Design of microstructured process modules based on empirical approaches is time- and cost intensive. This becomes especially important for complex continuous operations, where several unit operations have to be efficiently combined for maximum process efficiency and economy. A concept for a model-based design by an axial dispersion model is presented as a contribution to simplification and cost reduction. Simple microchannel structures with varying cross sections are evaluated with volume flows up to 20mLmin(-1). The predictive accuracy of the model is demonstrated and assessed by selected examples.