Identification of flow boiling patterns in mini channel with the use of analysis of pressure oscillations

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.The dynamics of pressure fluctuations occurring in flow boiling in a minichannel with diameter of 1 mm, which consists of the heated section and glass condenser has been experimentally investigated and analysed. The recurrence plot and PCA of recurrence plot quantities have been applied. High speed digital video camera has been used to identify two-phase flow patterns in the glass condenser. The low frequency pressure fluctuations with relatively high amplitude which are caused by presence of compressible volume in the system have been observed. These fluctuations are accompanied by high frequency pressure oscillations. It has been found that during those fluctuations the dominant frequency of pressure fluctuations changes chaotically in time. Such pressure oscillations are accompanied by the flow patterns changes in the condenser. In the paper the new method of two-phase flow identification has been presented. The method is based on the analysis of dynamics of signal recorded from the pressure sensor. It has been shown that in the plots of two first components the points are grouped in the six separated clusters, which correspond to different flow patterns.