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실측 및 모델베이스 계산을 통한 계사의 온열환경파악 및 THI 예측식 개발
하주완(Ha, Ju-Wan),장홍희(Chang, Hong-Hee),차광준(Cha, Kwang-Jun),송영학(Song, Young-Hak) 한국건축친환경설비학회 2020 한국건축친환경설비학회 논문집 Vol.14 No.2
The heat waves cause heat stress to livestock thereby degrading productivity and increasing the mortality rate. Thus, this study aims to identify the thermal environment of hen house through on-site measurements and depending on ventilation type to increase the efficiency of management of the laying house during severely hot weather by deriving a Temperature and Humidity Index (THI Index) prediction equation from the viewpoint of productivity. To do this, this study comparatively analyzed the exposure risk level to the heat stress of layers according to the ventilation method in the hen house using the THI, which was an index to quantitatively evaluate heat stress, for 26 summer days. In addition, the laying house in this study were modeled through simulations. The simulation results exhibited the highest reliability values under 25°C inside the cage and an 85.7% fan operating rate in the case of the cross ventilation method, which had 0.46 of mean bias error (MBE) and 10.58 coefficient of variation of the root mean square error (CVRMSE), while the tunnel ventilation method had 1.14 MBE and an 8.64 CVRMSE with temperature values under 27°C inside the cage, and a 100% fan operating rate. Since the above conditions were found for a simulated target building, the calculated values were utilized to derive the prediction equation. The regression analysis results showed that the coefficients of determination, which displayed the reliability of the correlation between THI and the outdoor air temperature and between THI and enthalpy, which were 0.9328 and 0.5149 respectively in the case of the cross ventilation method and 0.9551 and 0.6044 respectively in the case of the tunnel ventilation method.
하주완(Ha, Ju-Wan),김유진(Kim, Yu-Jin),김환용(Kim, Hwan-Yong),송영학(Song, Young-Hak) 한국건축친환경설비학회 2021 한국건축친환경설비학회 논문집 Vol.15 No.5
The chiller efficiency is an important factor for improving the efficiency of the central chilled water system. A low-condenser water temperature is required for the low cooling tower leaving water temperature, which affects the chiller efficiency. Various studies have been conducted to produce low-condenser water temperature, but an additional review is needed on a method to lower the approach temperature. This study developed a control algorithm for cooling tower low-approach temperature. The approach temperature changes within the same load, ambient conditions according to the liquid-to-gas ratio (LGR), which is the operating condition of the cooling tower system. It found that the lower the LGR, the lower the approach temperature could be secured. As the approach temperature is lowered, it is expected that the efficiency of the chiller and cooling water pump will be improved.
실측 및 모델베이스 계산을 통한 계사의 온열환경파악 및 THI 예측식 개발
하주완(Ha, Ju-Wan),장홍희(Chang, Hong-Hee),차광준(Cha, Kwang-Jun),송영학(Song, Young-Hak) 한국건축친환경설비학회 2020 건축환경설비 Vol.14 No.2
The heat waves cause heat stress to livestock thereby degrading productivity and increasing the mortality rate. Thus, this study aims to identify the thermal environment of hen house through on-site measurements and depending on ventilation type to increase the efficiency of management of the laying house during severely hot weather by deriving a Temperature and Humidity Index (THI Index) prediction equation from the viewpoint of productivity. To do this, this study comparatively analyzed the exposure risk level to the heat stress of layers according to the ventilation method in the hen house using the THI, which was an index to quantitatively evaluate heat stress, for 26 summer days. In addition, the laying house in this study were modeled through simulations. The simulation results exhibited the highest reliability values under 25°C inside the cage and an 85.7% fan operating rate in the case of the cross ventilation method, which had 0.46 of mean bias error (MBE) and 10.58 coefficient of variation of the root mean square error (CVRMSE), while the tunnel ventilation method had 1.14 MBE and an 8.64 CVRMSE with temperature values under 27°C inside the cage, and a 100% fan operating rate. Since the above conditions were found for a simulated target building, the calculated values were utilized to derive the prediction equation. The regression analysis results showed that the coefficients of determination, which displayed the reliability of the correlation between THI and the outdoor air temperature and between THI and enthalpy, which were 0.9328 and 0.5149 respectively in the case of the cross ventilation method and 0.9551 and 0.6044 respectively in the case of the tunnel ventilation method.
지역별 기상조건을 고려한 저온 냉각수 온도 및 제조 시간 파악에 관한 연구
하주완(Ha, Ju-Wan),김유진(Kim, Yu-Jin),김환용(Kim, Hwan-Yong),송영학(Song, Young-Hak) 한국건축친환경설비학회 2020 한국건축친환경설비학회 논문집 Vol.14 No.3
Generally, cooling towers are operated at the nominal value by fixing the condenser water temperature to 32℃. However, it is expected that based on outdoor air, condenser water can be produced at temperatures lower than the nominal value excluding daytime hours in the summer season. On the other hand, from the viewpoint of a refrigeration cycle, the chiller COP increases if the inlet temperature of the condenser is lower. Accordingly, in this study, total amount of time when low-temperature condenser water could be produced, thereby imparting an improvement on the chiller, and assess the condenser water temperature during that time are examined. For calculation, EnergpyPlus v.9.3 was used and the typical meteorological data for Busan, Seoul, Chuncheon, and Daegwallyeong, representing a total of 4 climate zones were applied. In addition, in order to produce low-temperature condenser water, a two-speed control cooling fan and a variable flow-rate pump were adapted. From the result of the simulation, 24 to 27℃ condenser water for 77% the cooling system operating time in Busan, and 94% of the cooling system operating time in Seoul was produced, and 21 to 24℃ condenser water for 55% of the cooling system operating time in Chuncheon and, 82% of the cooling season operating time in Daegwallyeong was produced. Additionally, during the intermediate season, 24 to 27℃ condenser water for 99% of the cooling system operation time in Busan and Seoul was produced, and 21 to 24℃ condenser water for 99% and 98% of the cooling system operation time in Chuncheon and Daegwallyeong was produced respectively.
입력변수의 불확실성 보정을 위한 인공신경망 대리모델 기반의 민감도 분석 및 베이지안 MCMC
박성철(Park, Seong-Cheol),하주완(Ha, Ju-Wan),박경순(Park, Kyung-Soon),송영학(Song, Young-Hak) 한국건축친환경설비학회 2021 한국건축친환경설비학회 논문집 Vol.15 No.4
To have a precise simulation of building and quantitative performance evaluation, it is necessary to have high accuracy of input variables to implement a simulation. Inherent uncertainties (unknown fault or rapid error generation, etc.) in input variables can have a significant impact on energy performance evaluation. To solve this, this study conducted Artificial Neural Network (ANN) surrogate model-based Sobol sensitivity analysis using data of water-cooled variable refrigerant flow air conditioning system and Bayesian Markov chain Monte Carlo (MCMC) using no-U-turn sampler (NUTS) algorithm was performed. The main results showed that the Coefficient of the Variation of the Root Mean Square Error of the ANN surrogate model was 23.4%, and the top 6 variables that affected the energy usage through the sensitivity analysis results were selected. Then, the prior and posterior probability distributions were plotted through Bayesian MCMC. The convergence verification result of MCMC verified that the mean R-hat value was 1.0, which ensured the accuracy of MCMC. For future study, a virtual sensor will be developed to detect and diagnose faults in building heating, ventilation, and air conditioning based on the study results.
저온냉각수 및 Free Cooling 적용에 의한 데이터센터의 냉방성능 검토
김유진(Kim, Yu-Jin),하주완(Ha, Ju-Wan),박경순(Park, Kyung-Soon),이건호(Lee, Keon-Ho),송영학(Song, Young-Hak) 한국건축친환경설비학회 2020 한국건축친환경설비학회 논문집 Vol.14 No.5
The size and number of internet data center (IDC) has been growing rapidly as IT demand has increased recently. IDC needs 10 times as much energy as regular office buildings, there are problems with global warming and increasing carbon emissions. IDC"s cooling energy consumption to maintain the IT equipment environment accounts for about 35% of total energy consumption. Therefore, the use of cooling energy was reviewed through simulation by applying the low cooling water temperature system and the free cooling system in this system. Based on this, cooling performance was analyzed using MLC (Mechanical Load Component) indicators. As a result of the simulation, energy consumption in low cooling water temperatures decreased by 8% compared to normal water-cooling systems, while WSE (Water Side Economizer) and ASE (Air Side Economizer) decreased by 26% and 32%, respectively. Since the MLC of conventional water-cooled system was 0.13 which is lower than Incheon"s maximum allowable value of 0.18. As a result of the MLC analysis, it was determined that the cooling system was properly designed. The cooling energy usage showed a significant reduction rate in the order of low cooling water temperature, WSE, and ASE, and the ASE was the most efficient operation with 26.3%.