INVESTIGATIONS OF THE FLOW INTO A STORAGE TANK BY MEANS OF ADVANCED EXPERIMENTAL AND THEORETICAL METHODS

Advanced experimental methods were applied to study flow structures of a water jet entering a tank from the bottom. A squared experimental glass tank with a volume of about 140 l was used. Above the inlet pipe a flat plate was installed, as shown in the figure. The goal of the investigations is to study the influence of the inlet device geometry and of the operating conditions (the flow rate, draw-off volume, and temperatures) on the thermal stratification in the tank. Measurements of the flow and temperature fields were carried out with two visualization techniques: - To visualize the flow field a method called Particle Image Velocimetry (PIV) was applied. Particles with a size of 1 to 10 mm were seeded in the water and then illuminated by a laser within a narrow plane. In order to measure the three velocity components of the flow within the plane, the particle displacements between laser pulses was recorded with two cameras. - The second experimental method applied is called Temperature Planar Laser Induced Luminescence (T-PLIF). With this method the temperature field can be visualized using a fluorescence dye (Rhodamine B). The dye is excited with a laser light sheet. Due to the fact that the luminescence intensity depends on the water temperature, the temperature fields in the tank can be visualized and also be recorded with a camera. The measurements were compared with calculations of the flow and temperature fields carried out with the Computational Fluid Dynamics (CFD) tool Fluent. In future investigations the validated CFD models can be utilized to develop more accurate simulation tank models for performance studies of solar domestic hot water systems and to enhance the geometry of inlet devices for solar storage tanks.