Frictional and collector pressure losses in rectangular microchannels

In this paper a new measurement method is developed to determine the friction factors in microchannels. Based on a set of experiments at variable microchannel lengths the friction factor can be derived by least-squares fitting well-established pressure loss correlations. Furthermore, collector losses and developing flow regime can be identified. An experimental set-up is build to demonstrate this method. It is found that the friction factors obtained with the new method correspond very well with the values obtained from conventional correlations. However the measurements also show a significantly lower critical Reynolds number (1400-1800) than the conventional value for channel flow. However the Obot-Jones model combined with the empirical correlations of Samoilenko do predict the critical Reynolds number well. For the collector losses the obtained values have a large spread but tend to values lower than the values obtained by conventional correlations. These losses also show a dependence on Reynolds number in the laminar regime which is not retrieved in macro scale correlations.