• Journal of the Korean Society of Industry Convergence
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• v.11 no.4
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• pp.157-163
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• 2008

The present study investigated the pressure drop and the total frost mass of the louvered fin type heat exchanger, which is widely used at the air-conditioning system. The pressure drop due to the frosting phenomenon and the total frost mass were investigated by changing the wet bulb temperature condition of the inlet air. Hence the brain of 55wt% was used as a cooling solution instead of a common refrigerant. The temperature difference between the brine and the tube outside wall at the outlet of heat exchanger was $10^{\circ}C$, at maximum, higher than that at the inlet of heat exchanger. As the wet bulb temperatures were increased, the pressure drop was linearly increased due to the increment of frost mass. And the increment of heat exchange rate was smaller than that of inlet air enthalpy due to the increment of frost mass. The pressure drop of air side was rapidly increased due to the progress of frosting phenomena. The run time that the pressure drop occurred rapidly was decreased by the growth of frost.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1614-1616
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• 1998

Insulation performance of major components of prefabricated joint such as epoxy insulation unit and premolded rubber cone are guaranteed by material selection design and proper manufacturing. On the other hand insulation performance of the interfaces between the premolded rubber cone and the epoxy insulation unit and the cable insulation is maintained by keeping the premolded rubber cone to close contact with such insulation by spring. Electric characteristics of a interface depend on the contact pressure, but the required characteristics are assured so far as a proper contact pressure is maintained. In this report, the interfacial pressure by pressure sensors both in the early stage and after heating cycle were measured and the simulation by FEM program were presented. The comparison of these two results show that interfacial pressure could be controlled optimally by changing the spring length and lubricant state of the interface.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.5
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• pp.702-710
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• 1999

U-shaped bellows are usually used to piping system pressure sensor and controller for refriger-ator. Bellows subjected to internal pressure are designed for the purpose of absorbing deformation. Internal pressure on the convolution sidewall and end collar will be applied to an axial load tend-ing to push the collar away from the convolutions. To find out deformation behavior of bellow sub-jected to internal pressure the axisymmetric shell theory using the finite element method is adopted in this paper. U-shaped bellows can be idealized by series of conical frustum-shaped ele-ments because it is axisymmetric shell structure. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displace-ments are added to r-z cylindrical coordinates of nodal points. The new stiffness matrix of the sys-tem using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacement that is the step by step method is used in this paper. The force required to deflect bellows axially is a function of the dimensions of the bellows and the materials from which they are made. Spring constant is analyzed according to the changing geometric factors of U-shaped bellows. The FEM results were agreed with experiment. Using developed FORTRAN PROGRAM the internal pressure vs. deflection characteristics of a particu-lar bellows can be predicted by input of a few factors.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.561-571
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• 1997

In this paper, the fundamental equations are developed for the pulsatile laminar flow generated by changing the oscillatory flow with $0{\leq}f{\leq}48Hz$ into a steady one with $0{\leq}Re{\leq}2500$ in a rigid circular pipe. Analytical solutions for the wave propagation factor k, the axial distributions of cross-sectional mean velocity $u_m$ and pressure p are schematically derived and confirmed experimentally. The axial distributions of centerline velocity and pressure were measured by using Pitot-static tubes and strain gauge type pressure transducers, respectively. The cross-sectional mean velocity was calculated from the centerline velocity by applying the parabolic distribution of the laminar flow and it was confirmed by using the ultrasonic flowmeter. It was found that the axial distributions of cross-sectional mean velocity and pressure agree well with theoretical ones and depend only on the Reynolds number Re and angular velocity $\omega$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.1 s.244
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• pp.52-59
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• 2006

The vibration of hydraulic piston pumps is induced by the periodically changing cylinder chamber pressure whose waveform is significantly influenced by valve plate geometry. In this study, the force input to the housing of a bent-axis type hydraulic piston pump was computed by deriving the dynamic equations of its piston and cylinder barrel. The vibration intensity of the pump was represented by the acceleration amplitude of its housing. In order to comparatively evaluate the influence of valve plate geometry on the vibration of pump housing, two different types of valve plate were tested. The computed results showed good agreement with the experimental data, indicating that the vibration acceleration of pump housing is rather dependent on the variation amplitude of balance coefficient than the changing slope or overshoot of cylinder chamber pressure. It was also confirmed that the design effect of valve plates could be directly examined out by monitoring the vibration acceleration of pump housing.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.847-852
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• 2009

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle inside feed-water heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare wall thinning range according to change entrance nozzle diameter and position with reference numerical analysis model's wall thinning range, various numerical analysis models applied. In case of changing diameter, four different diameter is applied. And a side of nozzle position, two different position-vertical type and parallel type-is applied. And then this paper describes operation of numerical analysis which is composed similar condition with real feed water heater. In conclusion, this study shows effective design for shall wall thinning by changing nozzle diameter and position.

• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.4 s.23
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• pp.146-151
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• 2005

The burning rates of combustible cartridge cases(CCCs) of 120mm kinetic energy ammunition were measured by CBT(Closed Bomb Tester). The burning coefficient was 1.4 for CCC fabricated by Post Impregnation(PI) process, and 1.0 for that by Beater Additive(BA) process. The BA process CCC showed the fixed burning coefficient of 1.0 in spite of changing the composition of CCC. As the Korean Future Main Battle Tank is requiring the high penetration performance compared with that of KlAl tank ammunition(K276), CCC was designed to have higher impetus composition than that of K276 composition(525J/g). The optimum impetus was 600J/g when considering the increases of pressure and muzzle velocity with increasing impetus. When impetus of CCC by changing the composition increased from 525J/g to 600J/g, the muzzle velocity of 12m/s at pressure increase of 3500psi increased in case of using SCDB propellant.

• Journal of Korea Multimedia Society
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• v.22 no.11
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• pp.1280-1287
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• 2019

For developing a wireless implantable device to monitoring the artery variation in real-time. The concept of a special vessel variation measurement capacitive sensor is presented in this paper. The sensor consists of two part; main sensor to measuring the arterial variation, and reference sensor is used to improve the accuracy of the capacitance value variation. Before sensor manufacture, a model of the sensor attached on the artery was designed in 3D to conduct in the FEA simulation to validate the validity and feasibility of the idea. The artery model was designed as layered structures and made of collagenous soft tissues with intima inside, followed by the media and the adventitia. Also, a grease layer was designed in the inner of the arterial wall to imitate the clogged arteries. The simulation was divided into two parts; sensor performance test by changing the diameter of the grease layer, and arterial wall tension test by changing the blood pressure. As the simulation results, the capacitance value measured by the proposed sensor is decreased follow the diameter of the grease increased. Also, large elastic deformation of the arterial wall since changing the blood pressure has been observed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.4
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• pp.337-345
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• 2008

this study, three dimensional surface pressure distributions of SWIM whose main wing has NACA4412 airfoil with NACA0012 flaps were experimentally measured by pressure sensitive paint. Surface pressures on suction and pressure sides of the wing were measured by changing an angle of attack at a Reynolds number of 3.1x105 in KARI 1m subsonic wind tunnel. The experimental results showed that as an angle of attack increases minimum pressure region on a suction side moved from the wing root to the tip and low pressure region around trailing edge of the wing tip which causes wing tip vortex was observed. Although low pressure region at the tip still observed at an angle of attack 15 deg., other area on a suction side showed flat pressure distribution in a span-wise direction. It was also observed that the mean value of pressure coefficients was about 0.077 through a comparison between PSP and pressure taps at the same test conditions.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3056-3061
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• 2007

The technology of AC solenoid valves is now considered as a core technology in the fields of the production line of semi-conductor chips and the micro fluid chips for medical applications. And AC solenoid valves, which operate by compressed air, are characterized by high speed response, great repeatability and that the pressure on the cross sectional area of poppet is kept constant regardless of the fluctuation of the pressure exerted on the ports. In this study, AC solenoid valves that posses the high-speed responsibility and the high rate of flow have designed and analyzed through the law of equivalent magnetic circuit and Finite Element Method (FEM) respectively. In case of poppet, Flow field characteristic was analyzed by the variation of poppet and it was able to display flow field by changing the location of the poppet. Also, we verified possibility of the design through the static and dynamic pressure and the 3D distribution curve of the force by working the front poppet.