The advantages of microstructure devices concerning heat and mass transfer are well known. However, the usage of microstructure devices in chemical industry is still limited today. A limitation for industrial application is the liability of microstructures to blocking due to impurity of the fluid or by unintended deposition ( fouling) in the microchannels. Fouling can lead to a degradation of the heat transfer performance, to an increase of the pressure drop, to a change of the fluid distribution in the microstructures and to a shorter residence time of the fluid. In the framework of this research project a micro heat exchanger for fundamental experimental investigations on crystallization fouling of CaCO3 in microchannels was developed and manufactured.