竖直及倾斜环隙流道内自然对流沸腾临界热负荷

以水为工质 ,在常压下对垂直和倾斜环隙流道内的自然对流沸腾临界热负荷进行了实验研究和理论分析 ,得到了计及进出口局部阻力的计算公式 ,讨论了流道几何尺寸、几何形状、倾角、压力和进出口局部阻力等因素对临界热负荷的影响 ,最后提出了一个新的 ,可用于计算竖直环隙、圆管及长方形流道内自然对流沸腾临界热负荷的半经验公式 ,其计算精度和适用范围较现有的计算公式有显著提高 ,原则上不受H/De 值大小的限制。     

竖直窄矩形通道内过冷沸腾传热模型

通过引入池式沸腾-流动沸腾汽泡脱离直径比对沸腾抑制因子S进行了修正,并将修正后的S引入Lee-Mudawwar过冷沸腾CHF模型,通过结合竖直窄矩形通道内的汽泡行为进行分析,建立了适应于竖直窄矩形通道的过冷流动沸腾传热模型,探讨了影响过冷沸腾传热系数的主要因素,并通过将模型预测值与实验值进行对比,验证了模型的可靠,表明当前模型可用于计算竖直窄矩形通道内的过冷沸腾传热特性。     

倾斜窄长套管内自然对流沸腾临界热流密度的实验研究

用实验方法对浸没在饱和液体中的倾斜窄长加热套管内的自然对流沸腾临界热流密度进行了实验研究,考察了套管间隙、管长、倾斜角和工质对临界热流密度的影响,并考虑了倾斜角对重力的影响,对用于预测垂直套管内自然对流沸腾临界热流密度的半理论半经验公式进行了修正。修正后的公式能较好地预测本实验和他人实验的结果。     

环形窄缝双面加热通道内欠热沸腾传热实验研究

在压力0.84～6.09 MPa、质量流速41.9～300.2 kg/(m2·s)、热流密度2.61～114.41 kw/m2范围内,以去离子水为工质,对间隙为1.5 mm环形窄通道实验段竖直向上流动的欠热沸腾传热特性进行了实验研究,得出了适用环形窄缝通道的欠热沸腾传热经验关系式。     

液钠沸腾两相流流型与临界热流密度(CHF)机理实验研究

通过大量的液态金属钠临界热流密度 (CHF)的实验研究 ,结合液钠两相传热流动特性及液钠的物性特点 ,分析了起始沸腾流型 ,泡状流 ,块状流 ,环状流和双向环状流的热工水力特性 ;并从实验结果出发 ,深入分析了液钠发生临界热流密度时的气泡爆炸和液膜撕裂或局部蒸干的两种传热恶化机理     

The Effect of Vibration on Critical Heat Flux in a Vertical Round Tube

This paper deals with the results of experimental investigations on the effects of tube vibration on critical heat flux (CHF) in order to gain an understanding of the relationship between CHF and flow-induced vibration (FIV). The experiment was carried out in the following range of parameters: diameter (D)=0.008 m; heated length (L)=0.2, 0.4 m; pressure (P)=101 kPa; mass flux (G)=403–2,551 kg/m².s; quality (x)=-0.045–0.289; amplitude (a)=0.0001–0.001 m; frequency (f)=0–70Hz. The CHF generally increases with vibration intensity, which is represented by vibrational Reynolds number (Re _v ); the CHF enhancement is more dependent on amplitude than on frequency. CHF enhancement seems to come from the reinforced flow turbulent mixing effect by vibration in the vicinity of heat transfer surface. Based on the experimental results, an empirical correlation is proposed for the prediction of CHF enhancement by tube vibration. The correlation predicts the CHF enhancement ratio (En) with reasonable accuracy, with an average error rate of -2.18% and 27.75% for RMS.     

Experimental Studies on Heat Transfer by Natural Convection and Pool Boiling of Sodium in a Strong Magnetic Field

This report deals with an experiment on the heat transfer of liquid sodium, with particular reference to the effects brought by the application of a magnetic field on pool boiling. The test section, a heater pin of 6.5 mm diameter, was inserted vertically into the center of a sodium tank. The heating surface of the pin was parallel to the magnetic field as well as to the direction of gravity.

Under conditions of natural convection in a magnetic field, a sharp rise of the heating surface temperature was always seen to occur at some point when the heat flux was gradually increased, accompanied by the onset of sharp temperature oscillations.

The surface superheat required for the initiation of boiling decreased with increasing intensity of the applied magnetic field, reached a minimum, then increased again.

The surface temperature fluctuations in nucleate boiling was higher under magnetic field than when free of such influence. The critical heat flux for burn-out was not appreciably affected by magnetic field.