• Title/Summary/Keyword: S-245

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Flow Condensation Heat Transfer Characteristic of R245fa in a Horizontal Plain Tube (수평 평활관내 R245fa의 흐름 응축 열전달 특성)

  • Park, Hyun-Shin;Park, Ki-Jung;Jung, Dong-Soo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.2
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    • pp.87-96
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    • 2008

  • Flow condensation heat transfer coefficients(HTCs) of R123 and R245fa are measured in a horizontal plain tube. The main test section in the experimental flow loop is made of a plain copper tube of 9.52 mm outside diameter and 530 mm length. The refrigerant is cooled by passing cold water through an annulus surrounding the test section. Tests are performed at a fixed saturation temperature of $50\;{\pm}\;0.2\;^{\circ}C$ with mass fluxes of 50, 100, $150\;kg/m^2s$ and heat flux of $7.3{\sim}7.7\;kW/m^2$. Heat transfer data are obtained in the vapor quality range of $10{\sim}90%$. Test results show that the flow condensation HTCs of R245fa are overall 7.9% higher than those of R123 at all mass fluxes. The pressure drop of R245fa is smaller than that of R123 at the same heat flux. In conclusion, R245fa is a good candidate to replace ozone depleting R123 currently used in chillers from the view point heat transfer and environmental properties.

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Evaluation of Small Current Breaking Performance for 245kV GCB with or without Shield (쉴드 유무에 따른 245kV GCB의 소전류차단성능 평가)

  • Song T. H.;Lee H. G.;Kim Y. P.;Yoon J. H.
    • Proceedings of the KIEE Conference
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    • summer
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    • pp.824-826
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    • 2004

  • 상용 CFD(Computational Fluid Dynamics) 프로그램인 PHOENICS를 이용하여 245kV $SF_6$ 가스 차단기의 진상소전류 차단성능을 평가하였다. 소전류 차단시에는 아크가 발생 즉시 소호되므로 $SF_6$ 가스를 전리가 일어나지 않은 냉가스로 취급할 수 있다. 그러므로 PHOENICS를 이용하여 극간의 $SF_6$ 가스밀도 및 전계의 변화를 계산하였으며 이것으로부터 극간 $SF_6$ 가스의 절연내력(Dielectric Strength)을 계산하였다. 계산된 $SF_6$ 가스의 절연내력과 아크 소호 후 극간에 인가되는 회복전압(Recovery Voltage)을 비교하여 차단기의 진상소전류 차단성능을 평가하였다. 245kV 차단기에는 전계를 완화하기 위한 목적으로 차단부에 쉴드가 설치되어 있으며 이 쉴드에 의한 소전류차단성능의 변화를 해석하였다.

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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.

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External Condensation Heat Transfer Coefficients of R245fa on Low Fin and Turbo-C Tubes (낮은 핀관과 Turbo-C 촉진관에서 R245fa의 외부 응축 열전달계수)

  • Shim, Yun-Bo;Park, Ki-Jung;Jung, Dong-Soo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.3
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    • pp.167-175
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    • 2009

  • In this study, condensation heat transfer coefficients(HTCs) of R22, R123, R134a and R245fa are measured on both 26fpi low fin and Turbo-C tubes. All data are taken at the vapor temperature of $39^{\circ}C$ with a wall subcooling of $3{\sim}8^{\circ}C$. Test results show that HTCs of the newly developed low vapor pressure alternative refrigerant, R245fa, are $7.8{\sim}9.2%$ and $10.3{\sim}18.6%$ higher than those of R123 for 26fpi low fin tube and Turbo-C tube respectively. For all refrigerants tested, HTCs of Turbo-C enhanced tube are higher than those of 26fpi low fin tube. For the low fin tube, Beatty and Katz's prediction equation yielded 20% deviation for all fluids. The heat transfer enhancement ratio of R245fa on the Turbo-C tube is $5.9{\sim}6.4$ while that of R123 is $5.7{\sim}5.9$. From the view point of environmental safety and condensation heat transfer, R245fa is a long term candidate to replace R123 currently used in centrifugal chillers.

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