Micro channels for applications in liquid dosing and flow rate measurement

To investigate the performance of microengineered fluid channels in liquid dosing applications, flow rate measurements were performed with various channel geometries in a range from 0.01 ml/min up to 1000 ml/min. An optical flow measurement technique was developed to enhance the measurement range into the desired low flow range (10(exp -3)ml/min to 1 ml/min), and was compared to a standard gravimetric method, which is preferably used for flow rates above 1 ml/min. In addition, influences of the temperatur-dependent viscosity and effects arising from fluidmechanical characteristics were studied. These influences were also calculated from laminar flow theory and semi-empirical models to obtain a theoretical model. It was found, that the theoretical model is able to describe the measurement results well agreeing in the whole flow range. The model was implemented on a PC-based system, which measures the pressure drop across the microchannel and the fluid temperature and calculates the flow . In a temperature range from 20 deg C to 50 deg C an excellent compensation effect was found.