• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.1
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• pp.19-24
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• 2003

The objectives of this paper are to develop a new method of wettability mea-surement and to study the effect of surface roughness on the wettability in a $H_2O$/LiBr falling film absorber. Two absorber tubes with micro-scale roughness and a bare tube are tested in a falling film absorber installed in a test rig. Inlet solution temperature, concentration and mass flow rate are considered as key parameters. A new method is proposed to estimate the wettability of a tube by measuring a minimum mass flow rate to wet the tube completely. The wettability for the structured surfaces was higher than that for the bare tube. The wettability decreased linearly along the vertical location. The wettability increased with increasing the solution temperature and the solution mass flow rate. The experimental correlations of the wettability for the bare and the micro-hatched tubes were developed with error bands of$\pm20%\;and\;\pm10%$, respectively. This work can be used in the design of absorbers with micro-scale roughness.

• Proceedings of the SAREK Conference
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• 2004.11a
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• pp.106-106
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• 2004

• Proceedings of the SAREK Conference
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• 2005.06a
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• pp.185-185
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• 2005

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.05a
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• pp.183-189
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• 2004

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.85-85
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• 2004

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.121-125
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• 2007

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 is larger than the calculated one when the area ratio is larger than 1. 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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.1
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• pp.1-9
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• 1993

Mass transfer coefficients were measured for water vapor absorption into a LiBr-Water solution of 60wt% flowing down an absorber of vertical tube type. The absorber is copper tube of 25mm inner diameter and 1000mm length. The film Reynolds number were varied in the range of 35~130. The solution is fed from the top of the pipe, and the conditions of solution are supercooled liquid and superheated liquid. As results, the flowrates of LiBr solution which takes peak value of average absorption mass flux exist. Mass transfer coefficients decrease with increasing the flowrate of LiBr solution, and the decrease rate in the case of supercooled liquid is large as compared with that in the case of superheated liquid. But the absorption rate of supercooled liquid is decidedly superior to that of superheated liquid.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.4
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• pp.257-264
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• 1993

This is the second report of a three part study on the absorption and heat transfer characteristics of absorber, the correlation of refrigerating capacity and heating capacity. The 2nd report deals with the heat transfer characteristics of a vertical falling film type absorber of inner copper tube. The solute is LiBr-Water solution(60wt%) and the solvent is water vapor. The film Reynoles numbers are varied in the range of 35~130. The states of LiBr solution at the top of absorber are supercooled liquid and superheated liquid. The results are summarized as follows ; Heat transfer results reveal that for the absorption of falling film, the state of LiBr solution appears to be influential in determining the heat transfer. Thus, for the state of supercooled liquid, heat transfer coefficient decreases with increasing the film Reynolds number, but in the condition of superheated liquid, it increases conversely. The mass transfer coefficients that were presented in the 1st.report and heat transfer coefficients of this paper are presented as the dimensionless correlation. The optimum water flowrate which brings about maximum value of heat flux in the film exists, and that increases with increasing the cooling water temperature.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.4
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• pp.47-55
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• 2009

The purpose of this study is to verify the transfer function of input acceleration and output control force by linearizing a velocity-dependent damping term of Liquid Column Vibration Absorber (LCVA). Analytical and experimental research is conducted to identify natural frequency, damping ratio and participated mass ratio of LCVA with various section ratios of vertical and horizontal areas. Findings obtained experimentally by the shaking table test are compared with analytical findings using optimization technique with constraints. The results indicate that the level of liquid and section ratio of LCVA affect the characteristics of damping ratio and mass ratio. Damping and mass ratio increase as the section of vertical column of LCVA decreases, due to turbulence in the elbow of LCVA.

• Journal of Biosystems Engineering
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• v.37 no.6
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• pp.359-364
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• 2012

Purpose: This study was conducted to analyze the vibration absorption effect for the agricultural product transportation-trailer equipped with vibration absorbable connecting hitch, leaf spring suspension, and shock absorber simultaneously (HLS), comparing with the trailer equipped with vibration absorbable connecting hitch only(H), trailer equipped with connecting hitch and leaf spring suspension (HL), and existing trailer with no vibration absorption device (E). Methods: Vertical accelerations were measured at driver seat and front, middle, rear parts of trailer bottom with no load for 4 types of transportation-trailer, and analyzed using FFT analyzer. Results: The magnitude of average vibration accelerations occurred up to 20 Hz, at this low frequencies the severe damage for agricultural products could be represented, was lower (maximum 6 times) for HLS trailer compared with H trailer. And vibration absorption effect for HLS trailer was also higher up to 40-80 Hz and 80-100 Hz, but the difference was less. At driver seat, the vibration absorption effect was high severely for HL and HLS trailer, and the magnitude of vibration acceleration was showed less difference in comparing at trailer bottom. Conclusions: From the test results, it could be recommended that the agricultural products transportation trailer should be equipped with vibration absorption device of HLS.