INFLUENCE OF DEPOSITS BY CRYSTALLIZATION FOULING IN MICROCHANNELS ON THE HEAT TRANSFER PERFORMANCE OF MICRO HEAT EXCHANGERS

In the last few years many new microstructured devices were developed and manufactured for different applications in chemical industry and for process engineering. However, the use of micro structured devices in the chemical industry is still rare in spite of the potential benefits these devices offer. One essential reason for the limited use of micro structured devices could be the intrinsic advantage of these structures: the small dimension. In applications of micro structured devices it might be possible that the microchannels get blocked by contaminations in the fluid or that deposition (fouling) could induce flow restrictions in the microchannels. Fouling is defined as the deposition of material on surfaces, e.g. by chemical reactions or phase transition due to the crystallization of inversely soluble ions. This can yield in a reduction of the cross section of the microchannels up to total blocking. Furthermore, fouling can cause a degradation of the heat transfer performance, an increase of the pressure drop in the device, a change of the fluid distribution in the micro structure and a shorter residence time of the fluid. Experimental investigations concerning crystallization fouling in micro structures were carried out at the Institute for Micro Process Engineering (IMVT) of the Karlsruhe Institute of Technology (KIT) and at the Institute for Chemical and Thermal Process Engineering (ICTV) of the Technische Universitat Braunschweig. The intention of these investigations is the development of experimentally verified and generally applicable correlations to describe the crystallization fouling in micro heat exchangers.