• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.163-163
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• 1999

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.201-207
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• 2001

We modeled the liquid film dryout(LFD) process for both tube and annulus which have uniformly heated vertical channels. We set phenomenological initial conditions in the model. The initial void fraction on the onset of the annular flow location is derived from the physical chum-to-annular flow criterion with the help of the drift-flux-model. The initial thermodynamic-equilibrium-quality is calculated by iteration with the flow quality to find the onset of the annular-flow location. Present model tends to predict very well at the lower exit quality but under-estimates at the higher exit quality. We found that the prediction error of the present model is gradually bigger as the inlet subcooling approaches near the saturation. We obtained excellent results for both tube and annulus channels as the mean of 0.97 and root-mean-square error of 11% for the number of 3883 experimental data on tubes, and of 0.96 and of 12% for 593 on annuli. The present model extended the applicable range to the relatively low exit quality region than previous LFD models.

• The Korean Journal of Ecology
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• v.14 no.3
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• pp.327-343
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• 1991

Clonal growth and rhizome architecture of calmagrostis epigeios, were studied in a 15-year old coastal reclamed land. As c. epigeios patch grew from center to margin radially over time, concentric annuli were added. the radial increases of the mature patch were 80~130cm/yr. the patch ages of c. epigeios estimated by relationships between the diameter and is radial increament, were 1~6year old. There were the marked variations of density, phytomass, shoot height and inflorecence frequency with increasing age of rhizome system within the patch. the maximum performance occurred at 2-year-old concentric annuli of the patch. The growth phasic continuum with aging was divided into 5 grwth phases ; pioneer, building, matyre, senile and degenerate. The rhizome aging had a more significant effect on the inflorescence frequency than on the other attributes. new rhizomes tended to diverge from the direction of the parent ramet by sympodial growth. in a 1-year-old patch, average length of rhizome segment was 7cm, average number of internode was 6, and the tillering frequency was 27%. The tillering in the early stage resultd in the increase of shoot density and the producation of multibranching rhizome. as the result of that, circular patchwas formed in a year. The branching structure based on such facts was represented graphically in branching degree of 60 and 100. therefore, c. epigeios with clonal growth may establish and grow vigorously earlier than other glycophytes in high salt conditions such as the coastal reclaimed land.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.856-866
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• 1987

In the present paper a statistical method using probability density function has been applied to investigate experimentally the flow patterns and fluctuations of time-averaged local void fraction in air-water two-phase mixtures which flow vertically upwards in concentric annuli. This study was carried out using three vertical concentric annuli. The annular test section consists of a lucite outer tube whose inside diameter is 38mm and a stainless steel inner rod. The rod diameter is either 12mm, 16mm or 20mm. The two-phase flow patterns observed in the experiment were bubbly, slug, annular and each transition patterns. It was first demonstrated that the variance, coefficients of skewness and kurtosis calculated from probability density function on time-averaged local void fraction can be used to identify the flow patterns in the annular passage, and the fluctuation of time-averaged local void fraction varies with the radial position in annular gap and the flow pattern.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.325-330
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• 1996

The existing CHF correlations for internally heated concentric annulus channels are assessed using KAIST CHF database for uniformly heated vertical annuli. Six annulus correlations (Jannsen-Kervinen. Barnett, Levitan-Lantsman, Kumamaru et al., Doerffer et al., and Bobkov et at.) are chosen for assessment based on literature survey and Groeneveld et al.'s CHF table for round tube is also assessed for comparison. Among the above correlations, two are inlet-condition type and others local conditions type. To make the comparison meaningful, the local-condition-type correlations are assessed in two ways: direct substitution method (DSM) and heat balance condition method (HBM). Totally 1174 data are classified into 10 groups based on pressure and mass flux conditions and correlations are assessed to each group separately. Prediction capability of each correlation depends on the data group and none shows the best prediction over the entire group. In overall, the correlations by Doerffer et al. and Jannsen et al. appear to be the best, but Barnett or Levitan-Lantsman correlations also show reasonable prediction for most groups. However, the low-pressure, ]ow flow CHFs are not well predicted by any correlations. The CHF table for round tubes overpredicts the CHF in annuli at fixed local conditions.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.2
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• pp.169-175
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• 2014

The age and growth of rabbit fish, Siganus fuscescens were investigated from samples monthly collected in the coast of Jeju island, Korea from February to December 2012. Ages were determined from annuli in otoliths, and annuli were formed in one or two months immediately after spawning once a year. Also, main spawning period was estimated between July and August, thus rings were considered as annual marks. The von Bertalanffy growth equations estimated from a non-linear regression method were $L_t=37.24(1-e^{-0.33(t+1.24)})$ ($R^2=0.92$) for female and $L_t=31.44(1-e^{-0.45(t+1.23)})$ ($R^2=0.90$) for male, and the growth between female and male was different.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.28-35
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• 1988

Experimental study has been carried out on natural convection in the annuli formed by two isothermal horizontal inner and outer elliptic cylinders with uniform gap. The eccentricities of inner and outer elliptic cylinder and the gap ratio for the experimental model were 0.5078, 0.389 and 0.363 respectively. The temperature distributions were obtained through the analysis of interferograms which were taken by Mach-Zehnder interferometer in the range of Rayleigh number (Ra$_{L}$) from 0.34*10$^{4}$ to 3.07*10$^{4}$. It showed that flow was laminar when Ra$_{L}$.leg. 2.5 *10$^{4}$, while above the range of Rayleigh number we could get information on the fluctuation of interference fringe. Therefore, the upper limit of Ra$_{L}$ for the correlation equation of mean equivalent conductivity in reference(1) is confirmed. The flow pattern could be visualized by simple smoke test. The comparison of streamlines, isotherms, temperature distributions and local equivalent heat conductivity between existing numerical and present experimental results showed good agreement.ement.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.1-7
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• 2011

The paper concerns numerical study of fully developed laminar flow of a Newtonian water and non-Newtonian fluids, 0.2% aqueous of sodium carboxymethyl cellulose(CMC) solution in eccentric annuli with combined bulk axial flow and inner cylinder rotation. Pressure losses and skin friction coefficients have been measured when the inner cylinder rotates at the speed of 0~200 rpm. A numerical analysis considered mainly the effects of annular eccentricity and inner cylinder rotation. The present analysis has demonstrated the importance of the drill pipe rotation and eccentricity. In eccentricity of 0.7 of a Newtonian water, the flow field is recirculation dominated and unexpected behavior is observed. it generates a strong rotation directed layer, that two opposing effects act to create two local peaks of the axial velocity. The influences of rotation, radius ratio and working fluid on the annular flow field are investigated.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3313-3319
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• 2023

A phenomenological study on CHF in a bilaterally heated annulus with equal heat flux on both sides was experimentally performed. The working fluid of the present test was R-134a. Variation characteristics of CHF and transition of CHF occurrence location were investigated under different pressure, mass flux and quality conditions. With the increase of critical thermodynamic quality, it was found that CHF first occurred on the outer surface of the annulus, then simultaneously occurred on both sides, and finally occurred on the inner surface at relatively high critical quality. After the CHF location transitioned to the inner rod, the sharp fall of CHF in the limiting critical quality region was observed. The critical quality corresponding to the CHF location transition decreased with the increase of mass flux and pressure. Besides, CHF in tube, internally heated, externally heated and bilaterally heated annuli were compared under the same hydraulic diameter conditions. The present study is conducive to improving the understanding of complicated CHF mechanism in bilaterally heated annulus, enriching the experimental database, and providing evidence for developing accurate CHF mechanism model for annuli.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.44 no.4
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• pp.312-322
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• 2008

The age and growth of the sandfish, Arctoscopus japonicus were investigated from samples of the eastern sea danish seine and gill net fishery in the East Sea of Korea from February, 2004 to December, 2007. Ages were determined from annuli in otoliths and annuli were formed between December and February once a year. Also, the main spawning period was estimated to be between December and January, thus rings were considered to be annual marks. For the relationship between fork length and total weight, a multiplicative error structure was assumed because variability in growth increased as a function of the length. The relationship between fork length and total weight were $TW=0.0083FL^{3.01}(R^2=0.966)$ for female and $TW=0.0079FL^{3.04}(R^2=0.969)$ for male. The variability in growth was constant as a function of age, revealing an additive error structure. The von Bertalanffy growth parameters estimated by a non-linear method were $L_{\infty}=31.6cm$, K=0.266/year, $t_0=-0.835$ years for female and $L_{\infty}=27.7cm$, K=0.273/year, $t_0=-0.806$ years for male. Growth at age between male and female had a significant difference(P<0.001).