Adiabatic and Boiling Liquid–Vapor Flow Regimes in the Serpentine Microchannel

Serpentine microchannels have the extensive application potential and the increasing research value due to their compact structure and the high heat transfer performance. Serpentine microchannels with the hydraulic diameters of 0.65 mm and the turning curvature radii of 1.2 and 2.4 mm are used to study the influence of the centrifugal force, the vapor mass quality, and the mass velocity on the vapor–liquid flow pattern maps of adiabatic and boiling flow. Bubbly flow, slug flow and annular flow were studied in adiabatic and boiling flow. The patterns of adiabatic flow and boiling flow in serpentine microchannels were found. The centrifugal force is an important factor in the flow pattern transition in the case of two-phase flow in serpentine microchannels. The centrifugal force existing in the bend promotes transition of slug flow to annular flow and wavy-annular flow to stable annular flow. Experiment data is compared with the flow regime maps existing in the literature, finding that the classification of slug flow and annular flow is inconsistent. For flow boiling, heat transfer elongates the flow pattern transition channel length, due to the increasing vapor mass quality. Bubbles are usually initiated on the inner wall just out of turning sections, where a low-pressure zone exists.