Sprinkler Protection for Cloud Ceilings SUPDET 2013 Jason Floyd, Ph.D. 28 February 2013
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
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
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
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
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
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
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
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
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
Test Matrix 11
Sprinkler Results 12
FDS Simulations FDS 6 RC1 Clouds, moveable ceiling, region around the edges of the ceiling for spilling 13
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
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
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
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
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
Varies Simulation Geometry Cloud Panel 0.61 m (2 ft) 4.6 m (15 ft) Door 9.1 m (30 ft) 19
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
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
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 230 110 189 54 152 650 77 211 Plume Cloud-Wall 6.25 Med 167 121 N/A 41 132 209 93 123 Plume Cloud-Cross 6.25 Med 206 148 149 68 154 236 96 131 Plume C-C-Wall 6.25 Med 196 147 150 60 163 209 83 124 Plume C-C-Slot 6.25 Med 164 146 147 44 111 160 79 107 Plume Corner 6.25 Fast 133 66 118 63 208 744 94 274 Plume Cloud-Wall 6.25 Fast 101 79 N/A 41 223 221 78 136 Plume Cloud-Cross 6.25 Fast 125 95 95 73 206 274 108 150 Plume C-CWall 6.25 Fast 116 91 91 62 206 267 96 165 Plume C-C-Slot 6.25 Fast 99 95 96 41 153 185 105 116 Plume Corner 12.5 Med 273 110 185 73 138 582 84 251 Hot Layer Cloud-Wall 12.5 Med 196 128 N/A 63 162 263 89 166 Plume Cloud-Cross 12.5 Med 245 157 157 91 126 227 104 159 Plume C-C-Wall 12.5 Med 254 150 152 90 152 311 96 181 Plume C-C-Slot 12.5 Med 191 133 134 59 132 237 81 151 Plume Corner 12.5 Fast 164 66 117 94 222 618 101 263 Hot Layer Cloud-Wall 12.5 Fast 118 79 N/A 64 257 321 112 208 Plume Cloud-Cross 12.5 Fast 157 99 98 107 156 379 114 200 Plume C-C-Wall 12.5 Fast 148 92 91 98 200 423 110 211 Plume C-C-Slot 12.5 Fast 116 83 85 62 133 318 99 176 Plume 22
8 Ceiling, 2 Plenum, Fast Fire, 1 Gap Wall Fire Corner Fire 23
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 199 117 184 33 309 327 79 252 Plume Corner 6.25 Fast 120 71 116 31 152 587 89 206 Plume Cloud-Wall 6.25 Fast 99 94 N/A 37 222 186 129 120 Plume Cloud-Cross 6.25 Fast 116 N/A N/A 61 184 146 96 99 Plume C-C-Wall 6.25 Fast 111 101 100 44 165 175 91 132 Plume C-C-Slot 6.25 Fast 100 N/A N/A 40 218 130 101 74 Plume Corner 12.5 Med 263 121 182 56 133 590 72 256 Plume Corner 12.5 Fast 155 72 116 57 149 680 112 345 Plume Cloud-Wall 12.5 Fast 112 91 N/A 44 287 248 75 179 Plume Cloud-Cross 12.5 Fast 145 111 111 89 162 271 115 173 Plume C-C-Wall 12.5 Fast 146 97 97 77 195 308 102 220 Plume C-C-Slot 12.5 Fast 113 104 105 53 154 140 93 110 Plume 24
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
Next Steps Complete FDS Simulation Work Develop Installation Guidelines Recommend Additional Work Draft Report May 2013 Final Report June 2013 26