저온잠열저장을 위한 TMA-물계 포접화합물의 과냉각 특성에 대한 연구

김창오(Kim Chang-Oh),김진흥(Kim Jin-Heung),정낙규(Chung Nak-Kyu) 한국태양에너지학회 2006 한국태양에너지학회 학술대회논문집 Vol.- No.-

Ice storage system that water is used as low temperature latent heat storage material, refrigerator capacity is increased and COP is decreased because refrigerator is operated at low temperature due to supercooling of water in the course of phase change from solid to liquid. This study is investigated the cooling characteristics of the TMA-water clathrate compound including TMA(Tri-methyl-amine, (CH₃)₃N) of 20~25 wt% as a low temperature latent heat storage material at -5℃, cooling source temperature. The results showed that the phase change temperature, the specific heat is increased and the supercooling degree is decreased as the weight concentration of TMA became higher. Especially, low temperature latent heat storage material containing TMA 25 wt% has the average of phase change temperature of 5.8℃, supercooling degree of 8.0℃ and specific heat of 4.099kJ/㎏K inthe cooling process. Phase change temperature higher than that of water and inhibitory effect against supercooling can be confirmed through experimental study on cooling characteristics of TMA-water clathrate compound.

저온잠열저장을 위한 TMA-물계 포접화합물의 과냉각 개선에 대한 연구

김창오(Kim Chang-Oh),김진흥(Kim Jin-Heung),정낙규(Chung Nak-Kyu) 한국태양에너지학회 2007 한국태양에너지학회 학술대회논문집 Vol.- No.-

This study aims to find out cooling characteristics of TMA(Tri-Methyl- Amine, (CH₃)₃N) 25wt%-water clathrate compound with ethanol(CH₃CH₂OH) such as supercooling, phase change temperature and specific heat. For this purpose, ethanol is added as per weight concentration and cooling experiment is performed at -6˜-8℃, cooling heat source temperature, and it leads the following result. (1) Phase change temperature is decreased due to freezing point depression phenomenon. Especially, it is minimized as 3.8℃ according to cooling source temperature in case that 0.5wt% of ethanol is added. (2) If 0.5wt% of ethanol is added, average supercooling degree is 0.9℃ and minimum supercooling is 0.8, 0.7℃ according to cooling heat source temperature. The restraint effect of supercooling is shown. (3) Specific heat shows tendency to decrease if ethanol is added. It is 3.013~3.048 ㎉/㎏℃ according to cooling heat source temperature if 0.5wt% of ethanol is added. Phase change temperature higher than that of water and inhibitory effect against supercooling can be confirmed through experimental study on cooling characteristics of TMA 25wt%-water clathrate compound by adding additive, ethanol. This can lead to shorten refrigerator operation time of low temperature latent heat storage system and improve COP of refrigerator and efficiency of overall system. Therefore energy can be saved and efficiency can be improved much more.

저온잠열축열을 위한 TMA-물계 포접화합물의 냉각특성

김창오(Kim Chang-Oh),정현호(Chung Hyoun-Ho),정낙규(Chung Nak-Kyu) 한국태양에너지학회 2009 한국태양에너지학회 학술대회논문집 Vol.- No.-

The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity is increased and COP is decreased due to supercooling of water in the course of phase change from solid to liquid. This study investigates the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, (CH₃)₃N) of 20~25 wt% as a low temperature latent heat storage material. The results showed that the phase change temperature and the specific heat is increased and the supercooling degree is decreased as the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25wt% has the average phase change temperature of 5.8℃, the supercooling degree of 8.0℃ and the specific heat of 3.499 kJ/㎏K in the cooling process. This can lead to reduction of operation time of refrigerator in low temperature latent heat storage system and efficiency improvement of refrigerator COP and overall system. Therefore, energy saving and improvement of utilization efficiency are expected.

TMA 농도에 따른 저온잠열축열물질의 냉각특성

김창오(Kim Chang-Oh),정현호(Chung Hyoun-Ho),정낙규(Chung Nak-Kyu) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity is increased and COP is decreased due to supercooling of water in the course of phase change from solid to liquid. This study investigates the phase change characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, (CH₃)₃N) of 20~25 wt% as a low temperature latent heat storage material. The results showed that the phase change temperature and the specific heat is increased and the supercooling degree is decreased as the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25wt% has the average phase change temperature of 5.8℃ and the supercooling degree of 8.0℃ in the cooling process. This can lead to reduction of operation time of refrigerator in low temperature latent heat storage system and efficiency improvement of refrigerator COP and overall system. Therefore, energy saving and improvement of utilization efficiency are expected.

TMA 농도에 따른 저온잠열축열물질의 냉각특성

김창오(Kim Chang-Oh),정현호(Chung Hyun-Ho),정낙규(Chung Nak-Kyu) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.2

빙축열시스템은 저온잠열저장을 위해 물을 사용한다. 그러나 물은 액체에서 고체로 상변화를 하는 과정에서 물의 과냉각 현상에 의하여 냉동기의 냉동용량 증가와 COP감소의 원인이 되고 있다. 본 연구는 저온잠열축열물질로 적용 가능한 TMA(Tri-methyl-amine, (CH3)3 N) 20~25 wt%를 포함하고 있는 TMA-물계 포접화합물(TMA-water clathrate compound)의 냉각특성에 대한 실험적 연구를 수행하였다. 실험적 연구 결과, TMA 질량농도가 높을수록 상변화온도는 증가하였고, 과냉각도와 비열은 감소하였다. 특히, TMA 25wt%를 포함하고 있는 포접화합물은 냉각과정동안 평균 상변화온도 5.8℃와 과냉각도 8.0℃, 액상유지시간 651sec 및 비열 3.499 kJ/㎏K로서 다른 TMA 농도보다 양호한 냉각특성을 나타내었다. 이와 같이 저온잠열축열물질로서 TMA 25wt%-물계 포접화합물을 적용하는 것이 유리할 것으로 판단된다. The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity are increased and COP are decreased due to supercooling of water in the course of phase change from liquid to solid. This study investigates the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, (CH3)3N) of 20~25 wt% as a low temperature latent heat storage material. The results showed that the phase change temperature are increased and the supercooling degree and the specific heat are decreased according to the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25wt% has the average phase change temperature of 5.8℃ and the supercooling degree of 8.0℃, retention time of liquid phase for 651sec and specific heat of 3.499 kJ/㎏K in the cooling process. This expressed good than different concentration of TMA cooling characteristic. Like this, to apply TMA 25wt%-water clathrate compound is determined by advantageous as the low temperature latent heat storage material.

TMA 농도에 따른 저온축열물질의 과냉각 특성에 대한 연구

김창오(Chang-Oh Kim),김진흥(Jin-Heung Kim),정낙규(Nak-Kyu Chung) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

This study is investigated the supercooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, (CH3)3N) of 20~25 wt% as a low temperature latent heat storage material at -5℃, cooling source temperature. The results showed that as the concentration of TMA is increased, phase change temperature is increased, the supercooling and retention time of liquid phase are decreased. Especially, low temperature latent heat storage material containing TMA 25 wt% has the average of phase change temperature of 5.8℃, supercooling degree of 8.0℃, retention time of liquid phase for 10 minutes in the cooling process. Phase change temperature higher than that of water and inhibitory effect against superrcooling can be confirmed through experimental study on cooling characteristics of TMA-water clathrate compound. This can lead to shorten refrigerator operation time of low temperature thermal storage system and improve efficiency of refrigerator COP and overall system.

칸디다뇨증 환자에 있어서 칸디다혈증 동반과 관련된 위험인자 분석

김창오(Chang Oh Kim),김명환(Myoung Hwan Kim),심대근(Dae Keun Shim),조정호(Jung Ho Cho),김병극(Byoung Keuk Kim),김창년(Chang Nyun Kim),송영구(Young Goo Song),김준명(June Myung Kim) 대한내과학회 2001 대한내과학회지 Vol.60 No.5

Background : The early diagnosis of candidemia is critical for the management. The candidemia is known to be associated with 10% of candiduria. But the risk factors in patients with candiduria who are associated with candidemia are not known. We analyzed the risk factors in patients with candiduria who are associated with candidemia. Methods : We retrospectively reviewed 164 patients with candiduria in Yonsei Medical Center from January 1998 to December 1998. Candiduria patients were divided into two groups. Candiduria patients without candidemia (Group 1 , 147 patients) and candiduria patients with candidemia (Group 2 , 17 patients). Results : 1) The mean age of the patients were 57.5 years in group 1 and 62.5 years in group 2. There were no significant differences in the sex ratio between the two groups. 2) Central venous catheter insertion (53%, 100% in group 1 , 2 ), hypotension (14%, 59% in group 1, 2), other associated infections (64%, 100% in group 1, 2), intensive care (41, 76% in group 1, 2) and fever (46%, 82% in group 1, 2) were the very significant risk factors in patients with candiduria who were associated with candidemia. 3) Urinary tract procedure (11%, 88% in group 1, 2), urinary catheter insertion (63%, 94% in group 1, 2), thrombocytopenia (17%, 41% in group 1, 2) and DM (8%, 24% in group 1, 2) were the significant risk factors of candidemia. 4) Candida colony count (cfu/mL) of urine culture was not a significant risk factor 5 ) Mortality rate (27%, 59% in group 1, 2) was significantly high in patients with candidemia. Conclusion : Central venous catheter insertion , hypotension , other associated infections , intensive care and fever were the very significant risk factors of candidemia in patients with candiduria. (Korean J Med 60:479-484 , 2001)

포접화합물의 열물성에 미치는 첨가제의 효과 (Ⅲ) - TMA 물계 포접화합물에 Acetone을 첨가한 경우 -

김진흥(Jin Heung Kim),정낙규(Nak Kyu Chung),김석현(Suk Hyun Kim),김창오(Chang Oh Kim),강승현(Seung Hyeon Kang) 대한설비공학회 2004 설비공학 논문집 Vol.16 No.12

An experimental investigation is conducted to measure phase change temperature and supercooling when acetone is added to TMA 30 wt% clathrate during cooling process in heat source. Also rate of volume change is investigated when acetone is added to TMA 30 wt% clathrate during the cooling process in heat source -8℃. The results show that phase change temperature is about 4.5~5.5℃ when acetone is added to TMA 30 wt% clathrate during the cooling process for heat sink temperature of -6, -7℃ and -8℃. Supercooling is repressed about 2~10℃ when 0.08 wt% acetone is added to it and rate of volume change is decreased about 2.9% when 0.1 wt% acetone is added for the heat sink temperature of -8℃.

노동조합은 근로자의 임금불평등에 어떠한 영향을 미치는가?

김창오 ( Kim¸ Chang-o ) 한국산업노동학회 2020 산업노동연구 Vol.26 No.3

본 연구는 2003년 이후 노동조합이 우리나라 근로자의 임금불평등에 어떠한 영향을 미쳤는지를 규명하기 위하여 수행되었다. 이를 위해 2003-2017년 경제활동인구조사 부가조사를 사용하여 임금분위별 노조조직률과 노조임금효과의 변화추이를 기술하였고, RIF 회귀분석모형을 통해 지니계수로 측정되는 임금불평등에 대한 노동조합의 영향을 분석하였다. 연구결과 노조조직률은 2000년대 이후 점차 7분위 이상고임금 근로자에게 한정하여 증가하는 것으로 관찰되었다. 임금분위별 노조임금효과는 6분위 이상 고임금 근로자에서 점차 유의하게 증가하였고, 반면 1-5분위에 해당하는 저임금 근로자에서는 유의하게 감소하는 것으로 나타났다. 결과적으로 노동조합의 임금평준화 효과는 2012년 이후 크게 감소하여 통계학적 유의성을 상실하였다. 본연구결과는 향후 우리나라에서 노동조합을 통해 임금불평등이 증가하는 파급효과가 우세할 수 있음을 시사한다. This study has been conducted since 2003 to find out how labor unions have affected the wage inequality of Korean workers. For this purpose, the data of Economically Active Population Survey from 2003-2017 were used to describe the trend in union organization rate and union wage effects, and the effect of unions on Gini coefficients by using RIF regression analysis model. The results show that union organization rates has been increasing since 2000s to a limited number of high-wage workers above 0.7 percentile. The union wage effect has been increasing in high-wage workers above 0.6 percentile, while it decreased significantly in low-wage workers in the 0.1-0.5 percentile. As a result, the wage equalizing effect of labor union has declined significantly and lost its statistical significance since 2012. The results of this study suggest that the spill over effect of increasing wage inequality through labor unions in Korea may prevail. In the future, in order for labor unions to be recognized as agents of social justice for fair distribution, it would be more important to reconsider interests beyond the traditional working class and to combine collective action with social movements.

트리 구조를 이용한 연관규칙의 효율적 탐색

김창오(Chang-Oh Kim),안광일(Kwang-Il Ahn),김성집(Seong-Jip Kim),김재련(Jae-Yearn Kim) 대한산업공학회 2001 대한산업공학회지 Vol.27 No.1