• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.816-821
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• 2013

This paper reports numerical study results with respect to the thermal performance of various hybrid fins (HFs) and a pin fin (PF) passively cooled under natural convection state. Investigated HFs are a basic hybrid fin (BHF), a hollow hybrid fin (HHF), and a solid hybrid fin (SHF). CFD models for both HFs and the PF have been developed to explore their thermal performance under various heat dissipations. Thermal performances of fins have been analyzed by quantifying array-based heat transfer coefficients, $h_a$, and mass-based heat transfer coefficients, $h_m$, for each fin. Study results show that $h_a$ of the SHF is 23% greater than that of the PF. $h_m$ of the HHF is found to be even 140% greater than that of the PF, and the HHF is found to be 40% better than the BHF in terms of the mass-based performance, $h_{m{\cdot}}$.

• Journal of Energy Engineering
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• v.16 no.3
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• pp.149-154
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• 2007

An experimental study on the air-side pressure drop of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side pressure drop in the literature is not based on a consistent approach. This paper focuses on 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 pressure drop estimation in fin-tube heat exchanger. A comparison was made between the predictions of previously proposed empirical correlations and experimental data for the air-side pressure drop on design conditions of condenser and evaporator. Results are pre-sented as plots of friction f-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 $150{\sim}250\;kg/m^2s$ with air flows at velocity ranges from 0.38 m/s to 1.6 m/s.

• Proceedings of the SAREK Conference
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• 2005.06a
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• pp.100-100
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• 2005

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.7-7
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• 2004

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.9-9
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• 2004

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.169-171
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• 1989

The curved active layer inner stripe(CALIS) laser diode has been developed. The tight confinements of current and carrier result in low thershold current(20-30mA) with stable fundamental transverse mode operation up to the output power of 30mW CW.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.113-124
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• 1997

This work is performed to investigate the pressure drop and heat transfer characteristics in the air side of finned-tube heat exchanger for air conditioner. Experimental apparatus and method are described to simulate the heat exchanger performance by using the three times enlarged model. The pressure drop and heat transfer coefficient were measured and compared for the heat exchangers with a plane fin and a commercial strip fin. The measured data for the strip fin agree well with those of prototype within a few percentages. For the plane fin, the measured data had similar trend to Gray & Webb's correlation at high air velocity, however a new correlation is needed to give more accurate prediction at low air velocity. It is found that most heat was transferred around the front row of the two-row heat exchanger, and the ratio of thermal load at the front tube row was increased for decreasing air velocity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.9 s.240
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• pp.1032-1041
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• 2005

This study is performed to investigate the heat transfer characteristics of heat exchanger according to the arrangement of fins as well as fin configuration by using the four times enlarged model. Friction factor, Colburn j factor and goodness factors are compared to each other to estimate performance of each case for 4 different kinds of fins, which are plain, single side slit, double side slit and louver fin. Results show that heat transfer would be altered by fin arrangement and that friction loss is more affected by fin configurations than by the fin arrangements. In particular, heat transfer depends more on the shape of front row than that of rear row. The heat transfer rate of combined fin arrangement increases a lot more under the same pressure drop than that of conventional fin arrangement. This indicates that the heat exchanger of higher efficiency would be designed by the proper combination of fins, of different shapes.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.183-189
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• 2004

The flow and the heat transfer about the cross-flow fin-tube heat exchanger in an out-door unit of a heat pump system has been numerically Investigated. Using the general purpose analysis code, FLUENT, the Navier-Stokes equations and the energy equation are solved for the three dimensional computation domain that encompasses multiple rows of the fin-tube. The temperature on the fin and tube surface is assumed constant but compensated later through the fin efficiency when predicting the heat-transfer rate. The contact resistance is also taken into consideration. The flow and temperature fields for a wide range of inlet velocity and fin-tube arrangements are examined and the results are presented in the paper. The details of the flow are very well captured and the heat transfer rate for a range of inlet velocity is in excellent agreement with the measured data. The flow solution provides the effective permeability and the inertial resistance factor of the heat exchanger if the exchanger were to be approximated by the porous medium. This information is essential in carrying out the global flow field calculation which, in turn, provides the inlet velocity lot the microscopic temperature-field calculation of the heat exchanger unit.

• Journal of Institute of Convergence Technology
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• v.5 no.1
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• pp.27-31
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• 2015

A Pin-fin array is widely used to enhance the heat transfer in the internal cooling passage. The heat transfer distribution around the pin-fin is varied by the horseshoe vortex and flow separation. The difference of heat transfer coefficient induces the large thermal stress, which is one of the major reasons to break of hot components. So, it is required to enhance the heat transfer on the back side of pin-fin to solve the thermal stress problem. This study suggests the pin-fin with inclined jet hole and complex pin-fin/dimple array to enhance the heat transfer on the back side of pin-fin. The heat transfer coefficient is predicted by the numerical analysis, which is performed by CFX 14.0. The numerical results are obtained at Reynolds number, 10,000. The results show that the heat transfer on the back side of pin-fin is increased in both cases. Beside, the wake, which comes from dimple and jet, helps to develop the horseshoe vortex and increase the heat transfer on the next row pin-fin.