• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.496-500
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• 1996

An air flow measurement device is proposed. The thermal characteristic of a semiconductor element is adopted as a cooling parameter of thermal convection rate. The difference between forced convection and natural convection of two Zener diodes results enough difference in temperature. Experiment at various air flow conditions shows the measuring capability of the air flow in a duct. This measuring device has some merits, such as a reliability n hard field condition, simple circuit for signal processing, small volume of the element, less air flow resistance, independance of various ai temperature. The experimental result shows that it is an exact and usefull air flow measurement device.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.746-754
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• 1987

A method for measuring three-dimensional turbulent flows by the hot-wire anemometer is introduced. Mojolla's method using the X-type probe is adopted and modified for the slantwire probe without the linearizer. The probe is aligned with specified angles to the given uniform flow and the shear layer to verify the measuring errors due to the three-dimensionality and the turbulence level. Errors in the measurements of mean velocities and Reynolds stresses increase with the degree of three dimensionality in the flow. The incoming flow angle of 20 degree seems to be the limit of reasonable flow measurements. But there still appear large data scatterings in Reynolds shear stresses.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.79-82
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• 2002

Three-dimensional pipe flows with elbows and tees for few different pipe fittings are calculated to estimate the effect of swirling flow on measuring accuracy of orifice flow meter. It is evaluated how the pressure difference across the orifice is dependent on the length of upstream straight pipe in a branch and how swirl intensity, swirl angel and axial velocity distribution affect the measuring error of orifice flowmeter. From the results, it is found that, regardless of flow rate specified in this calculation, the effect of the straight pipe length can be neglected for the lengths larger than thirty diameters although there still remain significant swirl at the orifice

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.152-156
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• 2007

It is very important to understand about mass flow rate variations of propellants generated by pressure fluctuation in the combustion chamber. Therefore, we have studied quantifying the variation of mass flow rate generated by pressure fluctuation. The flow velocity in orifice is acquired through theoretical approach after measuring the pressure in orifice and the flow area in orifice is measured by film thickness measuring device. Our results agreed with it in the very small error range comparing our results with velocity and mass flow rate in steady state. Thus, our result based on theoretical approach will help about measuring mass flow rate in non-steady state.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1783-1788
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• 2004

In the present paper, a micro flow sensor, which can be used at bio-delivery systems and micro heat pumps, is developed. For this, the micro flow sensor is integrated on a quartz wafer ($SiO_2$) and is manufactured by simple and convenient microfabrication processes. The micro flow sensor aims for measuring mass flow rates in the low range of about $0{\sim}20$ SCCM. The micro flow sensor is composed of temperature sensors, a heater, and a flow microchannel. The temperature sensors and the heater are manufactured by the sputtering processes in this study. In the microfabrication processes, stainless steel masks with different patterns are used to deposit alumel and chromel for temperature sensors and nichrome for the heater on the quartz wafer. The microchannel is made of Polydimethylsiloxane(PDMS) easily. A deposited quartz wafer is bonded to the PDMS microchannel by using the air plasma. Finally, we confirmed the good operation of the present micro flow sensor by measuring flow rate.

• Transactions of The Korea Fluid Power Systems Society
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• v.4 no.3
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• pp.22-27
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• 2007

The source flow ripple and the source impedance in hydraulic pump are characteristic values showing fluid-borne vibration characteristics decisively. We cannot measure these two characteristic values directly, but can measure them by some indirect methods. One representative indirect measuring method is ISO 10767-1. The authors constructed a hardware and a software for the measuring method based on ISO 10767-1. Through the error evaluation of the measured results, accuracy of the measuring method using ISO 10767-1 was examined in detail.

• Journal of Periodontal and Implant Science
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• v.28 no.2
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• pp.309-320
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• 1998

The periodontal health has been evaluated clinically by various epidemiological indices, and in researches by measurement of gingival crevicular fluid. Laser Doppler flowmetry is a reliable and objective method that allows immediate measurement of erythrocyte flux in approximately one cubic mm of the capillary bed without disturbing the tissues. The purpose of the present study was to determine whether human gingival blood flow was different according to measuring area, measuring time, and sex or not. Forty volunteers with good general and periodontal health, aged early twenties and unmarried, were selected. Laser Doppler flowmetry($floLAB^{(R)}$, Moor Instruments Ltd., England) was applied to measure the gingival blood flow of marginal gingiva, interdental papilla, attached gingiva and alveolar mucosa. The blood flow of interdental papilla was measured at 9-10 AM, 1-2 PM, and 5-6 PM. The difference of blood flow according to measuring area and measuring time was statistically analyzed by one way AOVA and Dunkan test, and the difference of blood flow between men and women was statistically analyzed by t-test. (1) Mean blood flow was significantly higher in alveolar mucosa than in the gingiva(p<0.05), and there was no significant difference in blood flow between marginal gingiva and interdental papilla(p>0.1). (2) Mean blood flow was significantly higher at 5-6 PM than at 9-10 AM and 1-2 PM(p<0.05). But there was no significant difference in gingival blood flow between 9-10 AM and 1-2 PM(p>0.1). (3) There was no significant difference in gingival blood flow between men and women(p>0.1). The above results suggest that the measurment of gingival blood flow using laser Doppler flowmetry may be clinically applicable to early determination of gingival inflammation and evaluation of healing status, but further studies are necessary to standardize and simplify the measuring procedure.

• Nuclear Engineering and Technology
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• v.32 no.5
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• pp.433-445
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• 2000

The interfacial area concentration (IAC) is one of the most important parameters in the two-fluid model for two-phase flow analysis. The IAC can be measured by a local conductivity probe method that uses the difference of conductivity between water and air/steam. The number of sensors in the conductivity probe may be differently chosen by considering the flow regime of two-phase flow. The four sensor conductivity probe method predicts the IAC without any assumptions of the bubble shape. The local IAC can be obtained by measuring the three dimensional velocity vector elements at the measuring point, and the directional cosines of the sensors. The five sensor conductivity probe method proposed in this study is based on the four sensor probe method. With the five sensor probe, the local IAC for a given referred measuring area of the probe can be predicted more exactly than the four sensor probe. In this paper, the mathematical approach of the five sensor probe method for measuring the IAC is described, and a numerical simulation is carried out for ideal cap bubbles of which the sizes and locations are determined by a random number generator.

• Journal of the Korean Society of Visualization
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• v.1 no.2
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• pp.29-37
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• 2003

During the past five decades or so, the characteristics of turbulent swirling flow have been studied extensively because of its great technological and scientific importance. It is well known that the swirling flow improves heat transfer in duct flow. The reason for this is due to the effect of streamline curvature associated with the tangential velocity component. Although many studies have been carried out to investigate the characteristics of the swirling flow in a circular tube. The experimental methods for measuring the velocity components are by hot-wire or LDV (Laser-Doppler-Velocimetry) measuring single point velocity so far. The present study was aimed to analyse the flow characteristics of swirling flow such as time-mean velocity vector, local velocity turbulence intensity and turbulence kinetic energy by using PIV(Particle-Image Velocimetry). The experiment was carried out for four Reynold numbers $1.0\times10^{4}$, $1.5\times10^{4}$, $2.0\times10^{4}$ and $2.5\times10^{4}$ of the measuring area.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.218-225
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• 2008

When the heat release and acoustic pressure fluctuations are generated in the combustor by irregular combustion, these fluctuations affect the mass flow rate of the propellants injected through the injectors. Also, the variations of the mass flow rate by these fluctuations again bring about irregular combustion and furthermore that is related with combustion instability. Therefore, it is very important to identify the mass variation for the pressure fluctuation on the injector and to investigate its transfer function. So, we first have studied quantifying the variation of mass flow rate generated in simplex swirl injector by injection pressure fluctuation. To acquire the transient mass flow rate in orifice with time, we have tried to measure of the flow axial velocity and liquid film thickness in orifice. The axial velocity is acquired through theoretical approach after measuring the pressure in orifice and the flow area in the orifice is measured by electric conductance method. As results, mass flow rate calculated by axial velocity and liquid film thickness measuring in orifice accorded with mass flow rate acquired by direct measuring method in the small error range within 1 percents in steady state and within 6 percents as average mass flow rate in pulsated state. Hence this method can be used to measure the mass flow rate not only in steady state but also in unsteady state because the mass flow rate in the orifice can acquire with time and this method shows very high accuracy based on the experimental results.