• 제목/요약/키워드: Micro-Fin Tube

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마이크로핀관에서 프로판과 이소부탄의 증발 열전달 특성에 관한 연구 (Evaporation Heat Transfer Characteristics of Propane and Iso-butane in Micro-fin Tubes)

  • 손창효;노건상
    • 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.

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수평 평활관 및 전열촉진관내 대체 냉매 R-407C의 응축 열전달 특성에 관한 연구 (Heat Transfer Characteristics of R-407C During Condensing Inside Horizontal Smooth and Micro-Fin Tubes)

  • 노건상;오후규
    • 대한기계학회논문집B
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    • 제23권2호
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    • pp.210-217
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    • 1999
  • This paper reports the experimental results on heat transfer characteristics of R-22 and R-407C(HFC-32/125/134a 23/25/52 wt%) condensing inside horizontal smooth and finned tubes. The test condensers used In the study are double pipe heat exchangers of 7.5 mm ID, 9.5 mm OD smooth tube, and 60 finned micro-fin tube with 8.53 mm ID, 9.53 mm OD. Each of these tubes was 4 000 mm long tubes connected with an U-bend. These U type two-path test tubes are divided In 8 local test sections for the identification of the local condensing heat transfer characterisitcs and pressure drop, U-bend effects on condensing flows. Inlet quality is maintained 1.0, and refrigerant mass velocity is varied from 102.0 to $301.0kg/m^2{\cdot}s$. From the results, it was found that the pressure drop of the R-407C Increased, and heat transfer coefficient decreased compared to those of R-22. In comparison condensing heat transfer characteristics of micro-fm tube with those of smooth tube, increasing of condensing heat transfer coefficient was found outstanding compared to the increasing ratio of pressure drop. Furthermore, pressure drop In U-bend showed at most a 30 % compared to the total pressure drop in the test section.

미소 전열촉진관내 R-22 및 R-410A의 증말열전달 및 압력강하 특성 연구 (Evaporation Heat Transfer and Pressure Drop of R-22 and R-410A in Small Sized Micro-Fin Tubes)

  • 황준현;윤린;김용찬
    • 대한기계학회논문집B
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    • 제25권7호
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    • pp.981-988
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    • 2001
  • Characteristics of evaporation heat transfer in 6.2 and 5.1mm OD micro-fin tubes were investigated in the present study. The data were taken at evaporation temperatures of -5$^{\circ}C$ and 5$^{\circ}C$ and heat fluxes 5kW/$m^2$ to 10kW/$m^2$. Mass flux was consequently maintained at 210, 300 and 410kg/$m^2$s for the 6.2mm OD tube and 465, 500 and 600kg/$m^2$s for the 5.1mm OD tube. The effects of heat flux, mass flux, and outer diameter on the heat transfer coefficient are explored in the present study. The data showed that the evaporation heat transfer coefficient for the 6.2mm OD tube was averagly higher by 16% than that for a 7.0mm OD tube, while the 5.1mm OD tube had approximately 30% higher value than the 6.2mm OD tube.

전열관 형상과 냉동기유 효과를 고려한 공조기기의 성능예측 (Effects of Oil and Internally Finned Tubes on the Performance of the Air-Conditioning Unit)

  • 윤점열;이관수;이동진
    • 설비공학논문집
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    • 제6권4호
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    • pp.388-398
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    • 1994
  • Computer simulation model for predicting more accurately the heat transfer performance of the evaporator and condenser which have significantly affected on the performance of air-conditioner has been suggested. In this model oil and micro-fin tube used in a actual unit are considered to simulate the more realistic case. The effects of oil and micro-fin tube on the performance of an air-conditioner have been investigated. It is found that the present model requires higher pressure than the existing model due to the characteristics of the tube considered. However, it turns out that the present model is very close to an actual cycle. As the amount of oil inside the tube increases, condensation heat transfer coefficient shows a linear decrease irrespective of a kind of oil, while evaporation heat transfer coefficient increases slightly in the oil with low viscosity and decreases exponentially in the oil with high viscosity. Pressure drop in both evaporator and condenser increases linearly irrespective of a kind of oil. It is also found that the effect of the variation of oil concentration on the magnitude of two-phase region is negligible.

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프로판/부탄 혼합자연냉매의 평활관과 마이크로핀관 내의 응축성능평가 (Condensing Performance Evaluation in Smooth and Micro-Fin Tubes for Natural Mixture Refrigerant (Propane/Butane))

  • 이상무;이주동;박병덕
    • 설비공학논문집
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    • 제17권9호
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    • pp.816-823
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    • 2005
  • This paper deals with the heat exchange performance prediction of a counter flow type double-tube condenser for natural refrigerant mixtures composed of Propane/n-Butane or Propane/i-Butane in a smooth tube and a micro-fin tube. The local characteristics of heat transfer, mass transfer and pressure drop are calculated using a prediction method developed by the authors. The total pressure drop and the overall heat transfer coefficient are also evaluated on various heat exchange conditions. The calculated results of the natural refrigerant mixtures are compared with HCFC22. In conclusion, natural refrigerant mixtures composed of Propane/n-Butane or Propane/i-Butane are appropriate candidates for alternative refrigerant from the viewpoint of heat transfer characteristics.

알루미늄 다채널 평판관내 R-22 및 R-410A 응축에 관한 연구 (R-22 and R-410A Condensation in Flat Aluminum Multi-Channel Tubes)

  • 정호종;김내현;윤백;김만회
    • 설비공학논문집
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    • 제14권7호
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    • pp.575-583
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    • 2002
  • In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-410A, and the results are compared with those of R-22. Two internal geometries were tested; one with a smooth inner surface and the other with micro-fins. Data are presented for the following range of variables; vapor quality (0.1~0.9), mass flux (200~600 kg/$m^2$s) and heat flux (5~15 ㎾/$m^2$). Results show that the effect of surface tension drainage on the fin surface is more pronounced for R-22 than R-410A. The smaller Weber number for R-22 may be responsible. For the smooth tube, the heat transfer coefficient of R-410A is slightly larger than that of R-22. For the micro-fin tube, however, the reverse is true. Possible reasoning is provided considering the physical properties of the refrigerants. For the smooth tube, a correlation of Akers et at. type predicts the data reasonably well. For the micro-fin tube, the Yang and Webb model was modified to correlate the present data.

마이크로 채널 관에서의 응축 열전달 성능에 관한 연구 (A study on condensation heat transfer performance in microchannel tube)

  • 이정근
    • Design & Manufacturing
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    • 제13권2호
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    • pp.22-29
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    • 2019
  • This study conducted a research as to condensation heat transfer by using three types of flat micro multi-channel tubes with different processing of micro-fin and number of channels inside the pipes and different sizes of appearances. In addition, identical studies were conducted by using smoothing circular tubes with 5mm external diameter to study heat transfer coefficient. The condensation heat transfer coefficient showed an increase as the vapor quality and mass flux increased. However, each tube shows little differences compared to 400kg/m2s or identical in case the mass flux are 200kg/m2s and 100kg/m2s. The major reason for these factors is increase-decrease of heat transfer area that the flux type of refrigerant is exposed to the coolant's vapor with the effect of channel aspect ratio or micro-fin. In addition, the heat transfer coefficient was unrelated to the heat flux, and shows a rise as the saturation temperature gets lower, an effect that occurs from enhanced density. The physical factor of heat transfer coefficient increased as the channel's aspect ratio decreased. Additionally, the micro pin at the multi-channel type tube is decided as a disadvantageous factor to condensation heat enhancement factor. That is, due to the effect of aspect ratio or micro-fin, the increase-decrease of heat transfer area that the flux type of a refrigerant is exposed to the vapor is an important factor.

R-22 and R-410A Condensation in Flat Aluminum Multi-Channel Tubes

  • Kim, Nae-Hyun;Min, Chang-Keun;Jung, Ho-Jong
    • International Journal of Air-Conditioning and Refrigeration
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    • 제11권3호
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    • pp.114-124
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    • 2003
  • In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-410A, and the results are compared with those of R-22. The flat tubes have two internal geometries; one with smooth inner surface and the other with micro-fins. Data are presented for the following range of variables; vapor Quality (0.1∼0.9), mass flux (200∼600 kg/$m^2$s) and heat flux (5∼15 kW/$m^2$). Results show that the effect of surface tension drainage on the fin surface is more pronounced for R-22 than R-410A. The smaller Weber number of R-22 may be responsible. For the smooth tube, the heat transfer coefficient of R-410A is slightly larger than that of R-22. For the micro-fin tube, however, the trend is reversed. Possible reason is provided considering physical properties of the refrigerants. For the smooth tube, Webb's correlation predicts the data reasonably well. For the micro-fin tube, the Yang and Webb model was modified to correlate the present data. The modified model adequately predicts the data.

Advances In Air-Cooled Heat Exchanger Technology for Residential Air-Conditioning

  • Webb Ralph L.;Kim Nae-Hyun
    • International Journal of Air-Conditioning and Refrigeration
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    • 제13권4호
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    • pp.184-195
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    • 2005
  • This paper describes the recent work on advanced technology concepts applied to air cooled heat exchangers for residential air-conditioning. The concepts include vortex generators for the air-side, micro-fin or flat tubes for the refrigerant-side. Advances in understanding of heat transfer mechanisms, predictive models are discussed.

외경 5mm 수직 평활관 및 마이크로핀관 내의 이산화탄소/프로판 혼합냉매의 증발열전달 특성에 관한 실험적 연구 (An Experimental Study on the Evaporative Heat Transfer Characteristics of $CO_2$/Propane Mixtures Flowing Upward in Vertical Smooth and Micro-fin Tubes with an Outer Diameter of 5 mm)

  • 조진민;김민수
    • 설비공학논문집
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    • 제21권4호
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    • pp.243-251
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    • 2009
  • Refrigerant mixtures provide an opportunity to adjust their properties to fit design criteria and a possibility to create new blends that can improve heat transfer characteristics. Therefore, mixture of $CO_2$ and propane is chosen which may be a promising refrigerant and has good environmental compatibility. This paper presents measured heat transfer coefficient data during evaporation process of $CO_2$/propane mixtures flowing upward in vertical smooth and. micro-fin tubes. Smooth and micro-fin tubes with outer diameters of 5 mm and length of 1.44in were selected as test tubes. The tests were conducted at mass fluxes of 212 to $656kg/m^{2}s$, inlet temperatures of -10 to $30^{\circ}C$, heat fluxes of 15 to $60\;kW/m^2$ and for several compositions (75/25, 50/50, 25/75 wt%). Among $CO_2$/propane refrigerant mixtures, the heat transfer characteristics are much better than that of any compositions when the composition is 75/25 (wt%).