• Journal of Energy Engineering
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• v.17 no.1
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• pp.1-7
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• 2008

The present study has been conducted to understand the heat and mass transfer characteristics of humid airflow in frosting conditions. A flat plate of aluminum was used for the simulation of flat surface part of the fin of the heat exchanger. The aluminum surface temperatures were measured and analyzed to clarify the heat and mass transfer characteristics under frosting conditions. Also, the pressure drops were measured to clarify the air-blocking effect of frost in the mini channel of the air-side hoot exchangers. A data reduction method was developed far the analysis of local characteristics of humid air under frosting conditions.

• Clinical and Experimental Reproductive Medicine
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• v.36 no.3
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• pp.151-162
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• 2009

착상, 태반생성 및 임신 유지 등 생식과정에서 semi-allograft인 배아 및 태아가 생존하기 위해서는 모체 면역계의 면역관용이 요구된다. 면역관용은 분자 생물학적으로 염증반응과 항염증반응의 적절한 균형을 유지하는 인식되고 있으며, 생식과정에서 모체 면역계의 T 림프구, 자연살해세포, 수지상 세포, 대식세포 등 여러 면역세포의 유기적인 협조하에 이루어진다. 면역세포들은 특정 항원 및 사이토카인의 자극에 따라 정반대의 성질을 가진 사이토카인을 생산, 분비할 수 있는 특성을 가지고 있어 각각을 염증성 또는 항염증성 면역세포로 명확히 구분할 수 없으며 면역세포의 이러한 특성에 의해 생산 및 분비되는 사이토카인의 종류에 따라 Th0 형 (Th 0 cell, Tc 0 cell, NK 0 cell), Th1형 (Th 1 cell, Tc 1 cell, NK 1 cell), Th2 형 (Th 2 cell, Tc 2 cell, NK 2 cell), Th3 형 세포 (Th 3 cell, Tc 3 cell, NK 3 cell)로 분류하기도 한다. 즉, 착상 시기에 혈관신생 및 영양막의 자궁 내 침투를 위한 적절한 염증성 사이토카인(inflammatory cytokine)의 분비 및 임신의 지속을 위한 항염증성 (anti-inflammatory) 사이토카인의 분비 등 생식과정에서 수반되는 염증성과 항염증성 면역반응의 적절한 균형을 유지하는 기전은 특정 면역세포만의 작용으로 결론 지을 수 없으며 면역 세포간 network의 산물이라 할 수 있다 (Figure 5). 면역세포 중 최근 그 존재가 알려진 면역조절 T림프구 (T reg cell)는 여러 연구자들에 의해 면역관용에 관여함이 일관되게 보고되고 있어 자궁 내모체-태아간 접촉면에서 면역세포들 간의 network에 중추적인 역할을 할 것으로 인식되고 있으나 작용기전으로 제시되고 있는 가설들을 뒷받침 할 만한 객관적인 연구가 필요한 실정이다. 본 고찰에서는 착상과 임신 유지 등 생식과정에 수반되는 면역세포 및 그 세포들의 작용기전중 T 림프구의 역할에 중점을 두고 그 분류 및 기능에 대해 정리해 보았다. 결론적으로 착상과 임신의 유지 등 생식과정에서 T 림프구는 면역관용과 거부에 적극적으로 작용하며 착상부전, 습관성유산 등 면역학적 병인이 유사한 생식장애 (poor reproductive performance)들의 발병에 중요한 역할을 하는 것은 의심할 여지가 없다. 하지만 향후 T 림프구 및 그와 연관된 면역세포들의 작용에 대한 확실한 분자학적 규명이 요구된다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.10
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• pp.781-785
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• 2002

The effects of different surfaces on dry and wet frosting test were experimentally investigated. The results of experiment were compared by the performance evaluation coefficient (PEC). Results showed that the air-side pressure drop of lacquer coated evaporator increased by 5% as compared to the plasma treated one. It was also found that the Plasma coated evaporator is lower than lacquer coated one in the PEC ratio.

• Proceedings of the SAREK Conference
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• 2004.11a
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• pp.38-38
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• 2004

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.41 no.10
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• pp.36-43
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• 2012

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.6
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• pp.525-531
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• 2002

The effects of different surface hydrophilicity on frosting and defrosting characteristic were experimentally investigated. Mass of frost and water hold-up was measured. Results showed that no significant difference in the frost mass was found between the two different surfaces while the water hold-up of heat exchanger court be reduced by the enhancement of surface hydrophilicity. Also, the defrosting efficiency m hydrophilic surface was improved by 76%. It was expected that hydrophilic heat exchanger could provide the improvements in both thermal-hydraulic performances and system reliability during frost/defrost operating in refrigeration systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.7
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• pp.373-379
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• 2009

In this study, frosting experiment was conducted to investigate the characteristics of frost formed on heat exchanger fins of non-uniform temperature distribution. Temperature distribution and frost characteristics of a 2-D fin surface were investigated in the airflow direction and the direction perpendicular to airflow. Temperature gradient was very small in the airflow direction, while it was large in the direction perpendicular to airflow due to fin heat conduction. The variations of the frost thickness gradient and the frost density gradient in the direction perpendicular to airflow were significant. On the other hand, the temperature gradient on frost surface in the direction perpendicular to airflow was significant at the early stage of frosting, while it decreased gradually as time elapsed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.12
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• pp.1071-1078
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• 2010

The objective of this study is to investigate the heat transfer characteristics of evaporators that have various fin configurations and are used in household refrigerators. The frosting and defrosting characteristics of a spirally coiled circular fin-tube evaporator, a discrete-plate fin-tube evaporator, and a continuous-plate fin-tube evaporator were measured and compared. Under non-frosting conditions, the heat transfer coefficient of the spirally coiled circular fin-tube evaporator was 22.3% and 40.2% higher than the coefficients of the discrete- and continuous-plate fin-tube evaporators, respectively. Under frosting conditions, the heat transfer coefficient of the spirally coiled circular fin-tube evaporator was 27.0% and 46.3% higher than the coefficients of the discrete- and continuous-plate fin-tube evaporators, respectively. In addition, the defrosting water amount of the spirally coiled circular fin-tube evaporator was 3.2% and 9.4% lower than the amounts in the case of the discrete- and continuous-plate fin-tube evaporators, respectively.

• Journal of Power System Engineering
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• v.14 no.4
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• pp.5-10
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• 2010

This study was investigated the effect on operating characteristics of apparatus according to frosting and defrosting to develop of new defrosting equipment. The results showed as following. Frost was almost removed using the defrosting equipment with roll brush type that defrosting is possible under operating condition. Also, the temperature of compressor inlet, evaporator inlet and outlet showed higher value because of heat transfer resistance of cooling pipe frost comparing with defrosting condition. And the compressor work showed 10% lower and COP was presented 24% higher values than defrosting condition. Therefore, defrosting for cooling coil of refrigeration and low temperature storage was effected on operation and performance characteristics of equipment. This highly effects on real refrigeration apparatus which is operated in year-around.

• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.1141-1144
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• 2010

본 연구에서는 난방운전시 저온 및 착상 조건에서 히트펌프 칠러의 성능을 조사하고자 하였다. 실험은 항온항습 기능을 가진 공기엔탈피 방식의 칼로리미터와 항온수조를 사용하여 수행되었으며, 실외온도조건을 설정한 후에 히트펌프 칠러의 성능을 실험으로 측정하였다. 외기조건이 $-7^{\circ}C$에서 $-15^{\circ}C$까지 변화함에 따라 시스템의 성능과 COP는 표준온도 조건의 실험값 보다 약 48~87%까지 감소하였다. 착상 실험에서는 시간 변화에 따라 출구수온이 표준온도를 기준으로 74% 감소하였다. 본 연구로부터 히트펌프 칠러의 설계 기초자료 획득 및 신뢰성을 확인할 수 있었다.