The selection of the most appropriate airflow model for designing indoor air sensor systems

Current indoor air sensor system design is mostly by intuition or experience rather than by design. Sensor systems that are intended to ensure the safety and well-being of building occupants should be systematically designed and their performance evaluated. The literature shows that selection of an airflow model for sensor system design has been either out of convenience (thus choosing a simpler multizone model) or for proven accuracy (thus choosing a more complex computational fluid dynamics (CFD) model). In this study, the most appropriate airflow model for use in designing indoor air sensor systems was selected without compromising design objectives for 12 test zones. The test zones differed in the diffuser location, furniture presence and location, and airtightness level. Simulated contaminant concentrations from multizone, zonal, and CFD models were used to design sensor systems that either minimized detection time or occupant exposure. In lieu of experimental data, the performance of the sensor systems designed using multizone and zonal model data were benchmarked using CFD data. The sensor systems designed using CFD data were considered the “best-performing” in lieu of actual performance data. It was found that multiple-sensor systems designed using multizone model (the simplest of the three airflow models tested) data performed just as well as the best-performing sensor systems. For 1-sensor systems, common engineering practices resulted in performance comparable to the best-performing ones. These results applied even though the test zones were not considered well-mixed, and furniture and infiltration was modeled.