Author(s): Anastasios I. Stamou; Ioannis Katsiris
Linked Author(s): Anastasios I. Stamou
Keywords: Flow Through Curves (FTCs); Mathematical models; Hydraulic efficiency
Abstract: The Terpsithea tank in Athens (Greece) is used for water balancing with dead spaces, which results in insufficient chlorination and high dosages of chlorine. To improve the hydraulic efficiency of the tank, the use of a deflector (which consists of three sides) is examined. Flow Through Curves (FTCs) are used to investigate the effect of this modification. To derive a FTC, a known mass of tracer is injected instantaneously at the inlet of the tank. The resulting plot of the tracer concentration vs. time at the outlet is the FTC. The shape of the FTC and its characteristics provide information on the hydraulic efficiency of the tank. In the present work, the FTCs are not derived experimentally, but are calculated with a mathematical model. Calculated flow fields are used as input to the FTC calculations. The calculation of the FTCs and their characteristics permits the correlation of FTCs with the flow fields. The comparison of the flow fields and the FTCs for the initial and the modified geometry leads to the following conclusions: (1) The flow for the initial geometry is characterized by a high level of short-circuiting and two main re-circulation regions. Due to the large size of these regions, a high degree of mixing occurs. (2) The flow for the modified geometry shows limited short-circuiting. Two main re-circulation regions are formed, which occupy significantly less volume than the corresponding for the initial geometry and thus create less mixing. In a significant portion of the tank flow resembles to “plug flow”. Therefore, the use of the deflector improves dramatically the hydraulic efficiency of the tank.
Year: 2001