• 한국군사과학기술학회지
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• 제14권6호
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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.

• Journal of Advanced Marine Engineering and Technology
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• 제26권1호
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.229-234
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• 2001

An adiabatic counter-current vertical two-phase flow of air and water in narrow rectangular channels with offset strip fm was investigated experimentally. Tests were systematically performed with downward liquid superficial velocities and upward gas velocities covering 0 to 0.06 m/s and 0 to 2.5 m/s ranges, respectively. Two-phase flow regimes were classified by examining the video images of flow patterns in transparent test sections of 760 mm long and 100 mm wide channel with gaps of 3.0 and 5.0 mm. The channel average void fraction was measured by the quick-closing valve method. Unlike the flow regimes in the channels without fin, where bubbly, slug, chum, and annular flow were identified, only bubbly and chum flow regimes were found for the channels with offset strip fin. However the existence of fin in the channels showed negligible effects on the void fraction. Instead counter-current flow limitations were found to happen at lower air superficial velocity once offset strip fin was introduced in narrow rectangular channels.

• 설비공학논문집
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• 제26권8호
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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.

• 설비공학논문집
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• 제14권9호
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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.

• 대한기계학회논문집B
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• 제34권5호
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• pp.531-537
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• 2010

본 연구에서는 옵셋 스트립 휜 열교환기에서 휜 형상에 대한 최적화를 수행하였다. 압력강하량은 감소시키고 열전달량을 증가시키기 위해 이 둘을 동시에 나타낼 수 있는 j/f, $j/f^{1/3}$, JF 등의 성능 인자가 고려되었다. STDQAO, PQRSM, MGA 등의 최적화 기법이 사용되었으며, MGA 를 통해 기존 옵셋 스트립 휜보다 JF 인자는 36%, 열전달 성능은 280% 향상된 최적화된 휜 형상을 제안하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.771-781
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• 1998

A highly compact and thermally efficient water cooled oil cooler for automotive use without offset strip fin and casing is developed in this study. The study result has shown that eliminating the fin and casing in the oil cooler the manufacturing process and cost and can be simplified and reduced greatly without sacrificing the thermal capacity. The oil cooler developed in the study uses the dimply type heat transfer core element design instead of offset strip fin and eliminates the outer casing for coolant water flow by applying specially made parallel loop flow design. In the study the thermal design program for the present oil cooler also was developed and validated experimentally.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1237-1242
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• 2004

In this study, single-phase heat transfer experiments were conducted with oil cooler with offset strip fin using water. An experimental water loop has been developed to measure the single-phase heat transfer coefficient in a vertical oil cooler. Downflow of hot water in one channel receives heal from the cold water upflow of water in the other channel. Similar to the case of a plate heat exchanger, even at a very low Reynolds number, the flow in the on cooler with offset strip fin remains turbulent. The present data show that the heat transfer coefficient increases with the Reynolds number. Based. On the present data, empirical correlation of the heat transfer coefficient was proposed. Also, performance prediction analysis for oil cooler were executed and compared with experiments. ${\varepsilon}-NTU$ method was used in this prediction program. Independent variables are flow rates and inlet temperature. Compared with experimental data, the accuracy of the program is within the error bounds of ${\pm}5$% in the heat transfer rate.

• 설비공학논문집
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• 제13권11호
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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.

• 설비공학논문집
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• 제13권4호
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• pp.271-287
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• 2001

This paper has been made to investigate the thermal performance characteristics for the several types of layered aluminum heat sinks with offset-strip fin. Heat sinks with different fin height, fin length, number of fin layer and slanted fin are prepared and tested for natural convection as well as forced convection. The experimental results for layered heat sink(LHS) are compared to those for advanced pin fin heat sink (PHS) so that the appropriate heat sink can be designed or chosen according to the heating conditions. The overall heat transfer performances for LHS are almost comparable to those of PHS under natural convection, and become 1.2∼1.5 times as high as those of PHS under forced convection situation. This study shows that fin height and number of fin layer re important parameters, which have a serious influence on thermal performance for layered heat sinks.