• Title/Summary/Keyword: In-tube condensation

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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%.

Condensation Heat Transfer Coefficients of R245fa on a Plain Tube (수평관에서 R245fa의 응축 열전달계수)

  • Shim, Yun-Bo;Park, Ki-Jung;Jung, Dong-Soo;Kim, Jong-Seong
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.19 no.8
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    • pp.555-562
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    • 2007
  • In this study, condensation heat transfer coefficients (HTCs) of R22, R134a, R245fa and R123 are measured on a horizontal plain tube. All data are taken at the vapor temperature of $39^{\circ}C$ with a wall subcooling temperature $3-8^{\circ}C$. Test results show the HTCs of newly developed alternative low vapor pressure refrigerant, R245fa, on a plain tube are 9.5% higher than those of R123 while they are 3.3% and 5.6% lower than those of R134a and R22 respectively. Nusselt's prediction equation for a plain tube underpredicts the data by 13.7% for all refrigerants while a modified equation yielded 5.9% deviation against all data. From the view point of environmental safety and condensation heat transfer, R245fa is a long term good candidate to replace R123 used in centrifugal chillers.

Condensation heat transfer coefficients of CFC-11 and its alternative refrigerants (CFC-11과 그 대체냉매의 응축 열전달 계수)

  • Joo, Jae-Kil;Cho, Seong-Joon;Jung, Dong-Soo;Kim, Chong-Bo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.6
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    • pp.830-840
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    • 1997
  • In this study, condensation heat transfer coefficients(HTCs) of CFC-11, HCFC-123 and HCFC-141b are measured, which are used/or considered as working fluids in centrifugal chillers. The main objectives of this study are to measure and compare the HTCs of various refrigerants on plain and low fin tubes and also to find out the optimum fin density of the low fin tubes. To accomplish these goals, HTCs of three refrigerants are measured for the plain tube as well as 4 types of low fin tubes. All measurements are carried out at the vapor temperature of 39.deg. C with the wall temperature difference of 3 .deg. C ~ 8.deg. C. For all the refrigerants tested, a low fin tube of 28 fins per inch yielded the best performance among all the tubes tested. For the plain tube, the HTCs of CFC-11 and HCFC-141b were very similar and those of HCFC-123 were 10% lower than those of CFC-11.Thus, it can be concluded that HCFC-123 and HCFC-141b are acceptable as alternative refrigerants for CFC-11 from the view point of condensation heat transfer.

A Study of External Condensation Heat Transfer of Flammable Refrigerants (가연성 냉매의 외부 응축 열전달에 관한 연구)

  • 배동수;하종철;유길상;정동수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.6
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    • pp.522-529
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    • 2004
  • In this study, external condensation heat transfer coefficients (HTCs) of flammable refrigerants of propylene, propane, isobutane, butane, DME, and HFC32 were measured on a horizontal plain tube, 26 fpi low fin tube, and Turbo-C tube. All data were taken at the temperature of 39$^{\circ}C$ with a wall subcooling of 3∼8$^{\circ}C$. Test results showed a typical trend that condensation HTCs of flammable refrigerants decrease with increasing wall subcooling. HFC32 had the highest HTCs among the tested refrigerants showing 44% higher HTCs than those of HCFC22 while DME showed 28% higher HTCs than those of HCFC22. HTCs of propylene and butane were similar to those of HCFC22 while those of propane and isobutane were similar to those of HFC134a. Based upon the tested data, Nusselt's equation is modified to predict the plain tube data within a deviation of 3%. For 26 fpi low fin tube, Beatty and Katz equation predicted the data within a deviation of 7.3% for all flammable refrigerants tested. The heat transfer enhancement factors for the 26 fpi low fin and Turbo-C tubes were 4.6∼5.7 and 4.7∼6.9 respectively for the refrigerants tested indicating that the performance of Turbo-C tube is the best among the tubes tested.

The Condensation Heat Transfer of R-22 and R-410A in an Inner Diameter Tube of 1.77 mm (내경 1.77 mm관내 R-22와 R-410A의 응축열전달)

  • Son, Chang-Hyo;Roh, Geon-Sang
    • Journal of the Korean Institute of Gas
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    • v.12 no.1
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    • pp.48-53
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    • 2008
  • The condensation heat transfer coefficients of R-22 and R-410A in a small diameter tube were investigated. The main components of the refrigerant loop consist of a receiver, a variable-speed pump, a mass flowmeter, an evaporator (preheater), and a condenser (test section). The test section consists of smooth, horizontal copper tube of 3.38 mm outer diameter and 1.77 mm inner diameter. The refrigerant mass fluxes varied from 450 to $1050\;kg/(m^2s)$ and the average inlet and outlet qualities were 0.05 and 0.95. The main results were summarized as follows : the condensation heat transfer coefficient also increases with increasing mass flux and quality. The condensation heat transfer coefficient of R-410A was slightly higher than that of R-22. Most of correlations proposed in the large diameter tube showed significant deviations with experimental data except for the ranges of low quality and low mass flux.

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Heat Transfer Characteristics of Fin-Tube Heat Exchanger using Two-Port Tube of Small Inner Diameter by Mechanical Expansion (연결세경관을 이용한 휜관형 열교환기의 기계확관에 의한 전열특성)

  • Lee, Sangmu;Park, Byung-Duck
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.28 no.11
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    • pp.428-433
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    • 2016
  • The fin and tube heat exchanger using a two-port tube has in air-conditioner heat exchanger because heat transfer performance. This study investigates the feasibility of a fin and tube heat exchanger using two-port copper tube by mechanical expansion. The optimum size of the tube-expanding bullet for the heat exchanger using two-port tube was through numerical calculation. The heat exchanger using a two-port tube was fabricated by mechanical expansion, and the heat exchanger performance was evaluated condensation and evaporation experiments. Compared to the heat exchanger of a conventional circular tube, the pressure drop per unit length of the heat exchanger with a two-port tube decreased. Compared to the heat exchanger using a conventional circular tube, the overall heat transfer coefficient of heat exchanger with a two-port tube increased up to 13% in the case of condensation, and up to 25% in the case of evaporation. The two-port tube heat exchanger outperforms conventional heat exchanger for air conditioner with a inner grooved circular tube.

Condensation Heat Transfer of R22, R407C, and R410A in Slit Fin-and-Tube Heat Exchanger

  • Jeon, Chang-Duk;Lee, Jin-Ho
    • International Journal of Air-Conditioning and Refrigeration
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    • v.11 no.4
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    • pp.188-198
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    • 2003
  • R410A and R407C are considered to be alternative refrigerants of R22 for the air-conditioners. An experimental study is carried out to investigate the effect of the change of mass flow rate on the characteristics of heat transfer and pressure drop in three row slit finned-tube heat exchanger for R407C, R410A and R22. R407C, a non-azeotropic refrigerant mixture, exhibited a quite different condensation phenomenon from those of R22 and R410A and its condensation heat transfer coefficient was much lower than that of R22 and R410A. On the other hand, the condensation heat transfer coefficient of R410A, near-azeotropic refrigerant mixture, was a little higher than that of R22. R410A also showed the lowest condensation pressure drop across the test section. For all refrigerants, the condensation heat transfer coefficient and pressure drop increase as the mass flux increases. The condensation heat transfer coefficient correlation proposed by Kedzierski shows the best agreement with the experimental data within $\pm$20%.

Experimental study for the pressure drop of R-22 and R-4O7C during the condensation in the micro-fin tubes (마이크로핀관내에서 R-22와 R-4O7C의 응축압력강하 특성에 관한 실험적 연구)

  • Roh, Geon-Sang
    • Journal of Advanced Marine Engineering and Technology
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    • v.31 no.6
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    • pp.715-722
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    • 2007
  • Experiments were conducted for the investigation of pressure drop inside horizontal micro-fin tubes during the condensation of R-22 and ternary refrigerant. R-407C(HFC-32/125/134a 23/25/62 wt%) as a substitute of R-22. The condenser is a double-tube and counterflow type heat exchanger which is consisted with micro-fin tubes having 60 fins with a length of 4000mm, outer diameter of 9.53mm and fin height of 0.2mm. The mass velocity varied from 102.1 to $301.0kg/(m^2{\cdot}s)$ and inlet quality was fixed as 1.0. From the experimental results. the pressure drop for R-407C was considerably higher than that for R-22. The value of PF(penalty factor) for both of refrigerants was not bigger than the ratio of micro-fin tube area to smooth tube area. Based on the experimental data. correlation was Proposed for the prediction of frictional pressure drop during the condensation of R-22 and R-407C inside horizontal micro-fin tubes.

Assessment of RELAP5/MOD3.2 with Condensation Experiment in the Presence of Noncondensables in a Vertical Tube

  • Park, Hyun-Sik;No, Hee-Cheon
    • Proceedings of the Korean Nuclear Society Conference
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    • 1998.05a
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    • pp.547-552
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    • 1998
  • The standard RELAP5/MOD3.2 code were assessed with the condensation experiment in the presence of noncondensable gas in a vortical tube of PCCS of CP-1300. There are two wall film condensation models, the default model and the alternative model, in RELAP5/MOD3.2. The experimental apparatus was modeled with the two models, md simulations were performed for several sub-tests to be compared with the experimental results. In overall sense the simulation results showed that the default model of RELAP5/MOD3.2 under-predicts the heat transfer coefficients, while the alternative model over-predicts them throughout the condensing tube.

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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.