• KIEAE Journal
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• 제13권1호
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• pp.57-63
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• 2013

Building Energy Efficiency Rating system was enforced in 2001 to enhance spreading high-energy performance and saving buildings. It was only for the new apartments, but expanded to new office buildings in 2010, and moreover, government offices require 1st grade of Building Energy Efficiency Rating system. Green Building Act, which is established to reduce the emissivity of carbon dioxide by reducing building energy consumption, will be enforced in 2013, and new apartments and office buildings will be subjected to it. Henceforward, it will extend to other types of buildings and will be phased in. In general, pumps and fans consume approximately half of the air-conditioning energy consumption, and about a quarter of the total building energy consumption when office buildings have total floor area of more than 10000 square meters. This study analyzed the energy demand when applying VAV(Variable Air Volume) and VWV(Variable Water Volume) System to reduce energy returns of the pumps and the fans by ECO2, which is a computer simulation program used for Building Energy Efficiency Rating system.

• 한국지반환경공학회 논문집
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• 제12권3호
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• pp.27-35
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• 2011

본 연구는 터널발파에서 소음저감을 목적으로 설치되는 방음시설 개발을 위하여 현장에서 주로 사용되는 방음재와 물, 모래 등을 이용하여 각 재질에 따른 소음저감효과를 판단하였다. 최대 소음레벨과 주파수의 범위를 측정하여 방음재질별 소음감쇠도와 주주파수 대역의 음압레벨을 고찰하였다. 그리고, 방음재료 분석의 결과를 반영하여 물과 스펀지 등으로 채운 개량형 워터튜브 방음문과 기존 스펀지 부직포 등으로 채운 방음문을 축소 제작하여 화약을 사용하여 실대형 현장실험을 통한 검증을 하였다. 그 결과 물을 차음재료로 사용한 경우에 기존 방음문에 비해 약 10dB(A) 정도의 소음 저감효과를 나타내었다.

• 한국기계기술학회지
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• 제20권6호
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• pp.739-744
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• 2018

In this study, effects of reducing white smoke at a heat exchange system for white smoke reduction were studied in the winter season. For this purpose, the heat transfer processes on the exhaust air were investigated by Solidworks. Five wave heat exchangers of air-to-air and air-to-water type were applied for the exhaust air heat recovery. The analytical condition of the exhaust air was fixed and the computational analysis was performed according to the change of SA(supply air) inlet velocities. In order to evaluate the performance of the heat exchange system for white smoke reduction, W(water)/SA recovered capacities and the temperature/absolute humidity reduction rate were calculated. As SA inlet velocity increased, the exit temperature and absolute humidity of the mixing zone were reduced by up to about $40^{\circ}C$ and 0.12kg/kg respectively. Also, W/SA recovered capacities increased linearly up to about 35%.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2157-2163
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• 2018

Catalytic reactors have been essential for chemical engineering process, and different designs of reactors in multi-scales have been previously studied. Computational fluid dynamics (CFD) utilized in reactor designs have been gaining interest due to its cost-effective advantage in designing the actual reactors before its construction. In this work, butadiene synthesis via oxidative dehydrogenation (ODH) of n-butene using tubular reactor was used as a case study in the CFD model. The effects of coolant and reactor diameter were investigated in assessing the reactor performance. Based on the results of the CFD model, the conversion and selectivity were 86.5% and 59.5% respectively in a fixed bed reactor under adiabatic condition. When coolants were used in a tubular reactor, reactor temperature profiles showed that solar salt had lower temperature gradients inside the reactor than the cooling water. Furthermore, higher conversion (90.9%) and selectivity (90.5%) were observed for solar salt as compared to the cooling water (88.4% for conversion and 86.3% for selectivity). Meanwhile, reducing the reactor diameter resulted in smaller temperature gradients with higher conversion and selectivity.

• Geomechanics and Engineering
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• 제24권6호
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• pp.531-543
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• 2021

Freezing and thawing of pore water within backfill can affect the stability of retaining wall as the phase change of pore water causes changes in the mechanical characteristics of backfill material. In this study, the effects of freezing and thawing on the mechanical performance of retaining wall with granular backfill were investigated for various temperature and groundwater level (GWL) conditions. The thermal and mechanical finite element analyses were performed by assigning the coefficient of lateral earth pressure according to phase change of soil for at-rest, active and passive stress states. For the at-rest condition, the mobilized lateral stress and overturning moment changed markedly during freezing and thawing. Active-state displacements for the thawed condition were larger than for the unfrozen condition whereas the effect of freezing and thawing was small for the passive condition. GWL affected significantly the lateral force and overturning moment (Mo) acting on the wall during freezing and thawing, indicating that the reduction of safety margin and wall collapse due to freezing and thawing can occur in sudden, unexpected patterns. The beneficial effect of an insulation layer between the retaining wall and the backfill in reducing the heat conduction from the wall face was also investigated and presented.

• Journal of Advanced Marine Engineering and Technology
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• 제29권5호
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• pp.502-508
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• 2005

Fouling causes serious maintenance problems on heat exchanger tubes and process facilities. To avoid such fouling problems, numerous efforts have been tried. e.g., diagnosis of fouling, reducing and eliminating the fouling. etc.. The objective of the present study is to develop an innovative diagnostic system of fouling, which can detect the scaling attached to the wall non-homogeneously. The performance of the diagnostic system has been evaluated with a scaling simulator that generates scaling on tested tube wall. The measured values with the diagnostic system were compared with the amounts of the scaling generated by the simulator. In addition to, we showed the data that have been executed in field test for reliability verification.

• Journal of Microbiology and Biotechnology
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• 제5권3호
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• pp.177-180
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• 1995

In horseradish peroxidase-catalyzing polymerization of phenol under the water/dioxane solvent system, the optimal concentration of hydrogen peroxide was found to be 10 mmol/I. Feeding of hydrogen peroxide at its optimal concentration improved the polymerization performance by reducing reaction time and increasing molecular weights. Monomer conversions and the molecular weights of the enzymatically produced polymer were in the ranges of 83.1~94.2$%$ and 58000~68000, respectively.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2002년도 춘계학술대회논문집
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• pp.181-186
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• 2002

Fouling causes serious maintenance problems on heat exchanger tubes and process facilities. To avoid such fouling problems, numerous efforts have been tried, e.g., diagnosis of fouling, reducing and eliminating the fouling, etc.. The objective of the present study is to develop an innovative diagnostic system of fouling, which can detect the scaling attached to the wall non-homogeneously The performance of the diagnostic system has been evaluated with a scaling simulator that generates scaling on tested tube wall The measured values with the diagnostic system were compared with the amounts of the scaling generated by the simulator.

• 한국자동차공학회논문집
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• 제5권2호
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• pp.69-79
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• 1997

This paper deals with the measurement and analysis on the scavenging performance of the oppet-valve type two-stroke engine with different shroud system. The scavenging flow characteristics is investigated by flow visualization under steady condition, in which a dye is introduced into single-cycle method using the difference of specific gravity between two working fluids is used to evaluate the scavenging efficiency and the trapping efficiency. The 90° shroud system was found to be the highest efficiency system through both flow visualization and single-cycle test, as well as the shroud system to generally be efficient for reducing a short-circuiting flow during scavenging process in a two-stoke engine.

• 한국축산식품학회:학술대회논문집
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• 한국축산식품학회 2004년도 정기총회 및 제33차 춘계 학술대회
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• pp.384-387
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• 2004

The purpose of the present investigation was to develop a novel method for cell immobilization. Aureobasidium pullulans cells were mixed with an alginate solution, and the mixture was extruded to form small gel beads as hydrated- immobilized cells. The beads were then placed at $-15^{\circ}C$ for 6-24 h to induce freeze-dehydration. The freeze-dehydration resulted in shrinkage of beads due to water removal reducing bead volume by 82% and bead weight by 85%. The dehydrated beads were successfully used for the production of fructo-oligosaccharides in a model reactor system. This study showed that bioreactor performance can be improved up to 2 times by the use of the dehydrated beads.