The main objective of this diploma thesis was to conduct research on the already existing cold model of a circulating fluidized bed with external fluidized bed heat exchanger. The focus was laid on the external fluidized bed heat exchanger, to be more precise, on the heating chamber. The experiments carried out on the cold model can be divided into two parts: On the one hand a method was to be found in order to identify fluid dynamics at heat exchange pipes. For this purpose Particle Image Velocimetry (PIV) was applied. On the other hand the overall fluid dynamic of the heating chamber shall be analysed by to a residence time distribution (RTD) experiment using coloured tracer material. The PIV experiments made it possible to show local effects such as different velocities of flow and bubble formation close to the heat exchange pipes. The RTD analysis, however, showed that macroscopic conclusions can be made about the fluid mechanical behaviour (powder RTD and mixing) of the analysed heating chamber.