The Effects of Inlet Geometry on Gas-Liquid Two-Phase Flow in Microchannels (Keynote)

The effects of gas and liquid inlet geometry on adiabatic gas-liquid two-phase flow in a microchannel of 100 micron diameter have been investigated using different inlet sections and methods of gas and liquid injection and mixing. Two-phase flow patterns, void fraction and friction pressure drop were found to be significantly affected by the diameter of the inlet section and how the gas and liquid phases are injected and mixed upstream of the microchannel. Using a tee junction of the same diameter as the microchannel as the inlet, the two-phase flow pattern in the microchannel is mostly intermittent with short gas and liquid slugs flowing with nearly equal velocities. The void fraction then conforms nearly to that of a homogeneous two-phase flow, and two-phase friction multiplier applicable to larger channels is obtained. However, when the diameter of the inlet section is larger than the microchannel, the two-phase flow characteristics in the microchannel become highly dependent on the flow characteristics in the inlet section. Long gas slugs become prevalent and the void fraction decreases to values far below those given by a homogeneous void fraction. The practical implications for designing microchannel devices utilizing gas-liquid two-phase flow will be described.