Prediction of Temperature at the Outlet of Stormwater Management Structures

The primary objective of the project was to create a physics-based computer model of the current best management practice (BMP) stormwater management structures that allows prediction of outlet temperature as a function of time. The approach is physics based, depending on energy and mass balances, and heat and mass transfer predictions. A series of models of different configurations were prepared. Ultimately, the primary focus was on the sand filter configuration. An advection-diffusion model was written to predict the energy storage and temperature profiles in a sand filter. The model assumes uniform flow of water through the sand. In an attempt to validate the model, a series of experiments were run on several scales. A bench-scale experiment was run in a 4 inch pipe filled with sand. It was found that the outlet temperature responded more quickly than the model predicted. This was traced to non-uniform flow of water through the sand such that water flowed in preferential channels through the sand, probably due to wetting effects and rearrangement of smaller sand particles within the overall porous sand filter. Various treatments were attempted to obtain uniform flow without much success. Field data from an existing sand filter on campus were obtained to gain additional insight. The facility was instrumented with temperature and level sensors and flow rate was measured and correlated to water level. These data were found to be influenced significantly by weather variables. The field data did not yield unambiguous answers to questions about uniform flow and sand filter energy storage. The literature on the subject of preferential flow in sand and soil provides a number of theories to explain non-uniform flow and does not provide any predicative models. A conclusion from the effort is that the problem of predicting energy transfer between water and a sand filter is significantly more complicated than originally expected. The uniform flow model that was written provides a limit on energy storage but is not very appropriate for design because preferential flow occurs in real sand filters. It is concluded that a realistic model would need to include data to obtain accurate predictions of sand filter performance.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 19p

Subject/Index Terms

Filing Info

  • Accession Number: 01529444
  • Record Type: Publication
  • Report/Paper Numbers: MD-08-SP508B4P
  • Contract Numbers: SP508B4P
  • Files: TRIS, ATRI, STATEDOT
  • Created Date: Jun 2 2014 9:50AM