• Title/Summary/Keyword: Horizontal in-tube condensation

Search Result 67, Processing Time 0.027 seconds

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

  • Lee, Sang-Cheon;Park, Byeong-Deok;Han, Un-Hyeok;Lee, Jae-Hui
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.20 no.5
    • /
    • pp.1725-1734
    • /
    • 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.

Filmwise Condensation of Freon Vapor Including Air on a Horizontal Tube (공기를 함유한 프레온 증기의 수평관 외부에서의 막응축)

  • Kim, K.H.;Ko, H.J.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.7 no.1
    • /
    • pp.20-29
    • /
    • 1995
  • A theoretical model for film condensation of a vapor including a relatively lighter noncondensable gas on a horizontal tube has been formulated on the basis of the conservation laws and other fundamental physical principles. The model is applied to the prediction of the condensation heat transfer characteristics for the Freon vapor in the presence of air on a horizontal tube. Calculated results for the mean heat transfer coefficient, which is shown to depend strongly on the bulk concentration of air, are in good agreement with the available experimental results for a range of operating conditions. The distributions of physical quantities along the surface of tube are also calculated, such as the boundary layer thickness and local heat transfer coefficient. The present model is readily reduced to the Nusselt model as the bulk concentration of air decreases to zero. Therefore, the transition from the condensation of pure vapor to that of vapor-air mixture occurs continuously not abruptly.

  • PDF

Condensation Heat Transfer Characteristics of HCFC - 123 inside Horizontal Smooth Tube (HCFC-123의 수평 평활관내 응축 전열 특성에 관한 연구)

  • 권옥배;오후규;오종택;김성규
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.17 no.3
    • /
    • pp.24-32
    • /
    • 1993
  • Experimental data on the heat transfer characteristics of HCFC-123 and CFC-11 during condensation in horizontal smooth tube are presented. The experimental apparatus consisted of a closed working fluid loop, coolant loop, and measuring system. The major components of the working fluid loop made of a refrigerant pump, boiler, superheater, refrigerant flow meter, receiver and test section. The tube-in-tube type test section was made of smooth tube which were constructed form 9.52 mm outer diameter of smooth copper tube with 50 mm outside diameter of PVC tube duct. The ranges of parameter, such as refrigerant mass velocity, coolant flow rate, and quality were 90-325kg/($m^2$.s), 60-360kg/h, 5-95% respectively. Data were obtained under steady state condition for annular flow. As a result of these, the condensation heat transfer coefficients for HCFC-123 were slightly lower than those of CFC-11 from 8% to 15% inside horizontal smooth tube. Furthermore, a new generalized correlation for the heat transfer coefficients of HCFC-123 and CFC-11 during condensation inside horizontal smooth tube is proposed.

  • PDF

Measurement of Single Phase and Condensation Heat Transfer Coefficients of Ammonia in a Horizontal Tube (암모니아의 수평관내 단상 및 응축 열전달계수의 측정)

  • 백영진;장영수;김영일
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.12 no.6
    • /
    • pp.561-569
    • /
    • 2000
  • Single phase and condensation heat transfer characteristics of ammonia in a horizontal tube have been investigated experimentally The horizontal test section is composed of smooth SUS316 tube for refrigerant flow, surrounding annulus for water flow, and temperature and Pressure measuring sensors. For single phase test, subcooled ammonia mass flux was varied from 320 to 501 kg/mrs and temperature was varied from 18 to $47^{\circ}C$. For condensation test, mass flux and saturation temperature were varied from 86 to 128 kg/$m^2$s and 34 to $47^{\circ}C$, respectively. The equations of Gnielinski Soliman et al., Traviss et at., Cavallini and Zecchin, Shah, Chen et al., Tandon et al., and Chilli and Anand were compared with the experimental data. New correlations are proposed based on the experimental results and the absolute mean deviation of the experimental data becomes 1.0% for single phase test and 4.9% for condensation test.

  • PDF

A Study on the Condensation Performance for the Horizontal Heat Transfer Tubes with Various Fin Attached (형상이 다른 수평 원형 전열관의 응축 성능에 관한 연구)

  • Han, Kyu-Il;Park, Jong-Un
    • Journal of Fisheries and Marine Sciences Education
    • /
    • v.4 no.1
    • /
    • pp.47-61
    • /
    • 1992
  • An experimental study was carried out to investigate the condensation performance for the horizontal cylindrical heat transfer tube with various fin attached using R-11 vapor. The heat transfer tube used in this study was supplied by SUNG HYUNG METAL CO., LTD. Four different types of heat transfer tubes (plain tube, SH-CYR tube, thermocor tube and thermoexcel tube) were used. Each tube was surrounded by circular acrylate tube, and R-11 gas heated by boiler flows into the acrylate tube. Cooling water counter-flows in heat transfer tubes. Heat transfer coefficient of the plain tube from measured data was compared with those of three other tubes. The results are summarized as follows: 1. As the cooling water temperature decreased, the liquid film of R-11 turned to droplet drop on the top surface of the horizontal tube. 2. Heat transfer coefficient calculated theoretically was higher than that obtained from the experimental data. 3. As far as the condensation concerns the thermocor tube is the highest, the SH-CYR tube is the second, and the thermoexcel tube is the third excluding the plain tube.

  • PDF

Effects of Hydrophilic Surface Treatment on Condensation Heat Transfer at the Outside Wall of Horizontal Tube (수평관 외벽에서 친수성 표면처리가 응축열전달에 미치는 영향)

  • 황규대;박노성;강병하
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.12 no.6
    • /
    • pp.533-540
    • /
    • 2000
  • Condensation heat transfer characteristics have been investigated experimentally when a water vapor is condensed on the outside of a horizontal copper tube in a condenser. This problem is of particular interest in the design of a LiBr-water absorption system. Hydrophilic surface modification was performed to increase the wettability on the copper tube. The optimum hydrophilic treatment condition using acethylene and nitrogen as reaction gas is also studied in detail. The results obtained indicate that the optimum reaction gas ratio of acethylene to nitrogen for hydrophilic surface modification was found to be 7 : 3 for the best condensation heat transfer. In the wide ranges of coolant inlet temperatures, and coolant mass flow rates, both the condensation heat transfer rate and the condensation heat transfer coefficient of a hydrophilic copper tube are increased substantially, compared with those of a conventional copper tube used in a condenser. It is also found that the condensation heat transfer enhancement by the hydrophilic surface modification still emains even after a hundred cycles of wet/dry processes.

  • PDF

Experimental Study on the Enhancement of Condensation Heat Transfer on a Single Horizontal Tube Utilizing EHD (전장을 이용한 수평관 주위에서의 응축 열전달촉진에 관한 실험적 연구)

  • 유갑종;추홍록;김석준;이성진
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.18 no.11
    • /
    • pp.3008-3020
    • /
    • 1994
  • Condensation heat transfer on a single horizontal tube with electric fields (Electro-Hydro-Dynamics, (EHD)) has been studied experimentally. Results are presented for EHD enhanced condensation of R-113 on a single horizontal tube using several electrode geometries. Especially, its attention was focused on the effects of electrode geometry, electric field strength and the gap of the electrode. In this study, single wire, helical, ring and mesh electrode were used. The range of the imposed voltage was 0~20 kV. As the voltage was increased the surface of liquid became an unstable wave, stream jet, liquid column and then liquid extraction in sequence. Among the various kinds of electrodes, the single wire electrode is suitable for practical application.

Effects of Tube Diameter and Surface Sub-Cooling Temperature on R1234ze(E) and R1233zd(E) Film Condensation Heat Transfer Characteristics in Smooth Horizontal Laboratory Tubes (수평 평활관에서 관직경 및 표면 과냉도가 R1234ze(E) 및 R1233zd(E) 막응축 열전달에 미치는 영향)

  • Jeon, Dong-Soon;Ko, Ji-Woon;Kim, Seon-Chang
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.29 no.5
    • /
    • pp.231-238
    • /
    • 2017
  • HFO refrigerants have recently come to be regarded as promising alternatives to R134a for use in turbo chillers. This study provides results from experiments evaluating the film condensation heat transfer characteristics of HFO refrigerants R1234ze(E) and R1233zd(E) on smooth horizontal laboratory tubes. The experiments were conducted at a saturation vapor temperature of $38.0^{\circ}C$ with surface sub-cooling temperatures in the range of $3{\sim}15^{\circ}C$. We observe that the film condensation heat transfer coefficient decreases as surface sub-cooling temperatures increase. In the case of laboratory tubes with a diameter of 19.05 mm, the film condensation heat transfer coefficients of R1234ze(E) and R1233zd(E) were approximately 11% and 20% lower than those of R134a, respectively. Furthermore, our investigation of the effect of tube diameter on film condensation heat transfer coefficients, demonstrates an inverse relationship where the film condensation heat transfer coefficient increases as laboratory tube diameter decreases. We propose experimental correlations of Nusselt number for R1234ze(E) and R1233zd(E), which yield a ${\pm}20%$ error band.

Comparative Study of Condensation Heat Transfer Coefficients between R404A and R152a Flow in a Horizontal Smooth Tube (수평 평활관내 R404A와 R152a 냉매 유동의 응축 열전달 계수에 대한 비교 연구)

  • Lee, Sang-Yong;Kim, Man-Hoe;Lee, Chi-Young
    • Proceedings of the SAREK Conference
    • /
    • 2005.11a
    • /
    • pp.256-261
    • /
    • 2005
  • In the present experimental study, condensation heat transfer coefficients between R404A and R152a flow in a horizontal smooth tube were compared. The outer and inner diameters of the tube were 9.52 mm and 7.55 mm, respectively, and the heated length was 1045 mm. The mass flux ranged from 150 to 400 $kg/m^{2}s$ and the test section were uniformly heated from 8 to 12. $kW/m^2$. The quality range was from 0.2 to 0.8 at the saturation temperature from 27.3 to $34^{\circ}C$. Experimental condensation heat transfer coefficients increased as the quality and mass flux increased. Modified Dobson and Chato correlation reduced the mean deviation of 5.1% for R404A and 9.4% for R152a than the original correlation$^{(2)}$.

  • PDF

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

  • 박승준;박기원;노건상;정재천;오후규
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.12 no.1
    • /
    • pp.20-25
    • /
    • 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.

  • PDF