Simulation of a water mist curtain used as a radiation shield

The shielding capability of a high-pressure water mist curtain has been investigated. An appropriate test setup for large-scale fire testing was developed, corresponding to applications for modern building types. A three-storey concrete building at the Swedish Civil Contingencies Agency College in Revinge, Sweden, was used for the tests. This building has proven to give reliable and repeatable test results (1). The tests were conducted on a single floor in the building, consisting of three interconnected rooms. This is a multiple-room design representative of a typical apartment configuration. A heptane pool fire of about 1200 kW was placed in the middle room (fire room) close to a door opening. A high-pressure water mist curtain protects the door opening to the adjacent target room. Fresh air could enter from both sides of the fire room. The temperatures and thermal radiation levels were measured in the target room at different heights. The surface temperatures in the target room were measured with a Forward-looking infrared (FLIR) camera.

The performance evaluation of the high-pressure water mist curtain is based on the ability to attenuate temperatures and radiation through the door opening. Acceptance criteria of relevance were taken from the Nordic criteria of maximum allowed temperature and radiation. These criteria are very similar to the ones used by many countries which have implemented performance-based design, for example, Denmark, as shown by Sørensen (2).
A total of four tests were performed. One free burning test (test 0) and three tests (test 1-3) with 7.5, 10.5 and 11.9 L/min water pendent spraying in a door opening. It was found that the application of water mist dampens radiation and temperature levels considerably, as shown in Figure 1 and Figure 2. (3)

The experimental setup was simulated in FDS 6.9.1 using the Rosin Rammler Log-Normal droplet size distribution and activating turbulent dispersion in the Fire Dynamics Simulator. Activating turbulent dispersion improved the quality of the spray. Further, the varying outdoor wind conditions, which influenced the experimental results, were included in the simulations. Preliminary simulation results show that the model captured the overall physics and could adequately reproduce the experiments, which will be shown in the poster.