# Experimental and Numerical Evaluation of Toxic Pool Evaporation
## 2 Experimental Set-Up  
### General Considerations  
Evaporation tests were conducted in INERIS' fire test installations [19], more precisely in the 10 m\({}^{3}\) room for small-scale tests and in the fire gallery for medium-scale tests. Pictures of the installations are presented below in Figure 2. The sections were 0.465 m wide and 0.165 m high for the small-scale tests and approximatively 3 m \(\times\) 3 m for the medium-scale tests.  
The scale factor for the tests is based on a Froude scaling. Considering the Froude number, \(Fr=U^{2}/(g\cdot l)\), where \(l\) stands for a characteristic length, \(g\) for gravity, and \(U\) for representative velocity, we were able to evaluate the different physical quantities on the basis of length scaling. The actual pool was based on a basic size of 100 m\({}^{2}\), 10 m \(\times\) 10 m. The corresponding scale factor on length, \(\sigma\), can then be defined. For a given scale factor \(\sigma\) on length, the scale factor for the velocity is \(\surd\sigma\) to conserve the Froude number. For small-scale tests, the pool was 0.1 m\({}^{2}\), 0.316 m \(\times\) 0.316 m, and 0.03 m deep. In this  
Figure 2: Picture of the pool photography and instrumentation for small (**left**) and medium (**right**) scales.  
case, \(\sigma\) was equal to 31.6. For medium-scale tests, the reference size was 1 m\({}^{2}\), 1 m\(\times\) 1 m, and \(\sigma\) was equal to 10; the pool depth was also 3 cm.  
As previously mentioned, one of the key factors when studying pool evaporation is being able to reproduce a relevant velocity profile above the pool. Considering the atmospheric dispersion as target application, the velocity profile in both the small- and medium-scale tests were designed to be as close as possible to an atmospheric profile, somewhere between neutral and stable conditions. The reference velocity profiles for medium-scale tests are shown in Figure 3. \"Right\" and \"left\" on this figure indicate that the measure was taken in the center of the section where the ammonia pool was, right and left near the limit of the pool, in the same section of the duct. The reference experimental velocity was measured 1 m above the pool since the scale factor was 10 for length, with a reference experimental value of 1 m/s corresponding to a \"real\" velocity of 3.2 m/s, since the scale factor for velocity is \(\sqrt{10}\) for a Froude scaling.  
To ensure a realistic turbulence intensity in this profile, we managed the flow before it reached the pool using obstacles distributed on the ground. Pictures of the installations, including obstacle distribution and pool, are reproduced in Figure 4 for both scales. Small-scale obstacles were 55 mm long, 21 mm wide, and 21 mm high; the inter-obstacle distance was 2 cm along the wind direction and 5 cm in the other direction. They were distributed over an area 700 mm upstream of the pool. For large-scale tests, obstacles were approximate cubes with a length of 600 mm and were distributed over 15 m upstream of the pool. Distance between obstacles was about 60 cm in both directions.  
Figure 4: Picture of obstacle distribution for small (**left**) and medium (**right**) scales.  
Figure 3: Velocity profile for medium-scale configuration.  
The turbulent velocity measured in the duct using a high-speed MacCaffrey probe [20; 21] prior to the evaporation was about 4% of the averaged value for the 1 m/s tests.  
An additional configuration was tested by generating artificial turbulence upstream of the pool. A specific system that included horizontal obstacles was then used for the medium-scale test, as shown in Figure 5. This system dimensions were 1 m width and 10 cm height.