Simplified Modeling of Air Flow Dynamics in SSD Radon Mitigation Systems forResidences with Gravel Beds

摘要

In an attempt to better understand the dynamics of subslab air flow, the reportsuggests that subslab air flow induced by a central suction point be treated as radial air flow through a porous bed contained between two impermeable disks. (NOTE: Many subslab depressurization systems, those now considered most effective for mitigating residences for radon, do not perform entirely satisfactorily, even when designed and installed by professionals). The report shows that subslab air flow is most likely to be turbulent under actual field situations in houses with subslab gravel beds, but remains laminar when soil is present under the slab. The physical significance of a model is discussed, and simplified closed-form equations are derived to predict pressure and flows at various distances from a single central depressurization point. A laboratory apparatus was built to verify the model and experimentally determine the model coefficients of the pressure drop vs. flow for commonly encountered subslab gravel materials. These pressure drop coefficients can be used in connection with the simplified model as a rational way to assess subslab communication in houses. Preliminary field verification results in a house with gravel under the basement slab are presented and discussed.