• Title/Summary/Keyword: Offset-Strip Fins

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CFD Analysis of Offset Strip Fin with a Gap between Rows (CFD를 이용한 핀의 열 사이에 간극을 가지는 Offset Strip Fin의 성능 해석)

  • Hwang, Seongwon;Jeong, Ji Hwan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.8
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    • pp.381-387
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    • 2014
  • The off-set strip fins (OSF) have been widely used to construct plate-fin heat exchangers. Conventional OSF is constructed in successive rows of fins. New OSF structure is suggested to have a gap between adjacent rows of fins. The gap is intended to reduce fouling by allowing small objects to flow through fins. The objective of this work is to investigate the performance of off-set strip fins with gap between successive rows. Results showed that the performance of OSF with gap can't be predicted by previous correlation.

A NUMERICAL STUDY ON THE CONJUGATE HEAT TRANSFER OF AN OIL COOLER WITH OFFSET STRIP FINS FOR VARIOUS-FLOW RATES (오일의 유량 변화와 오프셋 스트립 휜을 고려한 오일쿨러의 복합열전달 해석)

  • Park, S.W.;Choi, H.G.
    • Journal of computational fluids engineering
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    • v.19 no.1
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    • pp.34-40
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    • 2014
  • Conjugate heat transfer of an automotive oil cooler with offset-strip fins was numerically investigated to predict the performance of the oil cooler for various flow-rates. The simulations were conducted by directly modeling offset-strip fins with unstructured meshes. The incompressible Navier-Stokes equations coupled with energy equation were used for the present simulations. Heat transfer characteristics of the oil cooler was compared well with experimental results and the errors were approximately within 5 percents. It was found that the performance of the oil cooler increased as the flow-rate increased up to the flow-rate of 12 L/min, but the performance seemed to be saturated beyond a critical flow-rate, which was estimated as 15 L/min. Furthermore, it was confirmed that compared to the performance without fins, that of the oil cooler with offset-strip fins was increased by about 75 percents.

Optimization for the Internal Structure of a Recuperator with Offset Strip Fins (오프셋 스트립 휜을 가지는 리큐퍼레이터의 내부 형상 최적화)

  • Do, Kyu-Hyung;Han, Yong-Shik;Choi, Byung-Il;Kim, Myung-Bae
    • Journal of the Korea Institute of Military Science and Technology
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    • v.14 no.6
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    • pp.1178-1185
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    • 2011
  • In the present study, a recuperator is suggested to improve the thermal efficiency of a micro gas turbine. Primary design parameters of the recuperator are determined from the ideal cycle analysis. The counter flow plate-fin heat exchanger with offset strip fins is chosen as the type of the recuperator. In order to satisfy the design constraints which are the minimum effectiveness and the maximum pressure drop, the optimization for the internal structure of the recuperator is performed with varying the fin spacing and the fin height of offset strip fins. Also the effects of the thermal conductivity of fins and separation plates and the longitudinal heat conduction on the thermal performance of the recuperator are investigated.

Comparison of the Thermal Performance of Recuperators with Corrugated Fins for a 500W Class Micro Gas Turbine Generator (500W 급 마이크로 가스터빈을 위한 파형 휜을 가지는 리큐퍼레이터의 열성능 비교)

  • Do, Kyu Hyung;Kim, Tae Hoon;Han, Yong-Shik;Choi, Byung-Il;Kim, Myung Bae
    • Journal of the Korea Institute of Military Science and Technology
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    • v.16 no.6
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    • pp.847-856
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    • 2013
  • In this study, thermal performance of recuperators with plain and offset strip fins is investigated to enhance the thermal efficiency of a micro gas turbine. Thermal cycle analysis is conducted to determine major design parameters of a single-pass counterflow recuperator. In order to evaluate the performance of the recuperator, the effectiveness and the pressure drop in the recuperators are chosen as the objective function and the design constraint, respectively. The optimized geometries for internal structure of the recuperators with plain and offset strip fins are obtained with varying the fin spacing and height. From the result, the recuperator with offset strip fins has better thermal performance when the fin spacing, s, is smaller than 1.45mm and the thermal performance of the recuperator with plain rectangular fins is higher than that with offset strip fins in the region of $s{\geq}1.45mm$. In addition, it is found that the entrance region effect and the longitudinal wall heat conduction effect should be taken into account for accurately predicting the thermal performance of the recuperators with both plain and offset strip fins.

Correlations of Heat Transfer and Pressure Drop for Offset Strip Fins (옵셋 스트립 핀에서의 열전달 및 압력 강하 상관식)

  • Kim, Min-Soo;Lee, Kwan-Soo
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2274-2279
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    • 2008
  • This paper numerically investigates thermo-flow characteristics of offset strip fins to obtain a correlation of heat transfer and pressure drop. The flow is divided into three regimes, i.e. laminar, transition and turbulent. The predicted j and f values from the SST k-w turbulence model agree with previous correlations with the error less than 20% in transition and turbulent regimes. Prandtl number is varied from 0.5 to 40 and a correlation to predict heat transfer and pressure drop for offset strip fins is suggested.

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A Study on the Heat Transfer Characteristics of Oil Flow over Offset Strip Fins (옵셋 스트립 휜에서 오일유동의 열전달 특성에 관한 연구)

  • 양대일;정형호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.11
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    • pp.1134-1140
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    • 2001
  • In the present study, heat transfer characteristics of oil flow over offset strip fins were predicted by the numerical methods. Oil flow in the plate-fin passage was idealized by 2 dimension. Power law scheme and SIMPLE algorithm were used for convective diffusion formulation and pressure term respectively. Governing equations were discretized by control volume formulation. The flow patterns and heat transfer were predicted in details. The convective heat transfer coefficients were affected by separation bubbles which appeared at the wake region of offset strip fins.

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2 Dimensional Correlations of Heat Transfer of Oil Flows over Offset Strip Fins (옵셋 스트립 휜을 가로지르는 오일유동의 열전달 2차원 상관관계식)

  • 강덕종;신성학;정형호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.9
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    • pp.734-740
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    • 2002
  • In the present study, heat transfer characteristics of oil flow over offset strip fins are predicted by the numerical methods. Oil flow in the plate-fin passage is idealized by 2 dimensions. Inlet velocity, Prandtl number and fin pitch ratio are chosen as parameters which affect the heat transfer of offset strip fins. The effect of parameters on pressure drops and convective heat transfer coefficients are described. Characteristic length is derived in case of 2 dimensional flow situation. Correlations for friction factor and convective heat transfer coefficient are derived.

Counter-Current Air-Water Flow in Narrow Rectangular Channels With Offset Strip Fins

  • Kim, Byong-Joo;Sohn, Byung-Hu;Koo, Kee-Kahb
    • Journal of Mechanical Science and Technology
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    • v.17 no.3
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    • pp.429-439
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    • 2003
  • Counter-current two-phase flows of air- water in narrow rectangular channels with offset strip fins have been experimentally investigated in a 760 mm long and 100 mm wide test section with 3.0 and 5.0 mm gap widths. The two-phase flow regime, channel-average void fractions and two-phase pressure gradients were studied. Flow regime transition occurred at lower superficial velocities of air than in the channels without fins. In the bubbly and slug flow regimes, elongated bubbles rose along the subchannel formed by fins without lateral movement. The critical void fraction for the bubbly-to-slug transition was about 0.14 for the 3 mm gap channel and 0.2 for the 5 mm gap channel. respectively. Channel-average void fractions in the channels with fins were almost the same as those in the channels without fins. Void fractions increased as the gap width increased, especially at high superficial velocity of air. The presence of fins enhanced the two-phase distribution parameter significantly in the slug flow, where the effect of gap width was almost negligible. Superficial velocity of air dominated the two-phase pressure gradients. Liquid superficial velocity and channel gap width has only a minor effect on the pressure gradients.

A Study on the Effect of Fin Pitch of Offsets Strip Fin on Heat Transfer of High Prandtl Fluid (옵셋 스트립 휜의 휜피치가 고 Prandtl 유체 열전달 특성에 미치는 영향)

  • 강덕종;양대일;전승환;정형호
    • Journal of Advanced Marine Engineering and Technology
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    • v.26 no.1
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    • pp.83-89
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    • 2002
  • In the present study, heat transfer characteristics of oil flow over offset strip fins were predicted by the numerical methods. Oil flow in the plate-fin passage was idealized by 2 dimensions. The flow patterns and heat transfer characteristics were predicted in details. Numerical results shows that the average convective heat transfer coefficients are almost independent on the raws of fins and affected by fin pitches. At the rear face of fin, there exists minimum point of heat transfer coefficients where stream are separated from the fin surfaces. The convective heat transfer coefficients were effected by separation bubbies which appeared at the wake region of offset strip fins.

Thermo-Flow Analysis of Offset-Strip Fins according to Blockage Ratio (옵셋 스트립 휜의 막음비에 따른 열 및 유동 분석)

  • Kim, Min-Soo;Yu, Seung-Hwan;Lee, Kwan-Soo
    • Proceedings of the SAREK Conference
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    • 2009.06a
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    • pp.1084-1089
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    • 2009
  • A numerical study of thermo-flow characteristics is presented to determine correlations of pressure drop and heat transfer for offset-strip fins. As a blockage ratio increased, previous correlations underestimate f values in laminar and turbulent regimes, and overestimate j values in laminar regime. Therefore, new correlations, which are applicable to fins with blockage ratios more than 15%, are presented.

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