The design of sprinkler and watermist systems is commonly done in good agreement with codes and guidelines. Therefore in most cases advanced CFD simulations are not required. Still in more complex structures or more exceptional situations CFD simulations are applied to test a design and achieve approval from the local authorities. Below you find some examples for what scope CFD can be an added value.
Response time analyses
When simulating a growing fire in time in a certain space we can monitor the temperature at specific locations (e.g. the sprinkler heads). The simulation incorporates the full 3 Dimensional representation of the space and the location of the sprinkler head. This simulation can predict which sprinkler head will open at what time during the fire growth. Any ventilation or process in the space can be taken into account in the simulation as well.
How the water droplets are distributed in the room, their size and path influence the performance of the system. With advanced multi-phase modelling and particle tracking each droplet can be traced and the effective absorption of heat due to evaporation calculated. This enhances designers to evaluate the design without costly and time consuming scaled tests. Besides, the information acquired from the simulation is far more complete.
Tunnels and car parks
A lot of research is done for tunnels and car parks on the effectiveness of sprinkler and watermist systems, especially in combination with (mechanically generated) air flows. CFD is the tool to make full scale tests with different setups to establish the required performance. Fluid-fluid and fluid-solid interactions is something CFD simulations can model very well.
A detailed study can be done to analyse the spray pattern from a sprinkler head and develop a spray pattern for special features. The software (ANSYS CFX) has special developed break up models to estimate the droplet air interaction. Similar studies has been carried out by us for the Fire Defender spray nozzle and high pressure water mist systems.
Other suppression systems
Besides water distribution CFD simulations can predict the spread of suppression gasses or foam for special rooms such as in datacentres. The effective spread and mixture with the combustibles can accurately be modelled. When knowledge of the chemical composition and reactions are available, the suppression of the combustibles can be modelled as well.