• 설비공학논문집
• /
• 제23권4호
• /
• pp.243-250
• /
• 2011

In order to investigate the effects of PAG oil concentration on heat transfer performance and pressure drop during gas cooling process of $CO_2$, the experiments on fin-tube heat exchanger of $CO_2$ heat pump were performed. The experimental apparatus consists of a gas cooler, a heater, a chiller, a mass flow meter, a pump and measurement system. Experiments were conducted in various experimental conditions, which were inlet temperature($110^{\circ}C$), mass flow rates (50, 55, 60, 65, 70 g/s) and PAG oil concentration(0 to 2.6 wt%). Heat transfer rate decreased with the increase of the oil concentration and the decrease of inlet pressure. And pressure drop increased with the increase of the oil concentration and mass flow rate of refrigerant. The COP reduction by deterioration of gas cooler performance with oil concentration was analyzed. When inlet pressure of gas cooler is 100 bar, the COP reduction was estimated by 6% under 1 wt% of oil concentration.

• 대한기계학회논문집
• /
• 제9권6호
• /
• pp.750-756
• /
• 1985

본 연구에서는 종횡비 0.1이고 상.하 수평경계면이 단열된 직각밀폐용기내에 서 Pr수가 1보다 큰 물(Pr=6.97, 20.deg. C) 및 실리콘 오일(Pr=1086.42, 20.deg. C)의 양단의 온도차에 의한 자연대류에서 아직 충분히 연구되지 않은 코어형상에 주안점을 두고 실 험적으로 관찰, 조사하였으며 그 결과를 Lee의 이론적인 예측과도 비교, 검토해 보았 다.

• 해양환경안전학회지
• /
• 제17권1호
• /
• pp.29-37
• /
• 2011

유속의 변화에 따른 오일펜스 만곡부 후면의 속도장과 압력장, 와도 및 난류 강도를 계측한 PIV 실험의 결과 유속이 증가함에 따라 유동 경계역의 후면부에서의 흐름 방향이 전면부의 흐름 방향에 가까워지는 현상이 나타났고, 압력 분포의 양상이 달라졌으며 난류도 더욱 불규칙적인 형태로 나타났다. PIV 실험과 동일 조건으로 수행한 CFD 해석 결과, 후류의 유동 패턴이 0.3m/s이하의 저속인 경우는 PIV 실험 결과와 유사하게 나타났으나, 유속이 0.4m/s일 때는 오일펜스 자체의 유연성으로 인해 다소 차이가 나타났고, 오일펜스 하단의 압력차로 인한 불규칙한 난류가 수면까지 영향을 주었다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제10권4호
• /
• pp.67-77
• /
• 1986

The information on the heat transfer characteristics, flow pattern and pressure drop, are very important for the desing of general heat exchanger, refrigerating system, air conditioning system and energy recovery system. In these systems, water or lubricating oil contained in working fluid affects greatly the flow and heat transfer condition and this phenomena must be considered in the practical design. An experiment has been performed for studying the flow and heat transfer characteristics of the forced convective horizontal flow of R-113 under the range of the liquid single phase state to the boiling flow state. Basic experimental results are obtained in the case that water or lubricating oil does not contaminate in the test fluid. Experimental results are as follows; (1) The local heat transfer coefficients in the nucleate boiling region and transition boiling region are almostly ten times as large as that of liquid single phase flow. (2) The measured heat transfer coefficient in the present experimental range is relatively agreed well with the predicted value from the various experimental results for the boiling flow.

• 설비공학논문집
• /
• 제8권1호
• /
• pp.45-54
• /
• 1996

An experimental investigation on the two-phase flow through tube orifices was performed with the refrigerant mixture of R32/125/134a(30/10/60). A series of tests were conducted to generate wide range of data at varying operation conditions with four short tubes. The tests include both single and two-phase flow conditions at the inlet of the short tube with different oil concentrations. Experimental data were presented as a function of major operating parameters and short tube diameter. Based on test results and data analysis, a semi-empirical flow model was developed to predict the mass flow rate through short tube orifices with a given set of conditions. The flow model was formed to cover both single and two-phase flow at the inlet of short tube with considering the effects of oil concentration.

• Food Science and Biotechnology
• /
• 제17권3호
• /
• pp.470-474
• /
• 2008

The whole berry, pulp, and seed of sea buckthorn fruit were extracted with supercritical $CO_2$ to produce edible oils. The effects of extraction pressure, temperature, and $CO_2$ flow rate on the oil yield and extraction rate were investigated, and the fatty acid composition, tocopherol, and carotenoid contents of the oils were compared. The results showed that the extraction rate was affected by pressure, temperature, and $CO_2$ flow rate and, in general, the yield increased with a rise in any of the 3 variables. Fatty acids in the whole berry and pulp oil were dominated by monounsaturated fatty acids (>64%), followed by saturated fatty acids (about 30%). In contrast, fatty acids in the seed oil consisted mainly of polyunsaturated (>60%) and monounsaturated fatty acids (>24%). The seed oil had a slightly higher content of tocopherols, but a much lower content of carotenoids, compared with the whole berry or pulp oil.

• Tribology and Lubricants
• /
• 제12권4호
• /
• pp.28-34
• /
• 1996

The lubrication characteristics of high-speed ball bearings have been investigated empirically using 45mm bore split inner ring ball bearings employed in small industrial gas turbine engines with oil-jet lubrication method. For the close structural simulation, experiments carried out with bearing mounting supports of real engines, such as bearing housings and oil nozzle assemblies with squeeze film dampers. Thus the results of tests can be directly applied to the design and the development of gas turbine engines. Testing was done by varying operating speeds, axial load on bearings, and lubricant flow rates. During testing, the temperature of bearing at outer-ring face, the power consumption of the driving motor, and the rotating resistance of the bearing were measured. From this study, the representative factors for lubrication characteristics at high speed was found, and the most important one was not operating speed but axial load up to 1.95 million dmN speed and 2969 N axial load. Furthermore, the detailed variation of the rotational resistance of the bearing could be visualized by measuring the change of the radial load under the bearing supports. The rotational resistance consists of the frictional resistance and the bearing-cavity oil resistance.

• 자원환경지질
• /
• 제44권2호
• /
• pp.153-159
• /
• 2011

본 연구에서는 포괄적 역학모델을 이용하여 석유 생산 시스템의 파이프 내 가스-오일 2상유동에 대한 유동패턴을 결정하였다. 2상의 유체는 운영 인자, 기하학적 변수, 유체 물성 등에 따라 특정의 유동패턴을 나타냈다. 광범위한 기액 겉보기 속도에 대하여 시스템의 인자들을 변화시키면서 유동패턴을 비교하였다. 다양한 인자들 중 경사각과 겉보기 속도가 파이프 내 가스-오일 2상유동의 유용패턴을 결정하는데 가장 지배적인 인자로 나타났다. 파이프 직경, 유체 물성 등의 인자들은 전이 경계선 부근을 제외하면 유동패턴 변화에 제한적인 영향 만을 미쳤다. 역학모델은 실험실 평가나 신뢰성있는 상관식 이용이 불가능할 때 유동패턴을 결정할 수 있는 유용한 도구이다.

• 한국자동차공학회논문집
• /
• 제12권3호
• /
• pp.37-43
• /
• 2004

Engine lubrication system is generally affected by vehicle driving conditions; acceleration, braking deceleration, and cornering. The oil supply system such as oil pan, baffle plate, and oil pick-up pipe should be optimized to cope with severe driving conditions. The main purpose of this paper is to understand the effect of the engine tilting angle on the oil supply system using engine tilting test rig. For the purpose, the oil pressure fluctuation and oil aeration in the main gallery are measured at various engine tilting angles. In addition, the oil flow is visualized by using transparent oil pan to investigate the cause of the formation of oil aeration. The test results show there is a strong correlation between the main gallery oil pressure fluctuation and oil aeration. It is also found that the visualization technique is helpful to stabilize the oil supply system at severe driving conditions.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.198-201
• /
• 2002

An internal finishing process by the application of magnetic abrasive machining has been developed as a new technology to obtain a fine inner surface of pipe. In this paper, a slurry circulation system was designed and manufactured. Its finishing characteristics was experimently investigated by various effective factors such as dry, water flow, oil flow with a slurry. From the experimental results, it was found that the materal removal and surface roughness were good in oil flow with slurry. The slurry circulation system is effective on the internal finishing of non-ferromagnetic pipe(SUS304).