• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.16 no.4
• /
• pp.147-152
• /
• 2017

In the present study, we used a loop thermosyphon heat exchanger consisting of condensers with internal fins and external plate fins which are 480 mm wide, 68 mm long, and 1,000 mm high. The heat transfer pipes in the heat exchanger were 15 mm in diameter and 1,000 mm in length, and 98 heat transfer pipes were installed in the heat exchanger. According to the experimental results, as the spaces between the internal discontinuous pins decreased, the frequency of pressure drops increased and changes in temperature at the outlet of the condenser were shown to be a little smaller. Therefore, we can see that as the spaces between internal discontinuous pins decreased, the heat transfer performance increased. For the loop heat pipe heat exchanger consisting of a condenser with internal and plate fins, as the temperature of the air flowing into the condenser increased, the condensation heat transfer rate also increased, and as the condenser refrigerant inflow temperature increased, the condensation heat transfer rate increased as well.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.25 no.6
• /
• pp.331-337
• /
• 2013

An experimental study on the performance of a liquid electric component cooling system was performed. The thermal resistance and pressure drop at a heat sink were measured, for aluminum waterblocks with four different internal shapes, with either smooth surface, porous media filling, or with fins of 5 mm height, or of 7 mm height. The fins had 0.5 mm thickness, and the gap between the fins was 0.5 mm. The waterblock internal dimension was $36.5{\times}36.5{\times}7mm$. Compared with the waterblock with smooth surface, the thermal resistance reduction was 11%, 46%, and 42% for waterblocks with porous media filling, 5 mm, and 7 mm fins, respectively. A new dimensionless parameter was suggested to evaluate the waterblock performance, with the simultaneous consideration of thermal resistance and pressure drop. The performance of the waterblock with fins of 5 mm height was best by parameter.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.14 no.6
• /
• pp.1178-1185
• /
• 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.

• Journal of Mechanical Science and Technology
• /
• v.17 no.3
• /
• pp.422-428
• /
• 2003

This study concerns the performance of the heat transfer of the thermosyphons having 60, 70, 80. 90 axial internal low-fins in which boiling and condensation occurr. Water, HCFC-141b and CFC-11 have been used as the working fluids. The operating temperature, the liquid charge ratio and the inclination angle of thermosyphons have been used as the experimental parameters. The heat flux and heat transfer coefficient at the condenser are estimated from experimental results. The experimental results have been assessed and compared with existing theories. As a result of the experimental investigation, it was found that the maximum heat flow rate in the thermosyphons is dependent upon the liquid charge ratio and inclination angle. A relatively high rate of heat transfer has been achieved by the thermosyphon with axial internal low-fins. The inclination of a thermosyphon has a notable influence on the condensation. In addition, the overall heat transfer coefficients and the characteristics at the operating temperature are obtained for the practical applications.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.360-365
• /
• 2007

This work is concerned with the topology optimization of three-dimensional cooling fins or heat sinks. Motivated by earlier success of the Internal Element Connectivity Method (I-ECP) method in two-dimensional problems, the extension of I-ECP to three-dimensional problems is carried out. The main efforts were made to maintain the numerical trouble-free characteristics of I-ECP for full three-dimensional problems; a serious numerical problem appearing in thermal topology optimization is erroneous temperature undershooting. The effectiveness of the present implementation was checked through the design optimization of three-dimensional fins.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
• /
• 2004.05a
• /
• pp.219-224
• /
• 2004

The present study was to investigate the heat transfer enhancement effect of coil wire fins in an ice storage system. For the two cases of tubes with internal brine flows, a finned tube with coil wires on its outer surface and a smooth tube, the rates of ice layer were tested and compared for both the icing processes. The coil fins were made of a stainless steel wire with a dia. of 2.0(mm), and the coil had an outer dia. of 10(mm) and a helix angle of 60($^{\circ}$). The experimental results showed that the coil fins could substantially reduce the thermal resistance of the ice layer, and enhance the heat flow rates between the water in the storage tank and the brine. The ice storing time was found to be shortened by 13(%) for the coil fins to get the same amount of ice layer that was built on the smooth tube wall for 10 hours of operation when the same thermal conditions were provided.

• Journal of the Korean Solar Energy Society
• /
• v.22 no.1
• /
• pp.23-30
• /
• 2002

This study concerns the performance of the heat transfer of the thermosyphon having 80 internal fins in which boiling and condensation occur. Water has been used as the working fluid. The Liquid filling as the ratio of working fluid volume to total volume of thermosyphon have been used as the experimental parameters. The heat flux and heat transfer coefficient at the condenser are estimated from the experimental results. The experimental results have been assessed and compared with existing theories. As a result of the experimental investigation we can state that the maximum heat flow rate in the thermosyphon prove to depend upon the liquid fill quantity. The relatively high rates of heat transfer have been achived operating in the thermosyphon with axial internal fins. Also, the thermosyphon with internal micro fins can be used to achieve some inexpensive and compact heat exchangers in low temperature. In addition, it is to obtain the overall heat transfer coefficients and the characteristics as a operating temperature for the practical applications.

• 한국전산유체공학회:학술대회논문집
• /
• 1999.11a
• /
• pp.139-144
• /
• 1999

There have been many studies for heat transfer enhancement. Particularly, the study of flow in heat exchangers which have fin device has been main theme in heat transfer area. Practically, the circular tube which has internal fins is widely used for developing heat transfer rate. In this study, flow and heat transfer analysis of the circular tube with fins are investigated. The height and the number of fins are arbitrary. The flow field is assumed to be laminar. The conformal mapping is used for analytic solution of the laminar flow field. Discretization of governing equation, namely, FDM was used for numerical analysis. The velocity field, flow rate and shear stress are calculated for some numbers of fins in circular tube and for some heights of fin. Temperature fields are plotted along the tube length. It can be shown that the numerical solution agrees with the analytical solution.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.9
• /
• pp.721-727
• /
• 2021

In this paper, aerodynamic characteristics of missile configuration with various grid fins in subsonic flow. To investigate the effects of grid fin shape, four types of experimental models were used. In addition, to examine aerodynamic characteristics of missile configurations with various grid fins according to effects of Reynolds numbers and configurations of grid fins, 6-components aerodynamic forces and moments were measured by internal balance in wind tunnel test.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.16 no.6
• /
• pp.847-856
• /
• 2013

In this study, thermal performance of recuperators with plain and offset strip fins is investigated to enhance the thermal efficiency of a micro gas turbine. Thermal cycle analysis is conducted to determine major design parameters of a single-pass counterflow recuperator. In order to evaluate the performance of the recuperator, the effectiveness and the pressure drop in the recuperators are chosen as the objective function and the design constraint, respectively. The optimized geometries for internal structure of the recuperators with plain and offset strip fins are obtained with varying the fin spacing and height. From the result, the recuperator with offset strip fins has better thermal performance when the fin spacing, s, is smaller than 1.45mm and the thermal performance of the recuperator with plain rectangular fins is higher than that with offset strip fins in the region of $s{\geq}1.45mm$. In addition, it is found that the entrance region effect and the longitudinal wall heat conduction effect should be taken into account for accurately predicting the thermal performance of the recuperators with both plain and offset strip fins.