• Journal of Korean Association for Spatial Structures
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• v.22 no.4
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• pp.15-22
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• 2022

Micro-climate measurements and computational fluid analysis were conducted to use it as basic data for the preservation and management of the old house of Kim Myung-kwan, a traditional building that is National Folk Cultural Property No. 26. As a result of the actual measurement, the temperature and humidity are relatively evenly distributed indoors unlike outdoors, but the temperature and humidity vary depending on the time change and the installation location in the outdoors. It was found that the temperature increases after dawn and the temperature varies depending on the installation position around 14:00-15:00, when the temperature becomes the highest. In particular, the temperature was high at the outdoor measurement point adjacent to the building and the fence. As a result of the computational fluid analysis, the temperature was high in the buildings and fences in the old house or in the area adjacent to the building, and it was about 1℃ higher than the surrounding area. In this area, it is judged that the thickening of wood will occur more severely than in other locations, and special preservation management is required.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.3
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• pp.128-137
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• 2013

Due to the global warming and air pollution, interest in renewable energies has increased in recent years. In particular, the crisis of the depletion of fossil energy resources in the near future has accelerated the renewable energy technologies. Among the renewable energy resources, oceans covering almost three-fourths of earth's surface have an enormous amount of energy. For this reason, various approaches have been made to harness the tremendous energy potential. In order to achieve two purposes: to improve harbor water quality and to use wave energy, this study proposed a sea water exchange structure applying an Oscillating Water Column (OWC) wave generation system that utilizes the air flow velocity induced by the vertical motion of water column in the air chamber as a driving force of turbine. In particular, the airflow velocity in the air chamber was estimated from the time variations of water surface profile computed by using 3D-NIT model based on the 3-dimensional irregular numerical wave tank. The relationship of the frequency spectrums between the computed airflow velocities and the incident waves was analyzed. This study also discussed the characteristics of frequency spectrums in the air chamber according to the presence of the structure, wave deformations by the structure, and the power of the water and air flows were also investigated. It is found that the phase difference exists in the time series data of water level fluctuations and air flow in the air chamber and the air flow power is superior to the fluid flow power.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.2_spc
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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.

• Transactions of the KSME C: Technology and Education
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• v.5 no.2
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• pp.135-143
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• 2017

The domestic unique research reactor, HANARO (Hi-flux Advanced Neutron Application ReactOr), has been constructed with the open-pool, the core is submerged in, for the multi-purpose neutron application. The reactor has a primary cooling system to remove the fission heat from the core and its connected fluidic systems. Since the works are required at the reactor pool top as a characteristic of the research reactor, the radiation shall be minimized with the operation of the hot water layer system to avoid unnecessary radiation exposure on the workers during work at the pool top. Moreover, the pool water management system is connected to the reactor pool to maintain the pool temperature below $50^{\circ}C$ to minimize the uprising radioactive gas or impurity from the colder pool bottom. For the efficient flow rate of the PWMS, the thermal capacity of heat exchanger is selected with 260 kW in the normal operation condition. In this paper, the modeling is formulated to figure out whether or not each pool temperature maintains below the temperature limit and the calculation results show that the designed PWMS heat exchanger has enough capacity with the design margin regardless of the reactor operation mode.

• Economic and Environmental Geology
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• v.50 no.6
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• pp.435-443
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• 2017

The Hanae deposit is located within the Cretaceous Gyeongsang Basin. The Cu-bearing hydrothermal quartz vein formed by narrow open-space filling along fracture in the sedimentary rocks as Jindong Formation. The Hanae Cu-bearing hydrothermal deposit shows a paragenetic sequence of pyrrhotite-pyrite $\rightarrow$ pyrite-chalcopyrite-sphalerite(${\pm}$Bi-bearing tellurides) $\rightarrow$ Ag-bearing telluride mineralization $\rightarrow$ secondary mineralization. Fluid inclusion data indicate that the Hanae Cu-bearing hydrothermal mineralization occurred from dominantly aqueous fluids at temperatures of $400^{\circ}C-200^{\circ}C$. Equilibrium thermodynamic interpretation of the mineral paragenesis and assemblages combined with fluid inclusion data indicate that early main Cu-bearing ore mineralization in the vein starts at about $350^{\circ}C$ which corresponds to sulfur fugacity from about $10^{-9.2}$ to $10^{-8.7}bar$ with oxygen fugacity of about $10^{-32.1}$ to $10^{-29.8}bar$. Late main Cu-bearing ore mineralization in the vein occurs at about $250^{\circ}C$ which corresponds to sulfur fugacity from about $10^{-13.5}$ to $10^{-11.7}bar$ with oxygen fugacity of about $10^{-38.4}$ to $10^{-35.2}bar$. The late Ag-bearing telluride mineralization in the Hanae hydrothermal system occurs at about $200^{\circ}C$ which corresponds to minium Tellirium fugacity value of about $10^{-18}bar$ with sulfur fugacity of about $10^{-14.0}$ to $10^{-10.9}bar$.

• Journal of the Korean Solar Energy Society
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• v.38 no.2
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• pp.33-43
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• 2018

PV/Thermal module is the combined system, which consist of a photovoltaic module and solar thermal collector that can obtain electrical power and thermal energy simultaneously. Thus the power generation can be increase by decreasing the temperature of photovoltaic module and thermal energy retrieved from module also can be used for heating system. In this study, Heat transfer performance of air type PV/Thermal module was confirmed with various bottom obstacles that can be installed easily to real photovoltaic module by CFD (computational fluid dynamics) analysis. Eight type obstacles were investigated according to the shape and arrangement. As a result, nusselt number represent heat transfer performance was increased about 86% compare with the basic type PV/Tthermal module that has no obstacle and triangle type obstacle had higher value than other types. But pressure drop was also increased with increment of heat transfer enhancement. Thus the performance factor considering both heat transfer and pressure drop was confirmed and V-fin type obstacle arranged in a row for Reynolds number below 9,600 and protrusion type obstacle arranged in zigzag for Reynolds number above 14,400 were shown higher performance factor than other types. From these results, V-fin type obstacle arranged in row and protrusion type obstacle arranged in zigzag were considered as a proper type for applying to real PV/thermal module according to operating condition. But the heat transfer performance can be changed by the geometric conditions of obstacle such as height, width, length and arrangement. Thus, it could also confirmed that the optimal condition and arrangement of this obstacle need to be found in further study.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.171-171
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• 2017

전산유체역학(CFD: Computational Fluid Dynamics)를 이용한 스마트팜 환경 내부의 정밀 제어 연구가 진행 중이다. 시계열 데이터의 난해한 동적 해석을 극복하기위해, 비선형 모델링 기법의 일종인 인공신경망을 이용하는 방안을 고려하였다. 선행 연구를 통하여 환경 데이터의 비선형 모델링을 위한 Tensorflow활용 방법이 하드웨어 가속 기능을 바탕으로 월등한 성능을 보임을 확인하였다. 그럼에도 오프라인 일괄(Offline batch)처리 방식의 한계가 있는 인공신경망 모델링 기법과 현장 보급이 불가능한 고성능 하드웨어 연산 장치에 대한 대안 마련이 필요하다고 판단되었다. CFD 해석을 위한 Solver로 SU2(http://su2.stanford.edu)를 이용하였다. 운영 체제 및 컴파일러는 1) Mac OS X Sierra 10.12.2 Apple LLVM version 8.0.0 (clang-800.0.38), 2) Windows 10 x64: Intel C++ Compiler version 16.0, update 2, 3) Linux (Ubuntu 16.04 x64): g++ 5.4.0, 4) Clustered Linux (Ubuntu 16.04 x32): MPICC 3.3.a2를 선정하였다. 4번째 개발환경인 병렬 시스템의 경우 하드웨어 가속는 OpenCL(https://www.khronos.org/opencl/) 엔진을 이용하고 저전력 ARM 프로세서의 일종인 옥타코어 Samsung Exynos5422 칩을 장착한 ODROID-XU4(Hardkernel, AnYang, Korea) SBC(Single Board Computer)를 32식 병렬 구성하였다. 분산 컴퓨팅을 위한 환경은 Gbit 로컬 네트워크 기반 NFS(Network File System)과 MPICH(http://www.mpich.org/)로 구성하였다. 공간 분해능을 계측 주기보다 작게 분할할 경우 발생하는 미지의 바운더리 정보를 정의하기 위하여 3차원 Kriging Spatial Interpolation Method를 실험적으로 적용하였다. 한편 병렬 시스템 구성이 불가능한 1,2,3번 환경의 경우 내부적으로 이미 존재하는 멀티코어를 활용하고자 OpenMP(http://www.openmp.org/) 라이브러리를 활용하였다. 64비트 병렬 8코어로 동작하는 1,2,3번 운영환경의 경우 32비트 병렬 128코어로 동작하는 환경에 비하여 근소하게 2배 내외로 연산 속도가 빨랐다. 실시간 CFD 수행을 위한 분산 컴퓨팅 기술이 프로세서의 속도 및 운영체제의 정보 분배 능력에 따라 결정된다고 판단할 수 있었다. 이를 검증하기 위하여 4번 개발환경에서 운영체제를 64비트로 개선하여 5번째 환경을 구성하여 검증하였다. 상반되는 결과로 64비트 72코어로 동작하는 분산 컴퓨팅 환경에서 단일 프로세서 기반 멀티 코어(1,2,3번) 환경보다 보다 2.5배 내외 연산속도 향상이 있었다. ARM 프로세서용 64비트 운영체제의 완성도가 낮은 시점에서 추후 성공적인 실시간 CFD 모델링을 위한 지속적인 검토가 필요하다.

• Journal of Energy Engineering
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• v.24 no.3
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• pp.109-114
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• 2015

Heat exchanger tube array in a heat recovery steam generator is exposed to the hot exhaust gas flow and it could cause the flow induced vibration, which could damage the heat exchanger tube array. It is needed for the structural safe operation of the heat exchanger to establish the characteristics of flow induced vibration in the tube array. The researches for the flow induced vibration of typical heat exchangers have been conducted and the nondimensional PSD(Power Spectral Density) function with the Strouhal number, fD/U, had been derived by experimental method. The present study examined the results of the previous experimental researches for the nondimensional PSD characteristics by CFD analysis and the basis for the application of flow induced vibration to the heat recovery steam generator tube array would be prepared from the present CFD analysis. For the previous mentioned purpose, the present CFD analysis introduced a single circular cylinder and calculated with the unsteady laminar flow over the cylinder. The characteristics of vortex shedding and lift fluctuation over the cylinder was investigated. The derived nondimensional PSD was compared with the results of the previous experimental researches and the characteristics of lift PSD over a single circular cylinder was established from the present CFD study.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.207-213
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• 2016

In this study, a thermal flow analysis was performed using the commercial code, ANSYS-FLUENT to reduce room temperature in a turbine building of power plant. The selected control volume of the operating floor and deaerator floor for the turbine building was respectively modelled. The skylight windows at the deaerator floor were employed for ventilation windows. Through the study, in the first we found that all window close of the deaerator floor is one alternative for reducing the temperature of the operating floor. The next thing we knew that for windows open at the front of the deaerator floor, the temperature of deaerator zone and crane zone can be respectively reduced to $1.5^{\circ}C$ and $1.6^{\circ}C$. In addition, for windows close at the rear of the deaerator floor, the temperature of deaerator zone and crane zone can be respectively reduced to 1.4 and $0.5^{\circ}C$. Therefore, it was concluded that a better choice is to open the front windows at deaerator floor to reduce the temperature of the entire deaerator floor having high temperature.

• Journal of the Korean Institute of Gas
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• v.19 no.4
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• pp.35-40
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• 2015

Heat exchanger tube array in a heat recovery steam generator is exposed to the hot exhaust gas flow and it could cause the flow induced vibration, which could damage the heat exchanger tube array. It is needed for the structural safe operation of the heat exchanger to establish the characteristics of flow induced vibration in the tube array. The researches for the flow induced vibration of typical heat exchangers have been conducted and the nondimensional PSD(Power Spectral Density) function with the Strouhal number, fD/U, had been derived by experimental method. The present study examined the results of the previous experimental researches for the nondimensional PSD characteristics by CFD analysis and the basis for the application of flow induced vibration to the heat recovery steam generator tube array would be prepared from the present CFD analysis. For the previous mentioned purpose, the present CFD analysis introduced a single circular cylinder and calculated with the unsteady laminar flow over the cylinder. The characteristics of vortex shedding and lift and drag fluctuation over the cylinder was investigated. The derived nondimensional PSD was compared with the results of the previous experimental researches and the characteristics of lift and drag PSD over a single circular cylinder was established from the present CFD study.