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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.
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.
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.
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.
장현재(Hyun-Jae Chang) 대한설비공학회 2006 대한설비공학회 학술발표대회논문집 Vol.2006 No.11
In this study, long term energy use at apartment house by operating mechanical ventilation system in winter season was investigated by energy simulation. Before conducting energy simulation, gas consumption rate for heating and power use to run mechanical ventilation system were examined for 1 month in winter season at one apartment house which was established the Ondol system, Korean traditional floor heating system and was established ventilation system of total heat exchanger type. The results of examination were compared with the results of energy simulation which was conducted for the same term with the examination and was simulated by considering sensible heat recovery only. Those results showed the difference of 13%. Energy simulation term was extended to the whole heating season which is from October to April, next year. Results of energy simulation for the whole heating season showed that more heating energy of 130㎾/month and more electrical energy of 79㎾/month are consumed by operating mechanical ventilation system.
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.
포러스 (Porous) 경계조건을 이용한 데이터센터의 기류 및 온도분포 해석 방법에 대한 연구
장현재(Chang Hyun-Jae),정응호(Jung Yong-Ho),서장후(Seo Jang-Hoo) 한국건축친환경설비학회 2013 한국건축친환경설비학회 논문집 Vol.7 No.4
With the development of IT industries in recent years, the needs for data centers has been increased together. Data centers in which so many server computers are arranged usually need a large cooling energy, and its energy conservation has been issued. The amount of cooling energy needed is concerned with the distribution of air flow and that of temperature in computer rooms. There are many studies on those conducted by CFD (computational fluid dynamics) simulation, and those have been conducted only in the space for computer rooms but without plenums for the supply and return. In those studies, the boundary conditions of airflow used to be given uniformly throughout the whole region of velocity outlet in the cold aisle. However, there may be a different distribution of air velocity at the velocity outlets constructed with perforated tiles, and the pressure drop through it needs to be applied to the simulation by utilizing porous boundary condition. In this study, the distributions of airflow and temperature formed in the space without plenums were compared with those formed in the space with plenums by CFD simulation. Indices of SHI, RHI, and RTI in each case were investigated. As a results, there were quite large differences between them, and conducting CFD simulations to the space including plenums was recommended as a simulation method.