• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.553-556
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• 2009

항공기 부품은 다양한 고도의 운용조건을 만족해야 하므로 고고도 성능평가는 필수적이다. 본 연구에서는 가스터빈 엔진의 고공 점화특성을 확인하기 위하여 실물형 보조동력장치를 바탕으로 축소형 모델 연소기를 설계, 제작하여 22,000ft에 해당하는 대기온도 조건을 모사, 점화실험을 수행하였다. 저온 환경 모사를 위해 공기 공급배관에 열교환기를 설치하였고 냉각제로는 드라이아이스를 사용하였다. 실험결과 연소기로 공급되는 공기의 온도가 낮아질수록 점화가 가능한 공기과잉 구간은 감소하였음을 확인하였다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1119-1122
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• 2009

The use of cooling towers in the air conditioning systems of buildings is increasing. In closed wet cooling towers, the heat transfer between the air and surface tubes can be composed of the sensible heat transfer and the latent heat transfer. The latent heat transfer is affected by the air and spray water. This study provides a designing methodology of heat exchanger for closed wet cooling tower. The correlation equation was derived to interpret the mass transfer coefficient based on the analogy of the heat and mass transfer and the experimental results. The results from this correlation equation showed fairly good agreement with experimental data.

• 한국수소및신에너지학회논문집
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• 제25권2호
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• pp.183-190
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• 2014

Our lab designs a heat exchangers for air and carbondioxide gas. Coolant is water, thus it is very difficult to determine heat transfer parameters in this gas-liquid system. Repeated experiments gives overdesign value 35%, overall heat transfer coefficient $33.8(kcal/m2-hr-^{\circ}C)$ for carbondioxide. Another series of experiments determine overdesign 18.7%, overall heat transfer coefficient $21.4(kcal/m2-hr-^{\circ}C)$ for Air. These parameters are in same range of literature. Overdesign is increasing as tube length increases, also increases as wall thickness of heat exchanger increases. To get proper fluid linear velocity in heat exchanger, we change the diameter of tube and finally we can have optimum fluid linear velocity in the heat exchanger.

• 한국지열·수열에너지학회논문집
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• 제12권4호
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• pp.1-7
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• 2016

This paper presents a design method for the horizontal straight ground heat exchanger (GHE) based on the Kavanaugh design method. In order to examine suitability of the suggested design method, a horizontal line type GHE was installed in a steel box of which the size was $5m{\times}1m{\times}1m$ filled with dried Joomunjin standard, and a thermal response test (TRT) was conducted for 21 hours. A numerical analysis was performed for a simulation of a peak month operation and for its verification by finite element method (FEM). According to the simulation results, it was concluded that the suggested design method for a horizontal straight GHE is reliable for the estimation of a design length.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.534-537
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• 2008

Growing attention has been given to sterilizing and antibacterial effects of nano-silver, recently. Nano-silver solution can be applied to the heat exchanger in an air conditioner to prevent bad smell or bacteria. The present study is directed at the nozzle spray characteristics over a heat exchanger. This problem is of particular interest in the design of a nano-silver HVAC system. The effects of nozzle position and flow rate on the spray area over a horizontal surface have been investigated for various nozzles. The results obtained indicate that spray area is increased as the height of spray position is increased or mass flow rate is increased. The wetted area over a practical heat exchanger is also studied at a given nozzle height. It is found that the wetted area is gradually increased with an increase in the flow rate. However, the effect of flow rate on the wetted area is a little affected by flow rate in the range of too much flow rate. It is also found that the wetted area is decreased as the inclination angle of a heat exchanger is increased.

• 대한기계학회논문집B
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• 제25권2호
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• pp.244-251
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• 2001

This paper describes a design study of heat exchanger assembly to be used for low NOx condensing gas boiler. In this study, specifications of each heat exchanger components(upper and lower fin-type HEX, coil-type HEX, baffle) were investigated experimently by using model apparatus and analytical model, and comprehensive performances of the pilot gas boiler were examined. As a result, the boiler efficiency for heating and hot-water reached 90% and 94%, respectively. NOx and CO emission are less than 50ppm and 200ppm (0$_2$0% basis), respectively, which are very improved results than those of conventional bunsen-type boiler. But it is considered that supplementary investigations necessary for CO emission improvement and optimum design with boiler capacity.

• 대한기계학회논문집B
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• 제31권4호
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• pp.367-375
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• 2007

The purpose of this study is to investigate the cooling performance of Heat Pipe Heat Exchanger(HPHE) for an electronic telecommunication system by adequate convection condition. Heat generation rates of electronic components, the temperature distributions of HPHE and surrounding air are analyzed experimentally and numerically. In order to perform the heat transfer analysis for the thermal design of telecommunication system, a program is developed. The program is useful to a user who is not familiar with an electronic telecommunication system. The simulation results showed that the HPHE were able to achieve a cooling capacity of up to 230W at the maximum temperature difference of $17.4^{\circ}C$. To verify the results from the numerical simulation, an experiment was conducted under the same condition as the numerical simulation, and their results were compared.

• 대한기계학회논문집
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• 제19권10호
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• pp.2657-2666
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• 1995

In this study, the effects of design factors of finned-tube heat exchanger, such as fin spacing and fin array on the frost growth and heat exchanger performance are investigated under a frosting condition. The results show that the amount of frost, frost density and blockage ratio of air flow passage increase with decreasing fin spacing. Heat transfer rate increases momentarily at the initial stage of frosting and then decreases. After that heat transfer rate continues to increase again to reach a maximum value and then decreases dramatically. It is shown that the time required for heat transfer rate to reach a maximum value becomes shorter with decreasing fin spacing, and after a maximum value, heat transfer rate decreases very fast. The maximum allowable blockage ratio is introduced to determine the operation limit of a finned-tube heat exchanger operating under frosting condition and is obtained as a function of fin spacing. It is also shown that heat transfer rate of heat exchanger with staggered fin array increases about 17% and the amount of pressure drop of air increases about 1~2 mmH$_{2}$O, compared with those of in-line type heat exchanger under frosting condition.

• 한국자동차공학회논문집
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• 제15권3호
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• pp.10-17
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• 2007

Design of experiments (DOE) technique has been used to design an exhaust heat exchanger to reduce the exhaust gas temperature under high load conditions in a spark-ignition engine. The DOE evaluates the influence and the interaction of a selected eight design parameters of the heat exchanger affecting the cooling performance of the exhaust gas through a limited number of experiments. The heat exchanger was installed between the exhaust manifold and the inlet of the close-coupled catalytic converter (CCC) to reduce thermal aging. To maximize the heat transfer between exhaust gas and coolant, fins were implemented at the inner surface of the heat exchanger. The design parameters consist of the fin geometry (length, thickness, arrangement, and number of fin), coolant direction, heat exchanger wall thickness, and the length of the heat exchanger. The acceptable range of each design parameter is discussed by analyzing the DOE results.

• 한국지열·수열에너지학회논문집
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• 제8권1호
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• pp.21-31
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• 2012

This paper reviewed and evaluated some of the commonly used prediction models for thermal conductivity of soils with the experimental data. Semi-theoretical models for two-component materials were found inappropriate to estimate the thermal conductivity of dry state soils. It came out that the model developed by Cote and Konrad gave the best overall prediction results for unsaturated soils available in the literature. However, it still needs to be improved to cover a wider range of soil types and degrees of saturation. In the present study, parametric analysis is also conducted to investigate the effect of soil type and moisture content on the horizontal ground heat exchanger design. The analysis shows that horizontal ground heat exchanger pipe length is reduced with the increase of soil thermal conductivity and water content. The calculation results also show that horizontal ground heat exchanger size can be reduced to a certain extent by using backfilling material with a higher thermal conductivity of solid particles.