机载喷雾冷却换热特性关键影响因素实验研究
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摘要
为详细研究喷雾冷却系统在大热沉表面积和无沸腾区下的换热特性,并为喷雾冷却系统的机载应用提供技术基础,搭建以水为冷却介质的开放式喷雾冷却实验台。基于实验数据从特征参数和无量纲数两方面研究加热功率、喷雾入口压力对换热性能的影响;并根据飞行工况考查重力角度的影响。得到实验结果:在加热功率500~1 400 W及入口压力0.45~0.85 MPa的条件下,热沉表面温度均能控制在80℃以下。加热功率一定时,系统表面传热系数随入口压力的增加而增加,且增加速率随着功率的增加而增加;热沉表面温度随入口压力增加而减小,且减小速率随着功率增加而增加;表面传热系数随Re和We的增加而增加,增加速率随功率增加主要是由于蒸发强度的增加。此外,与重力方向夹角为30°或120°时,喷雾冷却性能最好。结果表明各工况下喷雾冷却换热效果良好,表面参数均处于合理范围,为该技术在机载领域的应用提供技术参考。
An open-loop spray cooling platform using water as coolant was designed and established to thoroughly study the heat transfer characteristics of spray cooling systems on large heating surface and in non-boiling areas and to provide a technical reference for applying the systems to the field of aircraft cooling. Based on experiment data, the effects of heating power and inlet pressure on heat transfer performance were analyzed in respect to characteristic parameters and dimensionless numbers. Meanwhile, the influence of gravity angle was examined according to the aircraft operating condition. During the experiment, the heating surface temperature could be maintained below 80 ℃ when the heating power was 500 W-1 400 W and the inlet pressure 0.45 MPa-0.85 MPa. The results indicate that,if the heating power is constant,the heat transfer coefficient increases with the inlet pressure and the decrease rate varies with the heating power. On the other hand, the surface temperature decreases as the inlet pressure increases and the decrease rate varies with the heating power. The increase of the heat transfer coefficient is caused by the increase of Re and We and the increase rate is mainly influenced by evaporation intensity. Moreover, the best spray cooling performance is achieved when the gravity angle is 30° or 120°. The results show that the heat transfer performance is good and all the surface parameters are within a reasonable range, which can provide a technical reference for applying the spray cooling systems in the field of aircraft cooling.
An open-loop spray cooling platform using water as coolant was designed and established to thoroughly study the heat transfer characteristics of spray cooling systems on large heating surface and in non-boiling areas and to provide a technical reference for applying the systems to the field of aircraft cooling. Based on experiment data, the effects of heating power and inlet pressure on heat transfer performance were analyzed in respect to characteristic parameters and dimensionless numbers. Meanwhile, the influence of gravity angle was examined according to the aircraft operating condition. During the experiment, the heating surface temperature could be maintained below 80 ℃ when the heating power was 500 W-1 400 W and the inlet pressure 0.45 MPa-0.85 MPa. The results indicate that,if the heating power is constant,the heat transfer coefficient increases with the inlet pressure and the decrease rate varies with the heating power. On the other hand, the surface temperature decreases as the inlet pressure increases and the decrease rate varies with the heating power. The increase of the heat transfer coefficient is caused by the increase of Re and We and the increase rate is mainly influenced by evaporation intensity. Moreover, the best spray cooling performance is achieved when the gravity angle is 30° or 120°. The results show that the heat transfer performance is good and all the surface parameters are within a reasonable range, which can provide a technical reference for applying the spray cooling systems in the field of aircraft cooling.
引文
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[3]CHOW L C,SEHEMBEY M S,PAIS M R.High heat flux spray cooling[J].Annul Rev Heat Transfer,1997(8):291-318.
[4]司春强,邵双全,田长青,等.高功率固体激光器喷雾冷却技术[J].强激光与粒子束,2010,22(12):2789-2794.
[5]邵杰,李小莉,冯宇彤,等.激光二极管端面抽运Nd YVO4板条激光器及其热效应[J].光学学报,2008,28(3):497-501.
[6]史彭,李金平,李隆,等.抽运光分布对Nd YAG微片激光器热效应的影响[J].中国激光,2008,35(5):643-646.
[7]田长青,徐洪波,曹宏章,等.高功率固体激光器冷却技术[J].中国激光,2009,36(7):1686-1692.
[8]CHEN R H,CHOW L C,NAVEDO J E.Effects of spray characteristics on critical heat flux in sub-cooled water spray cooling[J].International Journal of Heat and Mass Transfer,2002,45(3):4033-4043.
[9]CHEN R H,CHOW L C,NAVEDO J E.Optimal spray characteristics in water spray cooling[J].International Journal of Heat and Mass Transfer,2004,47(5):5095-5099.
[10]HEIEH S S,FAN T C.Spray cooling characteristics of water and R-134a[J].Internal Journal of Heat and Mass Transfer,2004,47(9):5703-5712.
[11]王亚青,刘明侯,刘东,等.大功率激光器喷雾冷却中无沸腾区换热性能实验研究[J].中国激光,2009,36(8):1973-1978.
[12]周致富,辛慧,陈斌,等.激光手术喷雾冷却中单个液滴蒸发特性[J].中国激光,2008,35(6):952-956.
[13]陶毓伽,淮秀兰,李志刚,等.大功率固体激光器冷却技术进展[J].光学学报,2007,28(2):11-12.
[14]刘炅辉,孙皖,刘秀芳,等.喷雾腔压力及喷嘴孔径对相变喷雾冷却性能的影响[J].强激光与粒子束,2013,25(10):2546-2550.
[15]RVBICKI J R,MUDAWAR I.Single-phase and twophase cooling characteristics of upward facing and downward facing sprays[J].International Journal of Heat and Mass Transfer,2006(49):5-16.
[16]ESTES K A,MUDAWAR I.Correlation of sauter mean diameter and critical heat flux for spray cooling of small surfaces[J].Int J Heat Mass Transfer,1995,38(16):2985-2996.
[17]KLINE S J,MCCLINTOCK F A.Describing uncertainties in single sample experiments[J].Mechanical Engineering,1953,75(1):3-7.
[18]MUDAWAR I,ESTES K A.Optimization and predicting CHF in spray cooling of a square surface[J].J Heat Transfer,1996,118(3):672-680.