• Journal of Ocean Engineering and Technology
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• 제34권5호
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• pp.294-303
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• 2020

This study discusses data collection, calculation of wind and wave-induced resistance, and speed-power analysis of an 8,600 TEU container ship. Data acquisition system of the ship operator was improved to obtain the data necessary for the analysis, which was accomplished using SPA (Ship Performance Analysis, Park et al., 2019) in conformation with ISO15016:2015. From a previous operation profile of the container, the standard operating conditions of mean draft were 12.5 m and 13.6 m, which were defined with the mean stowage configuration of each condition. Model tests, including the load-variation test, were conducted to validate new ship performance and for the speed-power analysis. The major part of the added resistance of container ship is due to the wind. To check the reliability of wind-resistance calculation results, the resistance coefficients, added resistance, and speed-power analysis results using the Fujiwara regression formula (ISO15016:2015) and Computational fluid dynamics (Ryu et al., 2016; Jeon et al., 2017) analysis were compared. Wind speed and direction measured using an anemometer were used for wind-resistance calculation and the wave resistance was calculated using the wave-height and direction-data from weather information. Also, measured water temperature was used to calculate the increase in resistance owing to the deviation in water density. As a result, the SPA analysis using measured data and weather information was proved to be valid and able to identify the ship's resistance propulsion performance. Even with little difference in the air-resistance coefficient value, both methods provide sufficient accuracy for speed-power analysis. The differences were unnoticeable when the speed-power analysis results using each method were compared. Also, speed-power analysis results of the 8,600 TEU container ship in two draft conditions show acceptable trends when compared with the model test results and are also able to show power increase owing to hull fouling and aging. Thus, results of speed-power analysis of the existing 8,600 TEU container ship using the SPA program appropriately exhibit the characteristics of speed-power performance in deal conditions.

• Journal of Energy Engineering
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• 제22권4호
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• pp.362-369
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• 2013

Two-phase flow is frequently observed in many industries such as nuclear power plants and oil transportation. Two-phase flow regime depends on the flow rates, the fluid properties and the structure of flow channels. Since the identification of the flow regime is of great importance in the system design and the safety analysis, a number of theoretical and experimental investigations have been performed. This paper presents a basic research on the characteristics of each flow regime and transition boundary in the two-phase flows. The flow regime of the upward air-water flow in the vertical tube, 30 mm in the inner diameter, is distinguished by using the high-speed camera and the Wire-mesh sensor(WMS). The identified experimental data are compared with the flow regime maps proposed by Taitel et al, Mishima and Ishii. Even though there is slight difference in the transition boundary, the experimental data show general agreement with these flow regime maps.

• Wind and Structures
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• 제27권1호
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• pp.11-27
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• 2018

The straight-cone steel cooling tower is a novel type of structure, which has a distinct aerodynamic distribution on the internal surface of the tower cylinder compared with conventional hyperbolic concrete cooling towers. Especially in the extreme weather conditions of strong wind and heavy rain, heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind, but existing studies mainly focus on the impact effect brought by wind-driven rain to structure surface. In addition, for the indirect air cooled cooling tower, different additional ventilation rate of shutters produces a considerable interference to air movement inside the tower and also to the action mechanism of loads. To solve the problem, a straight-cone steel cooling towerstanding 189 m high and currently being constructed is taken as the research object in this study. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed with continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind sped and rainfall intensity on flow field mechanism, the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower cylinder is analyzed. On this basis, the internal pressures of the cooling tower under the most unfavorable working condition are compared between four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the 3D effect of equivalent internal pressure coefficient is the most significant when considering two-way coupling between wind and rain. Additional load imposed by raindrops on the internal surface of the tower accounts for an extremely small proportion of total wind load, the maximum being only 0.245%. This occurs under the combination of 20 m/s wind velocity and 200 mm/h rainfall intensity. Ventilation rate of shutters not only changes the air movement inside the tower, but also affects the accumulated amount and distribution of raindrops on the internal surface.

• Horticultural Science & Technology
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• 제32권4호
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• pp.473-483
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• 2014

In this work, the effects of shade combination, shade height and wind regime on greenhouse climate were quantified. A two-dimensional (2-D) computational fluid dynamics (CFD) model was developed based on an 11-span plastic greenhouse in eastern China for wind almost normal to the greenhouse orientation. The model was first validated with air temperature profiles measured in a compartmentalized greenhouse cultivated with mature lettuce (Lactuca sativa L., 'Yang Shan'). Next, the model was employed to investigate the effect of shade combinations on greenhouse microclimate patterns. Simulations showed similar airflow patterns in the greenhouse under different shade combinations. The temperature pattern was a consequence of convection and radiation transfer and was not significantly influenced by shade combination. The use of shade screens reduced air velocity by $0.02-0.20m{\cdot}s^{-1}$, lowered air temperature by $0.2-0.8^{\circ}C$ and raised the humidity level by 0.9-2.0% in the greenhouse. Moreover, it improved the interior climate homogeneity. The assessment of shade performance revealed that the external shade had good cooling and homogeneity performance and thus can be recommended. Furthermore, the effects of external shade height and wind regime on greenhouse climate parameters showed that external shade screens are suitable for installation within 1 m above roof level. They also demonstrated that, under external shade conditions, greenhouse temperature was reduced relative to unshaded conditions by $1.3^{\circ}C$ under a wind speed of $0.5m{\cdot}s^{-1}$, whereas it was reduced by merely $0.5^{\circ}C$ under a wind speed of $2.0m{\cdot}s^{-1}$. Therefore, external shading is more useful during periods of low wind speed.

• Journal of Energy Engineering
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• 제25권4호
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• pp.152-158
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• 2016

Nitrogen oxide is generated by the chemical reaction of oxygen and nitrogen in higher temperature environment of combustion facilities. The NOx reduction equipment is generally used in the power plant or incineration plant and it causes enormous cost for the construction and maintenance. The flue gas recirculation method is commonly adopted for the reduction of NOx formation in the combustion facilities. In the present study, the computational fluid dynamic analysis was accomplished to elucidated the cold flow characteristics in the flue gas recirculation burner with coanda nozzles in the flue gas recirculation pipe. The inlet and outlet of flue gas recirculation pipes are directed toward the tangential direction of circular burner not toward the center of burner. The swirling flow is formed in the burner and it causes the reverse flow in the burner. The ratio of flue gas recirculation flow rate with the air flow rate was about 2.5 for the case with the coanda nozzle gap, 0.5mm and it was 1.5 for the case with the gap, 1.0mm. With the same coanda nozzle gap, the flue gas recirculation flow rate ratio had a little increase when the air flow rate changes from 1.1 to 2.2 times of ideal air flow rate.

• Journal of the Korean Institute of Gas
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• 제23권3호
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• pp.20-26
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• 2019

Selective catalytic reduction(SCR) method is widely used among various methods for reducing nitrogen oxides in combustion devices of coal power plant. In the present study, the computational fluid dynamic analysis was accomplished to derive the optimal shape of ammonia-dilution air mixing device in a ammonia injection grid. The distribution characteristics of flow and $NH_3$ concentration had been elucidated for the reference shape of ammonia mixing device(Case 1). In the mixing device of Case 1, it could be seen that $NH_3$ distribution was shifted to the wall opposite to the inlet of the ammonia injection pipe. For the improvement of $NH_3$ distribution, the case(Case 2) with closing one upper injection hole and 4 side injection holes, the case(Case 3) with installing horizontal plate at the upper of ammonia injection pipe, the case(Case 4) with installing horizontal plate and horizontal arc plate at he upper of ammonia injection pipe were investigated by analyzing flow and $NH_3$ concentration distributions. From the present study, it was found that the % RMS of $NH_3$ for Case 4 was 4.92%, which was the smallest value among four cases, and the range of $R_{NH3}$ also has the optimally uniform distribution, -10.82~8.34%.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제20권7호
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• pp.353-362
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• 2019

Thermodynamic analysis of cascade refrigeration systems has attracted considerable research attention. On the other hand, a system evaluation based on thermodynamic analyses of the individual parts, including the evaporator, condenser, intercooler, expansion valve, etc., has received less attention. In this study, performance analysis was conducted on a cascade refrigeration system, which has an individual cooling and refrigeration evaporator, and equips the intercooler and air-cooled condenser in a series in a lower cycle. The thermo-fluid design was then performed on the major components of the system - upper condenser, lower condenser, cooling evaporator, refrigeration evaporator, intercooler, compressor, electronic expansion valve - of 15 kW refrigeration, and 8 kW cooling capacity using R-410A. A series of simulations were conducted on the designed system. The change in outdoor temperature from 26 C to 38 C resulted in the cooling capacity of the lower evaporator remaining approximately the same, whereas it decreased by 9% at the upper evaporator and by 63% at the intercooler. The COP decreased with increasing outdoor temperature. In addition, the COP of the cycle with the intercooler operation was higher that of the cycle without the intercooler operation. Furthermore, the increase in the upper condenser size by two fold increased the upper evaporator by 4%. On the other hand, the lower evaporator capacity remained the same. The COP of the upper cycle increased with increasing upper condenser size, whereas that of the lower cycle remained almost the same. When the size of the lower condenser was increased 2.8 fold, the intercooler capacity increased by 8%, whereas those of upper and the lower evaporator remained approximately the same. Furthermore, the COP of the lower cycle increased with an increase in the lower condenser. On the other hand, the change of the upper condenser was minimal.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• 제18권2_spc호
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• pp.327-336
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• 2020

The high-flux advanced neutron application reactor (HANARO) is a research reactor with thermal power of 30 MW applied in various research and development using neutrons generated from uranium fission chain reaction. A degasifier tank is installed in the ancillary facility of HANARO. This facility generates gas pollutants produced owing to internal environmental factors. The degasifier tank is designed to maintain the gas contaminants below acceptable levels and is monitored using an analyzer in the gas sampling panel. If condensate water is generated and flows into the analyzer of the gas sampling panel, corrosion occurs inside the analyzer's measurement chamber, which causes failure. Condensate water is generated because of the temperature difference between the degasifier tank and analyzer when the gas flows into the analyzer. A heating system is installed between the degasifier tank and gas sampling panel to suppress condensate water generation and effectively remove the condensate water inside the system. In this study, we investigated the efficiency of the heating system. In addition, the variations in the pipe temperature and the amount of average condensate water were modeled using a wall condensation model based on the changes in the fluid inlet temperature, outside air temperature, and heating cable-setting temperature.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제7권3호
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• pp.431-439
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• 2006

A lot of particulate matter and an offensive odor are emitted during the operations of an industrial waste incinerator (IWI), especially pre_treatment and waste input processes. These pollutants affect the labor efficiency of an operator. Therefore, in this study. we have studied the improvement of working surroundings in the industrial waste incinerator by designing a new control system. A computational fluid dynamics has been used to find the diffusion flows of air pollutants (mainly particles and odor) to the working surroundings of the waste treatment complexes. The results obtained from the simulation analysis applied to the basic design on the points (and/or site) and types of pollution control devices. When pollutant control devices are constructed, the concentration of each pollutant at site 1 and 2 decreased about 83-97% for toluene, 48-72% for styrene, 75-87% for xylene, and 23-36% for ammonia, respectively. In addition, the PM-10 and TSP were decreased about 87% and 86% at site 3 (lower part of the waste input), 87% and 85% at site 4 (side part of the waste input), respectively. These indicated that the new control system had an excellent performance of particulate matter and odor removal and it could be applied to other waste treatment plant in place of an industrial waste incinerator.

• Korean Journal of Environmental Biology
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• 제37권2호
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• pp.136-143
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• 2019

This study investigates the effect of denitrified biofloc water on changes in the water quality parameters and the physiological characteristics of shrimps. Biofloc rearing water contains a large number of microorganisms and can rapidly stabilize the water quality and energy saving if reusable due to high water temperatures. Rearing water contain floating bacteria with both aerobic and anaerobic bacteria. Therefore, when the carbon source is added in limited air supply, the anaerobic state is activated and the denitrification process is possible. In this study, the denitrification water had the following properties: ammonia (6.9 mg L^-1), nitrite (0.3 mg L^-1), nitrate concentration (9.2 mg L^-1), high pH (8.42) and alkalinity (590 mg L^-1). The experimental group consisted of seawater (SW, control), a mixture of Seawater and denitrified biofloc water (DNW) in the ratio of 3:1, 1:1 and DNW only. All experiments were done in triplicate. As a result, the survival rate never changed even when 100% of the denitrification water was utilized. However, a body fluid analysis showed that creatine and BUN were increased due to index of stress and the tissue damage resulting from the high denitrified water content. Body fluid ions (Na⁺, K⁺, and Cl^-) significantly decreased as the denitrified water content increased. It was recommended that the denitrification water be mixed with a certain ratio (less than 50%) in the future as it may affect the osmotic pressure control in shrimps.