• 한국지열·수열에너지학회논문집
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• 제8권2호
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• pp.48-54
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• 2012

To analyze the cooling performance of fin-tube evaporator in the refrigerator truck using R744 according to frost growth, the analytical model of evaporator was developed under frost and non-frost conditions. The performance of fin-tube evaporator was investigated with frost thickness and indoor temperature. Besides, the performance of evaporator under frost condition was compared to that under non-frost condition. As a result, area of air passage and system performance were decreased as the frost thickness increased. The cooling capacity was reduced by 10%, 20%, 30% when the frost thickness was 0.7 mm, 1.1 mm, and 1.6 mm respectively. At these conditions, the block ratio was 31%, 48%, and 71%. In addition, the outlet quality of refrigerant was not over 1 when the frost thickness was 1.6 mm in spite of high indoor air temperature.

• 한국태양에너지학회 논문집
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• 제22권1호
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• pp.23-30
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• 2002

본 연구는 축방향 내부 핀을 가진 열사이폰의 작동유체의 체적변화에 대한 응축 및 비등열전달 성능에 관한 연구이다. 열사이폰 내부의 작동유체는 증류수를 사용하였다. 열사이폰의 총체적에 대한 작동유체의 양을 변화시키면서 실험데이터를 산출하였다. 열사이폰의 응축부에 대한 열유속과 응축열전달계수를 구하였으며, 실험결과를 이론모델과 비교분석하였다. 실험결과로부터 열사이폰의 열전달 성능은 작동유체의 체적변화에 크게 의존하였다. 축방향내부 핀을 가진 열사이폰의 열전달 성능은 평튜브로 제작한 열 사이폰보다 크게 향상되었다. 이와 같은 열사이폰을 태양열 분야의 열교환기에 응용할 경우, 고성능화와 소형화할 수 있다. 그리고 산업현장에서 실제적으로 적용하기 위해 총열전달계수를 산출하였다.

• 한국태양에너지학회 논문집
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• 제36권3호
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• pp.53-61
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• 2016

Solar assisted heat pump system uses solar thermal energy as a heat source of evaporator of heat pump. So, COP can be enhanced as well as collector efficiency. For improving performance of this system, some research about hybrid solar collector that has fin-and-tube heat exchanger has been conducted. This collector can get a thermal energy from ambient air for liquid heating, so heated liquid can be used as a heat source of evaporator in heat pump even the solar radiation is not enough. In this study, numerical analysis was conducted for confirming heat gain of liquid according to fin height and pitch of fin-and-tube heat exchanger in collector. As a result, higher heat gain was obtained on lower fin height and narrow fin pitch, but the pressure drop also increased with increment of heat gain. Thus the JF factor considering both heat transfer enhancement and pressure drop was investigated and the maximum value was shown when the fin height and pitch were 40mm and 45mm. So it is considered that this installation condition has a highest heat transfer improvement when comparing with pressure drop. However heat gain of liquid at this condition was less than the other installation conditions of fin pitch on same height. Then, after establishing a proper minimum heat gain of liquid, actual production and experiment of collector will be conducted with fin height and pitch showing maximum JF factor and satisfying selected minimum heat gain of liquid on the basis of results of this study.

• 한국공작기계학회논문집
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• 제13권4호
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• pp.100-105
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• 2004

Fin-tube type(Fin-type) heat exchanger has been tested in order to replace the heat exchanger of parallel flow type(P.F -type) which is now widly used in automobile air conditioning system The following conclusions are drawn by the comparison of the characteristics of the heat exchangers. Evaporator and condenser capacities and COP(Coefficience of performance) were varied as with the compressor speed, outdoor air temperature and air flow rate changed, which much influenced on the characteristics of the air conditioning system Evaporator and condenser capacities were increased with increasing compressor speed and outdoor air temperature. Evaporator and condenser pressures of Fin-type were decreased by 7% and 5% respectively compared with those of P.F-type. The COP of Fin-type was decreased with increasing outdoor air temperature and compressor speed. The COP of P.F-type was decreased by 14% compared with that of Fin-type.

• 설비공학논문집
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• 제29권11호
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• pp.570-579
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• 2017

In this study, we examined the multi-stage piston-type air compressors typically used in a railroad vehicle, and the heat transfer efficiency was analyzed according to the design conditions of the heat exchanger (a compressor component module for cooling the compressed high temperature air). For the fin-tube heat exchanger used in the most air compressors, numerical analysis was performed to analyze heat transfer by defining the various rectangle tube sizes and the number of fin-per-unit area as design variables under the same flow rate of compressed air. Also, this analysis compared the temperature of the compressed air. Regarding environmental conditions for analysis, the flow rate of the external cooling air was measured and the mean value of the values was applied. And a "turbulence model" was considered in both the external flow of the cooling air and the internal flow inside the tube. From the results of analysis, it was found that the change of the aspect ratio value of the tube greatly influences the heat transfer efficiency of the compressed air, and influences if the fin density is relatively small. As a result, the optimum design specifications of the heat exchanger for air compressors were confirmed based on the analysis of the heat transfer efficiency, according to the design conditions of fin and tube by the operating temperature range of the compressed air.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1025-1030
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• 2008

We develop heat exchanger modules for a multi-burner boiler. The heat exchanger module is kind of a heat recovery steam generator (HRSG). This heat recovery system has 4 heat exchanger modules. The 1st module consists of 27 bare tubes due to high temperature exhaust gas and the others consist of 27 finned tubes. The maximum steam pressure of each module is 10 bar and tested steam pressure is 4 bar. In order to test these heat exchanger modules, we make a 0.5t/h flue tube boiler (LNG, $40\;Nm^3/h$). The test results of 100% boiler load show that heat transfer rate of 1st module is 49.7 Mcal/h which is 34% of total heat transfer rate and that of 2nd module is 82.6 Mcal/h which is 57% of total heat transfer rate. The reason of higher the heat transfer rate of 2nd module than that of 1st module is that the 2nd heat exchanger module has finned tubes instead of bare tube. The boiler load 50% results show that only 2 heat exchanger modules are needed to extract the heat from the flue gas to water. From this result, it is very important of optimum design of the first finned tube among all water tubes.

• 한국산학기술학회논문지
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• 제14권3호
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• pp.1003-1010
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• 2013

본 연구에서는 식료품의 진열과 보관에 사용되며 전시효과가 우수한 냉기 강제순환식 쇼케이스의 성능을 예측하는 프로그램을 개발하였다. 압축기의 성능해석에는 제조사에서 제공한 성능선도를 사용하였고 모세관 내 압력손실은 균질유동 모델을 사용하여 계산하였다. 증발기와 응축기는 미소체적으로 구분하여 에너지 균형을 고려하였고 관내측과 공기측 열전달계수는 적절한 상관식으로부터 구하였다. 압축기로 3/4 마력급 왕복동식 2개를 사용하고, 팽창장치로는 내경 1.6 mm의 모세관을, 응축기와 증발기로는 상호 공유형태의 핀-튜브 열교환기를 적용한 쇼케이스 시제품에 대해 성능시험을 수행하고 시험결과와 비교했을 때, 본 프로그램은 시제품의 증발 온도와 응축 온도를 적절히 예측함을 확인하였다.