• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.8
• /
• pp.1055-1062
• /
• 2011

The purpose of this study is to develop the shape of photocatalyst-coated module for improve the IAQ, which is installed at inside of ductwork and detachable. Including 3 column types(square, circle, diamond) and 2 fin types(diamond and square), totally 5 types are previously declared for numerical analysis and comparison, 5 types are. As the results of numerical analysis, almost the velocity varied at the range of ${\pm}0.3m$ from the module, except the Type A-3(diamond column type) which is affected to ${\pm}0.4m$ range and shows the biggest velocity differences. Among the 5 types, the diamond fin type(Type B-1) is analyzed as the most stable in velocity. And the results of local pressure drop show that the difference of pressure coefficient of Type B-1 is computed as 0.59, and that of Type A-3 is 2.44. Meanwhile, from the effect analysis of the number of module, the flow conflict happens and the pressure difference between before and after the module increases if there are over 3 modules inserted.

• Development and Reproduction
• /
• v.4 no.2
• /
• pp.195-201
• /
• 2000

Sex differentiation process of the spotted sea bass, Lateolabrax maculatus, was investigated by histological method. The fish samples were collected from just after hatching to 365 days later. The primordial germ cells and genital ridge were appeared separately hanging under air bladder in 30-day larva (total length: 11.7~13.2 mm), and were unified into the undifferentiated gonads in 40-day larva (12.5~14.0 mm). The ovarian differentiation was started in 60-day juvenile (23.6~27.0 mm). The somatic tissues were elongated in tip of both ends of undifferentiated gonad and were fused each other. The complete ovarian cavity was appeared in 80-days juvenile(33.1~42.5 mm). The testicular differentiation was initiated in 70-day juvenile (24.8~31.6 mm). The rudiment of sperm duct was appeared in the center of the undifferentiated gonad. The meiosis of germ cells in the ovary was started in 168-day juvenile (88.0~115.4 mm). In 287-day juvenile (175.1~233.6 mm), the ovary was filled with both of chromatin stage and perinucleolus stage oocytes. The meiosis of male germ cells was started in 245-day juvenile (124.4~168.3 mm). However, the seminiferous tubules of testis were filled with numerous sperm in 365-day juvenile (162.5~253.8 mm). The sex ratio of male and female was 1:1.38. Considering these results, the spotted sea bass was showed differentiated type in sex differentiation and gonochorism in sexuality.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.18 no.3
• /
• pp.77-86
• /
• 2010

In this study, the model of the indirect wind suction waste sorting machine for characteristics of the screening of waste was studied using computational fluid dynamics and the drag coefficient for the model and the suction wind speed were obtained. The wind separator are developing by installing a cyclone air outlet to the suction blower impeller waste is selective in a way that does not pass the features and characteristics of the inlet pipe of the pressure loss and separation efficiency can have a significant impact on. Using Wind separator for selection of waste in the waste prior research on the aerodynamic properties are essential. For plastic cases, it is reasonable to take the drag coefficient between 0.8 and 1.0, and for cans, compression depending on whether the cans, the drag coefficient is in the range from 0.2 to 0.7. The separation efficiency of waste as change suction speed was the highest efficiency when the suction speed was 25~26 m/s. Shape of the inlet, depending on how the transfer pipe of the duct pressure loss occurs because the inlet velocity changes through the appropriate design standards to allow for continued research is needed.

• Solar Energy
• /
• v.2 no.2
• /
• pp.29-36
• /
• 1982

The Solar Energy R&D Department of KIER under the auspice of the Korean government is pushing hard on the development of the passive solar technology with high priority for the expeditious widespread use of solar energy in Korea, since the past few years of experiences told us that the active solar technology is not yet ready for massive commercialization in Korea. KIER has completed the construction of the Solar Energy Research & Test Center in Seoul, which houses the major facilities for its all solar test programs. The Center was designed as a passive solar building with great emphasis on the energy conserving ideas. The Center is not only the largest passive building in Korea, but also the exhibit center for the effective demonstration of the passive heating and cooling technology to the Korean public. The Center was designed to satisfy the requirements based on the technical and economical criteria set by the KIER. Careful considerations, therefore, were given in depth in the following areas to meet the requirements. 1) Passive Heating Concepts The Center employed the combination of direct and indirect gain system. The shape of the Center is Balcomb House style, and it included a large built-in sunspace in front. A partition, consists of transparent and translucent glazings, separates the sunspace and the living space. Since most activities in the Center occur during the day time, direct utilization of the solar energy by the living spaces was emphasized with the limited energy storage capacity. 2) Passive Cooling Concepts(for Summer) Natural ventilation concept was utilized throughout the building. In the direct gain portion of the system, the front glazing can be openable during the cooling season. Natural convection scheme was also applied to the front sunspace for the Summer cooling. Reflective surfaces and curtains were utilized wherever needed. 3) Auxiliary Heat ing and Cooling System As an auxiliary cooling system, mechanical means(forced convection system) were adopted. Therefore forced air heating system was also used to match the duct work requirements of the auxiliary cool ing system. 4) Effect ive Insulation & Others These included the double glazed windows, the double entry doors, the night glazing insulation, the front glazing-frame insulation as well as the building skin insulation. All locally available construction materials were used, and natural lightings were provided as much as possible. The expected annual energy savings (compared to the non-insulated conventional building)of the Center was estimated to be about 80%, which accounts for both the energy conservation and the solar energy source. The Center is being instumented for the actual performance tests. The experimental results of the simplified tests are discussed in this paper.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.57 no.5
• /
• pp.51-60
• /
• 2015

In Korea, 69.4 % of duck farms had utilized conventional plastic greenhouses. In this facilities, there are difficulties in controlling indoor environments for raising duck. High rearing density in duct farms also made the environmental control difficult resulting in getting more stressed making their immune system weaker. Therefore, a facility is needed to having structurally enough solidity and high efficiency on the environmental control. So, new design plans of duck house have recently been conducted by National Institute of Animal Science in Korea. As a study in advance to establish standard, computational fluid dynamics (CFD) was used to estimate the aerodynamic problems according to the designs by means of overall and regional ventilation efficiencies quantitatively and qualitatively. Tracer gas decay (TGD) method was used to calculate ventilation rate according to the structural characteristics of duck houses including installation of indoor circulation fan. The results showed that natural ventilation rate was averagely 164 % higher than typically designed ventilation rate, 1 AER ($min^{-1}$). Meanwhile, mechanically ventilated duck houses made 81.2 % of summer ventilation rate requirement. Therefore, it is urgent to develop a new duck house considering more structural safety as well as higher efficiency of environmental control.

• Journal of Animal Environmental Science
• /
• v.16 no.2
• /
• pp.109-114
• /
• 2010

In South Korea, mora than 90% of swine barns had open-style side wall by winch operation, and less than 5% of swine barns were semi-windowless or windowless style. The aisle ventilation system of the barn was changed to roof-wall ventilation system, and the width and the length of barns were 10~12 m and 30~50 m, respectively. The width of aisle satisfying energy save was 2~3 m. The re-modeled barns inhaled air through duct which was opened to aisle and exhaled through forced ventilation fans on the windowless wall which was accomplished by installing planks on the open wall. After remodelling, the culling ratio and energy cost were decreased from 11% (47 heads) to 3% (12 heads) and from 1,550,000 won to 730,000 won, respectively. Hence, re-modeled swine barns raising 400 heads could save 2,835,680 won during winter (from December to March).

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.671-679
• /
• 2008

The effect of Pre-cooled Turbojet Engine installation and nozzle exhaust jet on Hypersonic Turbojet EXperimental aircraft(HYTEX aircraft) were investigated by three-dimensional numerical analyses to obtain aerodynamic characteristics of the aircraft during its in-flight condition. First, simulations of wind tunnel experiment using small scale model of the aircraft with and without the rectangular duct reproducing engine was performed at M=5.1 condition in order to validate the calculation code. Here, good agreements with experimental data were obtained regarding centerline wall pressures on the aircraft and aerodynamic coefficients of forces and moments acting on the aircraft. Next, full scale integrated analysis of the aircraft and the engine were conducted for flight Mach numbers of M=5.0, 4.0, 3.5, 3.0, and 2.0. Increasing the angle of attack $\alpha$ of the aircraft in M=5.0 flight increased the mass flow rate of the air captured at the intake due to pre-compression effect of the nose shockwave, also increasing the thrust obtained at the engine plug nozzle. Sufficient thrust for acceleration were obtained at $\alpha=3$ and 5 degrees. Increase of flight Mach number at $\alpha=0$ degrees resulted in decrease of mass flow rate captured at the engine intake, and thus decrease in thrust at the nozzle. The thrust was sufficient for acceleration at M=3.5 and lower cases. Lift force on the aircraft was increased by the integration of engine on the aircraft for all varying angles of attack or flight Mach numbers. However, the slope of lift increase when increasing flight Mach number showed decrease as flight Mach number reach to M=5.0, due to the separation shockwave at the upper surface of the aircraft. Pitch moment of the aircraft was not affected by the installation of the engines for all angles of attack at M=5.0 condition. In low Mach number cases at $\alpha=0$ degrees, installation of the engines increased the pitch moment compared to no engine configuration. Installation of the engines increased the frictional drag on the aircraft, and its percentage to the total drag ranged between 30-50% for varying angle of attack in M=5.0 flight.

• The Journal of the Acoustical Society of Korea
• /
• v.40 no.6
• /
• pp.555-565
• /
• 2021

The goal of this study is to improve flow and noise performances of existing backward-curved blade centrifugal fan system used for circulating cold air in a refrigerator freezer by optimally designing airfoil shape. The unique characteristics of the system is to drive cold airflow with two volute tongues in combination with duct system in a back side of a refrigerator without scroll housing generally used in a typical centrifugal fan system. First, flow and noise performances of existing fan system were evaluated experimentally. A P-Q curve was obtained using a fan performance tester in the flow experiment, and noise spectrum was measured in an anechoic chamber in the noise experiment. Then, flow characteristics were numerically analyzed by solving the three-dimensional unsteady Navier-Stokes equations and noise analysis was performed by solving the Ffowcs Williams and Hawkins equation with input from the flow simulation results. The validity of numerical results was confirmed by comparing them with the measured ones. Based on the verified numerical method, blade inlet and outlet angles were optimized for maximum flow rate using the two-factor central composite design of the response surface method. Finally, the flow and noise performances of a prototype manufactured with the optimum design were experimentally evaluated, which showed the improvement in flow and noise performance.