• 설비공학논문집
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• 제15권11호
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• pp.957-963
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• 2003

The present work was conducted to investigate the air-side thermal-hydraulic performance of the brazing fin-tube heat exchanger. Pressure drop and heat transfer coefficient for a plain and a louvered fin configuration were compared numerically and experimentally. It was found that the heat transfer characteristics for the plain fin were similar to the developing flow in the rectangular channel. The louver fin showed about twice better heat transfer coefficient than the plain fin. Previous empirical correlations presented by Davenport, Sunden and Svantesson, Sahnoun and Webb, Chang and Wang, Achaichia and Cowell, and Kang were compared with the present experimental data.

• 한국정밀공학회지
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• 제12권11호
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• pp.125-131
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• 1995

Pneumatic System has been mainly used as main equipment for actuation and control of fluid force in manufacturing industry. For velocity control of piston, meter-out restriction method is used in many cases. In this systems, meter-out restriction method is adopted for analysing the Dynamic Charging and Discharging Process which is Variable Volume Chamber. Experiments has been conducted for different supply pressure condition. As a experimental result, charge side chamber pressure rises to supply pressure rapidily and discharge side chamber pressure decreases. Also, when the air in the cylinder is discharged, tempdrature of air decreases steeply. Restriction of the Cylinder sometimes freeze and it dose not function. The result will be useful for the analysis of pneumatic system.

• 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.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.306-310
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• 2005

The air-side particulate fouling in the heat exchangers of HVAC applications degrades the performance of cooling capacity, pressure drop across a heat exchanger, and indoor air quality. Indoor and outdoor air contaminants foul heat exchangers. An empirical modeling equation is derived from the experimental results using accelerated tests and it shows good predictions of the fouling characteristics of the slitted finned tube heat exchangers. However the modeling equation predicts only the fouling characteristics of new heat exchangers and it can not predicts fouling characteristics obtained from actual field data. The purpose of this study is to modify the previous modeling equation using the actual field data Therefore an modified modeling equation is proposed and it shows good predictions of the actual fouling characteristics of finned-tube heat exchangers.

• 설비공학논문집
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• 제15권10호
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• pp.802-808
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• 2003

The air-side particulate fouling of the HVAC heat exchangers degrades the performance of cooling capacity, pressure drop across a heat exchanger, and indoor air quality. The purpose of this study is to investigate the fouling characteristics using accelerated particle loading system. The fouling characteristics are analyzed as functions of a dust concentration, a face velocity and a wet or dry surface condition. The pressure drop increases with increasing test operation and reaches constant asymptotic level. For the saturated condition due to particle loading, the pressure drop across the slitted finned-tube heat exchangers at the face velocity of 1 m/sec increases up to 57% and the cooling capacity decreases about 2%. The cooling capacities are not affected greatly by the presence of the fouling deposits if the thickness of the fouling deposits can not change substantially the flow pattern through the fins.

• 대한설비공학회지:설비저널
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• 제10권4호
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• pp.304-315
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• 1981

This paper presents, the result of the study for the fluctuant temperature of the out-side air adopting the heat pump system in seoul, Taejean, Taegu, Busan and Jejeu among principle cities in korea for the purpose of checking the heating capacity, Heat pump capacity (outlet capacity), Coefficient of performance and running cost in comparison with the supporting the energy for the boiler's operation. According to the supply temperature changes of the out door coil by the out side air-return air mixing ratio, the Coefficient of performance is increased from 3. 1 to 5.0. Particularly, in Taegu, it is necessary to adopt the heat pump system against the supplement heat supply on the full outside air intake in January of the heating period, and it was recognized that the running cost is cheaper than that of the Boiler use. At the same time, if it is able to get $25\%$ of return air of the inside in the Seoul, it could be saved its costs when we use the supplementary boiler. And I think it is necessary to the development.

• 한국축산시설환경학회지
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• 제7권3호
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• pp.147-154
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• 2001

가축의 행동에 대한 관심이 치근 고조되고 있으며, 향후에는 가축복지법의 규제도 받게 될 실정인데 비하여 우리 나라는 아직 동물과 환경과의 관계에 대한 연구가 미진한 실정이다. 돈사의 구조적 특성은 돼지에게 여러 가지 측면에서 영향을 미쳐 생산성을 좌우하게 될 뿐만 아니라 동물복지 차원에서도 연구가 진행되어야 할 시점이다. 따라서 본 실험은 무창 육성·비육돈사에서 계절별 환기시스템에 따른 휴식공간을 파악하고자 하였으며, 또한 측벽밀폐 비율이 돼지의 배분 습성에 미치는 영향을 조사하고자 하였다. 1. 돈방 측벽밀폐율을 50%, 75%, 100% 세수준으로 하였을 때 돼지의 배분습성은 온도, 습도, 공기유속과 상관없이 일정한 지역에 배분하는 행동을 보였다. 따라서 돼지는 돈방내의 어두운 지점에서 배분하는 것으로 관찰되어 무엇보다도 조명의 영향을 받는 것으로 나타났다. 2. 측벽 밀폐율에 따른 분뇨의 배분집적 높이는 50% 일 때 10cm, 75%는 5cm 그리고 100%일 때는 3 cm가 직접 되었으며, 폭은 각각 30 cm, 25 cm, 20 cm로 나타났다. 3. 돈방의 휴식공간에서의 암모니아 농도는 각 돈방 측벽의 배분율이 50%일 때 $4.2mg/{\ell}$, 75%는 $5.1mg/{\ell}$ 그리고 100%일 때 $5.8mg/{\ell}$그리고 100% 일 때 $5.8mg/{\ell}$으로 측정되어 돈방바닥면에 분뇨가 넓게 분포되는 100%일 때 암모니아의 농도가 가장 높았다. 이것을 배분습관과 연관되어 돈방내의 어두운 부분을 최소한 줄일 경우 휴식공간에서의 암모니아 농도는 줄일 수 있는 것으로 판단되었다. 4. 요인중 돼지의 휴식공간의 위치 영향에서 환경변인은 무엇보다도 공기유속인 등 하다. 겨울철에는 0.03 m/g 지점에서 휴식을 하였으며, 여름철에는 0.24 m/g 지점에서 휴식을 취하였다. 따라서 돼지의 휴식공간은 공기의 유속에 의한 영향이 매우 큰 것으로 관찰되었다.

• 한국항공우주학회지
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• 제49권2호
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• pp.95-106
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• 2021

측방제트는 조종면에 비해 즉각적인 유도무기 기동이 가능하지만 자유류를 간섭하여 공력계수에 영향을 줄 수 있다. 공력계수에 대한 측방제트의 영향을 파악하기 위해 측방제트를 공기로 모사한 후 측방제트 유무에 따른 공력계수 차이를 다충실도 모형을 사용하여 살펴본다. 측방제트 유무에 따라 공력계수 예측 모형으로 추정된 공력계수 간 차이를 계산하여 측방제트의 영향을 마하수, 뱅크각, 받음각의 변화에 따라 조사한다. 분석 결과, 종방향 힘 및 모멘트 계수는 비대칭적으로 발달한 측방제트에 큰 영향을 받았으며, 횡방향 힘 및 모멘트 계수는 -30°와 +30° 사이 뱅크각에서 최대로 변동하였다. 이에 반해 축방향 힘 계수는 측방제트에 영향을 받지 않았으며, 축방향 모멘트 계수는 마하수 변화에 대한 표본 부족으로 측방제트의 영향을 판단하기 어려웠다. 종합하면 측방제트가 종방향 및 횡방향 공력계수에 주요한 영향을 주어 유도무기 자세 변화를 일으킨다는 것을 확인하였다.

• 대한설비공학회지:설비저널
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• 제25권2호
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• pp.161-173
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• 1996

• 설비공학논문집
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• 제1권1호
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• pp.82-86
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• 1989

A study has been conducted experimentally on heat transfer characteristics of the heat exchangers with louvered fins in air. The experimental results are as follows; 1. Mean heat transfer coefficient is decreased with increasing temperature difference and model III is the best at constant temperature difference. 2. Pressure drop is increased with increasing air velocity, but it is decreased as the heat transfer area increases. 3. $\bar{h}/^{\Delta}p$ is increased and then decreased as air velocity increases.