• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.252-257
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• 2007

The present study investigated the effect of air velocity on frost formation of slit fin-and-tube heat exchanger under frosting condition. The slit fin-and-tube heat exchanger with outer tube diameter 7.0mm and 1 row was used. Air side pressure drop, photographs of frost distribution, frost accumulation and frost thickness were presented with respect to the frosting time. In the early stage of experiment, the case with air velocity of 1.5m/s showed 403% higher for the air pressure drop than the case with the air velocity of 0.5m/s. As the frost was accumulated, the effect of air velocity on air pressure drop was decreased. In the end stage of test, air pressure drops of two cases were very close and air pressure drop for the air velocity of 0.5m/s was higher than that of 2.0m/s. It was also shown in the photographs of frost distribution, frost accumulation and frost thickness. From frost thickness, fanning friction factor was presented.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2738-2743
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• 2008

We conducted a study by computational simulation about the effects of frost thickness on the pressure drop and heat transfer characteristics as whole heat exchanger configuration changes. In order to perform the analysis for validation, we assumed that frost properties have constant values and the frost layers that are formed on the fin and tube surfaces are uniform. In order to find the constant thermal conductivity of frost layer, a variety of frost thermal conductivities are performed in our work and compared with the results by Lee et al. [4] and Yang et al. [5] proposed many experimental data about the 2-rows and 2-columns finned tube heat exchanger. The numerical results agreed well with the experimental data when frost conductivity is 0.07W/mK. After the validation had performed, we applied this procedure to the finned tube heat exchanger of domestic refrigeration and investigated the thermo-hydraulic characteristic of the heat exchanger affected by frost thickness according to the inlet velocities and temperatures of air considering the configuration change such as fin pitch.

• 대한기계학회논문집B
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• 제26권9호
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• pp.1325-1331
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• 2002

This study presents a numerical model to predict the behavior of frost layer growth. The characteristics of the heat and mass transfer inside the frost layer are analyzed by coupling the air flow with the frost layer. The present model is validated by comparing with the several other analytical models. It has been known that most of the previous models cause considerable errors depending on the working conditions or correlations used in predicting the frost thickness growth, whereas the model in this work estimates the thickness of the frost layer more accurately within an error of 10% in comparison with the experimental data. Simulation results are presented for variations of heat and mass transfer during the frost formation and for the behavior of frost layer growth along the direction of air flow.

• 설비공학논문집
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• 제11권4호
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• pp.448-456
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• 1999

Variations of thickness and effective thermal conductivity of frost forming on the horizontal] cylinder with respect to time were measured under cross flow. The local heat flux around the cylinder was determined by measuring the radial temperature distribution in the cylinder having small holes drilled axially in which T-type thermocouples were inserted, then by using one dimensional cylindrical heat conduction equation. The thickness and the surface temperature of the frost layer around the cylinder were measured periodically while developing the frost. Each experiment was peformed by varying the Reynolds number, the temperature, and the humidity condition. Specially the dew point temperature of the most cases was below the freezing point. Experimental data showed that the frost layers on the front and the rear surface were thicker than those on the top and the bottom one which was near the separation point. The thickness and effective thermal conductivity of the frost layer were affected by inlet air velocity, temperature, and humidity. Moreover, the effective thermal conductivity and the effective thermal resistance increase with respect to time.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.798-803
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• 2009

In this study, dimensionless correlations of frost properties (i.e. the thickness and surface temperature of frost) on heat exchanger fin with nonuniform temperature distribution are proposed from frosting experiments. We analyzed the local fin temperature distribution, frost thickness and frost surface temperature on a 2D fin; in the airflow direction and the direction perpendicular to airflow. As a result, the frost growth on the fin had a close relation with fin heat conduction. The dimensionless correlations for the average frost properties were expressed as a function of dimensionless temperature, humidity ratio, Reynolds number, and Fourier number. These correlations agreed well with experimental data with the error less than 14%.

• 설비공학논문집
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• 제11권4호
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• pp.440-447
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• 1999

The frosting characteristics on the vertical parallel plates with three cooling plates were experimentally investigated. The experimental parameters were the cooling plate temperature, the air humidity, the air temperature, the air Reynolds number, and the location. The frosting conditions were limited to air temperatures from 10 to $15^{\circ}C$ , air Reynolds numbers from 1600 to 2270, air humidity ratios from 0.00275 to 0.0037kgw/kga and cooling plate temperatures from -10 to $-20^{\circ}C$. Frost growth and density toward the front of the plate were more thick and dense than toward the rear. Frost growth increased with decreasing plate temperature and increasing humidity. In the conditions of the laminar flow, dew point below $0^{\circ}C$and non-cyclic frosting period, frost thickness increased with increasing air temperature. The reason of increasing frost thickness with increasing air temperature was sublimation-ablimation process. The average growth thickness along the locations showed little dependence on the Reynolds numbers.

• 대한기계학회논문집B
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• 제25권8호
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• pp.1046-1052
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• 2001

This study has been performed experimentally to measure the frost properties over a cold flat plate in order to obtain the correlations of the frost properties with various environmental parameters. Correlations of the frost surface temperature, thickness, density, and thermal conductivity are presented along with the experimental results as a function of environmental parameters, distance from the leading edge of test plate, and time. These correlations can be used to predict the frost properties with a maximum error of 8% in the following ranges : air temperature 15∼25$\^{C}$, relative humidity 60∼80%, air velocity 1∼3m/s and cooling plate temperature -15∼-25$\^{C}$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2091-2096
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• 2007

This paper presents a mathematical model for predicting the frost behavior formed on heat exchanger fins, considering fin heat conduction under frosting condition. The model is composed 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 a constant fin surface temperature assumed (Case B). The results indicate that the frost thickness and heat transfer rate for Case B are over-predicted in most regions of the fin, as compared to those for Case A. Also, for Case A, the maximum frost thickness varies little with the fin length variations, and the extension of the fin length over 30 mm contributes insignificantly to heat transfer.

• 한국철도학회논문집
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• 제19권4호
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• pp.506-514
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• 2016

철도 현장에 실험용 자갈궤도와 콘크리트궤도를 설치한 후 겨울철에 동결심도와 동상량을 측정하였다. 그 결과 같은 동결지수일 때 자갈궤도보다 콘크리트궤도의 동결심도가 깊게 나타나는 경향을 보였다. 또한 자갈궤도는 하부에 XPS, PE골재층을 포설할 경우 동결심도가 크게 감소하였고, 콘크리트궤도에서는 입도조정층의 두께를 늘릴 경우 동결심도가 감소하는 경향을 보였다. 동상량 역시 자갈궤도에서는 하부에 XPS, PE골재층을 설치할 경우 감소하였고, 콘크리트궤도에서는 입도조정층의 두께를 증가시킬 경우 감소하는 경향을 보였다.

• 설비공학논문집
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• 제18권2호
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• pp.122-128
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• 2006

In this paper, frosting experiments were conducted with variations of frosting parameters in order to obtain the correlations of frost properties. As a result, the local thickness, density, and surface temperature of the frost layer were presented. The dimensionless correlations for the frost thickness, frost density, frost surface temperature and heat transfer coefficient were derived as functions of dimensionless frosting parameters by using a dimensional analysis.