Sprinkler Spray Pattern

[Danish]

Dear FDS Experts,

I am working on the fire event scenarios with an operation of open head sprinklers. In my model we have three different sprinkler location types a) sprinkler head below the slab b) sidewall sprinkler c) sprinkler with an angle. I have the following queries for each type, please have a look and advice.

a)       Sprinkler head below the slab – In this type, we have a solid cone spray angle of 140 degrees with an extended coverage area of 5.0 m x 5.0 m based on the following parameters as per our MEP design Team:

a.       Flow rate – 113 L/min

b.       Jet Stream offset – 0.05 m

c.       Jet Stream velocity -6 m/s

To model the solid spray cone angle of 140 degrees, I am using Jet Stream Type “Conical” with “Latitude angle 1 – 0 degree” and “Latitude angle 2 – 70 degree”.

Query – Based on the above parameters I found that the modelled sprinkler covered only 1.5 m x 1.5 m area. I tested multiple simulations by changing the cone angle from Latitude angle 1 – 0 to 60 degrees keeping the “Latitude angle 2 – 70 degree” constant and I found that by changing the angles the coverage area increases, see attached “PDF - Page 1”. But by changing the angle, the cone also shifts from solid spray to hollow spay type. Can you please advise how to get the same coverage area in FDS keeping solid spray to validate the MEP design?

 

b)      Sidewall sprinklers – In this type of sprinkler to simulate the spray pattern I am following a section “Special Topic – Specifying the complex spray pattern”.  But I am not clear about the angles described for latitudes and longitudes. Can you please elaborate?

The spray pattern that I want to simulate is defined in “PDF - Page 2” and the one that I am defining within the model along with the resulting pattern mentioned within the “PDF - Page 3 and 4”

c)       Sprinkler with an angle: In this case, we have a sprinkler link with an angle of 50 degrees, I read the manual and I found that there is an option called “rotation” to define the angle of the sprinkler link. Can you please explain more in this direction, how to define?

Thanks for your precious time.

Regards

 

[Danish]

Dear all, 

Please advise on the above queries.

Regards

Wali

[dr_jfloyd]

You are showing screenshots from Pyrosim. Have you read the FDS User's Guide which discusses these inputs in detail?

a) the two angles define the region where water droplets are inserted. If the first angle is not zero, then you have specified a hollow cone.  If you are not getting a large enough coverage check that your drop size and velocity are correct. Also make sure you have a reasonable OFFSET for your grid size.

b) Look at and run the bucket_test_2 case in the User's Guide. A good way to learn how to use the spray pattern table is to take this case and play with the inputs and see what the effect is

c) ROTATION will have no effect if you are just using a simple cone for your spray. A sprinkler head as a set of arms that hold the deflector plate in front of the orifice. If you have a detailed spray distribution, you will generally see an effect from the arms in the distribution. ROTATION defines position of those arms.  The default value is 0, or the arms lie at 0 and 180 degrees.