• 설비공학논문집
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• 제14권11호
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• pp.871-879
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• 2002

The characteristics of flow and heat transfer in the heat exchanger of heat pipes with fins have been studied numerically for cooling enhancement of electronic components of KTX (Korea Train eXpress). Numerical analysis and methodology have been conformed by comparing the experimental results for inlined array of heat pipes. The staggered arrangement of heat pipes has been proposed in order to achieve heat transfer enhancement. As results, the geometry change to the staggered array is conformed to increase the heat transfer of the system accompanied by an increase of pressure drop. The current results of friction factor and Colburn j factor are presented in terms of Reynolds number and staggered distance, and are expected to use for design and manufacture of such a system.

• 설비공학논문집
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• 제15권12호
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• pp.1007-1017
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• 2003

An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry and wet surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of friction f-factor and Colburn j -factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of 150∼250 kg/$m^2$s with air flows at velocity ranges from 0.3 m/s to 0.8 m/s.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.152-158
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• 2004

An experimental study was performed to determine the fin-side heat transfer and pressure drop of a condenser for automobile. Five sample with different fin height and louver angle were tested, 9mm, 8mm, 7.5mm, 5.4mm and 4.5mm. Results are presented as plot of Colburn j-factor(or heat transfer coefficients) and friction factor(or pressure drop) against the Reynolds number(or inlet air velocity) based on louver pitch, in the range of 110 to 480. The results show that both heat transfer and pressure drop on the fin are mainly affected by the louver angle in a lower range of air velocity, but, by the fin height in a higher range of air velocity. The performance of 5.4mm fin is the highest, compared to other fin sample.

• 설비공학논문집
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• 제15권3호
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• pp.220-229
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• 2003

An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of friction f-factor and Colburn j -factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of 150~250 kg/$m^2$s with air flows at velocity ranges from 0.6 m/s to 1.6 m/s.

• 설비공학논문집
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• 제2권1호
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• pp.27-36
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• 1990

An experimental investigation was made to study the performance characteristics of evaporator having different fin configurations and tube inner grooves. Three different types of fin such as super slitted fin, slitted fin, plain fin, and two types of tube such as inner grooved tube, and bare tube, are tested varying the air velocity, evaporation temperature and superheat of refrigerant. Results show that in the range of air side Reynolds number $3{\times}10^3\;-\;1.5{\times}10^4$ evaporator with super slitted fin and inner grooved tube shows best performance. It is 80% higher in overall heat transfer coefficient and 2.6 times higher in pressure loss compared to that with plain fin inner grooved tube. Friction factor is found to be almost independent of evaporating temperature and degree of superheat, while Colburn j factor varies with evaporating temperature.

• 설비공학논문집
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• 제19권1호
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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.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.633-638
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• 2006

This study presents the air side heat transfer and friction characteristics of fin-tube heat exchangers with various fin types. A total of 8 samples of heat exchangers are tested. Fin patterns tested are slit, louver and plate fins. Each fin type has three cases of number of tube rows(N=1, 2, 3) and two different fin pitches. The results are plotted in terms of Colburn j-factor and friction factor f with respect to Reynolds number in the range of 200 to 510.

• 설비공학논문집
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• 제17권11호
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• pp.1014-1021
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• 2005

Flow channels with non-circular cross-sections are encountered in a wide variety of heat exchangers. Accurate friction factor and Colburn j factor data are essential for the design and viable applications of such heat exchangers. In this study, an analysis is con ducted on heat transfer and pressure drop characteristics for tube-bundle heat exchanger with various arrangements of tubes, of which their geometry could easily be modified from a circular one in a harsh environment. The parameters investigated are aspect ratio, pitch, and inclined angle of tubes. The results obtained are: (1) Aspect ratio has larger influence on the j and f factor than pitch; (2) As aspect ratio increases, both j and f factors decrease; (3) The high performance is achieved when the pitch and aspect ratio are in the range of 1.5${\~}$2.5 and 1.25${\~}$2.0, respectively; and (4) the inclined arrangements of tubes show unfavorable results for both heat transfer and pressure drop characteristics in spite of the positive possibility of condensate removals in a latent heat recovery system.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1159-1165
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• 2009

In the present study, the flow and heat transfer characteristics of a large plate heat exchanger are investigated numerically. The flow passages are very complicated due to the grooved corrugation patterns of the plate surface so that the detailed mesh and the large amount of the computation time have to be required in the numerical simulation for the conjugate heat transfer analysis. In order to accomplish the efficient and fast analysis of the heat transfer characteristics in the plate heat exchanger, a semimicroscopic method using the porous media model has been investigated numerically. The results showed that the characteristics of the heat transfer and pressure drop, which are respectively presented with Colburn j-factor and Fanning f-factor, are in a good agreement between the detailed mesh and the porous media model. The results of the present study could be applicable to the numerical analysis of entire flow passages in the large plate heat exchanger using porous media treatment.

• 한국전산유체공학회지
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• 제22권1호
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• pp.67-80
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• 2017

The high-speed bypass effect on the heat exchanger performance has been investigated numerically. The plate-fin type heat exchanger was modeled using two-dimensional porous approximation for the fin region. Governing equations of mass, momentum, and energy equations for compressible turbulent flow were solved using ideal-gas assumption for the air flow. Various bypass-channel height were considered for Mach numbers ranging 0.25-0.65. Due to the existence of the fin in the bypass channel, the main flow tends to turn into the core region of the channel, which results in the distorted velocity profile downstream of the fin region. The boundary layer thickness, displacement thickness, and the momentum thickness showed the variation of mass flow through the fin region. The mass flow variation along the fin region was also shown for various bypass heights and Mach numbers. The volumetric entropy generation was used to assess the loss mechanism inside the bypass duct and the fin region. Finally, the correlations of the friction factor and the Colburn j-factor are summarized.