Gas-liquid hydrodynamics of a fractal flow mixer

Gas-liquid hydrodynamics of a micro-structured device (fractal flow mixer) was experimentally investigated. Experiments were conducted for a range of liquid-to-gas superficial velocity ratios (V-SL/V-SG). High-speed imaging was used to identify the flow regimes inside the microchannels of the device at different V-SL/V-SG. At different V-SL/V-SG, two or more flow regimes were observed simultaneously in different micro-channels. Consequently, a new flow regime map was developed. An optical probe was used to measure the bubble mean size and velocity. The effect of the V-SL/V-SG towards the bubble mean size, mean velocity, and frequency were analyzed. The bubble mean size decreases with the increase of the V-SL/V-SG, which can be attributed to the uniform shearing of gas slugs across all channels. To check the consistency of the fractal flow mixer in producing gas bubbles over a single experiment run, the global relative standard deviation (RSD) was used. The fractal flow mixer was able to generate equal flow distribution across the 16 outlets and maintain a Taylor flow over a range of V-SL/V-SG.. However, depending on the V-SL/V-SG, the G(B) and G(S) vary to a certain extent, governed by the capillary effect and the back-pressure.