• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.53-56
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• 2008

An ejector is a fluid machinery to be utilized for mixing fluids, maintaining vacuum, and transporting them. The Ejector is applied for a variety of industrial fields such as refrigerators and power plants. It is adopted to recycle anode off gas safely in 5kW Molten Carbonate Fuel Cell system of KEPRI(Korea Electric Power Research Institute). The ejector is placed at mixing point between the anode off gas and the cathode off gas or the fresh air. In this study, the entrainment ratio is measured according to the diametrical ratio of nozzle to throat. In addition, the performance curve of the ejector and the differential pressure in diffuser is observed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.700-705
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• 2003

The general cooling tower is a device for making a cooling water in refrigerant condensers or industrial process heat exchangers. The present cooling tower have defects with noises, complicated structure and environmental problems. In this paper, we constituted a new water cooling system by using a evaporating latent heat in an enclosed tank, and this system is consisted of an enclosed vacuum tank and water driving ejector system. Several experimental cases were carried out for improvement methods of high vacuum pressure and water cooling characteristics. The ejector performance was tested in case of water temperature variations that flows in the ejector. Based on the vacuum pressure by water driving ejector, the water cooling characteristics were investigated for the vaporized air condensing effects.

• 설비공학논문집
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• 제27권7호
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• pp.362-368
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• 2015

This paper presents a numerical study on the performance of a vapor compression cycle equipped with an ejector as an expansion device to improve the COP by reducing the expansion loss and compressor work. The simulation is carried out using a model based on the conservation of mass, energy and momentum in the ejector. From the results of the simulation, the vapor compression cycle equipped with an ejector showed a maximum COP improvement of 14.0% when using R134a refrigerant and 16.8% when using R1234yf. In addition, the performance of the system with an ejector represents the increased performance as the temperature difference between condensing and evaporating increased.

• 설비공학논문집
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• 제12권4호
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• pp.345-353
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• 2000

In this study, the performance of five ejectors has been investigated with working fluids of water and water vapor. The diameters of nozzle and mixing tube of five ejectors were 1 and 1.5(ejector A), 1 and 2(ejector B), 1 and 2.5(ejector C), 1 and 3(ejector D), 2 and 4(ejector E) in millimeters. The length of the mixing tube was 8-10 times of its diameter. For each ejector, the ratio of mass flow rate of ejected water to that of entrained water vapor, $\mu$, was evaluated in terms of evaporator pressure, mass flow rate of ejected water, and water temperature. It was found that the performance of an ejector was not stable when the ratio of diameters was too small or too large(ejector A and D) and $\mu$ was almost the same for two ejectors with the same diameter ratio(ejector B and E). It was also found that $\mu$ increased almost linearly with an increase of evaporator pressure and the ratio $\mu$ increased as water temperature decreased. As expected, $\mu$ converged to zero as the water temperature approached the evaporator temperature. Finally, a non-dimensional correlation has been developed to predict$\mu$ terms of evaporator pressure and saturation pressure of ejected water.

• Journal of Advanced Marine Engineering and Technology
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• 제18권1호
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• pp.51-59
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• 1994

The gas jet pumps serve to preduce a vacuum or can be used as gas jet compressors. These are operated on the same principle as a steam jet vacuum pump : in the driving nozzle the pressure energy of the motive medium is converted into the kinetic energy. In the diffuser the driving jet mixes with the suction medium and the kinetic energy is reconverted into the pressure enegy. The application fields of gas jet ejectors are the evacuation of siphoning installations, the elevation of liquids, the production of vacuum filters, the vacuum supporting airlift system, the evacuation of the suction line of centrifugal pumps and the ventilation of the dangerous gases to the atmosphere. The performance of gas jet ejector is influenced strongly to velocity coefficient of motive nozzle, the distance between the motive outlet to the diffuser inlet and the dimensions of diffuser. This study is performed for the computer aided design of gas jet ejectors in future. Through the present experiments, it is known that the velocity coefficient of the motive air nozzle ranges from 0.91 to 0.95 and the maximum efficiency of gas jet ejector is 24.6%.

• 한국추진공학회지
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• 제5권3호
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• pp.33-40
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• 2001

본 연구에서는 초음속 증기 이젝터의 작동특성을 조사하기 위하여 압축성 축대칭 Navier-Stokes 방정식의 수치계산을 행하였다. 2차 유동측의 압력 및 배압을 변화시켜 이들 압력이 혼입유량에 미치는 영향을 조사하였다. 연구의 결과로부터 초음속 증기 이젝터에서 2차 유동측 압력 및 배압은 임계 혼입유량에 상당한 영향을 미치며, 1차구동노즐의 형상과 2차유동의 압력이 주어지는 경우 임계혼입 유량비를 예측할 수 있음을 알았다. 수치계산 결과는 실험에서 얻은 임계혼입유량비를 잘 예측하였다.

• 한국추진공학회지
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• 제9권2호
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• pp.70-77
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• 2005

축소-팽창 디퓨저가 장착된 초음속 이젝터를 제작하여, 다양한 위치에서의 측정된 압력으로 부유동의 초음속 시동조건을 찾아내었다. 우선 부유동 흡입구의 크기의 영향을 알아내기 위하여 다양한 흡입구 직경으로 실험하였으며, 부유동의 초음속 시동은 흡입구 직경과 축소-팽창 디퓨저 직경의 비, d/D가 0.306 미만인 경우에만 일어났다. 이보다 큰 d/D에서는, 아음속 시동이 먼저 시작되고, 흡입구를 막으면서 주유동의 유입이 전 유동장을 채우게 되어 수직 충격파를 축소-팽창 디퓨저의 하류로 내려보내게 된다 이러한 상황에서 다시 흡입구를 열어도 히스테리시스의 영향으로 초음속 시동이 유지된다.

• Journal of Advanced Marine Engineering and Technology
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• 제30권6호
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• pp.677-684
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• 2006

An ejector is a fluid transfer device to be used for mixing of fluids, maintaining vacuum, and overcoming a poor suction condition. To date, most ejectors have been made from the casting process. which is time-consuming and high-cost process. Therefore, a new production method of ejectors is desired if any. In this experimental study, we proposed a new type ejector manufactured from the commercial fitting materials and the welding process, which is equipped with an orifice type nozzle. The proposed ejector has a good integrity compared with the conventional ejector because the fittings have manufactured by forging and they have more strength than the casting materials. Furthermore we adopted a multi-opening orifice type nozzle for improving a suction capacity and compared with a single-opening orifice type nozzle. From the experimental results. we confirmed that the multi-opening nozzle had a food suction capacity than the single-opening nozzle and the proposed new type ejector showed higher vacuum than the conventional type ejector in non-load condition. These improved characteristics suggests that a new type ejector by using the commercial fittings opens the feasibility to be adopted in various industry fields and that the increased suction capacity can be achieved by altering the nozzle design of a conventional ejector.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.526-531
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• 2003

A cone cylinder is used to obtain variable operation conditions of a sonic ejector-diffuser system. The cone cylinder is movable to change the ejector area ratio, thus obtaining variable mass flow rates. The present study investigates the effects of ejector throat area ratio and operating pressure ratio on the entrainment of secondary stream. The numerical simulations are based on a fully implicit finite volume scheme of the compressible, Reynolds-Averaged, Navier-Stokes equations. The ejector throat area is varied between 3.94 and 8.05, and the operating pressure ratio is changed from 3.0 to 9.0. The results show that the entrainment ratio and mass flux ratio become more dependent on the ejector throat area ratio, when the pressure operating ratio is low. The total pressure losses produced in the present ejector system increase with the operating pressure ratio and the ejector area ratio, but for a given operating pressure ratio, the losses are not significantly dependent on the ejector area ratio when it is larger than about 5.0.

• 한국태양에너지학회 논문집
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• 제30권6호
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• pp.137-143
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• 2010

In this study, the ejector design was modeled using Fluent 6.3 of FVM(Finite Volume Method) CFD(Computational Fluid Dynamics) techniques to resolve the flow dynamics in the ejector. A vacuum system with the ejector has been widely used because of its simple construction and easy maintenance. Ejector is the main part of the desalination system, of which designs determine the efficiency of system. The effects of the ejector was investigated geometry and the operating conditions in the hydraulic characteristics. The ejector consists mainly of a nozzle, suction chamber, mixing tube(throat), diffuser and draft tube. Liquid is supplied to the ejector nozzle, the fast liquid jet produced by the nozzle entrains and the non condensable gas was sucked into the mixing tube. In the present study, the multiphase CFD modeling was carried out to determine the hydrodynamic characteristics of seawater-air ejector. Two-dimensional geometry was considered with the quadrilateral-mashing scheme. The gas suction rate increases with increasing Motive flow circulating rate.