• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2004년도 하계학술발표 논문집
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• pp.170-170
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• 2004

• 수산해양교육연구
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• 제20권3호
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• pp.410-415
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• 2008

To evaluate the performance of nucleate boiling heat transfer between a plain and micro-fin surfaces, the experimental tests have been carried out under various conditions with fluorinert liquid FC-72, which is chemically and electrically stable. Two kinds of micro fins with the dimensions of $200{{\mu}m}{\times}20{{\mu}m}$ and $100{{\mu}m}{\times}10{{\mu}m}$ (width x height) were fabricated on the surface of a silicon chip. The experiments were performed on the liquid subcooling of 5, 10 and 20K under the atmospheric condition. The presented data showed a similar trend in the comparison with result of Rainey & You. Due to its expanded surface areas, the heat flux properties has been significantly enhanced on micro-fin surface comparing to the plain surface.

• 대한기계학회논문집B
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• 제35권10호
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• pp.1089-1095
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• 2011

열전달 향상을 위한 방법으로 많이 사용되고 있는 마이크로 핀을 포함한 표면 위에서의 핵비등을 액상과 기상에서 질량 및 운동량, 에너지에 대한 지배 방정식을 풀어 수치해석을 수행하였다. 핵비등에서의 기포거동을 계산하기 위해 sharp-interface 레벨셋(level-set) 방법을 상변화 효과와 핀과 캐비티와 같은 잠긴 고체에서의 점착 조건 및 접촉각, 마이크로 액체층에서의 증발 열유속을 포함하도록 수정하였다. 핀과 캐비티를 포함한 표면에서의 기포 생성, 성장, 이탈에 대한 해석을 통하여 핀-캐비티 배열, 핀-핀 간격이 핵비등에서의 기포거동에 중요한 역할을 하는 것을 확인하였다.

• 설비공학논문집
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• 제12권10호
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• pp.932-940
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• 2000

An experimental study on evaporative heat transfer characteristics in micro-fin tubes before and after expansion process has been performed with R-22. Single-grooved micro-fin tubes with outer diameter of 9.52 mm were used as test sections, and it was uniformly heated by applying direct current to the test tubes. Experiments were conducted at mass flow rates of 20 and 30 kg/hr. For each mass flow rate condition, evaporation temperature was set at 5 and $15^{\circ}C$and heat flux was changed from 6 to 11 kW/$m^2$ The evaporative heat transfer coefficient of micro-fin tubes after expansion is decreased because of the crush of fins and enlargement of inner diameter compared to that before expansion. Convective boiling effect decreased remarkably at higher quality range in the micro-fin tube after expansion, and the difference of the heat transfer coefficient in micro-fin tubes before and after expansion was greater for higher quality region. The evaporative heat transfer coefficient of the micro-fin tube after expansion was 19.9% smaller on the average than that before expansion.

• 한국태양에너지학회 논문집
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• 제22권1호
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• pp.23-30
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• 2002

본 연구는 축방향 내부 핀을 가진 열사이폰의 작동유체의 체적변화에 대한 응축 및 비등열전달 성능에 관한 연구이다. 열사이폰 내부의 작동유체는 증류수를 사용하였다. 열사이폰의 총체적에 대한 작동유체의 양을 변화시키면서 실험데이터를 산출하였다. 열사이폰의 응축부에 대한 열유속과 응축열전달계수를 구하였으며, 실험결과를 이론모델과 비교분석하였다. 실험결과로부터 열사이폰의 열전달 성능은 작동유체의 체적변화에 크게 의존하였다. 축방향내부 핀을 가진 열사이폰의 열전달 성능은 평튜브로 제작한 열 사이폰보다 크게 향상되었다. 이와 같은 열사이폰을 태양열 분야의 열교환기에 응용할 경우, 고성능화와 소형화할 수 있다. 그리고 산업현장에서 실제적으로 적용하기 위해 총열전달계수를 산출하였다.

• 대한기계학회논문집B
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• 제20권5호
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• pp.1725-1734
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• 1996

Experimental condensation and evaporation heat transfer coefficients were measured in a horizontal smooth tube and a horizontal micro-finned tube with HFC-134a. The test sections are straight, horizontal tubes with have a 9.52mm outside diameter and about 5000mm long. The micro-finned tube had 60 fins with a height of 0.12mm and a spiral angle of 25.deg.. The condensation test section was a double-pipe type with counter flow configuration. The evaporation test section employed an electic heating method. Enhancement factors which is defined as a ratio of the heat transfer coefficient for micro-finned tube to that for smooth tube, varied from 1.3 to 1.6(mass flux:110~190kg/m$^{2}$s) for condensation and 1.2 to 1.5 (mass flux:70~160kg/m$^{2}$s) for evaporation. The experimental data of condensation and evaporation heat transfer coefficients were compared to several empirical correlations. Based on these comparisons, modified correlations of the condensation and evaporation heat transfer coefficient for both smooth and micro-finned tubes were proposed.

• Journal of Advanced Marine Engineering and Technology
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• 제31권6호
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• pp.715-722
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• 2007

Experiments were conducted for the investigation of pressure drop inside horizontal micro-fin tubes during the condensation of R-22 and ternary refrigerant. R-407C(HFC-32/125/134a 23/25/62 wt%) as a substitute of R-22. The condenser is a double-tube and counterflow type heat exchanger which is consisted with micro-fin tubes having 60 fins with a length of 4000mm, outer diameter of 9.53mm and fin height of 0.2mm. The mass velocity varied from 102.1 to $301.0kg/(m^2{\cdot}s)$ and inlet quality was fixed as 1.0. From the experimental results. the pressure drop for R-407C was considerably higher than that for R-22. The value of PF(penalty factor) for both of refrigerants was not bigger than the ratio of micro-fin tube area to smooth tube area. Based on the experimental data. correlation was Proposed for the prediction of frictional pressure drop during the condensation of R-22 and R-407C inside horizontal micro-fin tubes.

• 대한기계학회논문집B
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• 제24권2호
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• pp.241-250
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• 2000

In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-22. Two internal geometries were tested ; one with smooth inner surface and the other with micro-fins. Data are presented for the followin~ range of variables ; vapor quality($0.1{\sim}0.9$), mass flux($200{\sim}600kg/m^2s$) and heat flux($5{\sim}15kW/m^2$). The micro-fin tube showed higher heat transfer coefficients compared with those of the smooth tube. The difference increased as the vapor quality increased. Surface tension force acting on the micro-fin surface at the high vapor quality is believed to be responsible. Different from the trends of the smooth tube, where the heat transfer coefficient increased as the mass flux increased, the heat transfer coefficient of the micro-fin tube was independent of the mass flux at high vapor quality, which implies that the surface tension effect on the fin overwhelms the vapor shear effect at the high vapor quality. Present data(except those at low mass flux and high quality) were well correlated by equivalent Reynolds number, Existing correlations overpredicted the present data at high mass flux.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.96-103
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• 2000

In this study, evaporation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-22. Two internal geometries were tested ; one with smooth inner surface and the other with micro-fins. Data are presented for the following range of variables ; vapor quality $(0.1{\sim}0.9)$, mass flux$(100{\sim}600kg/m^2s)$ and heat flux$(5{\sim}15kW/m^2)$. The micro-tin tube showed higher heat transfer coefficients compared with those of the smooth tube. Results showed that, for the smooth tube, the effects of mass flux, quality and heat flux were not prominent, and existing correlations overpredicted the data. For the micro-fin tube at low quality, the heat transfer coefficient increased as heat flux increased. However, the trend was reversed at high quality Kandlikar's correlation predicted the low mass flux data, and Shah's correlation predicted the high mass flux data. The heat transfer coefficient of the micro fin tube was approximately two times larger than that of the plain tube. New correlation was developed based on present data.

• 한국가스학회지
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• 제11권4호
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• pp.35-40
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• 2007

본 연구는 마이크로핀관에서 이소부탄과 프로판의 증발 열전달 특성에 대해 실험적으로 조사하였다. 시험부는 외경 12.70 mm이고, 높이가 0.25 mm인 75개 핀이 원주방향으로 삽입되어 있다. 실험결과, 탄화수소계 냉매의 평균 열전달계수는 프레온계 냉매인 HCFC22보다 높을 것으로 나타났고, 높은 질랑유속에서는 이소부탄 > 프로판 순으로 나타났다. 마이크로핀관에서 증발 열전달 계수는 평활관에 비해 약 $80{\sim}100%$ 정도가 향상되었다. 이러한 본 연구 결과로부터 탄화수소계 냉매를 냉동 공조 시스템의 냉매로 사용하여 열교환장치를 설계할 경우에는 유리하리라 생각된다.