Characteristics of heat transfer and homogeneous nucleation process during quenching high temperature surface with an impinging water jet

冲击水射流淬火高温表面的传热及均匀成核过程特征

基本信息

批准号：
17560189
负责人：
MONDE Masanori
金额：
$ 2.24万
依托单位：
Saga University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17560189/
关键词：
Quench Impinging jet Boiling Transition cooling Homogeneous nucleation Impinging Jet Maximum heat flux

项目摘要

An experimental study has been made of heat transfer characteristics and homogeneous nucleation with an impinging water jet. The experimental condition is varied from jet velocity of 3 to 15 m/s, liquid temperature of 20 to 95 ℃, jet diameter of 2 and 3 mm, and initial block temperature of 250 to 600 ℃. Three different materials of copper, brass and carbon steel are employed as tested block.When the block temperature higher than Leidenfrost temperature is cooled by liquid, condition whether an occurrence of wetting high temperature surface appears or not, strongly depends on whether in the case that the surface temperature is kept higher than the thermodynamic limit of liquid superheat the cooling capacity is enough or not. For the case of cooling the surface higher than the thermodynamic limit of liquid superheat and enough cooling capacity of liquid, the wet and dry conditions are alternatively repeated at very short time during which the surface temperature gradually goes down. When … More the surface temperature becomes lower than the thermodynamic limit of liquid superheat, a stable wetting is confirmed on a limited area of the surface, namely near the center of impinging jet zone, but the wetted area never expand over the heated surface. This condition is lasting until the surface temperature reaches a surface temperature. We define this lasting time as a resident time, t^*, and then can determine the surface temperature, Tw^*, at the resident time. The resident time and the surface temperature can be predicted by the following equations,(1)(2)After the resident time, the wetted area starts expanding to cover the entire surface. We can clarify how the surface temperature and surface heat flux change with moving the wetted area. For example, we can point out the position at which the maximum heat flux, q_<max>, appears within the wetted zone and can estimate the maximum heat flux by the following equation ;(3)where p, c and λ are density, heat capacity and thermal conductivity, respectively and q_c is critical heat flux under the steady cooling with impinging jet. Less

一项实验研究是针对传热特性和均匀构成的构成水射流的。实验条件从3至15 m/s的射流速度，20至95℃的液体温度，2和3毫米的射流直径以及250至600℃的初始阻滞温度变化。铜，黄铜和碳钢的三种不同材料被用作测试块。当高于Leidenfrost温度高于Leidenfrost温度时，是否出现润湿高温表面的情况是否出现，很大程度上取决于是否在表面温度保持高于液体过热的热力学极限的情况下，冷却能力足够。对于将表面冷却高于液体过热的热力学极限和液体的足够冷却能力的情况，潮湿和干燥的条件在很短的时间内逐渐重复，在此期间，表面温度逐渐下降。当……更多的表面温度变得低于液体超热的热力学极限时，在表面有限的区域（即撞击喷气区的中心附近）确认稳定的润湿，但是润湿区域永远不会在加热的表面上膨胀。这种情况一直持续到表面温度达到表面温度为止。我们将这个持久时间定义为居民时间T^*，然后可以在停留时间确定表面温度Tw^*。居民的时间和表面温度可以通过以下等式预测，（1）（2）居民时间后，湿区开始扩展以覆盖整个表面。我们可以阐明表面温度和表面热通量如何随着湿区移动而变化。例如，我们可以指出最大热通量q_ <ax>出现在湿区内的位置，并可以通过以下等式估算最大热通量；（3）P，C和λ分别是密度，热容量和热导率，并且Q_C在稳定的稳定冷却下与撞击射流的稳定冷却。较少的