• 한국전산유체공학회:학술대회논문집
• /
• 2003.10a
• /
• pp.2-2
• /
• 2003

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.1
• /
• pp.9-18
• /
• 2010

There are two kinds of models in two-phase pressured drop; homogeneous flow model and separated flow model. Many previous researchers have developed correlations for two-phase pressure drop in a microchannel. Most correlations were modified Lockhart and Martinelli's correlation, which was based on the separated flow model. In this study, experiments for adiabatic liquid water and nitrogen gas flow in rectangular microchannels were conducted to investigate two-phase pressure drop in the rectangular microchannels. Two-phase frictional pressure drop in the rectangular microchannels is highly related with flow regime. Homogeneous model with six two-phase viscosity models: $Owen^{(21)}$'s, $MacAdams^{(22)}$'s, Cicchitti et ${al.}^{(23)}$'s, Dukler et ${al.}^{(24)}$'s, Beattie and ${Whalley}^{(25)}$'s, Lin et ${al.}^{(26)}$'s models and six separated flow models: Lockhart and $Martinelli^{(27)}$'s, ${Chisholm}^{(31)}$'s, Zhang et ${al.,}^{(15)}$'s, Lee and ${Lee}^{(5)}$'s, Moriyama and ${Inue}^{(4)}$'s, Qu and $Mudawar^{(8)}$'s models were assessed with our experimental data. The best two-phase viscosity model is Beattie and Whalley's model. The best separated flow model is Qu and Mudawar's correlation. Flow regime dependency in both homogeneous and separated flow models was observed. Therefore, new flow pattern based correlations for both homogeneous and separated flow models were individually proposed.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.12
• /
• pp.1708-1715
• /
• 2003

An experimental study was made of turbulent separated and reattaching flow over a backward-facing step, where unsteady wake was generated by a spoked-wheel type wake generator with cylindrical rods in front of the separated flow. The influence of unsteady wake was scrutinized in terms of the rotating speed of the wake generator (0$\leq$S $t_{H}$$\leq$0.4). A conditional averaging technique in corporation with SBF was employed to elucidate the influence of the unsteady wake on the large-scale vortical structures of the separated flow. Special attention was made during two-dimensional measurements of wall-pressure with or without unsteady wake. The wall-pressure fluctuations were used to predict dipole sound source by Curie's integral formula. It was found that the reduction of the dipole sound source was due to the reduction of turbulent kinetic energy by unsteady wake in the recirculation region.n.

• Journal of Animal Environmental Science
• /
• v.12 no.2
• /
• pp.85-94
• /
• 2006

The effects of turning frequency of in-vessel composting on ammonia emissions during composting of separated solids from swine slurry/sawdust mixtures and performance of biofiltration using the chicken manure compost were investigated. Separated solids from swine manure amended with sawdust was composted in a 226 L laboratory-scale in-vessel reactors under various turning frequency and continuous airflow (0.6 L/min.kg.dm) for three weeks. Three laboratory-scale manure compost biofilters were built to treat effluent gas from the composting of separated solid from swine manure amened with sawdust process. These experiments were continued over a period of three weeks. The composting of separated solid swine manure amended with sawdust and manure compost biofiltration system were evaluated to determine the turning frequency type that would be adequate for the rate of decomposition and compost odour reduction. The compost odour cleaning was measured based on ammonia gas concentration before and after passing through the manure compost biofilter. The average ammonia odor reduction in the manure compost biofilter was 96.9 % at R1 (no turning), 99.4 % at R2(once a day turning) and 89.0 % at R3(twice a day turning), respectively. The efficiency of ammonia reduction was mainly influenced by the turning frequency.

• Journal of KIISE:Software and Applications
• /
• v.36 no.2
• /
• pp.109-121
• /
• 2009

Although a prior knowledge is a factor to improve the clustering performance, it is dependant on how to use of them. Especial1y, when the prior knowledge is employed in constructing initial centroids of cluster groups, there should be concerned of similarities of a prior knowledge. Despite labels of some objects of a prior knowledge are identical, the objects whose similarities are low should be separated. By separating them, centroids of initial group were not fallen in a problem which is collision of objects with low similarities. There can use the separated prior knowledge by various methods such as various initializations. To apply association rule, proposed method makes enough cluster group number, then the centroids of initial groups could constructed by separated prior knowledge. Then ensemble of the various results outperforms what can not be separated.

• Journal of the Speleological Society of Korea
• /
• no.89
• /
• pp.27-33
• /
• 2008

Solar energy is most green and clean, unlimited and sustainable energy source on the earth. It is almost 97% of imported consumer energy in Korea. Because of resource poor nation, it is necessary to do their best to make alternative energy to allot their deficiency of the matter in hand of energy resources of petroleum. In a point of view of this problems, the natural solar energy should be improved by any methods as much, possible as we need. Photovoltaic generation with solar tracking system for obtaining optimal power is one of most benefit equipment to improve power of solar-cell panel producing clean electric power efficiently. Solar tracker is a device for orienting a solar photovoltaic panel toward the sun perpendicularly to sunlight, especially in widely separated place. For this reason, we are very interested in developing the equipment system of tracker, specially in solar cell applications, obtaining a high degree of accuracy to ensure that the optimal sunlight could be directed precisely against to the powered device. As a result, it was obtained of 12.46 volts at 90$^\circ$toward solar panel and 9.44 volts at 45$^\circ$, furthermore, improved efficiency more than 30% of average output voltage between tracker system (12.41V) and fixed system (8.55V), respectively. It is also very useful for optimum power system of widely separated cave.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.1
• /
• pp.87-95
• /
• 2001

A numerical study was made of heat transfer in locally-forced turbulent separated and reattaching flow over a backward-facing step. The local forcing was given to the flow by means of sinusoidally oscillating jet from a separation line. A Rhee and Sung version of the unsteady $\kappa$-$\varepsilon$-f(sub)u model and the diffusivity tensor heat transfer model were employed. The Reynolds number was fixed at Re(sub)H=33,000 and the forcing frequency was varied in the range 0$\leq$fH/U(sub)$\infty$$\leq$2. The condition of constant heat flux was imposed at the bottom wall. The predicted results were compared and validated with the experimental data of Chun and Sung and Vogel and Eaton. The enhancement of heat transfer in turbulent separated and reattaching flow by local forcing was evaluated and analyzed.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.1
• /
• pp.94-99
• /
• 2008

The characteristics of the flowfield of a square prism having fences on the corner was investigated by the PIV. Strouhal numbers, velocity vectors and velocity profiles around the square prism were observed at various positions of the fences, and Reynolds number of $Re=0.6{\times}10^4{\sim}1.0{\times}10^4$. As the results in case of the prism having fences the Strouhal numbers were all smaller than in case of the prototype prism. In case of the prism having vertical fences on the front corners the concentrated intensity of the vorticity was the strongest and the size of separated shear layer was the largest. While in case of the prism having vertical fences on the rear corners the concentrated intensity of the vorticity was the weakest and the size of separated shear layer was the smallest. Also in this case, the flow separated in front corner was reattached around the rear corner and made circulation.

• Korean Institute of Interior Design Journal
• /
• v.13 no.6
• /
• pp.107-114
• /
• 2004

The purpose of this study is to propose the unit plan for home office which can substitute the existing unvaried unit plan in housing and homogeneous working space in office building through the recognition of necessity and possibility about whether home-basedworkandhomeofficecanbeformedornot. Based on the above contents of a research, the following conclusions were summarized; 1. The unit plan of home office was divided into 'jointly-used type' and 'independent-separated type' in accordance with the relationship between housing and working space, 'dwelling-emphasis type' and 'working-emphasis type' in accordance with the grade of ranks between housing and working space. And the universal validity which could accept properly the dweller's characteristics was drawn by the above classification of unit types. 2. The required characteristics in a unit plan for home office were classified into flexibility, privacy, efficiency, identity, amenity. And the analyzing system of planning methodology was assigned according to dividing interior components into space-functional, space-designing interior facts. The planning methodology would have to be considered on the correlation with each required characteristic. As a result of the study, through a planning of independent-separated type, In especial, 'vertical-separated type', it was certificated that vertical-separated type could satisfy a variety of required characteristic in space-designing as well as space-functional aspect.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.9 no.4
• /
• pp.403-413
• /
• 1985

Hot-wire measurements of second and third-order mean products of velocity fluctuations have been made in the separated, reattached, and redeveloping boundary layer behind a vertical fence. Mean velocity, wall static pressure distributions have also been measured in the whole flow field. Upstream of the reattachment point, the separated shear layer developes as a free mixing layer, but the gradient of the maximum slope thickness, turbulent intensities and the Reynolds shear stress are higher than that of the mixing layer due to initial streamline curvature and the effects of highly turbulent recirculating flow region. In the reattachment region, Reynolds shear stress and triple products near the surface is far more rapid than the decrease of the shear stress; that is the presence of the solid wall has a marked effect on the apparent gradient diffusivity of intensity or shear stress and throws doubts upon the usefulness of the simple gradient diffusivity model in this region.