Examples of how CFD may be used to evaluate air quality, containment and ventilation performance of labs.

Medicinal Chemistry Lab with Many Fumehoods... This figure depicts two aisles of a lab with several fumehoods visible. The large red areas represent supply diffusers, yellow are lighting fixtures, green are the walls of each hood, translucent gray are the sashes, and the red stripes are the hood exhausts or bypass dampers. To simulate an ASHRAE standard 110 test, sulfur hexafluoride is injected into each fumehood at the rate of 4 liters per minute. Isosurfaces of 2 ppm are shown to determine if containment is acceptable. Additional calculations may be made and plotted for other standards or techniques.

Bio-safety hood... cut-away to show streaklines of airflow from the back wall to an exhaust on the work surface near the sash opening. Experimental results indicate an excellent correlation with CFD when comparing the flow speeds at various positions within the hood.

A conventional fumehood design … This figure shows streaklines on a cut-away view of a conventional fumehood with rear baffles, standard sash handle, sulfur hexafluoride ejector and airfoil. Note the characteristic swirl at the top of the hood cavity.

A high performance – low flow fumehood design … This figure shows the same cut-away as above, but the sash handle, airfoil, bypass and rear baffles are redesigned to prevent the characteristic swirl of the conventional hoods. Eliminating the swirls in a hood minimizes the possibility of a loss of containment.

A high performance – low flow fumehood design … CFD is capable of accurately calculating the concentrations of species gases in a domain. In the case of a fumehood, the ASHRAE 110 standard calls for sulfur hexafluoride gas injection into the cavity using highly sensitive sensors outside of the hood to check for containment loss. This figure uses a log-scale in units of parts per million SF6 (ppm) to show how well the gas is contained in the cavity.

A high performance – low flow fumehood design … By using iso-surfaces of predefined SF6 concentration levels (0.1, 1.0, 10.0 100.0 ppm), several surfaces may be superimposed on each other to form an “onion skin” cloud. These three-dimensional “clouds” may be cut away to expose each of the layers within.