Development of a high-speed capacitive surface sensor for fluid distribution imaging

Experimental investigation of multiphase flows plays an important role in many research and industrial application areas, such as chemical and petroleum industry and nuclear engineering. We introduce a novel surface sensor based on electrical capacitance (permittivity) measurements to visualize flows along the surface of objects. The prototype sensor is formed by a 32times32 pixel interdigital sensing structure and can be mounted onto the wall of pipes or vessels and thus has a minimal influence on the flow. An associated electronics measures the capacitance of the fluid on each sensing structure in a multiplexed manner. This way, images of the fluid distribution can be achieved directly without the need for any reconstruction procedure. Images at up to 10,000 frames per second can be obtained. The system was evaluated showing good reproducibility and accuracy. Initial results of a two-component mixing experiment are presented.