• 대한기계학회논문집B
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• 제28권8호
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• pp.989-995
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• 2004

This paper presents a semi-empirical model to predict the frost growth formed on the cold cylinder surface. The model is composed of the correlations for frost properties including the various frosting parameters and local heat transfer coefficient. The effects of varying the correlations for local heat transfer coefficient on the frost growth are examined to establish the model. The numerical results are compared with experimental data obtained by the previous researchers. The results agree well with the experimental data within a maximum error of $13\%$. As the results, the frost thickness decreases with changing angular position from front stagnation to separation point. Also, the effects of air velocity on the frost growth are negligible, as compared to the other frosting parameters.

• 설비공학논문집
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• 제14권3호
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• pp.261-267
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• 2002

The integral boundary layer equation for the air side and the diffusion equation for the frost layer are numerically analyzed in order to predict the behavior of frost layer growth. The thickness and density of the frost layer obtained from the present study agree well with those of previous numerical results and experimental data with a maximum error of 13%. The characteristics of heat and mass transfer within the frost layer and the frost layer growth along the flow direction are investigated by performing numerical analysis. The effects of operating conditions on the frost layer growth are also examined.

• 대한기계학회논문집B
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• 제27권3호
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• pp.374-380
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• 2003

This paper proposes dimensionless correlations predicting properties of the frost layer formed on a cold flat surface. Experiments are carried out to obtain the correlations with various environmental parameters such as air temperature, air velocity, absolute humidity, and cooling plate temperature. As a result, the frost properties (frost layer thickness, density, surface temperature, thermal conductivity) are correlated as a function of Reynolds number, Fourier number, absolute humidity and non-dimensional temperature by using a dimensional analysis. The correlations agree well with the previous and our experimental data within a maximum error of 10%, and are used to predict the frost properties in the following ranges: Reynolds number of 20216 to 53763, Fourier number of 0.1962 to 2.5128, absolute humidity of 3.22 to 8.47, and non-dimensional temperature of 0.125 to 0.5.

• 설비공학논문집
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• 제11권3호
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• pp.377-383
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• 1999

In this study, the behavior of frost formation according to surface characteristics in the fin-tube heat exchanger has been examined experimentally. The results show that the thickness of the frost which is attached to the hydrophilic heat exchanger becomes thin and the air pressure drop is smaller than that of bare aluminium heat exchanger However, the frost mass of hydrophilic heat exchanger is more than the bare one. Hence, high density frost is attached to hydrophilic heat exchanger. The sensible and latent heat flux of hydrophilic heat exchanger is bigger than that of bare one, but the increasing amount is very small and the improvement of thermal performance is also very small. The variation of fin-pitch of heat exchanger shows little influence on frost formation and hydrophilic heat exchanger loses its surface characteristics rapidly with increasing relative humidity.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1540-1545
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• 2004

This paper presents a semi-empirical model to predict the frost growth formed on the cold cylinder surface. The model is composed of the correlations for frost properties including the various frosting parameters and local heat transfer coefficient. The effects of varying the correlations for local heat transfer coefficient on the frost growth are examined to establish the model. The numerical results are compared with experimental data obtained by the previous researchers. The results agree well with the experimental data within a maximum error of 13%. As the results, the frost thickness decreases with changing angular position from front stagnation to separation point. Also the effects of air velocity on the frost growth are negligible, as compared to the other frosting parameters.

• 설비공학논문집
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• 제21권7호
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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.

• 한국지반공학회지:지반
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• 제14권1호
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• pp.49-58
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• 1998

폐타이어가 지반의 동상방지 건설재료로서 재사용될 수 있는지를 연구하였다. 동상방지에 대한 폐타이어의 기본적인 효과를 검토하기 위해 화강풍화토에 폐타이어가루를 몇 가지의 비율로 혼합해서 준비한 시료로서 영하 $17^{\circ}$하에서 동상시험과 화강풍화토에 대한 동결깊이시험을 실내에서 수행하였다. 역청포장의 보조기층 바로 아래에 폐타이어조각을 혼합한 쇄석층을 동상방지층으로 둠으로서 실용상으로 효과적이라는 사실을 알게 되었다. 그리고 이 동상방지 층의 소요두께와 동결 지수와의 관계식을 제안하였다.

• 설비공학논문집
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• 제7권2호
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• pp.319-328
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• 1995

In this study, the experiment with 2rows-2columns fin-tube heat exchanger under forced convection and frosting condition is performed. The influence of each operating condition(the temperature of air, the humidity of air, the velocity of air, the temperature of coolant) on the growth of frost layer, air-side pressure drop, and characteristics of heat transfer is investigated. The experimental results show that the frost thickness increases rapidly in the early stage of frost formation and increases linearly after sometime. The frost thickness increases with the increase of the inlet air humidity and velocity and the decrease of inlet air temperature and coolant temperature. It is also found that the total energy transfer rate increases with the increase of inlet air temperature and velocity and with the decrease of inlet air humidity and coolant temperature.

• 대한기계학회논문집B
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• 제32권4호
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• pp.307-316
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• 2008

The objective of this study is to provide numerical and experimental data that can be used to investigate the performance characteristics of a flat plate fin-tube evaporator in household and commercial refrigerators under frosting conditions. Computer simulations with variations of operating conditions such as air inlet temperature, relative humidity, and geometries were performed to find out optimal design parameters of a fin-tube evaporator for household and commercial refrigerators. The tube-by-tube method was used in the simulation and the frost growth model was considered under frosting conditions. The developed analytical model predicted the decreasing rates of heat transfer capacity and air flow rate ratio within ${\pm}$10% compared to the experimental results for a refrigerator under real operating conditions. As a result, the frost thickness at $3^{\circ}C$ & 80% is increased 40% than that of $-3^{\circ}C$ & 80%, and the frost thickness at $3^{\circ}C$ & 90% is increased 30% than that of $3^{\circ}C$ & 60%. Accordingly, the operating time of the evaporator in the refrigerator was reduced with the increase of the decreasing rate of air flow rate ratio at each condition.

• 대한기계학회논문집
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• 제18권12호
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• pp.3305-3314
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• 1994

In this study, the influence of a frost formed on the vertical plate for different operating conditions(the temperature of the air, the humidity of the air, the velocity of the air, and the temperature of the cooling plate) is investigated. The performance of the heat exchanger is examined by introducing a parameter such as the energy transfer resistance. Correlations which relate frost density, frost thickness and energy transfer resistance to Reynolds number, air temperature and humidity, and cooling plate temperature are developed. Static pressure drop and air flow rate are expressed as a function of free flow area of air.