• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.256-261
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• 2008

In this study, frost behavior on two dimensional fins of a heat exchanger was experimentally investigated. Temperature distribution on a 2-D fin surface and frost properties were measured in the directions perpendicular to and parallel to airflow. The results indicated that the temperature gradient in the direction perpendicular to airflow was large because of fin heat conduction, while that in the direction parallel to airflow was very small. Frost thickness in the airflow direction decreased from the leading edge towards the trailing edge of the fin due to leading edge effect. The reduction rate of frost thickness in the airflow direction, however, was very small compared with that in the direction perpendicular to the airflow, as affected by the temperature distribution.

• 설비공학논문집
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• 제7권1호
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• pp.161-170
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• 1995

This study is concerned with the numerical analysis of performance on fin-tube heat exchanger under frosting condition. In this work, tube-by-tube method using LMED is employed. The present results are compared with O'Neal's experimental and numerical results. A standard evaporator model with 2rows-2columns is selected to investigate the effects of the various parameters such as fin pitch, air flow velocity, and humidity. The results show that frost thickness and the amount of frost per unit area decrease as fin-pitch becomes narrower. In the meantime, frost thickness and accumulation rate increase with higher inlet air humidity. It is shown that heat transfer rate increases during 30minutes and then it decreases. Heat transfer rate and the amount of frost increase with air velocity, however frost thickness does not increase over a certain velocity.

• 대한기계학회논문집B
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• 제26권2호
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• pp.253-260
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• 2002

It is known that frost formation on surfaces of the heat exchanger seriously affects the performance of the refrigeration system. Accordingly, defrosting should follow, and effective defrosting is possible only when both analytic tools and comprehensive experimental data on frost formation are assailable. An experimental investigation was undertaken to characterize the effect of environmental parameters on frost formation on a horizontal cylinder in cross uniform flow. Several experiments were carried out with various environmental parameters such as inlet air temperature, inlet air humidity, air velocity and cooling surface temperature. Frost thickness, mass, surface temperature and cylinder inner and outer temperature were measured at front and rear positions of the cylinder. Thickness, mass, density, and effective thermal conductivity of the frost layer were obtained from measured data and effects of environmental parameters on the frost formation were analyzed. Data from experiments were correlated using dimensionless variables.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 추계학술대회 논문집
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• pp.55-58
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• 2002

To control the frost formation, a temperature variation of the cooling plate and characteristics on hydrophilic and hydrophobic surfaces was attempted. As a temperature variation of the cooling plate, being closely related to the frost layer density of frost layer is found to be affected by the melting process inside the frost layer during the heating period. At characteristics on surface, completely different structures of frost are appeared in the initial stage of frost formation due to the difference in surface conditions, while those effects are vanished with time. It is found that the frost thickness, density and heat flux characteristics are closely associated with the frost structure.

• 설비공학논문집
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• 제20권11호
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• pp.727-732
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• 2008

This paper presents a mathematical model to predict the behavior of frost formed on an one-dimensional fin of heat exchanger, considering fin heat conduction under frosting conditions. The computational domain consists of air-side, the frost layer, and fin region, and they are coupled to the frost layer. The frost behavior is more accurately predicted with fin heat conduction considered (Case A) than with constant fin surface temperature assumed (Case B). The results indicate that for Case B, the frost thickness and heat transfer are overpredicted in most regions of the fin, as compared with those for Case A. In addition, for Case A, the maximum frost thickness varies little with the fin length variations, and the extension of the fin length after 30mm contributes insignificantly to heat transfer.

• 한국도로학회논문집
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• 제15권1호
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• pp.47-56
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• 2013

PURPOSES: This study is to evaluate a ground water level effect on frost heaving in road pavements. METHODS: The effects of water table on frost heaving in pavement systems were evaluated from the mechanical analysis using FROST program. The input parameters and boundary conditions were determined by considering climates, pavement sections, and material properties specially subgrade soil types in Korea. RESULTS: When the water table located above the freezing depth, amount of frost heaving caused by freezing the water in pavement itself was big enough to damage in pavement system, although pavement system consists of fully non-frost-susceptible materials with sufficient thickness of anti-freezing layer. The amount of frost heaving was decreased rapidly with increasing the distance between the water table and freezing depth. CONCLUSIONS: It was concluded that there is no engineering problems related with frost heaving in practical sense when the distance between freezing depth and water table is over 1.5m for having subgrade soils less than 50% of #200 sieve passing to meet specification on quality control in Korea.

• 에너지공학
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• 제14권4호
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• pp.213-218
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• 2005

습공기 유동의 착상조건하에서의 열 및 물질 전달 특성을 이해하기 위해서, 미니 열풍동을 제작하고 열풍동의 시험부인 사각덕트 아랫면에 알루미늄 평판을 설치하고 평판의 중심력에 전기냉각모듈(Peltier device)을 부착하였다. 현미경(해상도 0.05mm)을 이용하여 습공기 유동 방향으로 알미늄 평판위의 7개점의 서리 두께를 측정하였으며, 전자저울(해상도 1mg)을 이용하여 각 운전시간대까지의 발생된 서리의 총괄 질량을 측정하였다. 여러 가지의 실험조건에서 서리두께와 서리질량 그리고 알미늄 평판상의 온도 분포 등을 구하고, 이로부터 습공기 유동의 습도 및 속도가 서리의 성장 특성에 미치는 영향을 분석하였다.

• 설비공학논문집
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• 제23권11호
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• pp.733-740
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• 2011

To analyze the cooling performance in the refrigerator truck according to frost growth, the analytical model of refrigeration system was developed under frost and non-frost condition using EES. The system performance was analyzed with outdoor temperature, storage temperature, outdoor front air velocity and compressor speed in order to investigate the system performance characteristics with operating conditions. Besides, the system performance under frost condition was compared with that under non-frost condition. As a result, the frost thickness was 0.9 mm when the refrigerating capacity of frost condition was decreased by 30%. The maximum of the system COP was shown at compressor speed of 1500 rpm for non-frost and frost condition, simultaneously. The performance under frost condition was more sensitive to the operating condition compared to that under non-frost condition.

• 한국건축시공학회지
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• 제19권2호
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• pp.131-138
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• 2019

최근에는 열악한 환경에 노출되는 콘크리트 구조물의 품질 확보에 대하여 관심이 증대되고 있다. 그 중에서 낮은 외 기온 조건에서의 초기양생 불량은 콘크리트 구조물의 초기 동해 피해를 일으킬 수 있는 것으로 알려지고 있다. 그러므로 본 연구에서는 겨울철 외기온 조건에서 결합재 종류 및 콘크리트 부재 두께 변화가 콘크리트의 초기동해 깊이에 미치는 영향 분석 및 초기동해 피해를 입은 구조체에 대하여 그 깊이를 명확히 판정하고자 하였다. 실험결과 초기동해피해의 경우 3성분계 혼합시멘트를 사용하고, 부재 두께가 얇을수록 초기동해 깊이가 깊고 코어 공시체의 명도 증가가 지연되었는데, 이는 초기발열량 저하로 콘크리트의 조직 이완이 용이하게 발생하여 흡수율이 증가하기 때문인 것으로 분석된다. 초기동해 깊이 판정은 24시간 침수 후 온도 $20^{\circ}C$, 상대습도 60 %전후인 실내에서 30분 전후로 건조를 시킬 경우 명도값(L) 45 이하의 짙은색과 밝은색으로 구별되는데, 짙은 색부분을 버니어캘리퍼스 등으로 측정하면 손쉽게 판단할 수 있다.

• 설비공학논문집
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• 제8권2호
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• pp.299-306
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• 1996

This work presents an analytical model, so called modified LMTD method, to predict the thermal performance of finned-tube heat exchanger under frosting conditions. In this model, the total heat transfer coefficient and effective thermal conductivity of the frost layer were defined as a function of frost surface temperature. The surface temperature of the frost layer formed on the heat exchanger was calculated through the analysis of the heat and mass transfer process in the air and frost layer. To examine the validity of this analytical model, the computed results from the present model, such as heat transfer rate, frost mass and thickness of frost, were compared with the ones of the expermental work and LMED method.