• Clean Technology
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• v.14 no.4
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• pp.265-270
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• 2008

In this study, the flow and heat transfer of the aligned pin-fin array of the air cooling module for electronic packaging application were numerically analyzed with various fin shapes. The geometric cross-sectional shapes of pin-fins considered in this study were ellipse, wing and circle. The fins had same cross-sectional area and height, but they had different surface areas. As the results, the surface area, the heat transfer coefficient, and the heat transfer performance of pin-fins greatly depended on their shapes. Of the three types of pin-fins, the wing type pin-fin with suitable shape produced the best heat transfer performance. This result implies that the cooling capacity of the pin-fin cooler can be significantly enhanced only by the change of fin shape without increasing air flow-rate or fin density.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.1-7
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• 2017

When implementing butt joint welding of two plates, it is useful to attach end-tabs made of a metal with high heat conductivity (e.g., copper) at the front and back sides of the welded plates to prevent the bead from rolling down and prevent defects that may occur at the tips of the weld zone. In this study, the fin shape, which is known to have good heat discharging characteristics by natural convection, has been applied to enhance the cooling performance of the end-tab. From both experiment and numerical analysis, it was confirmed that end-tabs with fin-shaped holes have better heat discharging performance than end-tabs without holes. Through thermal and fluid flow analysis, the cooling rates of end-tabs with different hole shapes were estimated in order to figure out characteristics of shape factor that are important for the heat discharging performance. As a result, we found that the structure including vertical fins with optimal fin gap was the best-performing shape.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.1
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• pp.1-9
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• 2003

The rectangular profile annular fin with fixed volume is optimized using 2-dimensional analytic method. For a base boundary condition, convection from fluid within the pipe to the inside wall of the pipe and conduction from the inside wall of the pipe to the fin base are considered. Heat loss from the fin tip radius is not ignored. The maximum heat loss, the optimum fin tip radius and the optimum fin half thickness corresponding to the maximum heat loss are presented as a function of fin base radius, Biot number over the fin surface and Biot number within the pipe. Results show 1) the maximum heat loss increases as both Biot number over the fin surface and Biot number within the pipe increase and as fin base radius decreases 2) the optimum fin thickness increases as Biot number within the pipe decreases or as fin base radius and Biot number over the fin surface increase.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.39 no.12
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• pp.30-35
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• 2010

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.402-407
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• 2008

This study is performed to investigate heat transfer characteristics for thermal performance of fin-and-tube sensible heat exchangers under the low air flowrate according to fin geometry combination and coolant flowrate control. Fins and tubes of samples were separated between front row and rear row. Experiment results are plotted heat transfer rate of each row, heat transfer coefficient and sensible heat ratio against water flowrate control of each row. It is observed that thermal performance can be enhanced by fin geometry combination and water flowrate control of each row under the low air flowrate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.531-537
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• 2010

This paper optimized the design parameters of the offset strip fin in a heat exchanger. To decrease the pressure drop and increase heat transfer, the performance factors such as j/f, $j/f^{1/3}$, and JF, which could be used to estimate the pressure drop and heat transfer simultaneously, were employed as the criteria for optimization. In the present study, STDQAO, PQRSM, and MGA were used for solving the constrained nonlinear optimization problem. The JF factor and heat transfer performance of the optimized offset-strip fin were greater than those of the reference offset-strip fin by 36% and 280%, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.484-491
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• 1999

Air side heat transfer and pressure drop for ø9.52 fin-tube heat exchanger with various types of slit and louver fins were measured, and compared with wave-slit fin. Longitudinal and transverse tube spacings of the heat exchangers are 21.65mm and 25mm respectively. Actual heat exchanger was tested using water, and the tests were performed for 2 row heat exchangers with 3 different fin spacings, 1.3, 1.5 and 1.7mm. The overall performance of the enhanced fins was evaluated by comparing heat transfer coefficient with respect to fan power.

• Journal of Energy Engineering
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• v.14 no.4 s.44
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• pp.241-247
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• 2005

Heat transfer enhancement and pressure loss penalty caused by three-row winglets built in three-row tube-bundles in an in-line arrangement, are compared between 'common flow up' and 'common flow down' winglet configurations. The 'common flow down' winglet-pairs recommended by the previous researchers bring about $10\%$ to $25\%$ increase in heat transfer enhancement and $20\%$ to $35\%$ increase in pressure loss penalty, in comparison with fin-tube bundles without winglets. For the 'common flow up' winglet-pairs, the spanwise distance between the trailing edges (${\Delta}y$) of winglet pairs was changed and investigated. Two types ot winglet are applied for triangular and rectangular shapes. In the triangular winglets with ${\Delta}y$=5 mm in in-line tube bundles, the heat transfer increased up to $10\%$, and simultaneously the pressure loss decreased by $8\%$ to $15\%$ for the Reynolds number (based on two times channel height) ranging from 300 to 2700, when the 'common flow up' winglets were built in. The performance of fin-tube bundles with triangular winglets is much superior to the rectangular one, because of the smaller pressure-loss penalty.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.291-299
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• 2010

Aspect-ratio-based numerical analysis is carried out to investigate the air-side convective heat transfer characteristics in compact heat exchangers with circular tubes and flat tubes-plate fins. The RNG $k-{\varepsilon}$ model is adopted for turbulence analysis. The numerical analysis is carried out for aspect ratios ranging from 3.06 to 5.44 and for Reynolds numbers ranging from 1,000 to 10,000. The calculated results indicate a correlation between the friction factor and Colburn j factor in the compact heat exchanger system for the range of aspect ratios under consideration. The results obtained for circular tubes and flat tubes-plate fins in this study can be utilized to realize the optimal design of an air conditioning system.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.5
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• pp.43-55
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• 2020

The effect of cutted pin in front of pin-fin array was analyzed for increasing the cooling performance of gas turbine blade. The numerical simulations were conducted to figure out the flow and thermal characteristics. The base case which is staggered pin-fin array, cut pin case 1 which has X₂/D_p=1.25 cut pin and cut pin case 2 which has X₃/D_p=1.75 cut pin were compared. The results showed that cut pin increases the strength of the horseshoe vortex which occurred at the leading edge of pin-fin array. Furthermore, the wake effect is reduced at the trailing edge of pin-fin array. As a result, the heat transfer distribution on the endwall increases. However, the friction factor increases owing to the installation of cut pin, but the thermal performance factor is increased maximum 23.8% in cut pin case 2. Therefore, installation of cut pin will be helpful for increasing the cooling performance of pin-fin array of gas turbine blade.