• Journal of computational fluids engineering
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• v.21 no.3
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• pp.98-109
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• 2016

The flow and heat transfer characteristics of a heat exchanger having rectangular pin-fin in the flow direction have been investigated numerically. On the bottom plate, the convective boundary conditions for the hot side was given, and the fins were arranged in a channel-type geometric model using the periodic boundary condition in the span-wise direction. Three-dimensional numerical calculations for the flow and conjugate heat transfer problem were conducted using SIMPLE algorithm and $k-{\varepsilon}$ turbulence model. For the slanted pin-fin models, it was found that the downward cooling flow is generated due to the downward pressure gradient component, which can enhance the heat transfer performance near the bottom surface and the fin stem region. Four different inclined angles were considered in the Reynolds number range of 13,500-55,000. The aero-thermal performance of the slanted pin-fin heat exchangers, such as the volume and area goodness factors, were summarized and compared with the baseline plate-fin type heat exchanger quantitatively.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.3
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• pp.180-188
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• 2021

This paper conducted a study on the ortho-para hydrogen conversion in the cryogenic heat exchanger filled with catalysts for hydrogen liquefaction by utilizing the numerical model of plate-fin heat exchanger considering catalytic reaction of ortho-para hydrogen conversion, heat and mass transfer phenomena and fluid dynamics in a porous medium. Various numerical analyzes were performed to investigate the characteristics of ortho-para hydrogen conversion, the effects of space velocity and activated catalyst performance.

• 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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.1
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• pp.1-9
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• 2007

Water condensate accumulated on the surface of a fin-and-tube heat exchanger significantly affects its thermal and hydraulic performance. The purpose of this study is to investigate the effect of condensate retention on the air-side heat transfer performance and flow friction. Total 12 samples of slit and plate fin-and-tube heat exchangers with varying fin spacing and number of tube rows are tested under dry and wet conditions. The thermal fluid measurements are made using a psychometric calorimeter. Frontal air velocity varies in the range from 0.7 m/s to 1.5 m/s. Using the experimental data, presented are the heat transfer coefficients in terms of Colburn j-factor and friction factor.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.1
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• pp.64-72
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• 1989

Laminar natural convection heat transfer from a horizontal heat exchanger tube with one infinitely long vertical plate fin has been studied by a finite-difference numerical procedure. In predicting convective heat transfer from a circular tube, the thermal boundary condition at solid fluid interface is usually assumed to be isothermal. However, in reality, the thermal boundary condition is not isothermal, and the tube has the thickness and the conductivity. So the temperature at the interface is not known a priori to the calculation. This problem has the conjugate phenomena which occur between the tube conduction and external natural convection, and between the fin conduction and external natural convection. Numerical results are obtained to determine the effects of the conductivity of solid wall and the thickness of tube wall on heat transfer. It is found that the conduction causes significant influence on the natural convection heat transfer at low K and high ${\delta}$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5655-5660
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• 2012

The objective of this study is theoretically to suggest the effective heat exchanger design method using boundary layer analysis. The boundary layer formation and interruption on rectangular plate and round plate fins are explained and the heat transfer coefficients showed with the variation of the velocity and temperature boundary layer. In addition, the flow pattern on one plate fin surface considered as external flow and flow pattern between fins considered as internal flow. As a result, theoretical method for the boundary layer interruption avoidance is suggested and the heat transfer coefficient of the round plate fin was higher than that of the rectangular plate fin because of the less thermal and velocity boundary layer thickness except the centerline.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.274-280
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• 2005

The objective of this study Is to investigate the heat transfer performance of plate discrete fin-and-tube heat exchangers with large fin pitch. In this study, twenty-two heat exchangers were tested with a variation of fin pitch, number of tube row, longitudinal tube pitch and fin alignment. Discrete fin type exchangers improved heat transfer performance more than 10% compared to tile continuous fin type heat exchangers. The air-side heat transfer coefficient decreased with a reduction of the fin pitch and an increase of the number of tube row, The staggered fin alignment improved heat transfer performance more than 6% compared to the inline fin alignment. The effect of longitudinal tube pitch was insignificant on the j-factor and experiments found opposite effects on the j-factor with respect to fin alignment. Heat transfer correlations were developed from the measured data for flat plate discrete fin-and-tube heat exchangers with large fin pitch. The correlations yielded good predictions of the measured data with mean deviations of 1,4% and 0.3% for tire inline and staggered tube alignment, respectively.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.1
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• pp.7-14
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• 2009

Water condensate accumulated on the surface of a fin-and-tube heat exchanger significantly affects its thermal and hydraulic performances. The purpose of this study is to investigate the effects of condensate retention on the air-side heat transfer performance and flow friction for various flow and geometric conditions. Total of twelve samples of slit and plate fin-and-tube heat exchangers are tested under dry and wet conditions. The thermal fluid measurements are made using a psychrometric calorimeter. Frontal air velocity varies in the range from 0.7 m/s to 1.5 m/s. Using the experimental data, presented are heat transfer coefficients in terms of Colburn j-factors and friction factors, and these data are compared with the existing correlations.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.4
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• pp.129-134
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• 2009

The objectives of this paper are to study the effects of thermal and geometric conditions on the performance of indoor heat exchangers with R-410A for Gas Engine Driven Heat Pump (GHP) application and to find the optimum design conditions of indoor heat exchangers by parametric analysis for the key parameters. The key parameters are number of tube row, number of tube pipe, fin pitch and transverse tube pitch. In the air side, moisture out of the humid air condenses on the fin surface while the refrigerant (R-410A) boils inside the smooth tube. Therefore this study uses Log Mean Enthalpy Difference (LMHD) method to analyze the heat transfer from the humid air to the refrigerant. This study determines the heat exchanger size, air side/refrigerant side pressure drop and overall heat transfer coefficient. Optimum design conditions for the key parameters are also determined by the parametric analysis. The results show that number of rows and pipes, fin pitch have significant effect on the heat exchanger size. It is also found that the tube length of the louver fin is $17{\sim}30%$ shorter than that of the plate fin.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.303-309
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• 2009

In this study, the heat transfer and flow field of condenser used on Kim-chi refrigerator is analysed with numerical method. Main objective is to present the base data for designing new condenser model with improvement of heat transfer performance. For CFD analysis, a commercial code, STAR-CCM+ was used. The water was used for the inner working fluid and the air was used for the outer fluid. The condenser type used in this study is a flat plate fin-and-tube heat exchanger. As factors for performance analysis, the effect of condenser geometry and air velocity was investigated. As a result, it has been observed that there is a suitable fin pitch with which heat transfer performance of condenser is maximized.