SPRINKLER ACTIVATION

[francesco ciani]

Hi all,

I am trying to simulate the effect of sprinkler suppression on a fire. I need to know at which temperature the sprinklers activates then I will estimate the sprinkler effect using the correlation for the effect of sprinkler on fires developed by Evans.

In order to estimate the sprinkler activation I am trying to enter all the required data, but I can’t understand the effect on the activation of the following data:

DROPLETS PER SECOND: The default data is 5000. Does it effect the sprinkler activation? Which real data of the sprinkler effect does it represent? Where can I find it?

LATITUDE ANGLE 1 and LATITUDE ANGLE 2: Do they define the spray pattern?Does it effect the sprinkler activation?

JET STREAM OFFSET: I have used the default value 0,05 m. But I can’t understand how this value change based on the sprinkler type. Does it change depending only on the fact that is an extended coverage sprinkler or not?Does it effect the sprinkler activation?

VELOCITY : The initial droplet default velocity. Was defined 5 m/s. Is this value acceptable also for ESFR sprinkler with, for example k-factpr 240 with a flow rate of 455 lpm?Does it effect the sprinkler activation?

Thank you

[Randy McDermott]

PARTICLES_PER_SECOND: This is a numerical parameter that determines the number of computational particles FDS uses.  It needs to be high enough so that both the mass flow rate and particle size distribution can be achieved.  FDS uses this number to compute a particle weight factor.   See section 8.2 of the FDS Tech Guide.

The remaining parameters you ask about all do affect the spray in various ways, as is discussed in the manuals, sec 16.3 of FDS User Guide.  Whether a certain parameter affects sprinkler activation would, of course, depend on the problem... if the sprinkler activation is based on local temperature, then it is possible that any one of these parameters could affect the flow field and hence the local temperature.  Someone else might have some experience about typical engineering problems, but theoretically the activation could be affected.

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[dr_jfloyd]

I would recommend you update your FDS version. DROPLETS_PER_SECOND is an FDS 5 input, the FDS 6 input is now PARTICLES_PER_SECOND. The FDS 6 User Guide has also been expanded.  For example:

PARTICLES_PER_SECOND is the number of droplets inserted every second per active sprinkler or nozzle (Default 5000). It is listed on the PROP line that includes other properties of the sprinkler or nozzle. Note that this parameter only affects sprinklers and nozzles. Changing this parameter does not change the flow rate, but rather the number of droplets used to represent the flow.

[francesco ciani]

Thank you!