• Title/Summary/Keyword: Liquid entrainment

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An Experimental Study on the Behavior of Twin-Spray with Flow Interaction in a Condensable Environment (주위기체내에서의 두 액체분무간의 유동간섭현상에 대한 정상적 고찰)

  • 이상룡;정태식;한기수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.10 no.3
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    • pp.326-334
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    • 1986
  • The effects of flow interaction between adjacent sprays in twin-spray system on the spatial distribution of injected liquid (water) and drop size distribution in condensable (steam) environment were carefully observed through experiments. The spatial distribution of injected liquid in twin-spray system appears to be more uniform than the simple superposition of the spatial distributions of liquid obtained from each individual spray. Drop size distribution was obtained by using the immersion sampling technique. It was found that, in the twin-spray, the larger numbers of small drops are collected throughout the spraying region due to the increase of entrainment velocity of ambient steam compared with the case of simple superposition of each individual spray. Moreover, in the overlapped portion of the twin-spray, the drop size distribution was changed also due to the collision between large drops. As a result, the behavior of twin-spray system (and eventually multiple-spray system) can not be predicted precisely by simple superposition of the behaviors of each constituting spray. Hence, for the design of multiple spray system, the effect of flow interaction between sprays should be taken into account seriously.

A Study on the Characteristics of the Liquid-gas Ejector (Liguid-gas Ejector의 구동성능 특성에 관한 연구)

  • Park, Gi-Tae;Jin, Zhen-Hua;Chung, Han-Shik;Jeong, Hyo-Min
    • Proceedings of the SAREK Conference
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    • 2008.06a
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    • pp.1047-1052
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    • 2008
  • The aim of this paper is that studies on the characteristics of the liquid-gas ejector. Could get data about various model using numerical analysis. Compare and analyze result that get by an experiment and numerical analysis. And studied Characteristics of the ejector. In this paper, Numerical analysis model is gotten divided according to each Throat ratio as three types. Each throat ratio is 0, 4 and 7.5. According to the result that analyze basic model, pressure became lower causing the volume flow rate increase. In CFD studies, Fixed volume flow rate by these result and analyzed ejector performance. As a result, there was no change of pressure to Throat's Enterance, and pressure became low while pass the throat. Since, pressure recovered while passing diffuser. The outer flow velocity did not change greatly to change of volume flow rate. This research expects that is utilized to data for performance elevation hereafter.

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Performance Characteristics of Refrigeration Cycles with Ejector using Refrigerants (이젝터를 적용한 냉동사이클의 냉매종류별 성능특성)

  • Yoon, Jung-In;Kim, Chung-Lae;Son, Chang-Hyo
    • Journal of Power System Engineering
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    • v.21 no.1
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    • pp.24-29
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    • 2017
  • Studies in liquid-vapor ejector, which performs a great efficiency in refrigeration cycle is highly concerned. This paper is based on basic refrigeration cycle and three ejector refrigeration cycles and the comparison and contrasts about when 6 different refrigerants are applied to such refrigeration cycles. All cycles had a percentage increase of COP from 4 to 74% when ejector was applied, and the source of increasement was the decrease of total work done due to ejector's pressure recovery function. When R-245fa is applied to cycle (d), results showed that COP was the most superior in such cycle, R-245fa showed high volume entrainment ratio in all cycles. Future studies in refrigeration cycles will require more knowledge and experiments on ejector's appliance to refrigeration cycles and the actuation of such functions.

Definition and Correlation for Spray Angle in Non-Reacting Diesel Fuel Sprays

  • No, Soo-Young
    • Journal of ILASS-Korea
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    • v.11 no.4
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    • pp.244-250
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    • 2006
  • Of the macroscopic spray characteristics of non-reacting diesel fuel sprays, the spray angle reflects directly the atomization and air entrainment processes downstream the nozzle. In addition, spray angle is important because it will be closely related to the spray penetration. The existing definitions for the measurement of spray angle as well as the correlations for the prediction of spray angle are, therefore, summarized and reviewed. The existing definition of spray angle can be classified into four groups: distance based on orifice diameter, distance based on spray tip penetration, definition based on surface wave, and definition based on atomization. It is strongly required to specify the definition and measurement method when the data for spray angle is reported. The existing correlations for spray angle can be classified into two groups: theoretical and empirical correlations. The study on the evaluation of the existing correlations fer spray angle is required.

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Reduced Quasi-Dimensional Combustion Model of the Direct Injection Diesel Engine for Performance and Emissions Predictions

  • Jung, Dohoy;Assanis, Dennis N.
    • Journal of Mechanical Science and Technology
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    • v.18 no.5
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    • pp.865-876
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    • 2004
  • A new concept of reduced quasi-dimensional combustion model for a direct injection diesel engine is developed based on the previously developed quasi-dimensional multi-zone model to improve the computational efficiency. In the reduced model, spray penetration and air entrainment are calculated for a number of zones within the spray while three zones with aggregated spray zone concept are used for the calculation of spray combustion and emission formation processes. It is also assumed that liquid phase fuel appears only near the nozzle exit during the breakup period and that spray vaporization is immediate in order to reduce the computational time. Validation of the reduced model with experimental data demonstrated that the new model can predict engine performance and NO and soot emissions reasonably well compared to the original model. With the new concept of reduced model, computational efficiency is significantly improved as much as 200 times compared to the original model.

Simulation of Spray Behaviors by Injection Rate Shapes in Diesel Injection System (분사율 형상에 따른 디젤분사계의 분무거동에 관한 시뮬레이션)

  • Wang, W.K.;Jang, S.H.;Koh, D.K.;Ahn, S.K.
    • Journal of Power System Engineering
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    • v.3 no.3
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    • pp.36-43
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    • 1999
  • Many of thermodynamic-based diesel combustion simulations incorporated a model of fuel spray which attempts to describe how the spray develops according to time. Because the spray geometry is an essential aspect of the fuel-air mixing process, it is necessary to be calculated quantitatively for the purpose of heat release and emission analysis. In this paper, we proposed the calculating method of non-evaporation spray behaviors by injection rate shapes under actual operating conditions of diesel engine. We confirmed the utility of this calculating model as the calculated results were compared with the measured results. This calculating program can be applied usefully to study on the diesel spray behavior.

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Theoretical Analysis of Factors Affecting to Heat Transfer Limitation in Screen Mesh Wick Heat Pipe (스크린 메쉬윅 히트파이프의 열전달한계에 영향을 미치는 인자의 이론적 해석)

  • 이기우;노승용;박기호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.11
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    • pp.880-889
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    • 2002
  • The purpose of the present study is to examine the factors affecting the heat transfer limitations of screen mesh heat pipe for electronic cooling by theoretical analysis. Diameter of pipe was 6 mm, and mesh numbers are 50, 100, 150, 200 and 250 and water was selected as a working fluid. According to the change of mesh number, wick layer, inclination and saturation temperature, capillary pressure, pumping pressure, liquid friction coefficient in wick, vapor friction coefficient, capillary limitation, entrainment limitation, sonic limitation and boiling limitation we analyzed by theoretical design method of a heat pipe. As some results, the capillary limitation in small diameter of heat pipe is largely affected by mesh number and wick layer.

Change of Spray Characteristics with Mixing Port Length of Y-Jet Atomizers (Y-Jet 노즐에서의 혼합관 길이변화에 따른 분무특성 연구)

  • 송시홍;이상용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.11
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    • pp.3021-3031
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    • 1994
  • Experiments have been performed to find out the effect of the mixing port length of Y-jet atomizers on the spray performance, using air and water as the test fluids. Water and air flow rates and drop sizes were measured at each injection pressure condition for different mixing port length. The air flow rate was almost unaffected by the change of the mixing port length. However, the water flow rate was relatively susceptible to the change of the mixing port length. The mixing point pressure was very much influenced by the mixing port length. Variations of spatial distribution of Sauter Mean Diameter (SMD, $D_{32}$) and the cross-section-averaged SMD ($D_{32,m}$) with different mixing port length and air/water mass flow rate ratio were examined. Generally, when the mixing port length was reduced, the mean drop size decreased and became spatially even.

Prediction of Critical Heat Flux for Saturated Flow Boiling Water in Vertical Narrow Rectangular Channels (얇은 수직 사각유로에서의 포화비등조건 임계열유속 예측)

  • Choi, Gil Sik;Chang, Soon Heung;Jeong, Yong Hun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.12
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    • pp.953-963
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    • 2015
  • There is an increasing need to understand the thermal-hydraulic phenomena, including the critical heat flux (CHF), in narrow rectangular channels and consider these in system design. The CHF mechanism under a saturated flow boiling condition involves the depletion of the liquid film of an annular flow. To predict this type of CHF, the previous representative liquid film dryout models (LFD models) were studied, and their shortcomings were reviewed, including the assumption that void fraction or quality is constant at the boundary condition for the onset of annular flow (OAF). A new LFD model was proposed based on the recent constitutive correlations for the droplet deposition rate and entrainment rate. In addition, this LFD model was applied to predict the CHF in vertical narrow rectangular channels that were uniformly heated. The predicted CHF showed good agreement with 284 pieces of experimental data, with a mean absolute error of 18. 1 % and root mean square error of 22.9 %.

An experimental study on the open channel flow with plane wall jet inlet boundary condition and effects of a baffle (평면벽면분류의 유입경계조건을 가지는 개수로 유동 및 배플의 영향에 관한 실험적 연구)

  • 방병렬;설광원;이상용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.6
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    • pp.1399-1406
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    • 1988
  • Flow behaviors of the open channel type flow with its geometric boundary conditions being similar to that of the Multi-Stage-Flash evaporator were studied qualitatively by measuring the velocity distribution. Without a baffle, the flow was in the shape of a simple submerged plane wall jet. At the downstream of this flow, the jet boundary made sharp curve toward the free surface ; this is because the entrainment of the ambient liquid is restricted by the free surface boundary, similar to the Coanda effect. According to the experimental results the level of the free surface appeared to be the most important parameter. The flow with a baffle was in much complicated shape ; especially the recirculating region at the downstream free surface was detected according to the experimental conditions imposed. Inlet liquid velocity, heights of the liquid level and the baffle, and the opening heights of sluice gate of the entrance were the most important parameters in the baffle flow.