Should We Model Sprinkler Cooling? Presented by: Ben Hume Kevin Weller

What’s the starting point? Don’t model sprinklers..

Why? “We don’t have enough data to accurately model sprinklers” “Modelling sprinkler cooling increases the level of error” “Other factors have a greater impact (HRR, Material, Modelled Space)”

So what we’re really saying is…. Modelling a fire with no sprinklers is more accurate (less error) than modelling a fire with sprinklers…..and there are more aspects to worry about….

Is this the case though? Sprinklers impact: –Upper layer temperature, hence volume, density and buoyancy –Down drag (typically local though and not a threat to occupants )

Literature Review Error 10-15% for temperature 7% -8% for velocity N. O’Grady and V. Novozhilov Large Eddy Simulation of Sprinkler Integration with a fire ceiling jet

Literature Review S.C.Li et al Studies of Cooling Effects of Sprinkler Spray on Smoke Layer

Proof of Concept 3D smoke view image of slice through FDS with no sprinkler so we can see the sprinkler and the smoke layer. Want to show how thin the layer is.

Sprinkler Inputs Particle diameter – 500μm Particle velocity – 5.58ms -1 RTI – 135 m 1/2 s 1/2 C – 0.85 m 1/2 s 1/2 T act – 68 o C

Spray Angle Common Use Pyrosim Default N. O’Grady & V. Novozhilov

Results – Spray Angle FDS no sprinkler Experiment no sprinkler Experiment Sprinkler 50, 60, 75Lpm

Results – Spray Angle

Results – Flow Rate

Resulting Sprinkler Input Velocity – 5.58ms -1 Spray Angle – 65 o -115 o Droplet size – 500μm RTI – 135 m 1/2 s 1/2 C – 0.85 m 1/2 s 1/2 T act – 68 o C

What impact on modelling do sprinklers have

Small Room Temperature (upper layer)

2m Small Room

Medium Room Temperature

Large Room Temperature

Large Room Visibility * At 2 m

Other factors Material (Medium Room) Plasterboard

Other factors Material (Medium Room) Plasterboard Concrete

Other factors Material (Medium Room) Plasterboard Concrete Steel

Other factors Material (Medium Room) Plasterboard Concrete Steel Inert

Other factors Material (Medium Room) Plasterboard Concrete Steel Inert Adiabatic

200s Other factors: Structure Graph of temperatures FDS and B-Risk

Other factors: Structure 500s Graph of temperatures FDS and B-Risk

Summary AspectTemperatureVisibility MaterialsMinimal StructureMinimalModerate Room ShapeTemperatureVisibility SmallSignificantMinimal MediumSignificantModerate LargeModerate Sprinkler Impact – Room Size Other Aspects Impact

Cooling and C/VM2? Perception: “C/VM2 was developed without consideration of cooling” Interpretation: No formal guidance Use your engineering judgement

Recommendations The error of not modelling sprinklers is greater than the error introduced by modelling them. Sprinklers should be considered when: –The space is Medium - Large –There are complex flow paths (Buoyancy driven interactions) –Natural or mechanical ventilation exists

Recommendations The use of Brisk over FDS should be reconsidered even when within accepted bounds where : –the above conditions exist and sprinklers should be considered –there is significant structure/complex flows (i.e. large warehouses with lattice beams or solid beams) Surface finishes and structure have significant impacts in models but less impact than sprinklers