• Title/Summary/Keyword: Condensation heat transfer

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Condensation Heat Transfer Correlation for Smooth Tubes in Annular Flow Regime

  • Han Dong-Hyouck;Moon C.;Park C.;Lee Kyu-Jung
    • Journal of Mechanical Science and Technology
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    • v.20 no.8
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    • pp.1275-1283
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    • 2006
  • Condensation heat transfer coefficients in a 7.92 mm inside diameter copper smooth tube were obtained experimentally for R22, R134a, and R410A. Working conditions were in the range of $30-40^{\circ}C$ condensation temperature, $95-410 kg/m^2s$ mass flux, and 0.15-0.85 vapor quality. The experimental data were compared with the eight existing correlations for an annular flow regime. Based on the heat-momentum analogy, a condensation heat transfer coefficients correlation for the annular flow regime was developed. The Breber et al. flow regime map was used to discern flow pattern and the Muller-Steinhagen & Heck pressure drop correlation was used for the term of the proposed correlation. The proposed correlation provided the best predicted performance compared to the eight existing correlations and its root mean square deviation was less than 8.7%.

Flow Condensation Inside Mini-Channels (I) -Development of New Experimental Technique- (작은 유로 내에서의 흐름응축 열전달 (I) -새로운 실험기법의 개발 -)

  • Shin, Jeong-Seob;Kim, Moo-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.11
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    • pp.1424-1431
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    • 2004
  • With traditional experimental methods such as the secondary fluid (e.g., water) calorimetric method, it is very difficult to accurately test the local condensation heat transfer inside mini-channels. Hence, there are large discrepancies between the results of previous studies. The experimental methods as well as unidentified sources of uncertainties could be reasons for such discrepancies. In this study, innovative experimental techniques were developed to measure the in-tube condensation heat transfer coefficient. With these techniques, very low heat dissipation rates such as several watts from the mini-channel could be estimated and low mass flow rates below the 0.1 ㎏/h could be measured with reasonable uncertainties. To the authors' knowledge, these techniques provide a unique experimental apparatus for measuring the condensation heat transfer coefficients inside the sub-millimeter hydraulic diameter single channels.

Experimental Study on R-22 Condensation Heat Transfer Characteristic in Plate and Shell Heat Exchanger (Plate and Shell 열교환기 내의 R-22 응축열전달 특성에 관한 실험적 연구)

  • Seo, Mu-Gyo;Park, Jae-Hong;Kim, Yeong-Su
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.6
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    • pp.860-867
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    • 2001
  • In this study, condensation heat transfer experiments were conducted with plate and shell heat exchangers(P&SHE) using R-22. An experimental refrigerant loop has been established to measure the condensation heat transfer coefficient of R-22 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°. Downflow of the condensing R-22 in one channel releases heat to the cold upflow of water in the other channel. The effect of the refrigerant mass flux, average heat flux, system pressure and vapor quality of R-22 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. A rise in the refrigerant mass flux causes an increase in the h(sub)r. Also, a rise in the average heat flux causes an increase in the h(sub)r. Finally, at a higher system pressure the h(sub)r is found to be slightly lower. Correlation is also provided for the measured heat transfer coefficients in terms of the Nusselt number.

A Study on a Heat Transfer Characteristics of Direct Contact Heat Exchanger for Steam Condensation According to Various Cooling Water Flow and Internal Pressure(The Purpose of Combination with LNG Evaporator) (증기응축용 직접접촉식 열교환기의 냉각수 유량과 내부압 변화에 따른 열전달 특성연구(LNG 기화기와의 조합목적))

  • Lee, B.C.;Han, S.T.;Kim, C.B.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.3 no.3
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    • pp.153-160
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    • 1991
  • Heat transfer characteristics of a direct contact heat exchanger utilizing sieve trays and spray nozzles for steam condensation for the purpose of combining with a LNG evaporator have been investigated with various cooling water flow rates and different vacuum pressures within the heat exchanger for the purpose of steam condensation. Temperature profiles and the volumetric overall heat transfer coefficients in a direct contact heat exchanger have been obtained for comparisons. The results show that the temperature differences between cooling water and steam along the direct contact heat exchanger height are rapidly decreasing and the volumetric overall heat transfer coefficients of the exchanger improves greatly as the inside vacuum pressure increases. The values of the overall heat transfer coefficients at P=-680mmHg have been increased significantly compared with at atmospheric pressure. At given pressure conditions, it is found that the values of average volumetric overall heat transfer coefficients for the sieve tray are found to be approximately 10% higher than those of the spray nozzle.

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Heat transfer characteristics of R - 407C condensing inside smooth horizontal tubes (냉매 R-407c의 수평평골 응축관내 열전달특성에 관한 연구)

  • 오후규;문정욱;노건상
    • Journal of Advanced Marine Engineering and Technology
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    • v.21 no.2
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    • pp.144-156
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    • 1997
  • Experimental results for forced convection heat transfer of pure refrigerant and nonrefrigerant mixtures during condensing inside horizontal smooth tubes, double pipe heat exchanger of 7.5 mm ID and 4 000 mm long inside tube, are presented. Pure refrigerant R - 22 and R - 407 c, the mixture of R - 32 + R - 125 + R - 134a (23/25/52, wt %) are used as the test fluids. The ranges of parameters are $114.3{\sim}267.1 kg/(m^2 {\cdot} s)$ of mass velocity, <0$\sim$1.0 of quality. The vapor pressure, vapor temperature and tube wall temperature were measured. Using these data, the local and average heat transfer coefficients for the condensation are obtained. At the same given experimental conditions, the condensation heat transfer coefficients for NARMs R - 407c were lower than those for the pure refrigerant of R - 22. Local heat transfer characteristics for R - 407c were different from pure refrigerant R - 22. The condensaheat transfer coefficients for R - 407c and R - 22 increased with mass velocity. Based on the data a prediction method was presented for the calculation of dimensionless average heat transfer coefficient.

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Study on R-l34a, R-407C, and R-410A Condensation Performance in the Oblong Shell and Plate Heat Exchanger (오블롱 셀 플레이트 열교환기에서의 R-l34a, R-407C, R-410A의 응축성능에 관한 실험적 연구)

  • Park, Jae-Hong;Kim, Young-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.12
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    • pp.1535-1548
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    • 2004
  • Condensation heat transfer experiments were conducted with the oblong shell and plate heat exchanger without oil in a refrigerant loop using R-l34a, R-407C and R-410A. An experimental refrigerant loop has been developed to measure the condensation heat transfer coefficient h$_{r}$ and frictional pressure drop $\Delta$p$_{f}$ of the various refrigerants in a vertical oblong shell and plate heat exchanger. The effects of the refrigerant mass flux(40∼80kg/$m^2$s), average heat flux(4∼8kW/$m^2$), refrigerant saturation temperature(30∼4$0^{\circ}C$) and vapor quality of refrigerants on the measured data were explored in detail. Similar to the case of a plate heat exchanger, even at a very low Reynolds number, the flow in the oblong shell and plate heat exchanger remains turbulent. A comparison of the performance of the various refrigerants revealed that R-410A had the highest heat transfer performance followed by R-l34a, and R-407C had the lowest performance of the refrigerants tested. The pressure drops were also reported in this paper. The pressure drops for R-410A were approximately 45% lower than those of R-l34a. R-407C had 30% lower pressure drops than R-l34a. Experimental results were compared with several correlations which predicted condensation heat transfer coefficients and frictional pressure drops. Comparison with the experimental data showed that the previously proposed correlations gave unsatisfactory results. Based on the present data, empirical correlations of the condensation heat transfer coefficient and the friction factor were proposed.tor were proposed.sed.

Condensation Heat Transfer Characteristics of Tube-in-Tube Heat Exchanger using Small Diameter Tubes with R-22, R-407C and R-410A (세관을 이용한 Tube-in-Tube 열교환기내 R-22, R-407C 및 R-410A 응축열전달 특성)

  • Park, Woo-Jong;Choi, Kwang-Il;Park, Ki-Won;Oh, Jong-Taek
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.657-662
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    • 2006
  • The present paper dealt with an experimental study of condensation heat transfer coefficients with refrigerant R-22, R-407C and R-410A, and was focused on pressure gradient and heat transfer coefficient in horizontal tube-in-tube heat exchangers using inner diameter of 4 mm, 3 mm and 2 mm in a 16.91 mm tube and length of 3,000 mm. Experiments were performed at inlet saturation temperature of 35 to $45^{\circ}C$ and mass flux ranges from 200 to $600 kg/m^2s$. The pressure gradient with inner tube diameter of 4.0 mm is higher 2.5 times than that of 8.0 mm. In tube-in-tube HEX, the pressure gradient of R-410A were lower than those of R-22 and R-407C. The condensation heat transfer coefficients increased with mass flux increase, but they decreased with saturation temperature increased. Condensation heat transfer coefficients of R-410A were a little higher than those of R-22 and R-407C. The condensation heat transfer coefficients of tube-in-tube HEX were about 40% higher than those of double tube HEX.

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Experimental Study of Air-cooled Condensation in Slightly Inclined Circular Tube (경사진 원형관에서의 공냉응축에 관한 실험적 연구)

  • Kim, Dong Eok;Kwon, Tae-Soon;Park, Hyun-Sik
    • The KSFM Journal of Fluid Machinery
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    • v.19 no.4
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    • pp.29-34
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    • 2016
  • In this study, the experimental investigation of air-cooled condensation in slightly inclined circular tubes with and without fins has been conducted. In order to assess the effects of the essential parameters, variable air velocities and steam mass flow rates were given to the test section. The heat transfer performance of air-cooled condensation were dominantly affected by the air velocity, however, the increase of the steam mass flow rate gave relatively weaker effects to total heat transfer capability. And in the experimental cases with the finned tube, the total heat transfer rate of the finned tube was significantly larger than that of the flat tube. From those results, it can be confirmed that the most important parameter for air-cooled condensation heat transfer is the convective heat transfer characteristics of air. Therefore, for the well-designed long-term cooling passive safety system, the consideration of the optimal design of the fin geometry is needed, and the experimental and numerical validations of the heat transfer capability of the finned tube would be required.

Analysis on condensation heat transfer and pressure drop to develop design program for plate heat exchangers (판형열교환기 설계프로그램 개발을 위한 응축열전달 및 압력강하 분석)

  • Ko, Jea-Hyun;Song, Young-Ho;Park, Kweon-Ha
    • Journal of Advanced Marine Engineering and Technology
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    • v.38 no.4
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    • pp.376-382
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    • 2014
  • The purpose of this study is to get the formulas of condensation heat transfer coefficient and pressure drop about the water to develop design program for plate type heat exchangers. The single phase flow of cold side was calculated with the correlation of Ko. Condensation heat transfer coefficient model proposed by Annaiev was used and Lockhart model was used to analyze the pressure drop. The calculation algorithm was proposed to calculate heat transfer rate and pressure drop simultaneously. The prediction errors remained within 20% compared to the commercial code in the working range of the plate heat exchangers.

Study on Pressure Drop and Condensation Heat Transfer Characteristics of R-404A in Brazed Plate Heat Exchanger (R-404A를 사용한 용접형 판형 열교환기의 압력강하 및 응축 열전달특성에 관한 연구)

  • 권오갑;전창덕;강종식;이진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.3
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    • pp.174-183
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    • 2001
  • Experimental study has been carried out on the characteristics of pressure drop and heat transfer of brazed plate heat exchangers using R-404A. Data are presented for the following range of variables: the mass flux ($20~80kg/m^2s$), chevron angle($20^{circ}C,\;35^{circ}C,\;45^{circ}C$) and inlet pressure of he refrigerant (1.4 and 1.6 MPa). for both subcooled and tow-phase flow, as chevron angle increases, pressure drop and heat transfer coefficient decrease. Condensation hat transfer coefficient and pressure drop was compared with the previously proposed correlations. Among them, Traviss correlation agreed with experimental results within -35~82% for heat transfer coefficient and -73~93% for pressure drop.

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