[en] An experimental study of interfacial condensation heat transfer was performed for countercurrent steam-water wavy flow in a horizontal circular pipe. The present experiments have been carried out using a horizontal pipe that has a length of 2m and inner diameter of 0.084m for wavy interface condition. By measuring the increase rate of local water bulk temperature, local condensation heat transfer coefficients were derived. In case of wavy flow in a pipe, comparing with the wide rectangular channel flow and with the circular pipe flow under smooth interface, there are great differences in the interfacial heat transfer characteristic. From the present experiments, total 105 data of heat transfer coefficient were obtained. The heat transfer coefficients were found to vary from 1.8 to 5 kW/m² .deg. C, the water and steam Reynolds numbers ranges from 3000 to 15000 and from 10000 to 24000, respectively. Based on the experiment data, new Nusselt number correlation was developed and the parametric effects of thick water layer, steam and water flow rates, and the degree of water subcooling were also examined. It was found that the local Nusselt number increase with steam and water Reynolds number and water Prandtl number. For the wavy interface condition, the local Nusselt number is more strongly sensitive to the steam Reynolds number than water Reynolds number in contrast to countercurrent stratified flow where the interface is smooth. It was visually observed that for a given water superficial velocity, the transition from smooth to wavy interface occurred at lower steam superficial velocity than previous air-water experiment. Comparison of the present data with existing correlations showed that the existing correlations are not directly applicable to the horizontal circular piping of Nuclear Power Plant

[en] An experimental study has been performed to investigate the droplet de-entrainment and air-water countercurrent flow limitation (CCFL) in the upper plenum during a loss-of-coolant accident (LOCA). Three separate experiments are performed in this study: (a) water accumulation and CCFL in the upper plenum with a multi-hole plate; (b) droplet de-entrainment by inertial impact on vertical rods in an air-droplet mixture flow; (c) droplet de-entrainment in the horizontal pipe. In the first experiment, an experimental study is conducted to investigate the onsets of water accumulation and CCFL through perforated plates inside a vertical tank. The thickness of plates is 1 cm and 4 cm, with a relatively large hole diameter of 5 cm. The numbers of holes are 4 and 12. We examine the effects of the number of holes, plate thickness, water injection method and the location of air vent line on the onset of water accumulation or on the onset of CCFL. In addition, we investigate the influence of the location of air vent line on water level distributions. Experimental results show that the onset of water accumulation is promoted as the number of holes decreases and the water injection lines increase, while the plate thickness and the location of air vent line have a negligible effect on the onset of water accumulation. The location of air vent line in the upper plenum does not affect the water level distribution on the plate. For given water flow rate, the onset of CCFL occurs at the nearly same air flow rate regardless of the plate thickness. The negligible effect of the plate thickness on the water accumulation and CCFL means that the water accumulation and CCFL are initiated at the top of the plate rather than at its bottom. The gas flow rate per hole required for the onset of CCFL is relatively higher in the multi-hole plate than in the single tube because some of tubes in the multi-hole plate provide a flow path for liquid with less air-liquid resistance than in the single tube. In the second experiment, we experimentally investigate the de-entrainment of droplets by inertial impaction on an array of vertical rods in an air-droplet mixture flow. The de-entrainment efficiencies are measured for a single rod, for a single row of rods, and for a multi-row of rods. We investigate the effects of the droplet mass flux (0.5 kg/²ms to 5.4 kg/²ms), the droplet Weber number (3000 to 8000), the air velocity (0 m/s to 6 m/s), the rod geometry, and the surface roughness and the rod diameter-to-pitch ratio effect on the de-entrainment. The results for a single rod show that the de-entrainment efficiency decreases slightly as the droplet mass flux increases; however, in our experimental ranges, there is negligible dependence on the droplet Weber number, the air velocity, and the surface roughness. The rod geometry affects the de-entrainment efficiency. The results for a single row of rods show that the existence of neighboring rods promotes de-entrainment due to droplet splashing, and we develop a correlation to show the effect of diameter-to-pitch ratio on the de-entrainment. Using information on the de-entrainment efficiencies of a single rod and those of a single row of rods, we propose a correlation that predicts the de-entrainment efficiency for a multi-row of rods with a staggered array. The RMS errors of the correlation from the de-entrainment efficiencies experimentally obtained are within 13.5 percent. In the third experiment, the de-entrainment of droplets in hot-legs is experimentally evaluated. To simulate the hot-leg, a horizontal pipe with a diameter of 0.084 m is connected to the upper plenum. The diameter-to-length ratio of the test section is 0.168. To evaluate the de-entrainment rate, liquid film is extracted at two different points (0.15 m and 0.65 m distant from pipe inlet) along the axial direction of the test section. The ranges of droplet mass flux are 0.52 to 1.7 kg/²ms. The ranges of superficial velocity of air are 15 to 20 m/s. The results show that about 80% of droplets are de-entrained within 0.5 m from the inlet of the test section regardless of droplet mass flux and air velocity. On the basis of the experimental data, a correlation is developed to predict the de-entrainment fraction in the horizontal pipe

[en] In designing electrical products, the joule heating phenomenon caused by the resistance of volume and contact should be considered to avoid damages and fire caused by overheating. This study established a joule heating analysis technique that considers volumetric and contact resistances by comparing with experimental results. Equivalent resistance was introduced to predict the joule heating generation of wires. Finite element models, including wires with equivalent volumetric resistance, a contact area with measured electrical contact resistance, and a block with perfect electrical insulation, exhibit good agreement between the results of the experimental measurements and the finite element analysis using five different materials.

[en] A new multi-dimensional component in MARS has been developed to get the flexible three dimensional capabilities in the system, and to allow the user to model more accurately the multi-dimensional hydrodynamic features of reactor applications. The previous study of Bae et al. showed that the MARS multi-dimensional analysis had meaningful agreement in the phenomenological validity about the ECC water behaviors in the upper plenum. In this study, UPTF UPI test (Test 20) is simulated to assess the predictability of MARS-KS multi-dimensional analysis for the behavior of ECC water. The preliminary calculation results are compared with the UPTF experimental data

[en] Comparison of the experimental data obtained by Kotsubo and Williams our theoretical values for the sound velocity as a function of atomic layers in two-dimensional sup(4)He films is made. This comparison is performed only within the region D<=3.2(atomic layers). Numerical values of the Landau parameters which we obtained are in good agreement with those previously known. There is excellent agreement between the experimental data and the theoretical values for the third sound velocity. (Author)

[en] The TRAC/RELAP Advanced Computational Engine (TRACE) is the latest in a series of advanced, best estimated reactor systems codes developed by U.S. Nuclear Regulatory Commission for analyzing transient and steady-state neutronic-thermal-hydraulic behavior in light water reactors. In this study, we assess the ability of TRACE code (version 5.0 patch 4) to predict the countercurrent flow limitation (CCFL) at the perforated plate. The tests conducted by NO et al. are used in this assessment. The results of TRACE calculation are compared with the CCFL curve derived from the experimental data. We assessed the ability of TRACE code (version 5.0 patch 4) to predict the CCFL at the perforated plate. The results show that the calculated results are in excellent agreement with the Wallis-type CCFL curve. This study provides the code users with the insight that TRACE code predicts fairly well the CCFL behavior of air-water countercurrent flow

[en] The wall condensation models of MARS-KS and SPACE codes adopt the Colburn-Hougen diffusion method to solve for the liquid-gas interface temperature in the presence of noncondensable (NC) gases. Recent studies reported that there was an error in the vapor mass flux term when the models were implemented in the codes. This error causes the codes to underestimate the steam condensation rate. This tendency becomes more noticeable with the increase in the mole fraction of NC gases. In this study, we assess the modified condensation model of MARS-KS and SPACE codes. The calculation results of modified version of the codes (MARS-KS 1.3r1 and SPACE 2.16r1) are compared to those of the original version (MARS-KS 1.3 and SPACE 2.14) and the experimental data. The modified model predicts higher heat fluxes and HTCs than the original model due to the increase in the steam condensation rate. At relatively high air mass fraction, the modified model increases the discrepancy between the measured data and calculated values

[en] Ti-8Ta-3Nb has been developed as a new biomaterial. The experimental specimens are as-cast and forged Ti-8Ta-3Nb alloys. Treatment in a solution, ranging from 760 to 960 .deg. C has carried out. The microstructural research has carried out after the solution treatment and the hardness was measured. The specific heat and the length variations of Ti-8Ta-3Nb were also measured. The optimum temperature for the solution heat treatment of Ti-8Ta-3Nb was found to be 880 .deg. C. This was based on the mechanical properties and the volume fraction of α phase and their phases shown from the results of the solution heat treatment. From the results, the β transition temperature of Ti-8Ta-3Nb was found to be between 860 .deg. C and 880 deg. C

[en] Neurofibromas are common benign tumors and can originate from any nerve tissue in the body. A solitary neurofibroma in breast parenchyma has rarely been reported, however. We report a neurofibroma originating from breast parenchyma in a 61-year old woman. On mammography, the mass appeared as a well marginated and circumscribed mass, suggesting a benign tumor, and after excisional biopsy, was pathologically proven to be a neurofibroma

[en] In order to validate the operational performance of the PAFS, KAERI has performed the experimental investigation using the PASCAL (PAFS Condensing heat removal Assessment Loop) facility. In this study, we simulated the KAERI PASCAL SS-540-P1 test with MARS-KS V1.4 and TRACE V5.0 p4 codes to assess the code predictability for the condensation heat transfer inside the passive auxiliary feedwater system. We simulated the KAERI PASCAL SS-540-P1 test with MARS-KS V1.4 and TRACE V5.0 p4 codes to assess the code predictability for the condensation heat transfer inside the passive auxiliary feedwater system. The calculated results of heat flux, inner wall surface temperature of the condensing tube, fluid temperature, and steam mass flow rate are compared with the experimental data. The result shows that the MARS-KS generally under-predict the heat fluxes. The TRACE over-predicts the heat flux at tube inlet region and under-predicts it at tube outlet region. The TRACE prediction shows larger amount of steam condensation by about 3% than the MARS-KS prediction