• 설비공학논문집
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• 제9권2호
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• pp.153-162
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• 1997

In this study, the wet surface heat transfer coefficients and friction factors of the heat exchanger with slit-wavy fin were measured. Four sample cores of two or three row with fins of 12 fpi or 16 fpi were tested. Tests were conducted in a closed loop wind tunnel, where the heat exchanger was mounted at 45 degree inclination angle. The wet surface heat transfer coefficient was reduced following the procedure given in ARI 420-81. During the course, new definitions of the $\varepsilon$-NTU applicable to enthalpy driving system were introduced. The wet surface heat transfer coefficients were approximately equal to the dry surface values. However, the friction factors were approximately 120% to 170% higher than those of the dry surface. Both the heat transfer coefficient and the friction factor of the wet surface increased as the relative humidity increased, fin pitch decreased, and the number of row decreased, although the difference was not large.

• 대한기계학회논문집B
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• 제21권1호
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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.

• Journal of Mechanical Science and Technology
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• 제18권9호
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• pp.1590-1603
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• 2004

In this study the optimization of plate-fin type heat sink with vortex generator for the thermal stability is performed numerically. The optimum solutions in the heat sink are obtained when the temperature rise and the pressure drop are minimized simultaneously. Thermal performance of heat sink is influenced by the heat sink shape such as the base-part fin width, lower-part fin width, and basement thickness. To acquire the optimal design variables automatically, CFD and mathematical optimization are integrated. The flow and thermal fields are predicted using the finite volume method. The optimization is carried out by means of the sequential quadratic programming (SQP) method which is widely used for the constrained nonlinear optimization problem. The results show that the optimal design variables are as follows; B$_1$=2.584 mm, B$_2$=1.741 mm, and t=7.914 mm when the temperature rise is less than 40 K. Comparing with the initial design, the temperature rise is reduced by 4.2 K, while the pressure drop is increased by 9.43 Pa. The relationship between the pressure drop and the temperature rise is also presented to select the heat sink shape for the designers.

• 대한기계학회논문집B
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• 제22권4호
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• pp.520-529
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• 1998

Heat and mass transfer behaviors of metal hydride beds were predicted by solving a set of volume-averaged equations numerically both for the gas (hydrogen) and the solid(metal hydride) phases. Time variations of temperature and hydrogen concentration ratio distributions were obtained for internally cooled, cylindrical-shaped beds with metal(aluminum) fins imbedded in them. Also, time variations of the space-averaged hydrogen concentration ratio were obtained. Temperature and velocity of the coolant, hydrogen pressure at the gas inlet, and the fin spacing were taken as the parameters. The hydrogen absorption rate increases with the higher velocity and the lower temperature of the coolant, and with the decrease of the fin spacing. Increasing of the hydrogen pressure at the gas inlet also promotes the rate of absorption though the increasing rate gradually slows down. The amount of the hydrogen storage per unit volume of the bed decreases with the tighter fin spacing despite of the higher absorption rate ; therefore, there should be an optimum fin spacing for a given volume of the system and the amount of the hydrogen storage, in which the absorption rate is the highest.

• 설비공학논문집
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• 제18권6호
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• pp.459-467
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• 2006

Rapid development of electronic technology requires small size, high density packaging and high power in the electronic devices, which results in more heat generation. Suitable heat dissipation is required to ensure the guaranteed performance and reliable operation of the current state-of-the-art electronic equipment. The aim of the present study is to find out the forced-convective thermal-hydraulic characteristics of a pin-fin heat exchanger as a candidate for cooling system of the electronic devices through the analysis and experiment. Various configuration of the pin-fin array is selected in order to find out the effect of spacing and diameter of the pin-fin on the heat transfer and pressure drop characteristics. Experimental results are compared with the analyses and correlations of several researchers. Finally, the design guide are provided for the required pressure drop and/or the heat transfer characteristics of the heat exchanger.

• 대한기계학회논문집B
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• 제20권12호
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• pp.3938-3948
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• 1996

This study is related with the experimental investigation on the heat transfer and pressure drop characteristics of the fin-and-tube heat exchangers with three different interrupted fins and a plane fin for air-conditioning application. Experiments were conducted accordingly following the appropriate development process. Geometry similitude experiment was introduced to predict the performance of fins, and prototype experiment was also performed to confirm the validity of geometry similitude experimental results. However, these experimental results were limited to the sensible heat transfer characteristics of the heat exchangers. Hence, additional experiment was performed using refrigerant to investigate the latent heat transfer characteristics. This paper presents an appropriate process for the development of a new type heat exchanger. Sensible and latent heat transfer characteristics for each fin configuration is also provided along with the optimal fin configuration.

• 수산해양교육연구
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• 제5권1호
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• pp.31-44
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• 1993

Through the early 1900's, the evolution of the surface condenser was closely tied to the development of steam engine and the turbine. As the chemical and petroleum industries evolved in the 1900's, the use of surface condensers in many different processes. Today, industry uses condensers in many shapes and sizes. The actual condensation process occurs on the outside surface of tubes. The nature of this surface geometry affects the condenser's heat transfer performance. The first condensers were built with plain tubes. As tube manufacturing techniques advanced, manufacturers started making tubes with integral fins. In the 1940's, fin densities were limited to about 600 to 700 fins per meter(fpm) because of manufacturing procedure. Today new manufacturing techniques allow production of tubes with fin densities ranging from 750 to 1600 fpm. The integral-fin tubes investigated in this paper are nominally 19 mm diameter. Eight tubes have been used with trapezodially shaped integral-fins having fin density from 748 to 1654 fpm and 10, 30 grooves. For comparison, tests are made using a plain tube having the same inside diameter and an outside diameter equal to that at the root of the fins for the finned tubes. Betty and Katz's theoretical modelis is used to predict the R-11 condensation coefficient on horizontal integral-fin tubes having 748, 1024 and 1299 fpm. Experiments are carried out using R-11 as working fluid. The refrigerant condensates at a saturation state of $30^{\circ}C$ on the outside tube surface cooled by coolant. The amount of noncondensable gases present in the test loop is reduced to a negligible value by repeated purging. For a given heat input to the boiler and given cooling water flow rate, all test data are taken at steady state. The observed heat transfer enhancement for the finned and grooved tubes significantly exceeded that to be expected on grounds of increased area. For the eight fin tubes and one plain tube tested, the best performance has been obtained with a tube having a fin density of 1299 fpm, and a fin bight of 1.2mm and 30 grooves.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2321-2326
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• 2007

To return LNG to a gaseous state, it is fed into a regasification plant. For inland area, where pipelines do not exist or difficult to construct, the LNG is delivered to the inland-receiving terminal available at that area, regasified and delivered to consumers. At inland-receiving terminal, air-heating vaporizer type is usually used. To contribute in developing an efficient air-heating vaporizer, experiment on finned type air-heating vaporizer using 8 fins, 50 mm fin length (8fin50le) and 4 fins, 75 mm fin length (4fin75le) were conducted. The experiments were conducted by varying the ambient condition and the length of the vaporizer. The ambient air was controlled so that it has the same condition with air condition in every season available. $LN_2$ is used to substitute LNG because of safety reason. The results show that characteristics of the finned type 4fin75le vaporizer are comparable to finned type 8fin50le vaporizer at all season.

• 한국전기전자재료학회논문지
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• 제25권2호
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• pp.100-104
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• 2012

Fin-type SONOS (silicon-oxide-nitride-oxide-silicon) flash memory has emerged as novel devices having superior controls over short channel effects(SCE) than the conventional SONOS flash memory devices. However despite these advantages, these also exhibit undesirable characteristics such as corner effect. Usually, the corner effect deteriorates the performance by increasing the leakage current. In this paper, the corner effect of fin-type SONOS flash memory devices is investigate by 3D Process and device simulation and their electrical characteristics are compared to conventional SONOS devices. The corner effect has been observed in fin-type SONOS device. The reason why the memory characteristic in fin-type SONOS flash memory device is not improved, might be due to existing undesirable effect such as corner effect as well as the mutual interference of electric field in the fin-type structure as reported previously.

• 한국인터넷방송통신학회논문지
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• 제22권3호
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• pp.37-42
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• 2022

본 논문에서는 낮은 삽입 손실을 가지는 광대역 마이크로스트립-도파관 전이구조를 제안하였다. 제안하는 전이구조는 자연스러운 전계분포의 필드 변환과 마이크로스트립 선로와 fin-line 사이의 임피던스 정합의 관점에서 설계되었다. Offset DSPSL (double-sided parallel stripline)을 이용한 fin-line 테이퍼로 전이구조의 길이 및 그 구조를 결정할 수 있도록 하였다. 제작된 전이구조의 특성은 전이구조 당 85 ~ 108 GHz의 대역에서 0.67 dB 이하의 낮은 삽입 손실을 가지고 있으며, 83 ~ 110 GHz 이상의 대역에서 1 dB 이하의 삽입 손실을 가짐을 확인하였다. 본 논문에서 제시한 전이구조를 이용하여 W-대역의 초소형 레이다 및 다양한 응용 분야에 적용 가능하리라 예상된다.