• 에너지공학
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• 제15권3호
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• pp.166-173
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• 2006

본 연구에서는 상용 냉동 공조기기에서 사용하고 있는 휜-관 열교환기에서 R22와 이의 대체냉매로 채용하고 있는 R134a 압력강하와 열전달 특성에 대해 실험적으로 연구하였다. 실험은 입구온도 $60^{\circ}C$, 질량유량 $150,\;200,\;250\;kg/m^{2}s$의 범위에 대해 수행하였다. 이때 공기의 유입조건은 전구온도 $35^{\circ}C$, 상대습도 40%, 공기유속은 $0.68{\sim}1.6m/s$이다. 실험 결과 응축기 출구의 과냉도를 $5^{\circ}C$로 유지한 경우 Rl34a의 필요공기유속은 R22보다 5.9%작게 나타났으며, R134a의 압력강하는 R22보다 $18.1{\sim}20.4%$의 범위 내에서 크게 나타났다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2292-2297
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• 2008

Recently, a study on condensers for refrigerators has focused on new model which will cost less and will be more efficient. Some widely used condensers for domestic refrigerators are wire-and-tube type condenser, hot-wall type condenser, and spiral type condenser. Some companies which use the spiral type condenser at the moment try to develop a new type condenser which will cost less and will be as efficient as the spiral type. The new type condenser consists of a steel tube, steel plates and louver fins attached to the tube. The tube and the plate are bent into a single-passage serpentine shape.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2011-2016
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• 2008

A new method is presented for developing a simulation program which can analyze the heat transfer characteristics of fin-tube heat exchanger. This method is able to describe several types of refrigerant circuit arrangement. The delivery path of air and refrigerant properties is simplified by transforming three-dimensional array into one-dimensional array. By comparing simulated results with experiment results, the deviation was 8.2%. Several fin-tube heat exchangers of different design factors and operating conditions were simulated using this program. It was shown that this program could be used for designing practical fin-tube heat exchangers.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2023-2028
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• 2008

In present study, the flow field near the fin surface of plate fin - oval tube heat exchanger with delta wing vortex generator was numerically analyzed. As results, the well developed vortex behind delta wing was observed. These vortex can improve heat transfer fin surface behind delta wing vortex generators.

• 설비공학논문집
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• 제9권4호
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• pp.454-461
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• 1997

Heat transfer and pressure drop for single phase flow of water in circular smooth and micro-fin tubes are measured. Copper tubes of 9.52 and 7mm outer diameter were used. The internal roughness in micro-fin tubes was formed by spiral grooves having $25^{\circ}$ helx angle, 0. 12mm fin height and 0.454mm pitch in 9.52mm tubes; $18^{\circ}$ helix angle, 0.15mm fin height and 0.322mm pitch in 7mm tubes. The measured friction factor and heat transfer coefficient are compared with relevant previous works, and the correlations for micro-fin tube are developed.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.183-189
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• 2004

The flow and the heat transfer about the cross-flow fin-tube heat exchanger in an out-door unit of a heat pump system has been numerically Investigated. Using the general purpose analysis code, FLUENT, the Navier-Stokes equations and the energy equation are solved for the three dimensional computation domain that encompasses multiple rows of the fin-tube. The temperature on the fin and tube surface is assumed constant but compensated later through the fin efficiency when predicting the heat-transfer rate. The contact resistance is also taken into consideration. The flow and temperature fields for a wide range of inlet velocity and fin-tube arrangements are examined and the results are presented in the paper. The details of the flow are very well captured and the heat transfer rate for a range of inlet velocity is in excellent agreement with the measured data. The flow solution provides the effective permeability and the inertial resistance factor of the heat exchanger if the exchanger were to be approximated by the porous medium. This information is essential in carrying out the global flow field calculation which, in turn, provides the inlet velocity lot the microscopic temperature-field calculation of the heat exchanger unit.

• 설비공학논문집
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• 제16권4호
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• pp.355-367
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• 2004

The heat transfer and friction characteristics of the heat exchangers having sinusoidal wave fins were experimentally investigated. Twenty-nine samples having different waffle heights (1.5 mm and 2.0 m), fin pitches (1.3mm to 1.7mm) and tube rows (one to three) were tested. Focus was given to the effect of the waffle configuration (herringbone or sinusoidal) on the heat transfer and friction characteristics. Results show that the sinusoidal wave geometry provides higher heat transfer coefficients and friction factors than the herringbone wave geometry, and the difference increases as the number of row increases. The i/f ratios of the herringbone wave geometry, however, are larger than those of the sinusoidal wave geometry. Compared to the herringbone wave geometry, the sinusoidal wave geometry yielded a weak row effect, which suggests a superior heat transfer performance at the fully developed flow region. Possible explanation is provided considering the flow characteristics in wavy channels. Within the present geometric range, the effect of the waffle height on the heat transfer coefficient was not prominent. The effect of the fin pitch was also negligible. Existing correlations highly overpredicted both the heat transfer coefficients and friction factors. A new correlation was developed using the present data.

• Journal of Advanced Marine Engineering and Technology
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• 제32권1호
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• pp.73-81
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• 2008

Intercooling and aftercooling are required in order to operate air compressor, these are conducted through air-cooled or water-cooled heat exchangers. This study aims to find more suitable type of heat exchanger as a water-cooled intercooler of air compressor. Comparative performance evaluation among fin-tube heat exchanger and shell-and-tube (S&T) heat exchanger having various tubes such as circular tube, spiral tube, and internally finned tube was conducted. Thermal-hydraulic performance of each heat exchanger type is evaluated in terms of temperature drop and pressure drop. The comparisons show that shell-and-tube heat exchangers may have similar and larger heat transfer capacity to the fin-tube heat exchanger if tube diameter is reduced and multiple pass is adopted. For these cases, however, compressed air pressure drop in shell-and-tube heat exchanger become much larger than that in fin-tube heat exchanger.

• 설비공학논문집
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• 제15권12호
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• pp.1007-1017
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• 2003

An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry and wet surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of friction f-factor and Colburn j -factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of 150∼250 kg/$m^2$s with air flows at velocity ranges from 0.3 m/s to 0.8 m/s.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.9-16
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• 2007

This study aims to suggest an evaluation method of thermal environment using CFD, not an experiment, which is usual in the field. Model train is the newly introduced Mugunghwa train. Since its compartment occupies a large space and chairs and other accessories make it a complicated structure, 3-D calculation might take too much time and effort to make evaluation itself possible. Therefore, we suggest a 2-D model to replace the original 3-D model for averaged temperature and temperature distribution in the cabin.