• Title/Summary/Keyword: Multi-Channel Flat Tube

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A Comparison of Flow Condensation HTCs of R22 Alternatives in the Multi-Channel Tube (다채널 알루미늄 평판관내 R22와 R134a의 흐름 응축 열전달 성능 비교)

  • 서영호;박기정;정동수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.6
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    • pp.589-598
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    • 2004
  • Flow condensation heat transfer coefficients (HTCs) of R22 and R134a were measured on a horizontal 9 hole aluminum multi-channel tube. The main test section in the refrigerant loop was made of a flat multi-channel aluminum tube of 1.4 mm hydraulic diameter and 0.53 m length. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in the vapor qualities of 0.1∼0.9 at mass flux of 200∼400 kg/$m^2$s and heat flux of 7.3∼7.7 ㎾/$m^2$ at the saturation temperature of 4$0^{\circ}C$. All popular correlations in single-phase subcooled liquid and flow condensation originally developed for large single tubes predicted the present data of the flat tube within 20% deviation when effective heat transfer area is used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Thermal insulation for the outer tube section surrounding the test tube for the transport of heat transfer fluid is very important in fluid heat-ing or cooling type heat transfer experimental apparatus.

Flow Condensation Heat Transfer Coefficients of R22, R410A and Propane in Aluminum Multi-Channel Tube (알루미늄 다채널 평판관내 R22, R410A, Propane의 흐름 응축 열전달 성능 비교)

  • Park Ki-Jung;Lee Ki-Young;Jung Dongsoo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.7
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    • pp.649-658
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    • 2005
  • Flow condensation heat transfer coefficients (HTCs) of R22, R410, Propane (R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of $0.1\~0.9$ at mass flux of $200\~400kg/m^2s$ and heat flux of $7.3\~7.7kW/m^2$ at the saturation temperature of $40^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within $25\%$ deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than $20\%$ for all data.

Flow Condensation Heat Transfer Coefficients of R22 Alternative refrigerants in Aluminum Multi-Channel Tube (알루미늄 다채널 평판관내 R22 대체냉매의 흐름 응축 열전달 성능 비교)

  • Lee, Ki-Young;Lee, Min-Hang;Jung, Dong-Soo
    • Proceedings of the SAREK Conference
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    • 2005.11a
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    • pp.249-255
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    • 2005
  • Flow condensation heat transfer coefficients(HTCs) of R22, R4IO, Propane(R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53 m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of 0.1 ${\sim}$ 0.9 at mass flux of $200{\sim}400$ $kg/m^2s$ and heat flux of $7.3{\sim}7.7$ $kW/m^2$ at the saturation temperature of $4^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within 25% deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than 20% for all data.

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An Experimental study on R-22 Evaporation in Flat Aluminum Multi-Channel Tubes (알루미늄 다채널 평판관내 R-22 증발에 관한 실험적 연구)

  • Kim, Jung-Oh;Cho, Jin-Pyo;Kim, Jong-Won;Jeong, Ho-Jong;Kim, Nae-Hyun
    • Proceedings of the KSME Conference
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    • 2000.04b
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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.

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

  • Jung, Ho-Jong;Kim, Nae-Hyun;Yoon, Baek;Kim, Man-Hoi
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.7
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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.

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

  • Kim, Jung-Oh;Cho, Jin-Pyo;Kim, Nae-Hyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.2
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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.

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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    • v.11 no.3
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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.

A Comparison of Flow Condensation HTCs of R22 Alternatives in the Multi-Channel Tube (알루미늄 다채널 평판관내 R22의 흐름응축 열전달 성능 비교)

  • Seo, Young-Ho;Lim, Dae-Taeg;Park, Ki-Jung;Jung, Dong-Soo
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1270-1275
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    • 2004
  • Flow condensation heat transfer coefficients(HTCs) of R22 and R134a were measured on horizontal aluminum multi-channel tube. The experimental apparatus was composed of three main parts ; a refrigerant loop, a water loop and a water-ethylene glycol loop. The test section in the refrigerant loop was made of aluminum multi-channel tube of 1.4 mm hydraulic diameter and 0.53 m length. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. The data scan vapor qualities $(0.1{\sim}0.9)$, mass flux ($200{\sim}400$ $kg/m^{2}s$) and heat flux ($7.3{\sim}7.7$ $kW/m^{2}$) at $40{\times}0.2^{\circ}C$ saturation temperature in small hydraulic diameter tube. It was found that some well-known previous correlations were not suitable for multichannel tube. So, It must develop new correlations for multi-channel tubes.

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Experiment on condensation heat transfer and pressure drop characteristics in the multi-channel flat tube (다채널 편평관의 응축 열전달 및 압력강하특성에 관한 실험)

  • Jeon, C.D.;Chung, J.W.;Lee, J.H.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.9 no.3
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    • pp.376-388
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    • 1997
  • In this study, an experiment was performed to investigate the characteristics of pressure drop and heat transfer of multi-channel tubes for automotive condenser using HFC-134a as an alternative refrigerant. The mass flux and inlet saturation pressure of the refrigerant were controlled, respectively, in the range of 200 to $500kg/m^2s$ and 1.0 to 1.6MPa. Pressure drop and heat transfer coefficient were compared with the previously proposed correlations and new correlations based on Traviss' correlation were suggested. Prediction of pressure drop and heat transfer coefficient based on the new correlations agrees with experimental results within ${\pm}9%$ and -18~+11%, respectively.

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Development of design technique for automotive condenser (자동차용 에어컨 응축기의 설계기술 개발)

  • Cho, Y.D.;Han, C.S.;Yoo, S.Y.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.1
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    • pp.10-17
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    • 1999
  • The present work presents condensation heat transfer and pressure drop data for the flow of R-12 in flat extruded aluminum tubes with small hydraulic diameters. The tube outside dimensions are $18mm(width){\times}1.7mm(height)$. Three types of internal geometry with the same outside dimensions are tested : sample 1 (7 tube holes), sample 2 (13 tube holes) and sample 3 (7 tube holes, micro-fin). The overall heat transfer coefficient is obtained for air-to-refrigerant heat transfer, and the Wilson plot method is used to determine the heat transfer coefficient for refrigerant flow. The sample 2 and sample 3 show significantly higher performance than sample 1. The heat transfer rates for the sample 2 and sample 3 are 9% and 12% higher, respectively, than sample 1. The friction factors for the sample 2 and sample 3 are 11.9% and 2.4% higher, respectively, than sample 1.

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