压力旋流喷嘴喷雾冷却热传递特性数值模拟
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摘要
雾化形成液膜的传热系数与厚度是决定喷雾冷却效果的重要因素。采用数值模拟方法,基于加热壁面上的液膜厚度、传热系数与温度分布三个角度,分析喷雾的压力、高度与倾斜角度对喷雾冷却传热特性的影响。结果表明:喷雾压力是影响换热效果重要的因素。相比于低压力工况,高压力工况时壁面上形成的液膜厚度小,壁面平均温度低,换热能力较强。压力工况越大,壁面温度下降程度越高。主要因为喷射压力提高后,液膜的运动速度加快,导致与空气之间的扰动作用加强,促进了液膜破碎和液滴的形成。改变高度使喷射到壁面的液滴密度程度不同,导致温度分布不均匀。研究还发现喷雾高度对换热影响存在一个最优值,H=6 mm时,换热效果最好。同样,改变倾斜角度导致壁面分为喷雾密集区跟稀疏区,换热效果区别大。喷雾倾角θ=30°时壁面换热效果最好且温度分布相对均匀。通过分析得到的变化规律为喷雾参数的设定和喷雾效果的优化提供了理论依据。
The heat transfer coefficient and thickness of the atomized liquid film are important factors in determining the spray cooling effect.The numerical simulation method is used to analyze the effect of spray pressure, height and tilt angle on the heat transfer characteristics of spray cooling based on three angles of liquid film thickness, heat transfer coefficient and temperature distribution on the heating wall. The results show that the spray pressure is an important factor affecting the heat transfer effect. Compared with the low pressure working condition, the liquid film formed on the wall surface is small in the high pressure working condition, the average wall temperature is low, and the heat exchange capacity is strong. The greater the pressure condition, the higher the wall temperature drop. Mainly because the injection pressure is increased, the movement speed of the liquid film is increased, resulting in a strong disturbance between the air and the air, which promotes liquid film breakage and droplet formation. The height is changed so that the density of the droplets ejected to the wall is different,resulting in uneven temperature distribution. The study also found that there is an optimal value of the effect of spray height on heat transfer.When H=6 mm, the heat transfer effect is best. Similarly, changing the angle of inclination causes the wall to be divided into a spray-intensive area and a sparse area, and the heat exchange effect is largely different. When the spray angle θ=30°, the heat transfer effect of the wall surface is best and the temperature distribution is relatively uniform. The variation rule obtained by the analysis provides a theoretical basis for the setting of the spray parameters and the optimization of the spray effect.
The heat transfer coefficient and thickness of the atomized liquid film are important factors in determining the spray cooling effect.The numerical simulation method is used to analyze the effect of spray pressure, height and tilt angle on the heat transfer characteristics of spray cooling based on three angles of liquid film thickness, heat transfer coefficient and temperature distribution on the heating wall. The results show that the spray pressure is an important factor affecting the heat transfer effect. Compared with the low pressure working condition, the liquid film formed on the wall surface is small in the high pressure working condition, the average wall temperature is low, and the heat exchange capacity is strong. The greater the pressure condition, the higher the wall temperature drop. Mainly because the injection pressure is increased, the movement speed of the liquid film is increased, resulting in a strong disturbance between the air and the air, which promotes liquid film breakage and droplet formation. The height is changed so that the density of the droplets ejected to the wall is different,resulting in uneven temperature distribution. The study also found that there is an optimal value of the effect of spray height on heat transfer.When H=6 mm, the heat transfer effect is best. Similarly, changing the angle of inclination causes the wall to be divided into a spray-intensive area and a sparse area, and the heat exchange effect is largely different. When the spray angle θ=30°, the heat transfer effect of the wall surface is best and the temperature distribution is relatively uniform. The variation rule obtained by the analysis provides a theoretical basis for the setting of the spray parameters and the optimization of the spray effect.
引文
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[21]高亚军,姜汉桥,李俊键,等.双液滴同时垂直撞击壁面的数值模拟[J].物理学报,2017,66(2):229-238.GAO Yajun,JIANG Hanqiao,LI Junjian,et al.Numerical study of two drops simultaneously hitting walls vertically[J].Acta Physica Sinica,2017,66(2):229-238.
[22]曹建明.喷雾学[M].北京:机械工业出版社,2005.CAO Jianming.Sprayology[M].Beijing:China Machine Press,2005.
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[24]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试验研究[J].中国激光,2009(8):1973-1978.WANG Yaqing,LIU Minghou,LIU Dong,et al.Experimental study on heat exchange performance of no evaporation in high power laser spray cooling[J].Chinese Journal of Lasers,2009(8):1973-1978.
[2]PAUTSCH G.An overview on the system packaging of the CRAY SV2 supercomputer[C]//Pacific Rim/Internaional,Intersociety Electronic Packaging Technical/Business Conference&,Exhibition,2001:617-624.
[3]TUQAN A T,KELLY K M,AGUILAR G,et al.Evaluation of single versus multiple cryogen spray cooling spurts on in vitro model human skin[J].Lasers in Medical Science,2005,20(2):80-86.
[4]陈斌,周致富,辛慧.制冷剂瞬态闪蒸喷雾冷却研究进展[J].化工学报,2018,69(1):57-68.CHEN Bin,ZHOU Zhifu,XIN Hui.Research progress of refrigerant transient flash spray cooling[J].Jounal of Chemical Industry,2018,69(1):57-68.
[5]MAJARON B,AGUILAR G,BASINGER B,et al.Sequential cryogen spraying for heat flux control at the skin surface[J].Proc SPIE,2001,4244:74-81.
[6]刘健,吕继组,计时鸣.柴油机缸内辐射换热的多维数值模拟研究[J].机械工程学报,2009,45(12):311-317.LIU Jian,LüJizu,JI Shiming.Multidimensional numerical simulation of radiative heat transfer in diesel engine cylinder[J].Journal of Mechanical Engineering,2009,45(12):311-317.
[7]王菁菁.油田高含盐污水喷雾干燥的数值模拟研究[D].北京:中国科学院大学,2017.WANG Jingjing.Numerical simulation of spray drying of high salty sewage in oilfield[D].Beijing:University of Chinese Academy of Sciences,2017.
[8]陈华,程文龙,章玮玮.喷雾参数对闪蒸冷却换热效果影响的数值研究[J].工程热物理学报,2016,37(2):361-365.CHEN Hua,CHENG Wenlong,ZHANG Weiwei.Numerical study on the effect of spray parameters on the heat transfer efficiency of flash cooling[J].Journal of Engineering Thermophysics,2016,37(2):361-365.
[9]潘飞,王亦飞,颜留成,等.喷雾洗涤冷却室内雾化液滴粒径变化规律的试验研究[J].中国电机工程学报,2015,35(2):396-403.PAN Fei,WANG Yifei,YAN Liucheng,et al.Experimental study on the change of drop size of atomized droplet in spray washing and cooling chamber[J].Chinese Society for Electrical Engineering,2015,35(2):396-403.
[10]侯燕.多喷嘴喷雾冷却试验研究与数值模拟[D].北京:中国科学院研究生院,2014.HOU Yan.Experimental study and numerical simulation of multiple nozzles spray cooling[D].Beijing:Graduate University of Chinese Academy of Sciences,2014.
[11]何志霞,王芬,刘菊燕,等.柴油机喷嘴结构对喷雾特性影响的耦合模拟研究[J].机械工程学报,2014,50(24):145-151.HE Zhixia,WANGF en,LIU Juyan,et al.Study on coupling simulation of the effect of diesel nozzle structure on spray characteristics[J].Journal of Mechanical Engineering,2014,50(24):145-151.
[12]CHENG W L,LIU Q N,ZHAO R,et al.Experimental investigation of parameters effect on heat transfer of spray cooling[J].Heat&Mass Transfer,2010,46(8-9):911-921.
[13]XIE J L,ZHAO R,DUAN F,et al.Thin liquid film flow and heat transfer under spray impingement[J].Applied Thermal Engineering,2012,48(1):342-348.
[14]王亚青,刘明侯,刘东,等.倾斜喷射时喷雾冷却无沸腾区换热特性[J].化工学报,2009,60(8):1912-1919.WANG Yaqing,LIU Minghou,LIU Dong,et al.Spray cooling no-boiling zone heat transfer characteristics when tilted[J].Jounal of Chemical Industry,2009,60(8):1912-1919.
[15]刘秋升.喷嘴雾化特性及传热特性的数值模拟研究[D].保定:华北电力大学,2017.LIU Qiusheng.Numerical simulation of spray characteristics and heat transfer characteristics of a pressure swirling nozzle[D].Baoding:North China Electric Power University,2017.
[16]刘妮,李丽荣,黄千卫,等.喷雾参数对喷雾冷却换热特性影响的试验研究[J].制冷学报,2016,37(5):93-99.LIU Ni,LI Lirong,HUANG Qianwei,et al.Experimental study on influence of spray parameters on spray cooling heat transfer characteristics[J].Journal of Refrigeration,2016,37(5):93-99.
[17]V I S A R I A M,M U D AWA R I.T h e o r e t i c a l a n d experimental study of the effects of spray inclination on two-phase spray cooling and critical heat flux[J].International Journal of Heat&Mass Transfer,2008,51(9):2398-2410.
[18]ABBASI B,KIM J.Development of a general dynamic pressure based single-phase spray cooling heat transfer correlation[J].Journal of Heat Transfer,2011,133(5):746-758.
[19]刘妮,李丽荣,钟泽民.微结构表面喷雾冷却性能试验研究[J].机械工程学报,2017,53(6):158-165.LIU Ni,LI Lirong,ZHONG Zemin.Experimental study on spray cooling performance of microstructured surface[J].Journal of Mechanical Engineering,2017,53(6):158-165.
[20]张震.微纳米表面喷雾冷却的机理研究[D].北京:清华大学,2013.ZHANG Zhen.Mechanism of spray cooling on micronano surfaces[D].Beijing:Tsinghua University,2013.
[21]高亚军,姜汉桥,李俊键,等.双液滴同时垂直撞击壁面的数值模拟[J].物理学报,2017,66(2):229-238.GAO Yajun,JIANG Hanqiao,LI Junjian,et al.Numerical study of two drops simultaneously hitting walls vertically[J].Acta Physica Sinica,2017,66(2):229-238.
[22]曹建明.喷雾学[M].北京:机械工业出版社,2005.CAO Jianming.Sprayology[M].Beijing:China Machine Press,2005.
[23]文华.基于CFD的柴油机喷雾混合过程的多维数值模拟[D].武汉:华中科技大学,2004.WEN Hua.Multidimensional numerical simulation of spray mixing process of diesel engine based on CFD[D].Wuhan:Huazhong University of Science and Technology,2004.
[24]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试验研究[J].中国激光,2009(8):1973-1978.WANG Yaqing,LIU Minghou,LIU Dong,et al.Experimental study on heat exchange performance of no evaporation in high power laser spray cooling[J].Chinese Journal of Lasers,2009(8):1973-1978.