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여름철 통풍시의 아파트 실내 온열환경에 대한 기초적 연구
장현재(Chang Hyun-Jae) 한국건축친환경설비학회 2008 한국건축친환경설비학회 논문집 Vol.2 No.1
Wind driven ventilation has been used actually to endure high temperature and high humidity in summer, in Korea. If it is insufficient to cool indoor area only with wind driven ventilation, it is hard to sleep in night time and air conditioner has been used. It is considered that weight structure of reinforced concrete, which is usually used for apartment housing in Korea, affect indoor thermal environment in day time and in night time. In this study, indoor thermal environment in an apartment house was measured to understand thermal specificities in summer. As a results, surface temperatures of furniture, ceiling, floor, wall have a small band of temperature change than a band of indoor air temperature change.
겨울철 난방시 탑상형 아파트 구조체의 축·방열 특성에 대한 현장측정 연구
장현재(Hyun-Jae Chang),조근제(Keun-Je Cho) 대한설비공학회 2012 설비공학 논문집 Vol.24 No.2
In this study, as a complementary study of the former study on indoor thermal environment in a tower type apartment house at tropical nights, a field measurement was conducted in winter season. Mainly, characteristics of heat storage and heat emission in apartment structures, in this study, were investigated. As results, indoor air temperature was changed in the range of 22.5℃±1.0℃, and followed not the change of outdoor air temperature but the changed pattern of floor surface temperature. Wall surface temperature was unresponsive to the change of floor surface temperature compared with the change of indoor air temperature because wall structure was composed of concrete which has large heat capacity, and was changed in the range of 22.3℃±0.6℃. Heat was stored continuously into the structures of wall and ceiling through the measurement term. and this means that a large heat capacity of the apartment structure acts as a disadvantage in winter season, too. As a total review of the study with the former study, a large heat capacity of the apartment structure acts against indoor thermal comfort in winter season as well as in summer season.
데이터센터의 급기온도 변화가 서버 냉각 성능에 미치는 영향에 대한 연구
장현재(Hyun Jae Chang) 대한설비공학회 2018 설비공학 논문집 Vol.30 No.2
A datacenter is a high energy consuming facility whose cooling energy consumption rate is 10~20 times larger than general office buildings. The higher the temperature of supply air from a CRAC (computer room airconditioner) is supplied, the more energy efficient cooling is possible because of improving the COP of a chiller and advanced range of outdoor air temperature available for the economizer cycles. However, because the temperature of cold air flowing into server computers varies depending on air mixing configurations in a computer room, the proper supply air temperature must be considered based on the investigation of air mixing and heat dissipation. By these, this study aims to understand the effects of variation of the supply air temperature on the air flow distributions, temperature distributions and rack cooling efficiencies. Computational fluid dynamics (CFD) aided in conducting the investigation. As a result, the variation of the supply air temperature does not affect the air flow distributions. However, it mainly affects the temperature distribution. From the results of CFD simulations, Rack cooling indices (RCIHI and RCILO) were evaluated and showed the ideal state set at 19℃ of the supply air temperature.
탑상형 아파트 만곡부의 외부 통풍환경 개선에 대한 연구
장현재(Hyun-Jae Chang),김형진(Hyung-Jin Kim) 대한설비공학회 2012 설비공학 논문집 Vol.24 No.1
Recently, tower type apartment has been a main stream at the apartment market, in Korea. Tower type apartment has features that is easy to maintain a proper distance between apartment buildings, and to keep a prospect comparing to flat type apartment However, there is usually a inner curved area at tower type apartment, and it is able to make an unhealthy environment because of shaded area through a day and a bad air flow. In this study, the duration of sunshine and the exterior air flow environments are examined. As results, the duration of sunshine at the inner curved area of tower type apartment was extremely short, and the exterior air flow environment was very bad for the low air velocity of about 0.08m/s. Installing pilotis in the 1st floor which faces to the inner curved area makes the good improvement of exterior air flow environment.
장현재(Hyun-Jae Chang),김형진(Hyung-Jin Kim) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.3
Total heat recovery type ventilators that are connected to each room with ducts are mainly installed in Korea, but they raise concern over duct pollution. In this study, indoor environments made by thin line type ventilators installed in dwelling units of apartment houses are investigated by CFD. Results show the case that thin line type ventilators installed in each room-including kitchens-make the best indoor environment that maintains air velocity at under 0.25㎧, and evenly distributes the age of air in all areas.
여름철 열대야 발생시 탑상형 아파트의 실내온열환경에 대한 연구
장현재(Hyun-Jae Chang),김형진(Hyung-Jin Kim) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.1
In this study, As a basic research for improving indoor thermal environment at tower type apartment houses, specifications of heat storage and heat emission in the structures of apartment houses were investigated, and the ratio of indoor and outdoor air velocity at tower type apartment house was examined, too. Indoor temperature at night time was higher than outdoor air temperature because heat emission from the structure of wall, ceiling and floor those are constructed by use of reinforced concrete which has large heat capacity. The ratio of indoor and outdoor air velocity was lower than 0.1 and this was caused by the plan of tower type apartment house. PMV was in the range of 0.3~1.9, and was about 1.0 (it means slightly warm) at 10:00 p.m.. To improve indoor thermal environment in summer season at tower type apartment houses, it needs more investigation on specifications of heat storage and heat emission in the structure including winter season, and on the improvement of the ratio of indoor and outdoor air velocity.
서버 컴퓨터의 발열량이 변화한 경우의 데이터센터 내의 기류 및 온도분포 특성에 대한 연구
장현재(Hyun-Jae Chang),김제영(Je-Young Kim) 대한설비공학회 2014 설비공학 논문집 Vol.26 No.3
On a large scale of data center, heat generation rates from sever computers occupy almost the entire cooling load of the building, and it is gradually increasing. The efficiency of air distribution system in data centers can be affected by heat generation rates of server computers. In this study, the distributions of airflow and temperature in a data center have been investigated by CFD simulations under various conditions of heat generation rates for server computers. From the results, air around the cold aisle which has high temperature flows tremendously into the cold aisle according to the increase of heat generation rates for server computers and the air temperature in the cold aisle becomes higher. The SHI (supply heat index) and RHI (return temperature index) show almost similar values to the cases study because the air inflow rates to server computers increase with the heat generation rates of server computers.
냉복도 밀폐시스템의 적용에 의한 데이터센터 서버실의 냉방에너지 절감 효과 분석
장현재(Chang Hyun-Jae),정용호(Jung Yong-Ho),서장후(Seo Jang-Hoo) 한국건축친환경설비학회 2012 한국건축친환경설비학회 논문집 Vol.6 No.3
In order to keep the server room temperature condition, energy consumption has been rapidly increased as the increasing internal heat gain of server room in data center. And the cooling units for server systems are fully operated to satisfy the indoor temperature condition, it results in the excessive energy consumption. There are many wastes of cooling energy which is caused by the structural problems in data center server room. For example, a leakage by the electric cable hole, mixing or recirculation of hot air from the hot aisle to the cold aisle, short circulation of the CRAC(Computer Room Air Conditioning), and others. So there are many strategies to reduce the waste of cooling energy in data center. In this study, cold aisle containment system was proposed among the various strategies to reduce the waste energy by recirculation air from the hot aisle. To verify the effectiveness of the cold aisle containment system, test bed which is same with exist server room was set up in IDC(Internet Data Center) building. And comparative experiments, conventional open type cooling system and cold aisle containment sysetm, were carried out in actual conditions. As the result, the range of inlet temperature of server system was 20~25℃ in exist cooling system and the range of inlet temperature dropped below 20℃ by cold aisle containment system. After all, was possible by the cold aisle containment system and cold aisle containment system was proved to be the solution for energy saving cooling system.