• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.11a
• /
• pp.224-229
• /
• 1996

An experimental study on critical heat flux (CHF) and two-phase flow visualization has been performed for water flow in internally-heated, vertical, concentric annuli under near atmospheric pressure. Tests have been done under stable forced- circulation, upward and downward flow conditions with three test sections of relatively large gap widths (heated length = 0.6 m. inner diameter = 19 mm, outer diameter = 29, 35 and 51 mm). The outer wall of the test section was made up of the transparent Pyrex tube to allow the observation of flow patterns near the CHF occurrence. The CHF mechanism was changed in the order of flooding, chum-to-annular flow transition, and local dryout under a large bubble in churn flow as the flow rate was increased from zero to higher values. Observed parametric trends are consistent with the previous understanding except that the CHF for downward flow is considerably lower than that for upward flow.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.33 no.4
• /
• pp.360-369
• /
• 1997

We calculated the residual current forced by buoyancy, wind stress, and tidal stress in the Chinhae Bay using a three-dimensional diagnostic model. The calculated current was also compared with the observation. The flow directs outward from the central area of the Bay in the upper layer, and also forms eddy-shape stucture in the upper and middle layers. The flow of bottom layer shows an opposite pattern compared to those of top and middle layers. The maximum speed was 6.05 em/see (September) and 3.49 cm/sec (November) in the upper layer, and 4.39 cm/sec on both month in the middle layer. The Kinetic energy of November (8.39xlO' W) was larger than that of September (1.24xlO 'W), mainly resulting from larger buoyancy effect in September. In spite of the roughness of the grid size(1 km) and wind date, the calculated flow shows eorrelation(r=0.71) with the observation. We expect that the correlation be increased by increased by adopting the fine grid and the variable coefficients of diffusion and viscosity.

• Solar Energy
• /
• v.20 no.4
• /
• pp.9-16
• /
• 2000

This paper represents the heat storage performance of the flat plate solar collector. This research aims to application for fishing ship on the sea, and the solar collector has among of motions with pitching and rolling thus, this collector has to be a forced type circulation. In this research, we investigated the solar collector performance for the various collector tilt angle. As the experimental results with three types, we found that the S-type collector was excellent.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.7
• /
• pp.563-571
• /
• 2003

The forty vapor-liquid equilibrium data of the binary system, HFC125＋Propane, were measured between 273.15 and 313.15 K at 10 K interval and the composition range 0.2∼0.75, respectively. Experiments were performed in a circulation type apparatus in which the vapor phase was forced through the liquid phase. The composition at equilibrium were mea-sured by gas chromatography, and its response was calibrated using gravimetrically prepared mixtures. Vapor-liquid equilibrium data were calculated by using CSD equation of state and compared with the experimental data.

• Proceedings of the SAREK Conference
• /
• 2006.06a
• /
• pp.105-110
• /
• 2006

Several types of solar water heating system were analyzed in characteristics and proper systems were proposed under Korean climates. In particular, the forced circulation type with a spiral-jacketed storage tank has a potential to be used widely in a small and a part of middle systems when the stratification of the storage tank can be enhanced by a precise design.

• Nuclear Engineering and Technology
• /
• v.18 no.4
• /
• pp.261-266
• /
• 1986

The purpose of this research was to investigate the de-entrainment of boron for evaporators used in nuclear power plants. The forced circulation and semi-continuous type evaporator was used in the experiment. Cyclone and glass-wool packed column which is supposed to provide good decontamination factor as well as easy maintenance, were selected as de-entrainment devices to be used in the evaporation of radioactive liquid wastees. The de-entrainment device combined with cyclone and glass-wool column has shown overall DF more than 1, 000 for boron.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.4 no.3
• /
• pp.168-177
• /
• 1992

Some features of tidal energy horizontal flux in the ocean are considered. using the concept of “energy flux ellipses” which is a hodograph of momentary fluxes over a tidal semi-period. A number of characteristics of this ellipse are considered as well as some peculiarities of energy flux field in different types of tidal waves and their combinations (plane, Kelvin, Sverdrup, Poincare, amphidromic system). For forced tidal waves in equatorial channels some results are obtained explaining the dependence of energy flux direction on the channel dimensions.

• Journal of Aquaculture
• /
• v.16 no.1
• /
• pp.1-7
• /
• 2003

A new technique combining forced-feeding and dorsal aorta cannulation was developed to monitor concentration of nutritions in the blood circulation and their metabolites in rainbow trout. To study the effect of dorsal aorta cannulation on stress, 30 rainbow trout (523$\pm$5.4 g; Mean$\pm$SD) were divided into 6 groups of 5 individuals each. A group was anesthetized and blood samples were taken at 0, 3, 6, 12, 24 or 48 h after dorsal aorta cannulation. Hematocrit peaked at 6 h and returned to 0 values by 12 h after dorsal aorta cannulation. Plasma cortisol and glucose concentrations also peaked at 6 h and returned to 0 values by 48 h after dorsal aorta cannulation. Based on the plasma cortisol and glucose concentrations, the rainbow trout recovered from the operation of dorsal aorta cannulation within 48 h. To compare the patterns of plasma free amino acid concentrations after force-feeding in the fish with dorsal aorta cannulation, 5 dorsal aorta cannulated individuals (511$\pm$6.2 g) were kept in a cage. After 48 h starvation, they were anesthetized and blood samples were taken at 0, 4, 8, 12, 24, 36 or 48 h after forced-feeding. The concentration of all plasma free amino acids, except isoleucine, leucine, phenylalanine, and tryptophan, also peaked at 4 h and returned to 0 values by 24 h after feeding. The combined technique allows forced-feeding and repeated sampling of blood in rainbow trout with minimum stress.

• Nuclear Engineering and Technology
• /
• v.18 no.4
• /
• pp.273-280
• /
• 1986

The purpose of this study is to obtain the experimental data of the forced flow dryout heat flux in a heat generating debris bed which simulates the degraded nuclear reactor core after severe accident. An experimental investigation has been conducted of dryout heat flux in an inductively heated bed of steel particles with upward forced flow rising coolant circulation system under atmospheric pressure. The present observations were mainly focused on the effects of coolant mass flux, particle size, bed height, and coolant subcooling on the dryout heat flux The data were obtained when carbon steel particles in the size distribution 1.5, 2.5, 3.0 and 4.0 mm were placed in a 55 mm ID Pyrex glass column and inductively heated by passing radio frequency current through a multiturn work coil encircling the column. Distilled water was supplied with variation of mass flux from 0 to 3.5 kg/$\textrm{cm}^2$ s as a coolant in the tests, while the bed height was selected as 55 mm and 110 mm. Inlet temperature of coolant varied by 2$0^{\circ}C$ and 8$0^{\circ}C$. The principal results of the tests are: (1) Dryout heat flux increases with increase of upward forcing mass flux and particle size; (2) The dryout heat flux at the zero mass flux obviously depends on the Particle size as Previous studies; (3) The forced flow dryout heat flux in the shallow bed is somewhat higher than that in the deep bed,

• Journal of the Korean Society of Safety
• /
• v.35 no.3
• /
• pp.96-104
• /
• 2020

The numerical simulations were conducted to investigate the thermal-fluid phenomena occurred inside the experimental apparatus during a PCCS, used to remove heat released in accidents from a containment of light water nuclear power plant, operation. Numerical simulations of the flow and heat transfer caused by wall condensation inside the containment simulation vessel (CSV), which equipped with 18 vertical heat exchanger tubes, were conducted using the commercial computational fluid dynamics (CFD) software ANSYS-CFX. Shear stress transport (SST) and the wall condensation model were used for turbulence closure and wall condensation, respectively. The simulation using the actual size of the apparatus. However, rather than simulating the whole experimental apparatus in consideration of the experimental cases, calculation resources, and calculation time, the simulation model was prepared only in CSV. Selective simulation was conducted to verify the effects of non-condensable gas(NC gas) concentration, CSV internal pressure, and wall sub-cooling conditions. First, as a result of the internal flow of CSV, it was observed that downward flow due to condensation occurred surface of the vertical tube and upward flow occurred in the distant place. Natural convection occurred actively around the heat exchanger tube. Due to this rising and falling internal flow, natural circulation occurred actively around the heat exchanger tubes. Next, in order to check the performance of built-in condensation model using according to the non-condensable gas concentration, CSV internal flow and wall sub-cooling, the heat flux values were compared with the experimental results. On average, the results were underestimated with and error of about 25%. In addition, the influence of CSV internal pressure and wall sub-cooling was small, but when the condensate was highly generated due to the low non-condensable gas concentration, the error was large compared to the experimental values. This is considered to be due to the nature of the condensation model of the CFX code. However, in spite of the limitations of CFD, it is valid to use the built-in condensation model of CFD for PCCS performance prediction from a conservative perspective.