Investigation Of Distributive Characteristics And Optical Measurement For Gas-liquid Flow In Parallel Microchannels

Microtechnology is currently a research frontier of chemical engineering, which has also turn into a typical method of process intensification after recent years of development. This dissertation focus on the gas-liquid flow experiments in multichannel microreactors, using low-price easy-fabricated capillaries with inner diameter of 0.5 mm to make comb-like microchannels, and investigating the air-water two-phase flow in the parallel microchannels. Aiming to explore novel numbering up models and fluids distribution principle, this work attempts to enrich the theoretical and experimental fundamentals for industrialization of microreactors.The experiment verified the feasibility of capillary fabricated parallel microchannels, and the device was effectively used for the air-water two-phase flow experiments and modeling calculation. The experiments set the inlet volumetric flow rate range from 1 to 20 mL/min, and maintained two-phase flow rates to be equal and to specifically generate desired Taylor flow. Flow patterns in the parallel microchannels can be divided into two zones, which is bubble flow and phase splitting zones, respectively. In the bubble flow zone, the bubble flow was more stable, and produced relatively even size of bubbles and liquid slugs; phase splitting zone was very unstable due to vortex effects caused by orientation change in the main channel. Moreover, the greater the volumetric flow rate, the bigger channel number occupied by two phase splitting. To better describe and predict the flow patterns in this parallel microchannels, quantitative calculation method was established based on the volume conservation and pressure relations, the results agreed well with the actual situation, and desired operation interval can be determined by comparing simple experimental parameters.In addition, this dissertation also reported the construction and experiments of a new optical measuring system. The system based on the principle of transmittance variance when infrared light transmits through different medium. By installing multiple optical fibers above the microchannels, this system successfully applied in accurate measurement of bubble length, velocity and phase holdup in microchannels, and the system is efficient and reliable.