• 설비공학논문집
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• 제8권1호
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• pp.140-150
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• 1996

CFC-12, which has been used most widely in automobile air conditioners and household refrigerators is scheduled to be phased out soon because of its high ozone depletion potential. Now HFC-134a is suggested as an alternative refrigerant for CFC-12. In this Study, we intended to investigate how PAG oil influence evaporation heat transfer and flow pattern, using R-134a and PAG oil influences evaporation heat transfer and flow pattern, using R-134a and PAG oil in the horizontal miro-fin evaporation tube. Experiments were conducted under the flowing est conditions : mass velocity 86-250kg/$m^2$s, heat flux 5-30 ㎾/$m^2$, oil concentration 0-21 wt.% and saturation temperature 5$^{\circ}C$. Local evaporation heat transfer coefficients were found to be higher at the top, side and bottom of the tube in this order. Average heat transfer coefficients turned out to increase with oil concentration increment up to 3 wt.% oil concentration, whereas heat transfer coefficients gradually decreased over 3 wt.% oil concentration, because of oil-rich liquid film was formed on the heat transfer surface. Flow patterns were rapidly transitioned to annular regimes up to 3 wt.% oil concentration. In case of pure refrigerant, measured heat transfer coefficients in the experiments were similar to those of Kandlikar＇s correlation.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.610-615
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• 2015

In order to study and obtain the mathematical relation between the electrification degree of transformer oil flow and the electrostatic current, a small amount of data about the electrification degree of oil flow and the corresponding electrostatic current is studied by linear regression method and grey model method. The results show that the linear correlation between the electrification degree and the electrostatic current was not good, and the relation between the electrification degree of oil flow and electrostatic current (i) could be expressed as ${\rho}(0)=0.2049\;i^{(0)}+169.4419$ according to grey model GM (0, 2) when the electrification degree of oil flow is represented by the charge number generated from transformer oil per unit volume, namely the charge density (${\rho}$).

• 한국전산유체공학회지
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• 제19권1호
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• pp.34-40
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• 2014

Conjugate heat transfer of an automotive oil cooler with offset-strip fins was numerically investigated to predict the performance of the oil cooler for various flow-rates. The simulations were conducted by directly modeling offset-strip fins with unstructured meshes. The incompressible Navier-Stokes equations coupled with energy equation were used for the present simulations. Heat transfer characteristics of the oil cooler was compared well with experimental results and the errors were approximately within 5 percents. It was found that the performance of the oil cooler increased as the flow-rate increased up to the flow-rate of 12 L/min, but the performance seemed to be saturated beyond a critical flow-rate, which was estimated as 15 L/min. Furthermore, it was confirmed that compared to the performance without fins, that of the oil cooler with offset-strip fins was increased by about 75 percents.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.195-199
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• 2005

As vehicles are recently becoming more important in our life, the study for engine capacity has been conducted for many years. Specially, the study on lubrication in the engine is needed to develop engine capacity. The role of lubrication is to reduce fraction, manage the temperature and protect from corrosion etc. At the view point of the engine, lubrication and cooling of the engine have an effect on the life and efficiency, so we have to study this problem. Ball check valve is located in the inlet of the Oil Jet. Ball check valve is used to control the flow rate of the engine oil, which cools and lubricates the engine. Flow rate at the oil jet is very important, so the study for this problem is needed to conduct researches. The point of this study is to compute the flow rate and the flow in oil jet. The results of this study is that the mass flow rate is satisfied with the research which is obtained at the experiment.

• 한국응용과학기술학회지
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• 제26권4호
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• pp.394-399
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• 2009

The esterification of palmitic acid in Jatropha Oil using 8wt% p-TSA catalyst was done at the 1:8 molar ratio of oil to methanol and $65^{\circ}C$. The conversion of palmitic acid appeared to be 95.3% in 60min. After that, the continuous transesterification of the oil using 0.5wt% KOH, 0.8wt% TMAH mixed catalyst[40vol% KOH(0.5wt%) + 60vol% TMAH(0.8wt%)] and 1.1wt% TMAH was conducted with the flow rates and the molar ratios at $65^{\circ}C$. The overall conversion of Jatropha Oil increased with the decrease of flow rate and showed 95.6% with 9ml/min of flow rate at the 1:8 molar ratio of oil to methanol and $65^{\circ}C$. But it showed 87% with 15ml/min of flow rate at the same conditions. The recovery of methanol(%) appeared to be 86% at the 1:8 molar ratio of oil to methanol, mixed catalyst and $65^{\circ}C$.

• Tribology and Lubricants
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• 제20권1호
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• pp.27-32
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• 2004

This paper presents unsteady oil flow behaviors in the engine lubrication network to clarify the differences between continuous and discontinuous oil supply crankshaft system. Using commercial network analysis program, Flowmaster2, engine lubrication network system analysis were carried out. And effects of crankshaft speed and supplied oil pressure on pressure fluctuation in oil groove and oil flow rate to each bearing were analyzed.

• International Journal of Fluid Machinery and Systems
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• 제8권1호
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• pp.46-54
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• 2015

Thrust-ring-pump is a kind of extreme-low specific speed centrifugal pump with special structure as numerous restrictions from thrust bearing and operation conditions of hydro-generator units. Because the oil circulatory and cooling system with thrust-ring-pump has a lot of advantages in maintenance and compactness in structure, it has widely been used in large and medium-sized hydro-generator units. Since the diameter and the speed of the thrust ring is limited by the generator set, the matching relationship between the flow passage inside the thrust ring (equivalent to impeller) and oil bath (equivalent to volute) has great influence on hydrodynamic performance of thrust-ring-pump. On another hand, the head and flow rate are varying with the operation conditions of hydro-generator units and the oil circulatory and cooling system. As so far, the empirical calculation method is employed during the actual engineering design, in order to guarantee the operating performance of the oil circulatory and cooling system with thrust-ring-pump at different conditions, a collaborative hydrodynamic design and optimization is purposed in this paper. Firstly, the head and flow rate at different conditions are decided by 1D flow numerical simulation of the oil circulatory and cooling system. Secondly, the flow passages of thrust-ring-pump are empirically designed under the restrictions of diameter and the speed of the thrust ring according to the head and flow rate from the simulation. Thirdly, the flow passage geometry matching optimization between thrust ring and oil bath is implemented by means of 3D flow simulation and performance prediction. Then, the pumps and the oil circulatory and cooling system are collaborative hydrodynamic optimized with predicted head-flow rate curve and the efficiency-flow rate curve of thrust-ring-pump. The presented methodology has been adopted by DFEM in design process of thrust-ring-pump and it shown can effectively improve the performance of whole system.

• 대한기계학회논문집B
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• 제32권9호
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• pp.712-719
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• 2008

Light Oil Flow Standard System(LOFSS), as a national oil flow standard system, in Korea Research Institute of Standards and Science(KRISS) was developed for oil flowmeter calibration, and the expanded uncertainty of flow quantity determination was estimated within 0.04 %. In order to improve the reliability of the LOFSS measurement, a proficiency test was carried out in the flow range of 20 and $240\;m^3/h$ (Reynolds number $20,000{\sim}900,000$). A turbine flowmeter was used as a transfer package in round robin test. The water flow standard system of KRISS, the pipe prover of the national calibration and test organization and the master meter calibrator of the turbine flowmeter supplier, which used the different working fluid respectively, were compared with the turbine flowmeter measurement. The maximum difference of measurement was 0.15 % between the LOFSS and the pipe prover. The En numbers of the each system measurement were evaluated at the same Reynolds number. It was found that the En numbers were less than 1 in the comparison, which means the procedures of the uncertainty estimation of the each calibrators were reasonable and reliable.

• Tribology and Lubricants
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• 제17권3호
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• pp.198-208
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• 2001

A Parametric study based on a computer analysis of the lubrication system of a four-cylinder gasoline engine is illustrated. Through the parametric study, the effects of various aeration levels on the change of oil flow rate and pressure are investigated. Also, at high oil temperature and low engine speed, the effect of oil aeration level on oil flow characteristics in lubrication system is investigated. The illustrated results may give to designers the guide lines of oil aeration level for the safe design of engine lubrication systems in terms of minimum pressure at crank oil bore.

• 한국산학기술학회논문지
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• 제16권3호
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• pp.1664-1670
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• 2015

저널 베어링은 샤프트와 베어링이 윤활유를 사이에 두고 서로 미끄러지는 유체윤활 상태에서 운동하고 있으며, 넓은 마찰 면에 하중을 분산하여 받기 때문에 큰 힘을 받을 수 있다. 저널 베어링이 유체 윤활 상태에서 원활한 동작으로 운전되기 위해서는 저널 베어링의 표면에 오일 구멍이나 오일 홈을 더하여 베어링 틈새로 충분한 윤활유가 공급되어야 한다. 이러한 급유 홈의 형상이나 크기 및 급유 위치에 따라 베어링의 성능이 달라진다. 따라서 본 연구에서는 여러 급유 조건 중 저널 베어링의 오일 홈의 형상(삼각형, 사각형, 반원형)에 따른 유량을 측정하여, 어느 형상에서 가장 많은 유량을 토출하는지 알아봄으로써, 저널 베어링을 설계하는데 최적의 성능을 나타내는 홈의 형태를 파악하고자 하였다. 온도가 낮을수록 유량이 많으며, 회전수가 높아질수록 온도의 영향이 작아지고, 삼각형의 오일 홈일 때 유량이 가장 많은 것으로 나타났다.