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이강현(Kang Hyun Lee),윤승환(Seung Hwan Yoon),정성진(Sung Jin Jung) 대한설비공학회 2017 대한설비공학회 학술발표대회논문집 Vol.2017 No.6
One of main trend of environmentally friendly building is definitely UFAD system which has great advantage in LEED certification. This case study is aimed to show the mechanical, control design concept of pressurized plenum UFAD system which is the mainstream in North America and has increasing reference in Korea. It is investigated how the plenum zoning, AHU configuration, supply duct, diffuser selection and pressure/temperature control system are designed for three applications such as office, concert hall and library. In addition, several considerations are summarized for the pressurized plenum UFAD system design.
CFD를 이용한 등압식 바닥공조시스템의 냉방기 열환경 평가
채영태,정용호 청운대학교 건설환경연구소 2013 청운대학교 건설환경연구소 논문집 Vol.8 No.1
The conventional UFAD(Under Floor Air Distribution) system has come into wide use as the improved air conditioning system by the performance of thermal environment and energy efficiency. But, it has some problem of nonuniform air distribution and air temperature due to the distance from the AHU(Air Handling Unit) and pressurized under floor plenum. Equal Pressure UFAD system is composed of AHU, FTU(Fan Terminal Unit), BPG(Bypass Grille). It keeps the under floor air plenum atmospheric pressure and it is possible to realize the uniform air distribution and air temperature. The purpose of this study is to evaluate the UFAD system by examining air pattern and thermal environment condition using CFD(Computational Fluid Dynamics) in cooling season. 바닥취출 공조방식은 에너지 효율적인 측면과 실내 온열환경의 측면에 장점 때문에 기존의 천정취출방식의 개선방으로서 널이 보급되어 왔다. 그러나 현재 적용되고 있는 바닥취출공조방식은 공조기로부터의 거리 차이에 따른 압력분포 불균형, 온도분포 불균일 등의 문제를 가지고 있다. 이에 비하여 공조기, 터미널 유니트, 바이패스 그릴로 구성된 등압식 바닥공조방식은 균일한 온도분포와 기류분포의 장점을 가지고 있다. 본 연구에서는 CFD를 이용하여 등압식 바닥공조시스템의 냉방기 실내 열환경을 평가하고자 한다.
연상훈(Sang Hun Yeon),이광호(Kwang Ho Lee) 대한설비공학회 2018 설비공학 논문집 Vol.30 No.6
An underfloor air distribution (UFAD) system is an air conditioning system that enables the maintenance of indoor temperature with a relatively small supply-return air temperature gap and at a low supply air flow rate. UFAD offers a variety of advantages compared to conventional overhead systems, including improvements in comfort, health, work efficiency, indoor air quality, and ventilation efficiency for occupants, and improvements in life cycle cost decrease and lay-out flexibility for building services. In addition, using a UFAD system reduces the floor height because the duct space becomes unnecessary. A key factor for the improved energy performance of the UFAD system is stratification, which refers to the inconsistent vertical temperature distribution from the floor to the ceiling resulting from the buoyant effect of air. Stratification plays a critical role in determining the heat, ventilation, and energy performance of a system. However, based on a domestic literature review, research into the stratification of UFAD is insufficient, reflected by a lack of understanding of stratification and a lack of detailed research related to UFAD. Therefore, this study, by using the EnergyPlus simulation and Phi-Gamma formula, aims to assess variations in stratification according to diffuser condition.
가압식 바닥공조 시스템과 야간 외기냉방의 병용에 따른 에너지저감 성능에 관한 연구
윤성훈(Yoon Seong-Hoon) 한국태양에너지학회 2020 한국태양에너지학회 논문집 Vol.40 No.1
It has been reported about the energy saving performance of UFAD(under floor air distribution) system and NPC(night purge cooling) system respectively which are applied for commercial buildings. However, when two systems are used at the same time, the effect of heat transfer from floor plenum to slab may vary depending on the operating conditions of NPC. In this study, cooling energy demands were analyzed for building models with UFAD and NPC by using TRNSYS 17 program. UFAD was applied as a cooling system of the base building model, and the cooling energy demands were compared for 64 cases in which the operating time, supply airflow rate, and outdoor air temperature(To) of NPC. As a result, i t was confirmed that the cooling energy demands were reduced to 30 ~ 80% level compared to UFAD alone, and in particular, the energy demand was reduced in proportion to the supply airflow rate or the operating time while To was 16 ~ 20℃. However, when To was 22℃, the increase in the supply airflow rate or the operating time results in a disadvantage in terms of cooling energy demands. In addition, the cooling energy demands for UFAD+NPC model were analyzed by applying weather data from three regions with different average outdoor air temperatures. As a result, the cooling energy demand of operating NPC only when To was below 20℃ was reduced by 27% compared to that of operating NPC continuously for 8 hours.
에너지 절약형 공조시스템 별 냉방 운전 특성 및 에너지 절감 효과 비교 분석
김철호(Chul Ho Kim),이승언(Seung Eon Lee),김강수(Kang Soo Kim) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.-
In this study, we conducted EnergyPlus dynamic simulation for the design and selection of energy conservational HVAC Systems. The air-conditioning systems selected for this study are CAV(Constant Air Volume), VAV(Variable Air Volume), UFAD(Under Floor Air Distribution), and Active chilled beam with DOAS(Dedicated Outdoor Air System). We analyzed indoor temperature, relative humidity, supply air flow, cooling energy and CO2 emissions for each HVAC system used during cooling season. For the same indoor setting temperature, CAV’s supply air flow was the highest, and Active chilled beam with DOAS was analyzed as being able to perform air conditioning only with minimum outdoor air volume. VAV and UFAD system operated by varying the supply air volume according to the changing indoor load. Cooling energy was reduced by about 24.8% by applying VAV compared to CAV, and by about 33.9% by applying UFAD, 39.1% by Active Chilled Beam with DOAS. CO2 emissions also showed similar savings as that of cooling energy.
CFD를 활용한 바닥공조시스템 디퓨저의 성층화 모델 예측
손정은(Jeong-Eun Son),유병호(Byeong-Ho Yu),방승기(Seung-Ki Pang),이광호(Kwang Ho Lee) 대한설비공학회 2017 설비공학 논문집 Vol.29 No.3
Underfloor air distribution (UFAD) is an air distribution strategy for providing ventilation and space conditioning in buildings. UFAD systems use the underfloor plenum beneath a raised access floor to provide conditioned air through floor diffusers that create a vertical thermal stratification during cooling operations. Thermal stratification has significant effects on energy, indoor air quality, and thermal comfort performance. The purpose of this study was to characterize the influence of a linear bar grille diffuser on thermal stratification in both interior and perimeter zones by developing Gamma-Phi based prediction models. Forty-eight simulations were carried out using a Computational Fluid Dynamics (CFD) technique. The number of diffusers, the air flow supply, internal heat gains, and solar radiations varied among the different cases. Models to predict temperature stratification for the tested linear bar grille diffuser have been developed, which can be directly implemented into dynamic whole-building simulation software such as EnergyPlus.
정재동(Jae Dong Chung),홍희기(Hiki Hong),유호선(Hoseon Yoo) 대한설비공학회 2006 대한설비공학회 학술발표대회논문집 Vol.2006 No.6
Despite the fact that UFAD (Under Floor Air Distribution) systems have many benefits and are being applied in the field in increasing numbers, there is a strong need for an improved fundamental understanding of several key performance features of these systems. This study numerically investigates the effect of design parameters on the performance of UFAD, especially focused on thermal comfort. The design parameters considered in this study include supplied air temperature, supplied flow rate, diffuser shape, swirl, diffuser location, and floor-to-floor height. Also this study has compared UFAD with over head system, on the point of thermal comfort by evaluating PMV using radiative mean temperature, which shows how inadequate the evaluation of thermal comfort can be when radiation is neglected. Until now, the radiative temperature has been the missing link between CFD and thermal comfort, but the present study paves the way for overcoming this weakness.
태양광을 이용한 증발냉각기반 전외기 공조시스템 적용 UFAD 시스템 설계를 위한 Design Tool 개발
석윤진(Seok, Youn-Jin),김민휘(Kim, Min-Hwi),진정탁(Jin, Jeong-Tak),조홍재(Cho, Hong-Jae),정재원(Jeong, Jae-Weon) 한국건축친환경설비학회 2011 한국건축친환경설비학회 논문집 Vol.5 No.4
The purpose of this study is to develop a design tool which can estimate the Indirect and Direct Evaporative Cooling assisted 100% Outdoor Air System (IDECOAS) integrated with Underfloor Air Distribution system (UFAD system) capacity approximately, the required PV array area and monthly power and evaluate the design tool compared with a installation case. For this, the simulation is conducted in the same condition of input parameters with case study on real building in Mokpo. The results show difference because solar radiation data and monthly PV module efficiency in real case have differences compared with simulation. But since monthly PV efficiencies in simulation have been corrected in the same condition of real case, the results show very similarity.
바닥공조시스템에서 복사온도가 열적 쾌적성에 미치는 영향
정재동(Jae Dong Chung),홍희기(Hiki Hong),유호선(Hoseon Yoo) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.11
Despite the fact that UFAD(Under Floor Air Distribution) systems have many benefits and are being applied in the field in increasing numbers, there is a strong need for an improved fundamental understanding of several key performance features of these systems. This study numerically investigates the effect of supplied air temperature and supplied flow rate on the performance of UFAD, especially focused on thermal comfort. Also this study has compared UFAD with conventional overhead air distribution system. In contrast to the well-mixed room air conditions of the conventional overheat system, UFAD system produces an overall floor-to-ceiling airflow pattern that takes advantage of the natural buoyancy produced by heat sources in the occupied zone and more efficiently removes heat loads and contaminants from the space. Thermal comfort parameters were evaluated by CFD approach and then PMV was computed to detect the occupants' thermal sensation. Results show that radiative mean temperature plays crucial role on the evaluating PMV. Until now, the radiative temperature has been the missing link between CFD and thermal comfort, but the present study paves the way for overcoming this weakness.