In this paper, the boiling synchronization of two-phase flow patterns in two parallel minichannels of 1 mm in diameter with connected compressible volumes was analyzed. The analysis was performed using images recorded with a high-speed camera. The degree of synchronization between channels was evaluated by assessing the presence of liquid flow in the small part of the minichannels. It can be concluded that boiling is synchronized when small bubble flow or wavy annular flow occur in neighboring channels. The occurrence of slug flow in one channel causes the boiling in neighboring channels to become unsynchronized. The result of the image analysis shows that the correlation coefficient based on the evaluation of the presence of liquid flow in the small part of the minichannels over a long enough time period allows for the detection of boiling synchronization.

In this study the flow boiling inside two parallel tubes with a diameter of 1 mm was analysed in order to determine synchronization level between the channels. An experimental setup was built to investigate the pressure and temperature oscillation in parallel minichannels. During the experiments, the two-phase flow patterns were recorded by high speed camera and also the presence of vapour in channel outlet was measured by laser-phototransistor sensor. Various types of two-phase flow instabilities were observed in investigated the system. Experiment was carried out for various heat rate and mass flux. The method of identifying synchronization between flow boiling between parallel channel will be presented on measurement data recorded for heat rate q equal to 50.15 W and the average mass flux ṁ equal to 38.8 kg/m²s. The signal was subjected to a nonlinear analysis based on the joint recurrence plot (JRP) method. The JRP method was carried out in order to determine synchronization level between signals from parallel channels. Results of pressure and laser-phototransistor oscillation analysis shows that during flow boiling phase synchronization and phase shift between the channels can be detected using appropriate RQA indicators.

The temperature fluctuations occurring in flow boiling in parallel minichannels with diameter of 1 mm have been experimentally investigated and analysed. The wall temperature was recorded at each minichannel outlet by thermocouple with 0.08 mm diameter probe. The time series where recorded during dynamic two-phase flow instabilities which are accompanied by chaotic temperature fluctuations. Time series were denoised using wavelet decomposition and were analysed using cross recurrence plots (CRP) which enables the study of two time series synchronization.