• 제목/요약/키워드: Condensation heat transfer coefficients

검색결과 130건 처리시간 0.021초

수평평활관내 탄화수소계 냉매의 응축전열 특성에 관한 연구 (Condensation heat transfer characteristics of hydrocarbon. refrigerants inside horizontal tubes)

  • 이용언;박승준;정진호;장승환;오후규
    • 한국마린엔지니어링학회:학술대회논문집
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    • 한국마린엔지니어링학회 2001년도 추계학술대회 논문집(Proceeding of the KOSME 2001 Autumn Annual Meeting)
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    • pp.15-20
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    • 2001
  • This study investigated the condensation heat transfer coefficients of R-22, R-290 and R-600a inside horizontal tube. Heat transfer measurements were peformed for smooth tube with outside diameter of 12.7 mm Condensation temperatures and mass velocity were ranged from 308 K to 323 K and $51kg/\textrm{m}^2s$s to $250kg/\textrm{m}^2s$, respectively. The test results showed that the local condensation heat transfer coefficients increased as the mass flux increased, and also the effects of mass velocity on heat transfer coefficients of R-290 and R-600a were less than R-22. Average condensation heat transfer coefficients of natural refrigerants were superior to that of R-22. The present results had a good agreement with Haraguchi's correlation.

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코일형 나선 전열관의 내부 응축열전달 특성에 관한 실험 적 연구 (Experimental Study on In-Tube Condensation Heat Transfer Characteristics of Helically Coiled Spiral Tubes)

  • 박종운;권영철;한규일
    • 대한기계학회논문집B
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    • 제25권12호
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    • pp.1676-1683
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    • 2001
  • An experimental study on condensation heat transfer characteristics of helically coiled spiral tubes was performed. The refrigerant is R-113. A refrigerant loop was established to measure the condensation heat transfer coefficients. Experiments were carried out uniform heat flux of 15 kw/m$^2$, refrigerant quality of 0.1∼0.9, curvature ratio of 0.016, 0.025 and 0.045. The curvature of a coil was defined as the ratio of the inside diameter of the tube to the diameter of the bending circle. To compare the condensation heat transfer coefficients of coiled spiral tubes, the previous results on coiled plain tubes and straight plain tubes were used. The results shows that the condensation heat transfer coefficients of coiled spiral tubes largely increase, as increasing Re and quality, compared to those of coiled plain tubes and straight plain tubes. As increasing degree of subcooling, however, the condensation heat transfer coefficients on coiled spiral tubes decrease. It is found that the heat transfer enhancement is more better than coiled plain tubes and straight plain tubes, as increasing curvature ratio.

R407C 및 R410A의 수평원관내 응축열전달 (Condensation heat transfer of R407C and R410A in a horizontal smooth tube)

  • 서정현;김민수
    • 설비공학논문집
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    • 제11권5호
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    • pp.633-641
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    • 1999
  • Experiments were carried out to investigate the condensation heat transfer characteristics for R22 and its alternatives, R407C (R32/125/134a, 23/25/52wt%) and R410A (R32/125, 50/50wt%). A concentric tube heat exchanger was made to conduct condensation heat transfer tests. Mass flux and saturation temperature of refrigerants at the test section inlet were varied to get the corresponding heat transfer coefficients. Serial and parallel input of secondary fluid (water) were applied to the test subsections. Compared with existing correlations of condensation heat transfer, experimental heat transfer coefficients obtained in this study were generally higher than the predicted values, and mean absolute deviations from several correlations were shown. Wall subcooling was introduced to get a new correlation for condensation heat transfer coefficients by modifying Shah's equation. The RMS deviation of the measured heat transfer coefficients from the new correlation in this study for R22 is 9.9% and that for R407C and R410A are 10.2% and 14.6%, respectively.

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수평 평활관과 마이크로핀 관내에서 HFC-134a의 응축 및 증발열전달 특성 (Condensation and evaporation heat transfer characteristics of HFC-134a in a horizontal smooth and a micro-finned tube)

  • 이상천;박병덕;한운혁;이재희
    • 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.

액적이탈을 고려한 관내 응축열전달계수 계산 모델 (A modeling of in-tube condensation heat transfer considering liquid entrainment)

  • 권정태;안예찬;김무환
    • 대한기계학회논문집B
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    • 제22권7호
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    • pp.946-955
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    • 1998
  • Local condensation heat transfer coefficients in tubes were calculated by solving momentum and energy equations for annular film with liquid entrainment. The turbulent eddy distribution across the liquid film has been proposed and the calculated heat transfer coefficients were presented. Also turbulent Prandtl number effects on condensation heat transfer were discussed from three Pr$\_$t/ models. Finally, the calculated condensation heat transfer coefficients of R22 were compared with some correlations frequency referred to in open literature. This calculation model considering liquid entrainment predicted well the in-tube condensation heat transfer coefficient of R22 than the model not considering liquid entrainment. The effect of entrainment on heat transfer was predominant for high quality and high mass flux when the liquid film was turbulent.

마이크로핀관내 유동 양식과 응축 열전달 특성 연구 (Experiments on Condensation Heat Transfer Characteristics and Flow Regime Inside Microfin Tubes)

  • 한동혁;이규정
    • 설비공학논문집
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    • 제13권7호
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    • pp.602-611
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    • 2001
  • Experiments on the condensation heat transfer characteristics inside a smooth and a microfin tube with R410A/R22 are performed in this study. The test tubes 7/9.52 mm in outside diameters and 3m in length are used. Varying the mass flux of the refrigerant and the condensation temperatures, the average heat transfer coefficients and pressure drop are investigated. Most flows in this study are in the annular and/or wavy flow regime. It is shown that the heat transfer is enhanced and the pressure drops are larger in the microfin tube than the smooth tube. From the heat transfer enhancement coefficients and the pressure drops, it is found that the high heat transfer enhancement factors are obtained in the range of small mass flux while the penalty factors are almost equal. Experiments results show that average heat transfer coefficients of R410A is larger than that of R22 and pressure drop of R410A is less than R22.

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2중 관형 열교환기내 비공비혼합냉매 R-22+R134a의 응축열전달 특성에 관한 연구 (Condensation Heat Transfer Characteristics of Non-Azeotropic Refrigerant Mixture(NARMs) Inside Double Pipe Heat Exchangers)

  • 노건상;오후규;권옥배
    • Journal of Advanced Marine Engineering and Technology
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    • 제20권3호
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    • pp.91-100
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    • 1996
  • Experimental results for forced convection condensation of non-azeotropic refrigerant mixtures inside a horizontal smooth tube are presented. The mixtures of R-22+R-134a and pure refrigerants R-22 and R-134a are used as the test fluids and a double pipe heat exchanger of 7.5mm ID and 4800mm long inside tube is used. The range of parameters are 100-300kg/h of mass flow rate, 0-1.0 of quality, and 0, 33, 50, 67, and 100 weight percent of R-22 mass fraction in the mixtures. The heat flux, vapor pressure, vapor temperature and tube wall temperature were measured. Using the data, the local and average heat transfer coefficients for the condensation have been obtained. In the same given experimental conditions, the liquid heat transfer coefficients for NARMs were considerally lower than that of the pure refrigerant of R-22 and R-134a. Local heat transfer characteristics for NARMs were different from pure refrigerant R-22 and R-134a. In some regions, local heat transfer coefficients for NARMs were increased in the following order ; Bottom$\rightarrow$Top$\rightarrow$Side. The condensation heat transfer coefficients for NARMs increased with mass velocity, heat flux, and quality, but were considerably lower than that of pure refigerant R-22 and R-134a.

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탄화수소계 냉매 R-290, R-600a의 수평관내 응축 열전달 특성에 관한 연구 (Condensation heat transfer characteristics of hydrocarbon refrigerants R-290 and R-600a inside horizontal tubes)

  • 박승준;박기원;노건상;정재천;오후규
    • 설비공학논문집
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    • 제12권1호
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    • pp.20-25
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    • 2000
  • An experimental study on the condensation heat transfer coefficients of R-22, R-290 and R-600a inside horizontal tube was performed. Heat transfer measurements were performed for smooth tube with inside diameter of 10.07 mm and outside diameter of 12.07 mm and inner grooved tube having 75 fins whose height is 0.25 mm. This study was performed for condensation temperatures were from 308 K to 323 K, and mass velocity of $51 kg/m^2s - 250kg/m^2s$. The test results showed that the local condensation heat transfer coefficients increased as the mass flux increased, and also the effect of mass flow rate on heat transfer coefficients of R-290 was less than R-22. In addition, heat transfer coefficient of R-22 increased to a larger extent than R-290 and R-600a as the mass flow rate increased. Average condensation heat transfer coefficients of natural refrigerants were superior to that of R-22. The present results had a good agreement with Cavallini-Zecchin's correlation for smooth and inner grooved tubes.

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Study on Condensation Heat Transfer Characteristics of Hydrocarbons Natural Refrigerants

  • Oh, Hoo-Kyu;Park, Seung-Jun;Park, Ki-Won;Roh, Geon-Sang;Jeong, Jae-Cheon
    • International Journal of Air-Conditioning and Refrigeration
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    • 제9권3호
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    • pp.10-17
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    • 2001
  • This study investigated the condensation heat transfer coefficients of R-22, R-290 and R-600a inside horizontal tube. Heat transfer measurements were performed for smooth tube with inside diameter of 10.07 mm and outside diameter of 12.07 mm and inner grooved tube having 75 fins whose height is 0.25 mm. Condensation temperatures and mass velocity were ranged from 308K to 323 K and $51kg/m^2s$ to $250kg/m^2s$, respectively. The test results showed that the local condensation heat transfer coefficients increased as the mass flux increased, and also the effects of mass velocity on heat transfer coefficients of R-290 and R-600a were less than those of R-22. Average condensation heat transfer coefficients of natural refrigerants were superior to that of R-22. The present results had a good agreement with Cavallini-Zecchin's correlation for smooth and inner grooved tubes.

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판각형 열교환기내의 R-134a 응축열전달 특성에 관한 실험적 연구 (Experimental Study on R-l34a Condensation Beat Transfer Characteristics in Plate and Shell Heat Exchanger)

  • 이기백;박재홍;서무교;이희웅;김영수
    • Journal of Advanced Marine Engineering and Technology
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    • 제27권1호
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    • pp.108-116
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    • 2003
  • In this paper, the experimental results of condensation heat transfer were reported for the plate and shell heat exchangers(P&SHE) using R-l34a. An experimental refrigerant loop has been established to measure the condensation heat transfer coefficient of R-l34a in a vertical P&SHE. Two vertical counter flow channels were formed in the P&SHE by three plates of geometry with a corrugated trapezoid shape of a chevron angle of 45$^{\circ}$. Downflow of the condensing R-l34a in one channel releases heat to the cold up flow of water in the other channel. The effect of the refrigerant mass flux, average heat flux, system pressure and vapor quality of R-l34a on the measured data were explored in detail. The results indicate that at a higher vapor quality the condensation heat transfer coefficients are significantly higher. Condensation heat transfer coefficients were increased when the refrigerant mass flux was increased. A rise in the average heat flux causes an slight increase in the hr. Finally, at a higher system pressure the hr is found to be lower. Correlation is also provided for the measured heat transfer coefficients in terms of the Nusselt number.