• International Journal of Air-Conditioning and Refrigeration
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• 제9권3호
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• pp.46-56
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• 2001

The present study concerns the numerical simulation of a supply airflow control in a variable air volume (VAY) system. A stratified thermal model (multi-zone model) is suggested to predict a local thermal response of an air-conditioned space. The effects of various thermal parameters such as the cooling system capacity, the thermal mass of an air-conditioned space, the time delay of thermal effect, and the building envelope heat transmission are investigated. Further, the influence of control parameters such as the supply air temperature, the PI control factor and the thermostat location on a VAV system is quantitatively delineated. The results obtained show that the previous homogeneous lumped thermal model (single zone model) may overestimate the time taken to the set point temperature. It is also found that there exist the appropriate ranges of the control parameters for the optimal airflow control of the VAV system.

• 설비공학논문집
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• 제16권2호
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• pp.184-193
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• 2004

The purpose of this study is to evaluate the performance of various control strategies in commercial buildings which have been operated by the variable air volume (VAV) system. Two buildings in Seoul were chosen for the field study. The one (D building) combined by LonWorks has the constant airflow of supply fan and the proportional control of VAV units (damper type). The other (S building) combined by DDC has the PI control mode of the supply fan and the floating control of VAV units (venturi type). In estimating thermal comfort and energy performance through control modes of PI, PID, and CAV in the supply fan, we could identify several energy efficient operating control strategies for the VAV system.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.405-410
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• 2006

This paper presents a control algorithm of supply and exhaust diffusers by recognizing a contaminant source location. CFD analysis has been conducted to calculate steady state airflow and concentration distributions in a model room, which has two supply and two exhaust openings on the ceiling. Calculations have been performed for five cases out of nine different ventilation modes by combining on/off control of the supply and exhaust openings. Local mean residual life times are obtained and compared at 9 internal points for each ventilation case. Depending on the contaminant source location, the ventilation system is operated at an optimum ventilation mode, which can results in maximum exhaust performance.

• KIEAE Journal
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• 제13권5호
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• pp.43-50
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• 2013

Recent researches on plant factory system deal with the convergence of lighting technology, agricultural technology inclusive to the high-tech industries worldwide in order to respond to the decreasing crop harvest due to global warming and abnormal weather phenomena. However, the fundamental performance standard is not currently being introduced in the case of plants factory and its commercialization is not activated because of high initial investment and operating cost. Large portion of the initial investment and operating cost of a plant factory is ascribed to artificial light sources and thermal control facilities, therefore, innovation should be provided in order to improve the economics of the plant factory. As an alternative, new plant factory could harness solar thermal and geothermal systems for heating, cooling and ventilation. In this study, a natural light dependent multi-layer plant factory's thermal environment was analyzed with two-dimensional numerical methods to elicit efficient operation conditions for optimized internal physical environment. Depending on the supply air temperature and airflow rate introduced in the facility, the temperature changes around the crops was interpreted. Since the air supplied into the plant factory does not stay long enough, the ambient temperature predicted around the plating trays was not significantly different from that of the supplied air. However, the changes of airflow rate and air flow pattern could cause difference to the temperature around the planting trays. Increasing the amount of time of air staying around the planting trays could improve energy performance in case the thermal environment of a natural light based multi-layer plant factory is considered.

• 설비공학논문집
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• 제9권3호
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• pp.410-425
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• 1997

Buildings are mostly under part load conditions causing an inefficient system operation in terms of energy consumption. It is critical to operate building air-conditioning system with a scientific or optimal manner which minimizes energy consumption and maintains thermal comfort by matching building sensible and latent loads. Little research has been performed in developing general methodologies for the optimal operation of air-conditioning system. Based on this research motivation, system simulation program was developed by adopting various equipment operating strategies which are energy efficient especially for humidity control in summer. A numerical optimization technique was utilized to search optimal solution for multi-independent variables and then linked to the developed system simulation model within a mam program. The main goal of the study is to provide a systematic framework and guideline for the optimal operation of air-conditioning system focusing on air-side. For given cooling loads and ambient outdoor conditions the optimal operating strategies of a commercial building are determined by minimizing a constrained objective function by a nonlinear programming technique. Desired space setpoint conditions were found through evaluating the trade-offs between comfort and system power consumption. The results show that supply airflow rate and compressor fraction play main roles in the optimization process. It was found that variable setpoint optimization technique could produce lower indoor humidity level demanding less power consumption which will be benefits for building applications of humidity problem.

• KIEAE Journal
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• 제14권6호
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• pp.99-104
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• 2014

Recently supply of low energy house is increasing which can enhance energy efficiency and indoor environment comfort. Low energy house have to secure air tightness as well as thermal performance so house become high airtightness and inevitably need heat recovery ventilator to enhance indoor air quality. However, most of current ventilation systems are one-click, controlling the entire space so it causes increasing of heating load and fan power which makes it hard to save energy. Thus, Individual Control system is required which can achieve both enhancing indoor air quality and decreasing heating load and electric fan power. Thereby, in this study, we analyzed the correlation between ventilation and fan power through mock-up experiment and measured ventilation load under individual control system. As a result, under the condition of $24^{\circ}C$ of indoor temperature for 6 month(November to April) in Daejeon, ventilation load by fan speed was $10.9{\sim}19.6kWh/m^2{\cdot}a$ when operated 24 hours and $7.6{\sim}13.7kWh/m^2{\cdot}a$ when operated 12 hours in night time. In addition, it is possible to reduce at most 60% of ventilation load under the individual control system; measured ventilation load was $7.4kWh/m^2{\cdot}a$ when operated 24 hours, and $5.5kWh/m^2{\cdot}$ when operated 12 hours in night time.

• 한국산학기술학회논문지
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• 제10권3호
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• pp.463-469
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• 2009

시멘트 포장공정에서 발생하는 비산분진을 효율적으로 제거하기 위해 3가지 환기방식(국소배기시스템, 정전식스크러버시스템, 국소급기시스템)을 도입하고 풍량을 변화시키며 총 9가지의 조건에서 실험을 수행하였다. 분진의 농도는 시멘트분진 입자분포 특성을 고려하여 PM2.5, PM10, TSP로 구분하여 측정하였다. 3가지 환기방식에 대한 집진효율을 분석한 결과, 기존의 국소배기시스템과 정전식스크러버시스템이 같이 사용되는 경우 가장 효율적인 것으로 나타났다. 또한 정정식스크러버시스템의 풍량 증가에 따른 입자의 질량농도감소율이 큰 차이가 없는 것을 확인할 수 있었고 이로부터 정정식스크러버시스템을 $2,700m^3/h$ 풍량으로 운전하는 것이 에너지절약 관점에서 효율적인 것이라고 판단되었다. 각 환기방식별 환기성능을 국소배기시스템의 풍량으로 환산한 결과, 대체시스템(정전식스크러버시스템, 국소급기시스템)분진제거성능이 우수한 젓으로 나타났고 정전식스크러버시스템이 국소급기시스템보다 상당히 효율적인 것으로 나타났다. 따라서 기존의 국소배기시스템파 정전식스크러버시스템을 동시에 가동한다면 국소배기시스템의 풍량만을 증가시키는 경우에 비해 반송동력을 줄일 수 있어 분진제거와 에너지절감측면에서 훨씬 효율적이라는 것을 알 수 있었다.

• 한국농공학회논문집
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• 제64권5호
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• pp.9-16
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• 2022

Syngas, also known as synthesis gas, synthetic gas, or producer gas, is a combustible gas mixture generated when organic material (biomass) is heated in a gasifier with a limited airflow at a high temperature and elevated pressure. The present research was aimed at modifying the existing LPG engine generator for fully operated syngas. During this study, the designed gasifier-powered woodchip biomass was used for syngas production to generate power. A 6.0 kW LPG engine generator was modified and tested for operation on syngas. In the experiments, syngas and LPG fuels were tested as test fuels. For syngas production, 3 kg of dry woodchips were fed and burnt into the designed downdraft gasifier. The gasifier was connected to a blower coupled with a slider to help the air supply and control the ignition. The convection cooling system was connected to the syngas flow pipe for cooling the hot produce gas and filtering the impurities. For engine modification, a customized T-shaped flexible air/fuel mixture control device was designed for adjusting the correct stoichiometric air-fuel ratio ranging between 1:1.1 and 1.3 to match the combustion needs of the engine. The composition of produced syngas was analyzed using a gas analyzer and its composition was; 13~15 %, 10.2~13 %, 4.1~4.5 %, and 11.9~14.6 % for CO, H₂, CH₄, and CO₂ respectively with a heating value range of 4.12~5.01 MJ/Nm³. The maximum peak power output generated from syngas and LPG was recorded using a clamp-on power meter and found to be 3,689 watts and 5,001 watts, respectively. The results found from the experiment show that the LPG engine generator operated on syngas can be adopted with a de-ration rate of 73.78 % compared to its regular operating fuel.

• 터널과지하공간
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• 제28권1호
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• pp.38-58
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• 2018

갱내환기는 지하광산 안전성에 직접적인 영향을 미친다. 갱내환기는 정상시에는 작업공간내 유해물질의 희석을 위한 충분한 량의 급기를 통하여 쾌적한 환경을 유지하는 것이 목적이나 갱내화재와 같은 비상시에는 화재의 확산제어와 구조활동의 지원을 목적으로 한다. 본 연구를 통하여 작업공간 국부환기 뿐만 아니라 화재연 제어를 위한 방재팬을 개발하였다. 방재팬은 풍관없이 가동되며 작업공간내 유해물질의 희석 및 배기 기능을 갖추고 있으며 동시에 화재시 화재연 배기를 목적으로 한다. 본 논문은 개발된 방재팬과 기존 국부팬의 연결 운전을 통한 화재연의 배기효율 연구가 목적이다. 일련의 현장 실험 및 CFD분석을 통하여 맹갱도 작업공간내 방재팬의 화재연 배기효율을 분석하였으며 이를 위하여 SF6 추적가스를 이용한 공간내 기류 및 유해물질 유동을 검토하였다. 대단면 석회석 광산에서 수행한 현장실험과 CFD분석 결과를 비교한 결과, 갱내에서 가장 리스크가 큰 맹갱도 굴진 작업장에서 기존 국부팬 1대와 조합 운전하는 경우, 팬의 설치 위치 및 운전모드의 적절한 선택시에 효율적인 화재연 배기가 가능함을 보였다. 또한 CFD분석을 통하여 벤츄리효과에 의한 배기효율도 확인할 수 있었다. 팬 설치 위치 및 운전모드가 배기효율을 결정하는 가장 중요한 변수임을 보였다.

• 대한환경공학회지
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• 제30권9호
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• pp.948-954
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• 2008

침지형 MBR 공정에서 막 오염과 플럭스 감소의 주요 원인인 케이크층에 의한 저항을 저감하기 위하여 분리막 모듈의 외부에 원통형 관을 도입하였다. 도입된 원통형관 안에 노즐과 산기관을 적용하여 공기 주입량에 따른 공기와 액체의 2상흐름(Two phase flow)중 slug 흐름을 유도하여 공기 방울에 의한 막세정의 효과를 비교 분석하였다. 실험결과 동일한 유량의 공기를 공급할 경우 노즐에서 발생한 공기방울이 원통형관으로 유입되면서 효율적인 slug 흐름을 형성으로 산기관을 사용한 공급 방식보다는 막오염 방지에 효과적이었음을 알 수 있었다. 그러나 노즐로 공급되는 공기의 유량을 최적화하지 않는다면 원통형 관의 벽 부분부터 활성슬러지 혼합액이 퇴적하게 되거나 막간에 슬러지가 퇴적되어 관 내부의 급격한 막힘 현상이 발생하여 일정시간이 경과하면, 오히려 산기관보다 급격한 막오염 현상을 나타냄을 알 수 있었다. 또한 원통형 관 내부에 침지된 분리막의 면적의 최적 비율, A$_m$/A$_t$가 비율이 존재하는 것을 확인할 수 있었다. 산기관의 경우에는 A$_m$/A$_t$ 비율이 0.27일 때 최소화된 막오염이 관찰된 반면에, 노즐의 경우에는 A$_m$/A$_t$ 비율이 0.55일 때 막오염이 최소값을 보였다. 따라서 상승하는 공기방울에 의한 막오염 저감효과는 관 내부의 중공사막이 차지하고 있는 비율, A$_m$/A$_t$에 크게 의존하고 있으며, 산기관과 노즐의 경우 그 최적비율은 각각 다름을 알 수 있었다.