• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.341-346
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• 2009

The purpose of the present study is to investigate the flow resistance and the heat transfer characteristics of oval fin-tube heat exchanger. Six kinds of oval fin having the same fin area and the different diameter ratio tested numerically. Test data for the heat transfer, pressure drop and fin temperature were shown and discussed. The pressure drop and heat transfer increased for increasing the oval fin diameter ratio(diameter of span-wise direction to diameter of longitudinal diameter) up to 50% and 45% respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.1
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• pp.45-50
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• 2012

The plate fin and tube type of heat exchanger is widely used in air conditioner, and the heat exchanger is assembled by the mechanical expansion of copper tubes and fastening the aluminum fin. The objective of the present study is to investigate how the mechanical expansion of copper tube affects on the heat transfer performance of a plate fin and tube type heat exchanger. This study has been performed by experimental and numerical methods. The numerical and experimental results show that the tube expansion ratio has a influence on the heat transfer performance. Within the tested expansion ratio, the contact pressure shows the peak value and it decreases as the expansion ratio increases. Air-side heat transfer coefficient increases until the expansion ratio reaches 1.23, and then decreases with the similar pattern to the contact pressure. Also, contact heat transfer coefficient shows the maximum when the contact pressure is highest as well as the air-side heat transfer coefficient.

• Journal of Power System Engineering
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• v.12 no.3
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• pp.19-25
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• 2008

This paper deals with the heat transfer and pressure drop characteristics of R-290 (Propane), R-600a (Iso-butane) and R-1270 (Propylene) as an environment friendly refrigerant and R-22 as a HCFC's refrigerant for condensing. The test section is a horizontal double pipe heat exchanger. Condensing heat transfer and pressure drop measurements were Peformed for 12.70 mm micro-fin tube and compared with the results in smooth tube. The local condensing heat transfer coefficients of hydrocarbon refrigerants were superior to those of R-22 and the maximum increasing rate of heat transfer coefficient was found in R-600a. The average condensing heat transfer coefficients in hydrocarbon refrigerants showed 20 to 28% higher values than those of R-22. Hydrocarbon refrigerants have a higher pressure drop than that of R-22 with respect to refrigerant qualify and mass flux. Also, the condensing heat transfer coefficient and pressure drop of working fluids in smooth and micro-fin tube were compared. The heat transfer enhancement factor (EF) between smooth and micro-fin tube varied from 2.2 to 2.6 in all experimental conditions.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.83-89
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• 2000

This paper presents a pressure drop correlation for evaporation and condensation of alternative refrigerant with oil in micro-fin tubes. The correlation was developed from a data base consisting of oil-free pure and mixed refrigerants in micro-fin tube; Rl25 R134a. R32 R410a(R32/R125 50/50% mass), R22, R407c(R32/R125/R134a, 23/25/52% mass) and R32/R134a(25/75% mass). The micro-fin tube used in this paper had 60 0.2mm high fins with a 18 helix angle. The cross sectional flow area $(A_c)$ was $60.8 mm^2$ giving an equivalent smooth diameter$(D_e)$ of 8.8mm. The hydraulic diameter $(D_h)$ was estimated to the 5.45mm. The new correlation was obtained by replacing the friction factor and the tube-diameter in Bo Pierre correlation by a friction factor derived from pressure drop data for a micro-fin tube and the hydraulic diameter, respectively. This correlation was also used to predict some pressure data with a lubricant after using a mixing viscosity rule of lubricants and refrigerants. As a result, the new correlation was also well predicted to the measured data within a mean deviation of 19.0%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.9
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• pp.627-632
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• 2011

As an innovative effort to secure economically viable heat recovery system, various fin shapes for industrial fin-tube heat exchangers have been studied for better performance. In this study, the waste gas heat recovery from four different fin shapes was experimentally performed for heat transfer rate and pressure drop. According to the tested results, the twist and wavy shape fins of rectangular type show the superior performance in terms of Goodness factor and jH/f factor ratio, whereas the circular spiral fin shows the inferior values. Experimental results shows good comparison with the numerical results with a slight discrepancy of 5%, which is quite resonable.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.2
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• pp.210-218
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• 1998

Experimental results for forced convection condensationof Refrigerant-22 and ternary Refrigerant-407c(HFC-32/125/134a 23/25/52 wt%) considered as a substitute R-22 inside horizontal micor-fin tubes are presented. The test section was horizontal double-tubed counterflow condenser with a length 4000 mm micro-fin tube having 9.53 mm OD., 0.2 mm fin height and 60 fins. The refrigerants R-22 and R-407c were cooled by a coolant circulated in a surrounding annulus. The range of parameters of mass velocity was varied from 102.1 to 301.0kg/($\textrm{m}^{2}.s$) with inlet quality 1.0. Both refrigerant R-22 and its alternative refrigerant R-407c were tested within the same range of parameters. At the given experimental conditions for R-22 and R-407c the pressure drops for R-407c were considerably higher than those for R-22 at micro-fin tubes. Over the mass velocity range tested the PF(penalty factor)was lower than the increasing ratio of heat transfer area by fins. Based on the data correlation was proposed for predicting the frictional pressure drops for R-22 and R-407c for a duration of condensation inside a horizontal micro-fin tube.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.341-346
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• 2005

Nowadays, adsorption chillers have been receiving considerable attentions as they are energy-saving and environmental1y benign systems. A Fin & tube type heat exchanger in which adsorption/desorption take place is required more compact size. The adsorption chiller is expected to have high energy-efficiency in utilizing the waste heat exhausted from a process. The objectives of this paper are to investigate the effect of fin pitch of fin & tube on the adsorption performance and to develop an optimal design fin & tube heat exchanger in the silica gel/water adsorption chiller. Previous study concluded that optimal particle size selected 0.5mm, type HO silica gel, and fundamental heat transfer & mass transfer experiments carried out. From the numerical results, the adsorption rate for the fin pitch 2.5mm is the highest than that for the fin pitch 5mm, 7.5mm and 10mm. Also cooling water & hot water temperature affect the adsorption rate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.3
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• pp.244-251
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• 1989

A numerical study has been performed on the natural convection heat transfer from a conducting tube with two axial fins to a surrounding cylinder. As increasing dimensionless fin length ($L_F$), the center of flow moves to the bottom of annulus and the recirculating flow rate is decreased. The maximum local Nusselt number of conducting tube appears at ${\theta}=180^{\circ}$ for $L_F=0.0$, but at ${\theta}=130^{\circ}$ for $L_F{\geq}0.3$ and that of outer cylinder appears at ${\theta}=13^{\circ}$ for $L_F{\leq}0.6$ but at ${\theta}=33^{\circ}$ for $L_F=1.0$. The fin temperature is decreased by increasing radial distance and the temperature distribution of the downward fin is generally less than that of the upward fin. By increasing fin length, the local Nusselt number of the upward fin appears negative values for $L_F=1.0$, but appears positive values for $L_F<0.8$, and that of the downward fin appears positive values.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.96-96
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• 2018

금속재료 중 알루미늄(Al)은 일반적으로 많이 사용되는 철강재에 비해 그 비중이 약 $1/3(2.7g/cm^3)$인 경량이고 열전도율이 약 3배($196kcal/^{\circ}C$, $20^{\circ}C$)로 높은 특성 등을 갖고 있다. 또한 대량생산에 의한 경제성을 가지기 때문에 건축 구조재, 전기 및 가전 등 다양한 산업 분야에서 널리 사용되고 있다. 특히, 위와 같은 특성으로 인해 열교환기의 종류에서 응축기(Condenser) 및 증발기(Evaporator)는 알루미늄(Al)을 널리 사용하고 있다. 하지만 단일 응축기 부품에도 이종 알루미늄 소재가 사용됨에 따라 갈바닉 부식이 발생할 수 있다는 단점이 있다. 따라서 본 연구에서는 현재 상용되고 있는 열교환기 중 응축기에서의 이종 알루미늄 재료로 인해 나타나는 갈바닉 부식 특성을 관찰-분석-연구 하였다. 본 연구에 사용된 알루미늄 재료는 현재 응축기 재료 중에서 각각 Tube와 Fin으로 널리 상용되고 있는 Al 1100과 Al 3003을 사용하였다. 표면 모폴로지는 SEM을 통해 관찰하였고 EDS를 통해 조성원소를 분석하였다. 또한 내식성 평가를 위해 5% NaCl 환경에서의 SST(Salt spray test, 염수분무시험) 시험과 3% NaCl 용액 내 자연침지 시험 및 탈기된 3% NaCl 용액 내 전기화학적 동전위 양극 분극 시험을 진행하였으며 더불어 갈바닉 부식 시험에 따른 혼합 전위 측정 및 외관 관찰을 하였다. 각 재료는 실험에 대해 동일한 표면적을 노출시켜 시험하였다. 5% NaCl 환경에서의 염수분무 시험 결과 Fin(Al 3003)의 경우에는 Tube(Al 1100) 보다 빠른 부식거동을 보이며 국부적인 공식부식(Pitting corrosion)이 촉진되었다. Tube(Al 1100)의 경우에는 치밀한 Al2O3 형성과 부식에 따른 Al(OH)3를 생성함에 따라 Fin(Al 3003)에 비해 느린 부식거동을 보였다. 3% NaCl 용액 내 자연 침지 및 전위 측정 결과 초기 전위는 Fin(Al 3003, 약 -0.85V/SCE)이 Tube(Al 1100, 약 -1.05V/SCE)에 비해 더 높은 값을 가지며 약 72시간 이후 Tube(Al 1100) 시편이 더 안정적인 전위 값을 나타냈다. 이는 안정적인 Al(OH)3 피막 형성에 기인한 것으로 사료된다. 탈기된 3% NaCl 용액 내 전기화학적 동전위 양극 분극 시험 결과 Fin(Al 3003) 시편에서 더 귀한 부식 전위 값을 나타냈지만 부식 전류는 더 낮은 값을 나타냈다. 상기 시험 결과를 바탕으로 Fin-Tube 간 장기간 접촉 시에는 갈바닉 부식이 발생할 수 있을 것으로 사료된다. 갈바닉 부식 시험 결과 초기 혼합 전위는 약 -1.05 V/SCE를 나타냈으며 약 288시간 경과 후 약 -0.85 V/SCE 값을 나타냈다. 이는 자연 전위 측정 및 동전위 양극 분극 시험에서의 부식 전위 값에서 알 수 있듯이 더 비한 전위인 Tube(Al 1100) 시편이 Fin(Al 3003) 시편에 대해 희생양극적(Sacrificial anode)인 역할을 한 것을 확인할 수 있었다. 또한 갈바닉 부식 전위 측정 간 외관 관찰에서도 Tube(Al 1100) 시편은 빠르게 흑변 하는 것을 확인할 수 있었으며 Fin(Al 3003) 시편은 침지 300시간 이후에도 초기와 유사한 표면 상태 및 광택을 유지하였다. 이상의 SST 시험, 자연 침지 시험, 전기화학적 양극 분극 시험 및 갈바닉 부식 시험 결과를 바탕으로 단일 부품 내 이종 알루미늄 소재 간 접촉 및 그에 따른 갈바닉 부식 발생을 확인할 수 있었다. 따라서 동종 성분이라고 할지라도 단일 부품 제작 시에는 그 사용 환경에 따라 이종 금속 재료의 사용에 대한 재고가 필요할 것으로 사료된다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.205-215
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• 2001

An experimental study has been performed to investigate the heat transfer characteristics of fin and tube heat exchanger. The existing transient and steady methods are very difficult to apply for the measurements of heat transfer coefficients of a thin heat transfer model. In this study the lumped capacitance method was adopted. The heat transfer coefficients were measured by using the lumped capacitance method based on the liquid crystal thermography. The method is validated through impinging jet and flat plate flow experiments. The two experiments showed that the results of the lumped capacitance method with polycarbonate model showed very good agreements with those of the transient method with acryl model. The lumped capacitance method showed similar results regardless of the thickness of polycarbonate model. The method was also applied for the heat transfer coefficient measurements of a fin and tube heat exchanger. The quantitative heat transfer coefficients of the plate fin were successfully obtained. As the frontal velocity increased, the heat transfer coefficients were increased, but the color-band shape showed similar patterns regardless of frontal velocity.