Evaporating momentum force and shear force on meniscuses of elongated bubble in microchannel flow boiling

The evaporating momentum force and the shear force acting on the meniscus of an evaporating and elongating bubble in flow boiling in microchannel have been investigated theoretically and numerically. The concept of the effective evaporation region and the theory of the liquid layer supplement between elongated bubble and microchannel are proposed, and the analytical expressions of the evaporating momentum force and shear force have been obtained. The relative importance of both forces has been determined by the method of magnitude analysis and numerical simulation. It has been found that the evaporating momentum force can always be neglected in analyzing the bubble elongation process and the motion law of meniscus of elongated bubble in microchannel flow boiling, but whether the shear force should be considered or not is determined by its relative order of magnitude and the particular conditions such as channel dimension and the operating conditions.