• Journal of ILASS-Korea
• /
• v.14 no.4
• /
• pp.178-183
• /
• 2009

Spray cooling heat transfer was experimentally investigated for water sprays impacting on mico-fins structured surfaces in the single phase and nucleate boiling regions. The heat transfer surfaces consist of cubic fins and triangular grooved fins. The spray produced using full cone spray nozzles, and experiments were made under the test condition of $Q=4.92{\times}10^{-6}{\sim}15.83{\times}10^{-6}\;m^3/s$, $T_f=35{\sim}55^{\circ}C$. From the experimental results, it was found that cubic fins surface had the largest heat flux enhancement relative to the smooth surface.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.7
• /
• pp.557-570
• /
• 2014

The heat transfer, pressure loss, and thermal performance in a cooling channel were evaluated for various new fan-shaped pin-fin geometries using three-dimensional Reynolds-averaged Navier-Stokes equations. The turbulence was modeled using the low-Reynolds-number SST turbulence model in the Reynolds number range of 5,000-100,000. The numerical results for the area-averaged Nusselt numbers were validated by comparing them with the experimental data under the same conditions. A parametric study for three types of fan-shaped pin-fin geometries was performed with two parameters, namely, the leading and trailing reduction angles.

• Tribology and Lubricants
• /
• v.26 no.1
• /
• pp.52-55
• /
• 2010

This study investigates the friction of the roll stands in the high performance multi- holes slate fin machine which pin is using in heat transfer of radiator, oil cooler, inter cooler, condenser and evaporator. The roll stand part is very important to maintain the high performance fin machine. This multi-holes form roll type is the first time in our country so it will be helpful to increases the export and product of heat transfer. It was include the technical of form rolling system which was self development. Then it will be improve the electric home appliances, future motor vehicle device and industrial machine.

• Journal of the Korean Society of Industry Convergence
• /
• v.11 no.4
• /
• pp.157-163
• /
• 2008

The present study investigated the pressure drop and the total frost mass of the louvered fin type heat exchanger, which is widely used at the air-conditioning system. The pressure drop due to the frosting phenomenon and the total frost mass were investigated by changing the wet bulb temperature condition of the inlet air. Hence the brain of 55wt% was used as a cooling solution instead of a common refrigerant. The temperature difference between the brine and the tube outside wall at the outlet of heat exchanger was $10^{\circ}C$, at maximum, higher than that at the inlet of heat exchanger. As the wet bulb temperatures were increased, the pressure drop was linearly increased due to the increment of frost mass. And the increment of heat exchange rate was smaller than that of inlet air enthalpy due to the increment of frost mass. The pressure drop of air side was rapidly increased due to the progress of frosting phenomena. The run time that the pressure drop occurred rapidly was decreased by the growth of frost.

• Proceedings of the SAREK Conference
• /
• 2006.06a
• /
• pp.182-187
• /
• 2006

This research presented the heat resistance characteristics of heat sink which is newly designed through the experiment. For the same volume and base plate of heat sinks, the experiment of heat transfer characteristics was conducted for forced convection of layered type heat sink. The heat transfer and pressure drop characteristics of the layered type heat sink were compared for the various kinds of fin pitches, fin heights and heights of heat sink. The results show that thermal resistance is decreased as the height of heat sink increases and the fin height and fin pitch decrease, From the experimental data of layered type heat sink, the correlation equation of Nusselt number was obtained as follows ; $$Nu=0.845{\cdot}Re^{0.393}{\cdot}(\frac{f_h}{D_h})^{0.160}{\cdot}(\frac{f_p}{D_h})^{0.372}{\cdot}(\frac{H_{hs}}{D_h})^{-0.942}$$

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.5
• /
• pp.43-53
• /
• 2010

This study investigates a design optimization of a rotating two-pass rectangular cooling channel with staggered arrays of pin-fins. The radial basis neural network method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport turbulent model. The ratio of the diameter to height of the pin-fins and the ratio of the streamwise spacing between the pin-fins to height of the pin-fin are selected as design variables. The optimization problem has been defined as a minimization of the objective function, which is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. Results are presented for streamlines, velocity vector fields, and contours of Nusselt numbers, friction coefficients, and turbulent kinetic energy. These results show how fluid flow in a two-pass square cooling channel evolves a converted secondary flows due to Coriolis force, staggered arrays of pin-fins, and a $180^{\circ}$ turn region. These results describe how the fluid flow affects surface heat transfer. The Coriolis force induces heat transfer discrepancy between leading and trailing surfaces, having higher Nusselt number on the leading surface in the second pass while having lower Nusselt number on the trailing surface. Dean vortices generated in $180^{\circ}$ turn region augment heat transfer in the turning region and in the upstream region of the second pass. As the result of optimization, in comparison with the reference geometry, thermal performance of the optimum geometry shows the improvement by 30.5%. Through the optimization, the diameter of pin-fin increased by 14.9% and the streamwise distance between pin-fins increased by 32.1%. And, the value of objective function decreased by 18.1%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.4
• /
• pp.497-503
• /
• 1997

In the present study, the cooling package using the heat pipe has been developed to improve the thermal performance in the point of cooling characteristics of the electronic chip placed to the subrack being readily assembled and disassembled in ATM switching system. As the preliminary experiments, the cooling performances between a conventional way using a cooling fin and a proposed method applying the heat pipe are compared and analyzed. The cooling performance at a simulated electronic component packaging a heat pipe module is approximately achieved up to $5.0W/cm^2$ heat flux and the allowable temperature at the heated chip is sustained in the range within $70^{\circ}C$. From the results, it is confirmed that temperature oscillations are also settled by inserted wick in the evaporator section. From the user's viewpoint, the method to assemble and disassemble the heat pipe easily has been devised.

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

• Journal of the Korean Society of Propulsion Engineers
• /
• v.23 no.4
• /
• pp.28-34
• /
• 2019

In this study, pin-fin arrays, which are widely used for cooling turbine blades, were studied. The vortex generator in pin-fin arrays is located in front of the circular tube. The cross-section of the vortex generator is NACA-9410. The purpose of this study is to analyze heat transfer performance and flow characteristics of pin-fin arrays. The position of vortex generator is changed with the vertical flow direction on the bottom wall. Pin-fin arrays were calculated with 6000, 10000 and 15000 Reynolds number. The commercial program ANSYS v18.0 CFX and the turbulence model $k-{\omega}$ SST were used. As a result, the heat transfer performance increased up to 5.8% and pressure loss increased less than 1%.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.32 no.3
• /
• pp.102-110
• /
• 2004

A design code validated against the thermal analysis results of CFD and published RTE code for a regeneratively cooled combustion chamber has been developed. The major function of the code is to predict the regenerative cooling performance and stress of the chamber wall. Adopted are the empirical correlation for the evaluation of the heat transfer coefficient of hot gas and coolant, and theoretical formula for the fin effect of the channel rib. The hot-gas-side wall temperature from the present code shows 100 K difference at most compared to RTE results. It shows less than 10 % difference for the heat flux thrall through the chamber wall and hot-gas-side convective heat transfer coefficient. The major cause of the wall temperature difference is due to the underestimation of the fin effect of the channel rib.