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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
4.22.2 Slot Diffuser 
A typical slot diffuser is shown in figure 4.62. The slot diffuser provides high shear flow 
conditions at inlet, that result in high entrainment of the surrounding air into the jet flow, and 
consequently highly mixed conditions. 
The manufacturer’s (Gilberts) test facility in this instance measured 5m x 7m x 3m high (16.4’ x 
22.97’ x 9.84’). The diffuser is centrally located in the ceiling of the test room. The 
manufacturer’s data indicated the vertical distance of the 0.25 m/s (50 fpm) throw isovel from 
the diffuser, that was used in the validation exercise, for various flow rates. 
In the CFD representation, the flow rate that was chosen from the manufacturer’s data for 
validation purposes was that nearest the base case flow rate through a single radial diffuser. In 
particular, the base case flow rate was 270 cfm, while the nearest manufacturer’s data point was 
350 cfm. 
Figure 4.63 demonstrates that the CFD representation of the slot diffuser matches the location of 
the 0.25 m/s (50 fpm) isovel data very well. Confidence can therefore be placed in the 
representation of the CFD slot diffuser model in the animal facility simulations. 
4.22.3 Low Induction Diffuser 
A typical low induction diffuser is shown in figure 4.64. The low induction diffuser provides low 
shear flow conditions at inlet that result in low induction of the surrounding air into the jet flow. 
This diffuser therefore provides a solid column of clean air, purging the space of contaminants 
immediately below it. The disadvantage is then that large recirculations are formed either side of 
the diffuser jet. 
The manufacturer’s (Gilberts) test facility in this instance measured 5m x 7m x 3m high (16.4’ x 
22.97’ x 9.84’). The diffuser is centrally located in the ceiling of the test room. The 
manufacturer’s data indicated the vertical distance of the 0.25 m/s (50 fpm) throw isovel from 
the diffuser, that was used in the validation exercise, for various flow rates. 
In the CFD representation, the flow rate that was chosen from the manufacture’s data for 
validation purposes was that nearest the base case flow rate through a single radial diffuser. In 
particular, the base case flow rate was 270 cfm, while the nearest manufacturer’s data point was 
325 cfm. 
Figure 4.65 demonstrates that the CFD representation of the low induction diffuser matches the 
location of the 0.25 m/s (50 fpm) isovel data very well. Confidence can therefore be placed in the 
representation of the CFD low induction diffuser model in the animal facility simulations. 
