• Journal of The Korean Society of Agricultural Engineers
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• 제51권5호
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• pp.1-8
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• 2009

Photobioreactor (PBR) that houses and cultivates microalgae providing a suitable environment for its growth, such as light, nutrients, CO2, heat, etc. is now getting more popular in the last decade. Among the many types of PBRs, the bubble column type is very attractive because of its simple construction and easy operation. However, despite the availability of these PBRs, only a few of them can be practically used for mass production. Many limitations still holdback their use especially during their scale-up. To enlarge the culture volume and productivity while supplying optimum environmental conditions, various PBR structures and process control are needed to be investigated. In this study, computational fluid dynamics (CFD) was economically used to design a bubble-column type PBR taking the place of field experiments. CFD is a promising technique which can simulate the growth and production of microalgae in the PBR. To study bubble column PBR with CFD, the most important factor is the possibility of realizing bubble. In this study, multi-phase models which are generally used to realize bubbles were compared by theoretical approaches and comparing in a 2D simulation. As a result, the VOF (volume of fluid) model was found to be the most effective model to realize the bubbles shape as well as the flow inside PBR which may be induced by bubble injection. Considering the accuracy and economical efficiency, 0.005 second time step size was chosen for 2.5 mm mesh size. These results will be used as criteria for scale-up in the PBR simulation.

• Journal of Advanced Marine Engineering and Technology
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• 제36권6호
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• pp.756-761
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• 2012

Natural gas is converted in to LNG by chilling and liquefying the gas to the temperature of $-162^{\circ}C$, when liquefied, the volume of natural gas is reduced to 1/600 of its standard volume. This gives LNG the advantage in transportation. In this study, the effects of the pressure drop of refrigerant and natural gas in the LNG heat exchanger of cryogenic cascade refrigeration cycle were investigated and then the design criteria for the pressure drop of refrigerant and natural gas of the LNG heat exchanger were proposed. The pressure drop of the cascade liquefaction cycle was investigated and simulated using HYSYS software. The simulation results showed that the pressure drop in the LNG heat exchanger is set to 50 kPa considering the increase in the compressor work and COP of cryogenic cascade liquefaction cycle.

• Journal of Mechanical Science and Technology
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• 제19권5호
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• pp.1206-1215
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• 2005

The thermal stratification phenomena, frequently occurring in the component of nuclear power plant system such as pressurizer surge line, steam generator inlet nozzle, safety injection system (SIS), and chemical and volume control system (CVCS), can cause through-wall cracks, thermal fatigue, unexpected piping displacement and dislocation, and pipe support damage. The phenomenon is one of the unaccounted load in the design stage. However, the load have been found to be serious as nuclear power plant operation experience accumulates. In particular, the thermal stratification by the turbulent penetration or valve leak in the SIS and SCS pipe line can lead these safety systems to failure by the thermal fatigue. Therefore in this study an 1/10 scaledowned experimental rig had been designed and installed. And a series of experimental works had been executed to measure the temperature distribution (thermal stratification) in these systems by the turbulent penetration, valve leak, and heat transfer through valve. The results provide very valuable informations such as turbulent penetration depth, the possibility of thermal stratification by the heat transfer through valve, etc. Also the results are expected to be useful to understand the thermal stratification in these systems, establish the thermal strati­fication criteria and validate the calculation results by CFD Codes such as Fluent, Phenix, CFX.

• Journal of Korean Society of Transportation
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• 제22권1호
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• pp.19-30
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• 2004

Once baggage demand of passengers is forecast, BHS requirements must be analyzed, i.e., the number of originating/transferring/terminating bags to be handled, the number of conveyor lines to be installed, the number of containers for baggage make-up, the number of claim devices for baggage claim, and so on. Therefore, the determination of the baggage traffic volume is one of the most important analysis components for the airport design. Accordingly, this research proposes time-based distribution table models in order to accurately estimate BHS requirements to obtain design criteria in airport design phase. As the BHS requirements are ascertained, related requirements of the facilities can be determined by applying actual specifications of devices, i.e., throughput. This research found that the proposed mathematical model gives a good reflection of IIA (Incheon International Airport)'s operational condition. That means the model provides apparent reliability and feasibility. Furthermore, the specifications of devices are the newest figures. This fact supports that the research provides more effcient and reliable results.

• Journal of the Korea institute for structural maintenance and inspection
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• 제22권6호
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• pp.138-147
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• 2018

With the recent series of damage caused by earthquakes in Korea, such as Gyeongju and Pohang, we know that Korea is no longer a safe zone for earthquakes and that we need to be prepared for them. In addition, bridges built prior to the introduction of seismic design concepts remain without adequate seismic reinforcement measures, and earthquake reinforcement should be performed efficiently considering economic and structural safety. Preliminary assessment of seismic performance of existing bridges is divided into four seismic groups, taking into account seismicity, vulnerability and Impact, considering the magnitude of the existing bridge's seismic, and prioritization for further evaluation of seismic performance. In this study, unlike the existing anti-seismic reinforcement priority method, scores are calculated based on the seismic design criteria applied to bridges, importance coefficient of the bridge including the zone coefficient and the Importance, vulnerability index of the bridge including the soil condition and the elapsed years, detail coefficient of the bridge including the superstructure form, the span length, the width, the height, the design load, and the daily traffic volume. The calculated score items will be weighted and grouped according to the results. Using this, a simpler and more efficient algorithm was proposed to determine the priority of seismic reinforcement on a bridge.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제8권3호
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• pp.129-138
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• 1988

In order to develop the design and operational criteria in sewage treatment by indirect aerating submerged biofilter, experimental investigations were performed for the reasonable oxygen supply and effecting factors of treatment efficiency. The experiments were executed for the up-flowing synthetic wastewater and aerated water in the submerged biofilter at $20^{\circ}C$. The obtained results are as follows: 1) Appropriate mean diameter of gravels was about 11mm. 2) $BOD_5$ loading rate based on biofilter volume was more reasonable than that on surface area of gravel for operational criteria. 3) To remove the influent $BOD_5$ more than 90%, $BOD_5$ loading rate must be less than $1.0kg-BOD_5/m^3{\cdot}d$ and circulating flowrate must be more than $189m^3/m^3{\cdot}d$. 4) Reaction rate coefficient $K_1$ is related to diameter of gravel and circulating flow rate based on biofilter volume.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제31권5B호
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• pp.467-474
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• 2011

Debris flow is one of the most hazardous natural processes in mountainous regions. The degradation of discharge capacity of drainage facilities due to debris flows may result in damages of properties and casualty as well as road. Understanding and accurate reproducing flow behaviour of debris flows at various conditions, such as sediment volume concentration and approaching channel and culvert slopes, are prerequisite to develop advanced design criteria for drainage facilities to prevent such damages. We carried out a series of laboratory experiments of debris flows in a rectangular channel of constant width with an abrupt change of bottom slope. The experimental flume consists of an approaching channel part with the bed slope ranging $15^{\circ}$ to $30^{\circ}$ and the test channel with slope ranging from $0^{\circ}$ to $12^{\circ}$ which mimics a typical drainage culvert. The experiments have been conducted for 22 test cases with various flow conditions of channel slopes and sediment volume concentration of debris flows to investigate those effects on the behaviour of debris flows. The results show that, according to sediment volume concentration, the depth of debris flow is approximately 50% to 150% larger than that of fresh water flow at the same flow rate. Experimental results quantitatively present that flow behaviour and deposit history of debris flows in the culvert depend on the slopes of the approaching and drainage channels and sediment volume concentration. Based on the experimental results, furthermore, a logistic model is developed to find the optimized culvert slope which prevents the debris flow from depositing in the culvert.

• Journal of Korea Water Resources Association
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• 제47권1호
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• pp.83-93
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• 2014

This research was carried out for suggesting design criteria and procedure for maximizing flood control capacity by building flood control facilities like flood retention basin built in connection with existing facilities in order to cope with increased uncertainty due to factors such as urbanization and climate change. We suggested the procedure for the analysis under the various scenarios applicable for the cases of determining retention basin capacity as provision for the flood water level increase in main river channel or estimating flood water level reduction effect when retention basin capacity is given. Procedure for estimating design flood hydrograph at any duration using Intensity-Duration-Quantity (IDQ) originated from the existing IDF, and its application example were provided. Based on rainfall estimated by the IDQ analysis, it is possible to calculate an equivalent peak hydrographs under various scenarios, e.g. lower frequency hydrograph under same rainfall duration with water level higher than existing hydrograph, hydrograph with same peak and higher volume due to increased rainfall duration, hydrograph with higher peak and volume than existing hydrograph, etc.

• Journal of Biosystems Engineering
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• 제21권1호
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• pp.34-43
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• 1996

The present pesticide application technology widely used with a power sprayer in Korea is assessed as the problem awaiting solution in the point of view of its ineffectiveness, inefficiency, and environmental contamination. As one approach to get rid of these problems, the boom spraying with ultra-low volume and precision application technology has been recommended. The study was undertaken to investigate plants damages incurred by the self-propelled boom-sprayer vehicle, to develop the design criteria of vehicle wheel, and to compare plant damages caused by the front wheel steering vehicle, the 4-wheel drive vehicle and the articulated vehicle, by the computer simulation. The experiment showed that the amount of damaged plants incurred by the self-propelled boom sprayer were about 0.29% in average in the field size of 100m$\times$50m(0.5ha), about 60~80% of which recovering while growing. The recommandable wheel size was analyzed to be 70~100cm in diameter, 8~15cm in width from the vehicle-plant-soil relationship. The simulation on damaged plants anticipated to be incurred by various steering vehicles showed that the smaller the turning radius, the lesser the damaged plants within its range of 3~5m. Average plant damage rate by the front wheel steering vehicle, the 4-wheel drive vehicle and articulated vehicle was relatively assessed to be 2 : 1.8 : 1.

• Journal of Ocean Engineering and Technology
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• 제24권6호
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• pp.71-75
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• 2010

Although Graphite Compacted Vermicular (GCV) was first observed in 1948, the narrow range for stable foundry production precluded the high volume application of GCV to complex components such as cylinder blocks and heads until advanced process control technologies became available. This, in turn, had to await the advent of modern measurement electronics and computer processors. Following the development of foundry techniques and manufacturing solutions, primarily initiated in Europe during the 1990s, the first series production of GCV cylinder blocks began during 1999. Today, more than 40,000 GCV cylinder blocks are produced each month for OEMs, including Audi, DAF, Ford, Hundai, MAN, Mercedes, PSA, Volkswagen, and Volvo. Given that new engine programs are typically intended to support three to four vehicle generations, the chosen engine materials must satisfy current design criteria and also provide the potential for future performance upgrades without changing the overall block architecture. With at least a 75% increase in the ultimate tensile strength, a 40% increase in the elastic modulus, and approximately double the fatigue strength of either iron or aluminum, GCV is ideally suited to meet current and future of engine design and performance requirements.