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PTC 전열시트를 사용한 핀-관 열교환기의 제상 특성에 관한 실험적 연구
지성,이관수,Jhee, S.,Lee, K.S. 대한설비공학회 1999 설비공학 논문집 Vol.11 No.1
In this work, the defrosting characteristics of PTC heating sheet used as a defrosting heat source of fin-tube heat exchanger in a refrigerator have been experimentally compared with those of conventional electric heater. It is found that the characteristics of water draining rate with defrosting time show smoothly oscillating pattern when PTC heating sheet is used, and the drained water is completely melted. The defrosting efficiency of the PTC heating sheet is about 75%, which represents about 25% higher than that of the electric heater. A reduction of defrosting time and an increase of defrosting efficiency may be obtained by improving the arrangement of heating elements of the heating sheet. It is shown that the defrosting time of PTC heating sheet increases linearly with the amount of frost, however the defrosting efficiency is nearly constant. In the application to the refrigerating system, one should notice the fact that the defrosting performance of PTC heating sheet may be defraded due to the repeated operations.
이관수,지성,이태희,Lee, K.S.,Jhee, S.,Lee, T.H. 대한설비공학회 1997 설비공학 논문집 Vol.9 No.2
In this study, a numerical model for analyzing frost formation phenomena on a cold flat plate has been developed. Both regions of air flow and frost layer have been coupled to calculate the amount of the heat and mass transfer between air flow and frost layer. Experiments have been also conducted to validate the numerical model. The present numerical results show a good agreement with the experimental data. The present numerical model also provides some useful data such as the temperature distribution inside the frost layer which could not be obtained through the experiments.
핀-관 열교환기의 착상 거동에 대한 표면 접촉각의 영향
이관수,지성,이동욱,Lee, K. S.,Jhee, S.,Lee, D. W. 대한설비공학회 2000 설비공학 논문집 Vol.12 No.1
The effect of surface contact angle on the behavior of frost formation in a fin-tube heat exchanger is investigated experimentally. It is shown that both heat exchangers with hydrophilic and hydrophobic surfaces appear to have a better thermal performance than bare aluminium heat exchanger, but the improvements are very small. There is a little increase in the amount of the frost deposited onto the heat exchanger with both hydrophilic and hydrophobic surface. However, the effect of contact angle on the frost density is observed ; the frost with high density forms on the heat exchanger with hydrophilic surface ; and the frost with low density is deposited onto the heat exchanger with hydrophobic surface when compared with the frost deposited onto the heat exchanger with bare aluminium surface. This may be attributed to the fact that the shape of water droplets which condense on the surface of heat exchanger at the early stage of frosting varies with contact angle, and thus makes a difference on the structure of frost formation. From the experiments with different relative humidity of inlet air, it is shown that the variations of operating parameter make no influence on the effect of surface contact angle on the frosting behavior in the heat exchanger.