Enhanced heat transfer in microscale has been highlighted in the field of microelectronics. The gas-liquid flow patterns and pressure drop analysis are fundamental for the design and control of microfluidic systems. In this study

two-phase flow characteristics in parallel rectangular micro-channels with sudden expansion were studied by flow patterns visualization

theoretical analysis

and experimental study. Through visualization experiments

four typical flows

i.e.

bubble flow

plug flow

slug flow

and annular flow

were observed in parallel rectangular micro-channels with sudden expansion. When Qg = 110 mL/min and Ql = 20mL/min

the two-phase flow pattern achieves the maximum jet state

and a full fluid jet appears. By?means?of?setting?up?a?total pressure drop prediction?model of the parallel rectangular micro-channel with sudden expansion at the mass velocity of two-phase flow ranges from 367 kg/(m2·s) to 691 kg/(m2·s)

their applicability and accuracy were analyzed. The results showed that the average prediction?error is 18.56%

which is superior to the prediction accuracy in classical literature. Additionally

with the increase in the overall pressure drop

the prediction accuracy increases.