小通道并联管干涸热动力学特性实验

针对小通道并联管在沸腾传热过程中传热不稳定的问题，对小通道并联管在干涸时的热动力学特性进行研究。首先，通过观察小通道并联管内干涸点前后流型的转变，将流型分成环状预警区、干涸初始点区和雾状干涸区3个区域。对3个流型下并联通道沸腾传热过程中通道内工质干度和传热系数的变化进行分析，发现随着干涸的发展，通道沸腾传热系数下降明显。然后，对通道3个流型下的压降信号，通过自适应最优核时频表示法（AOK-TFR）、自回归（AR）模型功率谱分析法和递归图分析法进行分析，发现在干涸初始点区，通道内反复出现干涸现象，且回流现象严重。最后，通过对递归图分析法中特性参数归纳总结，得到干涸初始点区与环状预警区、雾状干涸区的区别，实现通过压降信号检测干涸的目的。研究结果可对小通道沸腾传热领域中的热动力学特性进行补充和完善。 

Experiment on thermodynamic characteristics of parallel mini-channel tube' dryout

Aiming at the unstable heat transfer of mini-channel parallel tubes in boiling heat transfer process, the thermodynamic characteristics of mini-channel parallel tubes during dryout were studied. Firstly, by observing the transition of the flow pattern before and after the dryout in the parallel mini-channels, the flow pattern is divided into three areas:the annular warning zone, the initial dryout zone and the mist dryout zone. The changes of dryness and heat transfer coefficient of working medium in mini-channel parallel tubes under three flow patterns were analyzed. It was found that the boiling heat transfer coefficient decreased significantly with the development of dryout. Then, the pressure drop signals under the three flow patterns are collected and analyzed by the adaptive optimal kernel time-frequency representation (AOK-TFR), auto regression (AR) power spectrum and recurrence plots analysis method to obtain the dynamic characteristics of the corresponding flow pattern. It is found that in the initial point of dryout, the phenomenon of dryout occurs repeatedly in the channel, and the phenomenon of reflux is serious. Finally, by summarizing the characteristic parameters in the recurrence plots, the difference among the initial dryout zone, annular warning zone and the mist dryout area is obtained. Based on the distribution of the recursive eigenvalues, the different zones can be identified, and then the dryout can be predicted by the pressure drop signals. The research of this paper hopes to supplement and improve the thermodynamic characteristics in the field of mini-channel boiling heat transfer.