• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.5
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• pp.444-452
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• 2010

This paper presents design and performance evaluation of electro-rheological(ER) shock absorber for electronic control suspension(ECS). In order to achieve this goal, a cylindrical ER shock absorber that satisfies design specifications for a mid-sized commercial passenger vehicle is designed and manufactured to construct ER suspension system for ECS. After experimentally evaluating dynamic characteristics of the manufactured ER shock absorber, the quarter-vehicle ER suspension system consisting of sprung mass, spring, tire and the ER shock absorber is constructed in order to investigate the ride comfort and driving stability. After deriving the equations of the motion for the proposed quarter-vehicle ER suspension system, the skyhook controller is implemented for the realization of quarter-vehicle ER suspension system. In order to present control performance of ER shock absorber for ECS, ride comfort and driving stability characteristics such as vertical acceleration and tire deflection are experimentally evaluated under various road conditions and presented in both time and frequency domain.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.31-39
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• 2011

This paper presents design and control of a quarter-vehicle magneto-rheological (MR) suspension system for ECS (electronic control suspension). In order to achieve this goal, MR shock absorber is designed and manufactured based on the optimized damping force levels and mechanical dimensions required for a commercial mid-sized passenger vehicle. After experimentally evaluating dynamic characteristics of the manufactured MR shock absorber, the quarter-vehicle MR suspension system consisting of sprung mass, spring, tire and the MR shock absorber is constructed in order to investigate the ride comfort and driving stability. After deriving the equations of the motion for the proposed quarter-vehicle MR suspension system, the skyhook controller is then implemented for the realization of quarter-vehicle MR suspension system. In order to present control performance of MR shock absorber for ECS, ride comfort and driving stability characteristics such as vertical acceleration of sprung mass and tire deflection are experimentally evaluated under various road conditions and presented in both time and frequency domain.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.3
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• pp.175-181
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• 1994

This paper deals with the correlation of absorption rate in absorber and evaporation rate in evaporator. The evaporator consists of a copper tube of 10mm dia, and 600mm long and chilled water flowing through the tube is fed by the chilled water circulator. The flowrate of LiBr-water solution in the absorber plays a significant role in determining the magnitude of the heat transfer rate from chilled water to refrigerant There exists a flowrate of solution which has a maximum value of heat transfer. It is interesting to note that the absorption rate of absorber increases with increasing the heat transfer rate of the evaporator. Also, absorption rate increases with evaportation rate, and the ratio(the former/the other) depends on the inlet temperature of LiBr-water solution in the absorber. The heating capacity in the absorber is higher than the refrigerating capacity in the evaporator.

• Journal of Energy Engineering
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• v.14 no.3 s.43
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• pp.194-202
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• 2005

The present study was analytically and experimentally carried out to predict the absorption characteristics on combined heat and mass transfer process in a vertical falling film of variable absorbers. Heat and mass transfer enhancements were analytically investigated. Effects of geometric parameters by insert device (spring) and corrugate, flow pattern on absorption performances has been also investigated. Especially, the optimal values of absorber geometry (ID=22.8mm, L=1150m) and kinetic variables (solution flow rate, flow pattern) for maximum absorption performance has been predicted by the numerical analysis. The maximum absorption performance in a numerical analysis and experiment was shown at the wavy-flow by insert device (spring).

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.8
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• pp.1239-1250
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• 2004

This research was concerned with the enhancement of heat transfer by surfactant added to the aqueous solution of LiBr. Different vertical tubes were tested with and without an additive of normal octyl alcohol. The test tubes are a bare inner surface. a groove inner surface, a corrugated inner surface and a spring inserted inner surface tubes. The additive concentration was about 0.08 mass%. The heat transfer coefficient was measured as a function of the film Reynolds number in the range of 20~200. Experiments were carried out at higher cooling water temperature of $35^{\circ}C$ to simulate an air cooling condition for several kinds of absorber testing tubes. The experimental results were compared with and without surfactant. The enhancement of heat transfer by Marangoni convection effect which was generated by addition of the surfactant is observed in each test tube. Especially, it is clarified that the tube with an inserted spring has the highest enhancement effect.

• Journal of Ocean Engineering and Technology
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• v.19 no.4 s.65
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• pp.9-14
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• 2005

In the present paper, the wave absorbing performance of the fully submerged horizontal porous plates has been investigated, numerically and experimentally. The submerged porous system is composed of multi-layered horizontal porous plates that are clamped at the vertical setwall, which are slightly inclined and placed vertically, in parallel, with spacing. The hydrodynamic interaction of incident waves with the rigid porous multi-layered plates was formulated within the context of linear wave-body interaction theory and Darcy's law. In order to validate the effectiveness of the present computing code, the numerical results were compared with the analytical and experimental results. It is found that triple horizontal porous plates with slight inclination, if properly tuned for wave energy dissipation against the standing waves in front of the vertical wall, can have high performances in reducing the reflected wave amplitudes against the incident waves over a wide range of wave frequency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.5
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• pp.604-611
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• 2003

This study was concerned with the enhancement of mass transfer by surfactant added to the aqueous solution of LiBr. Different vertical inner tubes were tested with and without an additive of normal octyl alcohol. The test tubes were a bare tube, groove tube, corrugate tube and inserted spring tubes. The additive concentration of normal octyl alcohol as a surfactant is about 0.08mass%. The Sherwood number was measured as a function of film Reynolds number 20~200. The experimental results were compared with those which use no surfactant. The enhancement of mass transfer by Marangoni convection effect which was generated by addition of the surfactant is proved for each testing tube Especially, it is clarified that the tube with the spring has the highest enhancement effect. A correlation of the experimental mass transfer data for the bare, groove, corrugate and insert spring tubes results expressed as the form of Sh=cㆍ Re$_{f}$ $^{n}$ .

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.653-658
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• 2008

LCVA has an advantage that its natural frequency can be easily controlled by changing the area ratio of the vertical column and horizontal part. The previous studies investigated the dynamic characteristics of the LCVA under harmonic load. This study experimentally obtained the first and second mode natural frequencies of the LCVA from shaking table tests using white noise and compared the values with the ones by previous study. Test results show that the measured first mode natural frequency of the LCVA has a different value compared with calculated one. The effective length($L_e$) was revised using by power equation. In the Case01 to 19, the standard deviation($s_r$) is 4.7292 and the coefficient of correlation(r) is 0.9856. In the Case21 to 61, the standard deviation ($s_r$) is 14.2143 and the coefficient of correlation(r) is 0.9935. The second mode frequency increases with the increasing area ratio, which is due to the sloshing motion effect resulting from the large area of the vertical column.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.2
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• pp.119-126
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• 2009

LCVA has an advantage that its natural frequency can be easily controlled by changing the area ratio of the vertical column and horizontal part. The previous studies investigated the dynamic characteristics of the LCVA under harmonic load. This study experimentally obtained the first and second mode natural frequencies of the LCVA from shaking table tests using white noise and compared the values with the ones by previous study. Test results show that the measured first mode natural frequency of the LCVA has a different value compared with calculated one. The effective length($L_e$) was revised using by power equation. In the case01 to 19, the standard deviation($S_r$) is 4.7292 and the coefficient of correlation(r) is 0.9856. In the case21 to 61, the standard deviation($S_r$) is 14.2143 and the coefficient of correlation(r) is 0.9935. The second mode frequency increases with the increasing area ratio, which is due to the sloshing motion effect resulting from the large area of the vertical column.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.8
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• pp.843-848
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• 2015

The objective of this study is to observe and optimize a typical ocean environment and reduce wave reflections in the wave flume. In order to generate ocean waves in the wave flume, a combination of a horizontal piston type wave generator and wave absorbers was installed in the channel. Two probes for measuring the wave heights, i.e., wave level gauges, were used to record the continuous variation of the wave surface, the phase difference, and the maximum (crest) and minimum (trough) points of the propagating waves. In order to optimize the shape and size of the propagating waves, several absorption methods were proposed. Apart from an active wave absorption method, we used methods that involved vertical porous plates, horizontal punching plates, and sloping-wall-type wave absorbers. To obtain the best propagating waves, a sloping-wall-type wave absorber was chosen and tested in terms of the constitutive filling materials and the location and shape of the plate. This study also focused on the theoretical prediction of the wave surface, separating them into the incident and reflective components. From the results, it is evident that the wave absorber comprising a hard filling material exhibits a better performance than the absorber comprising a soft material, i.e., the wave absorber can be a strong sink to control the energy of the incoming wave. In addition, larger wave absorbers correspond to lower reflectance because a larger volume can reduce the incoming wave energy. Therefore, at constant absorber conditions, the reflectance of the wave increases as the wave period increases. Finally, the reflectance of the wave was controlled to be less than 0.1 in this study so that the wave flume can be used to simulate an offshore environment.