A small municipality in cold region with relatively low consumption results in a longer residence time of treated water in a storage tank. Field measurements of chlorine residual over a summer identified low chlorine residual while in a winter period the water was beginning to freeze. A few remedial geometrical alteration options were proposed, including a plug-flow configuration in the tank. However, the effectiveness of each option cannot be verified easily because there are many confounding factors. CFD (computational fluid dynamics) software ANSYS CFX is utilized to model conditions of flow, temperature, and chlorine residual in the tank under three geometries. For the no-alteration option and stepped spillway configuration, the model showed that there were pockets of stagnant water with low chlorine residual during the summer. Flow channels were created to achieve a plug-flow option and the residual was found consistent. The latter geometric option is considered the best for freeze avoidance and maintaining optimum chlorine concentration. One of the drawbacks of the CFD modeling was the excessive duration of computational time running on regular desktop computers.
展开▼
