Sprinkler Protection for Cloud Ceilings. SUPDET 2013 Jason Floyd, Ph.D. 28 February 2013

Transcription

1 Sprinkler Protection for Cloud Ceilings SUPDET 2013 Jason Floyd, Ph.D. 28 February 2013

2 Background Cloud ceilings are a popular architectural feature Lack of clear guidance in the code for sprinkler installation When could one only place sprinklers below a cloud provided the structural ceiling was noncombustible? nei.org 2

3 Project Tasks 1. Review of prior work 2. Modeling/evaluation for large contiguous clouds (we defined as require at least one sprinkler) 3. Recommendations for installation 3

4 Prior Work Little directly applicable work Roof vents Gap around large cloud roof vent Roof vents < 4 % of ceiling have little impact on sprinkler activation 15 ft x 15 ft cloud = 4 inch gap bilco.com 4

5 Prior Work Perforated Ceilings Marshall, Feng, Morgan (1985): > 30 % free area reduces smoke layer formation SP (1997): large impact on smoke detection > 15 % porosity Coop (2000): Correlation for flow through perforated ceiling. < 10 % little impact on sprinkler activation 15 ft x 15 ft cloud: 15 % = 1 ft gap Armstrong 5

6 Prior Work Wellen (2010) 60+ FDS simulations Primarily large clouds Growth rate, gap size, ceiling height, cloud size, fire location Used to recommend a code change for no structural ceiling sprinklers < 8 inch gap Grid size of 4 to 8 inches: sufficient resolution for flow through gaps? 6

7 Modeling / Evaluation Plan Series of experiments to collect data for FDS validation Use of FDS to simulate a range of configurations guided by the validation results 7

8 Experimental Mockup Used moveable ceiling constructed for FPRF smoke detector and beamed corridor project Suspended two 8 ft x 8 ft clouds (0.375 inch drywall attached to 0.25 inch plywood) with a 6 inch gap 8

9 Experimental Mockup Two 8 ft x 8 ft moveable walls to allow for corner fire and wall fire configurations Tested four configurations of fire location with respect to walls and clouds 9 Cloud-Cloud Slot Cloud-Corner Wall Cloud Fire Ceiling Cloud-Wall Cloud-Cloud-Wall

10 Experimental Mockup Fire 1 ft 2 propane sand burner Instrumentation Cloud and structural ceiling thermocouples (2 inches below) Residential, quick response sprinkler w/pressure gauge (pressurized with air) TC Location Sprinkler 10

11 Test Matrix 11

12 Sprinkler Results 12

13 FDS Simulations FDS 6 RC1 Clouds, moveable ceiling, region around the edges of the ceiling for spilling 13

14 Grid Study Simulated Test 1 Three grid sizes Little change in bias from 4.8 to 3.2 cm, 3.2 cm slightly improved at cloud over 4.8 cm 3.2 cm selected for modeling tests 14

15 Processing of Results Compute bias and error following methodology in FDS Validation guide Computed separately for cloud and moveable ceiling Computed for all measurement locations FDS 6 ceiling jet validation results are 30 error with 7 % bias No attempt to correct for plume lean 15

16 FDS Results Generally over predict on moveable ceiling and under predict on clouds (conservative condition for this study) Removing Tests 4 and 5 (corner fires) the bias is < 20 % Expect plume lean to increase relative error 16

17 Plume Lean Correction Tests 1 and 2: Average pairs of TCs across symmetry plane (ceiling jet decays with 2/3 power) Post Correction (error/bias): Structural ceiling: 0.39/1.26 Cloud ceiling: 0.39/0.99 Total: 0.40/1.13 Similar to performance to validation manual results A C B Wall Cloud Fire Ceiling B TC Location A C 17

18 Simulation Plan Grid study suggests on the order of 3 to 5 cells are needed across the gap. Prior study had 1 cell in many cases. Grid study indicates that error in having one cell is likely conservative (i.e. prior study s recommendations may be overly restrictive) New simulations are proposed 18

19 Varies Simulation Geometry Cloud Panel 0.61 m (2 ft) 4.6 m (15 ft) Door 9.1 m (30 ft) 19

20 Simulation Variables Growth rate medium, fast Ceiling height 8, 14, 20, and 34 ft Gap size Begin with 6.25 % and 12.5 % of ceiling height based on literature review. Adjust based on results Configurations Cloud-Cloud Slot Cloud-Cloud Cross Wall Cloud Fire Cloud-Wall Slot 20 Cloud-Corner Cloud-Cloud-Wall

21 Simulation Metric Compare conditions for below cloud sprinkler activation to conditions with no gaps Compare conditions to following criteria: The temperature below the either the structural ceiling or the drop ceiling cannot exceed 315 C (600 F) at a distance of 50 % of the sprinkler spacing This criterion is intended to avoid damage to the structural ceiling, prevent the formation of a layer capable of rapid ignition of lightweight, flammable materials, and to avoid damage to the cloud ceiling. The temperature at 1.6 m (63 in) above the floor cannot exceed 93 C (200 F) away from the fire and cannot exceed 54 C (130 F) for over two minutes This criterion is intended to maintain tenable conditions for egress. 21

22 8 ft Clouds, 2 ft Plenum Setup Gap Size (%) Fire Growth Cloud Sprinkler (s) Ceiling 1st Sprinkler (s) Ceiling 2nd Sprinkler (s) Max Head Level TC ( C ) Closest Thermocouples Gas Temp ( C ) About 8ft away Gas Temp ( C ) Plume or Hot Layer CLOUD CEILING CLOUD CEILING Corner 6.25 Med Plume Cloud-Wall 6.25 Med N/A Plume Cloud-Cross 6.25 Med Plume C-C-Wall 6.25 Med Plume C-C-Slot 6.25 Med Plume Corner 6.25 Fast Plume Cloud-Wall 6.25 Fast N/A Plume Cloud-Cross 6.25 Fast Plume C-CWall 6.25 Fast Plume C-C-Slot 6.25 Fast Plume Corner 12.5 Med Hot Layer Cloud-Wall 12.5 Med N/A Plume Cloud-Cross 12.5 Med Plume C-C-Wall 12.5 Med Plume C-C-Slot 12.5 Med Plume Corner 12.5 Fast Hot Layer Cloud-Wall 12.5 Fast N/A Plume Cloud-Cross 12.5 Fast Plume C-C-Wall 12.5 Fast Plume C-C-Slot 12.5 Fast Plume 22

23 8 Ceiling, 2 Plenum, Fast Fire, 1 Gap Wall Fire Corner Fire 23

24 8 ft Clouds, 4 ft Plenum Setup Gap Size (%) Fire Growth Cloud Sprinkler (s) Ceiling 1st Sprinkler (s) Ceiling 2nd Sprinkler (s) Max Head Level TC ( C ) Closest Thermocouples Gas Temp ( C ) About 8ft away Gas Temp ( C ) Plume or Hot Layer CLOUD CEILING CLOUD CEILING Corner 6.25 Med Plume Corner 6.25 Fast Plume Cloud-Wall 6.25 Fast N/A Plume Cloud-Cross 6.25 Fast 116 N/A N/A Plume C-C-Wall 6.25 Fast Plume C-C-Slot 6.25 Fast 100 N/A N/A Plume Corner 12.5 Med Plume Corner 12.5 Fast Plume Cloud-Wall 12.5 Fast N/A Plume Cloud-Cross 12.5 Fast Plume C-C-Wall 12.5 Fast Plume C-C-Slot 12.5 Fast Plume 24

25 Preliminary Findings Wall/Corner configurations more severe entrainment pushes plume against wall Smaller plenums more limiting higher plenum spaces have lower ceiling temperatures and longer times for layer development Gap size as fraction of ceiling height looks appropriate In general high head level temperatures are not seen if the cloud sprinkler activates primarily due to the fire plume 25

26 Next Steps Complete FDS Simulation Work Develop Installation Guidelines Recommend Additional Work Draft Report May 2013 Final Report June