Liquid film characteristics measurement based on NIR in gas-liquid vertical annular upward flow

Liquid film plays a crucial role in void fraction, friction pressure drops, momentum and heat transfer in the two-phase flow. The film thickness measurement experiments of annular flow at four pressure conditions have been conducted using near-infrared sensor. The signal is processed by variational mode decomposition, whose parameters are optimized using the sparrow search algorithm. The envelope spectrum and Pearson correlation coefficient judgment criteria were adopted for signal reconstruction, and the value of the liquid film thickness is obtained. The effect (such as flow rate, pressure, entrainment, etc) of the liquid film thickness are analyzed theoretically. The characterization parameters We(g)'', We(l), N mu(l) and X (mod) have been extracted and optimized, and a new average liquid film thickness correlation is proposed. The laboratory results indicate that the mean absolute percentage error of the predictive correlation is 4.35% (current data) and 12.02% (literatures data) respectively.