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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
4.23.2 Comparison of Experimental Data and CFD Results 
This section compares data for two different room configurations, air velocity and temperature 
for an empty room, and air velocity, temperature and concentration for a stocked room. The 
challenge with this task largely relates to the measurement of the predominantly low air 
velocities. This is the case for two reasons. Firstly, the predominant air velocities are low and 
quite difficult to measure. Secondly, but probably more importantly, small temperature effects or 
infiltration can easily cause air currents of the order of the air speeds of interest. As a result CFD 
provides a good understanding of the key flow patterns and comparison is most easily made 
between the scalar quantities such as temperature and concentration. These are compared for the 
stocked or populated room 
4.2. 3. 2.1 Empty Room 
Due to the large amount of data, only two planes are considered for this experimental scenario. 
The two planes are plane 1, that is the experimental plane 0.15m (6”) from the north wall and so 
is near the comer exhaust, and plane 8, that is experimental plane 1.22m (48”) from the north 
wall, and so is located mid-way through both the room and the supply diffuser. For a full 
explanation of the experimental plane locations, see appendix I: section 4.3.2. 
Speed Results 
The fill plot of the experimental mean air velocity (speed) at experimental plane 1 (i.e. the plane 
0.15m (6”) from the north wall) is displayed in figure 4.68. Note that the left-hand side of the 
plot indicates the east wall, and the key range is between 0 and 40 fpm (0.2m/s). The plot clearly 
shows the locations of the various measurement zones. In particular, the upper left-hand side of 
the plot shows a region of relatively uniform speed flow, with the magnitude of the airflow 
velocity being typically around 0.15m/s (30 fpm) and higher. The spots of white in this region 
indicate velocity measurements that are higher than this: the peak velocity at this plane is 
0.28m/s (55 fpm). This region can be clearly seen to be the zone 1, upper east measurement 
region (see appendix I: section 4.3.2). Also in this plot, the upper right comer of the plot should 
show a clear increase in velocity near the ceiling, as this plane is close to the comer exhaust of 
the room. There is no such feature present in the plot. Moving further into the room, the fill plot 
of the experimental speed field at experimental plane 8 (i.e. 1.22m (48”) from the north wall) is 
displayed in figure 4.69. The white region at the center near the ceiling is the location of the 
diffuser, with the speeds here being above 0.20m/s (40 fpm). This is an expected feature. 
However, there are several spots within the plot that are either above or near 0.20m/s (40 fpm), 
that are well away from the diffuser region. In both plots, the appearance of the high speed 
sections in the experimental data is unexpected. In particular, appendix I: section 4.1.2 states 
that, based on theoretical considerations, the air velocity should not exceed 0.11m (22 fpm) 
outside the jet zone (within 0.30m (12”) of the central diffuser), unless there is disturbance to the 
airflow. As plane 1 is furthest from the jet zone, and the room is fundamentally empty apart from 
the supply and exhaust, the higher speed values are subject to doubt. 
