998

The vortex tube is a simple device for separating a compressed fluid stream into two flows of high and low temperature without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air conditioner for special purpose. The phenomena of energy separation through the vortex tube were investigated to see the effects of cold flow inlet-outlet ratios and partial admission rates on the energy separation experimentally. The experiment was carried out with various cold flow inlet-outlet ratios from 0.28 to 10.56 and partial admission rates from 0.176 to 0.956 by varying input pressure and cold air flow ratio. To find best use in a given cold flow inlet-outlet ratio and partial admission rate, the maximum temperature difference of cold air was presented. The experimental results were indicated that there are an optimum range of cold flow inlet-outlet ratio for each partial admission rate and available partial admission rate.

• 대한교통학회지
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• 제24권4호
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• pp.129-148
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• 2006

본 연구의 목적은 고속도로 교통운영상태 분석과 이로부터 도출된 하나의 평가척도(평균통행속도)에 의해 서비스수준평가 방법론을 구축하는 것이다. 본 연구는 고속도로를 분석하기 위해서는 고속도로의 어느 구간에서 정체가 발생될 것이며, 발생된 정체의 영향은 어느 정도가 될 것인가를 파악하는 것이 우선되는 과제라는 관점에서 출발하였다. 따라서 고속도로 상에서 발생되는 정체를 유형화하였고(이는 곧 잠재적 병목구간 및 병목구간에서 발생되는 정체메커니즘의 유형화를 의미한다), 이를 통해 병목구간의 수요교통량에 따른 최대통과가능교통량 및 최대통과교통량의 산출을 통해 정체류 분석을 수행하였다. 본 연구가 기존의 연구들과 구별되는 가장 큰 특징들 중의 하나는 병목구간의 용량으로 볼 수 있는 최대통과가능교통량(정상류에서의 용량) 및 최대통과교통량(정체류에서의 용량)이 기존의 용량개념과 같이 불변의 값이 아니고 수요교통량에 따라 변하는 가변적 용량이라는 점이다. 따라서 정체의 유형화와 가변적 용량 개념의 도입을 통해서 본 연구를 통해 구축된 고속도로 운영상태 분석 방법론은 고속도로 기하구조 조건에 의해 결정되는 물리적 병목구간에만 국한하지 않고 잠재적 병목구간(사고 및 공사 등의 돌발상황 발생구간 뿐만 아니라, 진출 연결로의 대기행렬이 본선으로 넘치는 분류부 등)에 대해서도 수요교통량에 따른 정체류 분석이 가능하였다.

• 동력기계공학회지
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• 제4권3호
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• pp.34-39
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• 2000

Performance data in the literature on air lift pumps have been based primarily on pumps of long length and large diameter (high lift pumps). Since mariculture operations involve pumps of relatively short length and small diameter, performance data are required for efficient operation. To provide such data, an experimental apparatus was designed and fabricated to test all lift pumps from 2.1 to 3.4 cm inside diameter and from 40 to 300 cm in length. Instrumentation was provided to measure water flow rate and air flow rate as well as water temperature, air temperature, and pressure throughout the system. Results from this study correlate well with high lift pump data in that, for a given pump geometry, maximum water flow occurs for a specific air flow rate. Driving the pump with air flows larger or smaller than this optimum flow rate will decrease the pumping rate. The optimum flows are significantly different for low lift pumps compared to high lift pumps. However, the pumping rate for low lift pumps approaches that for high lift pumps with increasing length.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1491-1496
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• 2009

Fluid flow and structural analyses of an electronic expansion valve (EEV) using CO2 as a working refrigerant are carried out to estimate the mass flow rate and maximum stress. An engineering sample EEV that the orifice diameter is 1.8 mm was fabricated. The mass flow rates were measured at various EEV inlet temperatures and pressures for several EEV openings using experimental heat pump system. The sample EEV has over 35 MPa burst pressure and the maximum mass flow rate of CO2 through the EEV increased to 100 g/s at full opening condition.

• Journal of Biosystems Engineering
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• 제31권3호
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• pp.146-152
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• 2006

Most upland in Korea have irregular field shapes. Boom sprayers working alone winding row will show considerable differences of spraying amount per unit area between left and right booms. If flow rates of both booms are equal. This phenomenon becomes significant as steering radius of sprayer decreases. This study was performed to seek a method which reduce the difference of the spray amount between left, right and center booms while spraying along curvy rows. A flow rate control method for keeping application rate of each boom section constant was proposed and experimentally proved using a boom sprayer attached to a cultivating tractor. The flow rate control device was composed of 3 ball valves and a rotary angle sensor. The rotary angle sensor showed a symmetric voltage output with respect to steering radius. The spray overlapping was happened in a boom nearby the steering center when steering radius of the sprayer was less than 5.2 m. Flow rates for left, right and center booms were regulated using ball valves based on the steering radius and spraying areas ration of right/left boom. The Maximum spraying area ratio ($S_{LR}$) of left to right boom section was 1:3.6 at the steering radius of 5.2 m. However, The Maximum achieved right and left spraying flow ratio was 1:2.7.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.542-545
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• 2008

Experiments have been performed to investigate effects of pulsating cathode flow on a 10-cell proton exchange membrane fuel cell (PEMFC) stack. For all the experiments, the flow rate, temperature and relative humidity of hydrogen at the anode inlet are fixed. The effects of the pulsating frequency, amplitude and flow rate at the cathode inlet on performance of 10-cell PEMFC are examined. The polarization and power curves show that the power output and limiting current is substantially increased when the pulsating component is added to cathode flow channel. The maximum power output increases by up to 38% and enhancement of the overall performance is more pronounced at lower flow rate region.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1037-1049
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• 2001

Considerable interest has evolved in the flow of non-Newtonian fluids in channels of noncircular cross section in compact heat exchanges. Analytical solution was developed for prediction of the flow rate and maximum velocity in steady laminar flow of any incompressible, time-independent non-Newtonian fluids in straight closed and open channels of arbitrary, but axially unchanging cross section. The geometric parameters and function of shear describing the behavior of the fluid model were evaluated for fluid flow among a bundle of rods arranged in triangular and square array. Numerical values of dimensionless maximum velocities, mean velocities, pressure-drop-flow parameters and friction factors were evaluated as a function of porosity and pitch-to-radius ratio.