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다공도가 다른 전열촉진관의 냉매-오일 풀비등에 관한 연구
이진욱(Jin-Wook Lee),김내현(Nae-Hyun Kim),심현민(Hyun-Min Sim) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
The effect of enhanced geometry(pore diameter, gap width) is investigated on the pool boiling of R-134a/oil mixture for the enhanced tubes having pores with connecting gaps. For the smooth tube, the heat transfer coefficient decreased as the oil concentration increased. For the enhanced tube, the heat transfer coefficient decreased significantly even at a small concentration (1%). The reason may be attributed to the accumulation of oil in sub-tunnels of the enhanced geometry. The tube with largest pore diameter yielded the highest heat transfer coefficient even with oil.
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사인 웨이브 핀과 타원관으로 구성된 핀-관 열교환기의 공기측 성능
최병남(Byung-Nam Choi),풍익(Fung Yi),심현민(Hyun-Min Sim),김내현(Nae-Hyun Kim) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.5
Heat transfer and pressure drop characteristics of fin-and-tube heat exchangers having sine wave fins and oval tubes were investigated. Oval tubes having an aspect ratio of 0.6 were made, by deforming 12.7 mm round tubes. Twelve samples, having different fin pitch and tube row, were tested. The effect of fin pitch on the j and f factors was negligible. The effect of the tube row on the j factor, however, was different from that of common fin-and-tube heat exchangers having plain fins and round tubes. The highest j factor was obtained for a two-row configuration, while the lowest one was obtained for a one-row configuration. A possible reason was attributed to the flow mixing characteristics of the sine wave channel of the present geometry. Comparison with a plain fin-and-tube heat exchanger having 15.88 mm O. D. round tube reveals that the present oval fin-and-tube heat exchanger shows generally superior thermal performance, except for the one-row configuration.
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구리 재질의 평판 핀과 나선형 핀이 사용된 핀-관 열교환기의 공기측 성능
이진욱(Jin Wook Lee),이정표(Jung Pyo Lee),심현민(Hyun Min Sim),김내현(Nae Hyun Kim) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
본 연구에서는 구리 재질의 평판 핀과 나선형 핀-관 열교환기에 대하여 핀 피치와 열수의 변화에 따른 공기측 전열성능을 검토하였다. 두 형상 모두 핀 피치가 열전달계수에 미치는 영향은 미미하였다. 마찰인자는 핀 피치가 증가하면 증가하였다. 열수가 미치는 영향은 형상에 따라 다르게 나타났다. 평판 핀-관 열교환기의 경우 열전달 계수는 열수가 증가할수록 감소하였다. 하지만 나선형 핀-관 열교환기의 열전달 계수는 열수가 증가하면서 그 값이 증가하는 경향을 보였다. 평판 핀-관 열교환기의 열전달계수는 나선형 핀-관 열교환기의 열전달계수보다 높게 나타났다. 하지만 열수가 증가하면 그 차이가 줄어들어 4열이 되면 거의 같았다. 한편 마찰인자는 평판 핀-관 열교환기에서 다소 높게 나타나고 열수의 영향은 크지 않았다. Heat transfer and pressure drop characteristics of fin-and-tube heat exchangers having copper plate or copper spiral fins were investigated. Twenty four samples having different fin pitch and tube row were tested. It is shown that, for both configurations, the effect of fin pitch on j factor is negligible. The f factor increases with the fin pitch. The effect of tube row is different between the two configurations. For p1ate fin-and-tube heat exchangers, j factor decreases as row number increases. The reverse is true for spiral fin-and-tube heat exchangers. Possible explanation is provided considering a flow pattern. Comparison of the j factor reveals that j factor is larger for plate fin-and-tube heat exchangers as compared with that of spiral fin-and-tube heat exchangers. The difference decreases as row number increases. The f factor of the plate fin-and-tube heat exchanger is also 1arger.
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