RIL 2020-08, Ril 2020-08 Heat Release Rates of Multiple Transient Combustibles
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RIL 2020-08 NIST TN2102 HEAT RELEASE RATES OF MULTIPLE TRANSIENT COMBUSTIBLES Research Information Letter Office of Nuclear Regulatory Research Date Published: July 2020 Prepared by:
K. McGrattan National Institute of Standards and Technology David Stroup, NRC Project Manager
This report was published as National Institute of Standards and Technology (NIST) Technical Note 2102 as part of a series of experiments funded by the U.S. Nuclear Regulatory Commissions Office of Regulatory Research. The report has been re-published as an NRC Research Information Letter (RIL).
Disclaimer Legally binding regulatory requirements are stated only in laws, NRC regulations, licenses, including technical specifications, or orders; not in Research Information Letters (RILs). A RIL is not regulatory guidance, although NRCs regulatory offices may consider the information in a RIL to determine whether any regulatory actions are warranted.
NIST Technical Note 2102 Heat Release Rates of Multiple Transient Combustibles Kevin McGrattan This publication is available free of charge from:
https://doi.org/10.6028/NIST.TN.2102
NIST Technical Note 2102 Heat Release Rates of Multiple Transient Combustibles Kevin McGrattan Fire Research Division Engineering Laboratory This publication is available free of charge from:
https://doi.org/10.6028/NIST.TN.2102 July 2020 U.S. Department of Commerce Wilbur L. Ross, Jr., Secretary National Institute of Standards and Technology Walter Copan, NIST Director and Undersecretary of Commerce for Standards and Technology
Certain commercial entities, equipment, or materials may be identi"ed in this document in order to describe an experimental procedure or concept adequately. Such identi"cation is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose.
National Institute of Standards and Technology Technical Note 2102 Natl. Inst. Stand. Technol. Tech. Note 2102, 55 pages (July 2020)
CODEN: NTNOEF This publication is available free of charge from:
https://doi.org/10.6028/NIST.TN.2102
i Abstract The method for analyzing transient fires in NUREG/CR-6850 (EPRI 1011989),
EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities, made use of limited available data, and its application resulted in conservative estimates of transient fire risk.
To counter the lack of available data, additional testing was performed based on the transient fire events observed in the Electric Power Research Institute (EPRI) fire events database. NRC and EPRI collaborated on a set of 290 experiments to measure the HRRs of transient combustibles. These experiments were documented in NUREG-2232 (EPRI 3002015997), Heat Release Rate and Fire Characteristics of Fuels Representative of Typical Transient Fire Events in Nuclear Power Plants. Additional analysis and guidance for use of the transient data in fire PRAs was published in NUREG-2233 (EPRI 3002018231), Methodology for Modeling Transient Fires in Nuclear Power Plant Fire Probabilistic Risk Assessment.
This report documents heat release rate measurements of various transient combustibles; that is, non-permanent items found in industrial settings that can potentially contribute to an accidental fire. These items are often included in hypothetical fire scenarios that are modeled as part of risk analyses. Of particular interest in these experiments is the func-tional relationship between the peak heat release rate and the number of replicate items.
The data in this report will be used to support the development and validation of a spreadsheet to calculate the combined HRR for multiple burning items. The results from this testing effort will support more realistic modeling and analysis of transient fire risk for licensing and other risk-informed applications.
Key words Oxygen consumption calorimetry, Transient combustibles.
ii
Contents 1
Introduction 1
2 Description of Experiments 2
3 Results 5
3.1 Test 1, Single Box with Crinkle Paper....................
7 3.2 Test 2, Two Boxes with Crinkle Paper....................
8 3.3 Test 3, Four Boxes with Crinkle Paper....................
9 3.4 Test 4, Eight Boxes with Crinkle Paper....................
10 3.5 Test 5, Two Pallets, Stacked 11 3.6 Test 6, Four Pallets, Stacked 12 3.7 Test 7, Four Pallets, Two Stacks of Two 13 3.8 Test 8, Eight Pallets, Four Stacks of Two...................
14 3.9 Test 9, Eight Pallets, One Stack........................
15 3.10 Test 10, Single Box of Rags 16 3.11 Test 11, Four Boxes of Rags 17 3.12 Test 12, Four Boxes of Rags, Separated 18 3.13 Test 13, Single Wood Crib 19 3.14 Test 14, Two Wood Cribs, Side by Side 20 3.15 Test 15, Four Wood Cribs, Two by Two Array................
21 3.16 Test 16, Eight Wood Cribs, Four Stacks of Two...............
22 3.17 Test 17, Single Plastic Trash Bin Filled with Crinkle Paper.........
23 3.18 Test 18, Two Plastic Trash Bins Filled with Crinkle Paper..........
24 3.19 Test 19, Four Plastic Trash Bins Filled with Crinkle Paper..........
25 3.20 Test 20, Four Plastic Trash Bins Filled with Crinkle Paper Atop Two Pallets 26 3.21 Test 21, Eight Boxes Filled with Crinkle Paper Atop Two Pallets......
27 3.22 Test 22, Single Hanging Plastic Tarp.....................
28 3.23 Test 23, Single Hanging Plastic Tarp, Replicate 2..............
29 3.24 Test 24, Two Hanging, Overlapping Plastic Tarps..............
30 3.25 Test 25, Single Box, Plastic Commodity...................
31 3.26 Test 26, Two Boxes, Plastic Commodity...................
32 3.27 Test 27, Four Boxes, Plastic Commodity...................
33 3.28 Test 28, Eight Boxes, Plastic Commodity 34 3.29 Test 29, Single Plastic Bin Filled with Rags and Paper............
35 3.30 Test 30, Two Plastic Bins Filled with Rags and Paper............
36 3.31 Test 31, Four Plastic Bins Filled with Rags and Paper............
37 3.32 Test 32, Single Box with Crinkle Paper, Single Ignition Point........
38 3.33 Test 33, Two Boxes with Crinkle Paper, Single Ignition Point........
39 3.34 Test 34, Four Boxes with Crinkle Paper, Single Ignition Point........
40 3.35 Test 35, Eight Boxes of Rags.........................
41 iii
3.36 Test 36, Two Plastic Trash Bins Filled with Crinkle Paper, One Inside the Other 42 3.37 Test 37, Four Boxes with Crinkle Paper, Separated 43 3.38 Test 38, Four Boxes with Crinkle Paper, Separated 44 3.39 Test 39, Four Plastic Trash Bins Filled with Crinkle Paper, Separated....
45 3.40 Test 40, Four Boxes, Plastic Commodity...................
46 4
Discussion 47 4.1 Boxes.....................................
48 4.2 Wood Pallets and Cribs............................
50 4.3 Plastic Trash Bins...............................
52 4.4 Combinations.................................
53 4.5 Separations..................................
54 5
Conclusion 55 Acknowledgments 55 References 55 List of Tables 1
Average heat and product yields of the various test items 5
2 Summary of test results............................
6 List of Figures 1
Description of test items 3
2 Description of test items (cont.)........................
4 3
Photographs of Test 1.............................
7 4
Photographs of Test 2.............................
8 5
Photographs of Test 3.............................
9 6
Photographs of Test 4.............................
10 7
Photographs of Test 5.............................
11 8
Photographs of Test 6.............................
12 9
Photographs of Test 7.............................
13 10 Photographs of Test 8.............................
14 11 Photographs of Test 9.............................
15 12 Photographs of Test 10............................
16 13 Photographs of Test 11............................
17 14 Photographs of Test 12............................
18 15 Photographs of Test 13............................
19 16 Photographs of Test 14............................
20 iv
17 Photographs of Test 15............................
21 18 Photographs of Test 16............................
22 19 Photographs of Test 17............................
23 20 Photographs of Test 18............................
24 21 Photographs of Test 19............................
25 22 Photographs of Test 20............................
26 23 Photographs of Test 21............................
27 24 Photographs of Test 22............................
28 25 Photographs of Test 23............................
29 26 Photographs of Test 24............................
30 27 Photographs of Test 25............................
31 28 Photographs of Test 26............................
32 29 Photographs of Test 27............................
33 30 Photographs of Test 28............................
34 31 Photographs of Test 29............................
35 32 Photographs of Test 30............................
36 33 Photographs of Test 31............................
37 34 Photographs of Test 32............................
38 35 Photographs of Test 33............................
39 36 Photographs of Test 34............................
40 37 Photographs of Test 35............................
41 38 Photographs of Test 36............................
42 39 Photographs of Test 37............................
43 40 Photographs of Test 38............................
44 41 Photographs of Test 39............................
45 42 Photographs of Test 40............................
46 43 Increase in peak HRR as a function of increasing surface area........
47 44 HRR of boxes "lled with paper and ignited at a single point.........
48 45 Heat Release Rate of boxes "lled with paper, plastic and rags........
49 46 Heat Release Rate of pallets and cribs....................
51 47 Heat Release Rate of plastic trash bins....................
52 48 Heat Release Rate of four boxes "lled with crinkle paper..........
54 v
vi
1.
Introduction In 2018, the Nuclear Regulatory Commission (NRC) and the Electric Power Research In-stitute (EPRI) collaborated on a set of experiments to measure the heat release rate (HRR) of transient combustibles; that is, items one might "nd in industrial spaces on a tem-porary basis, in particular nuclear power plants. For example, during maintenance work, items such as trash bins, pallets, cardboard boxes, and so on, might remain in an area for a limited time period. These items are typically not accounted for when designing the "re protection system, but they are considered as part of a probabilistic risk analysis (PRA). A key parameter in such an analysis is the maximum heat release rate an item can generate if it accidentally catches "re, and the time to reach that peak following ignition.
The results of 290 HRR measurements made by the NRC and EPRI are documented in Ref. [1]. Additional analysis is found in Ref. [2]. The purpose of the current report is to document additional experiments to determine the relationship between the peak HRR and the number of multiple combustible items. In other words, if the peak HRR of a single item is 100 kW, will the peak HRR of two such items be 200 kW? Or, if the peak HRR of item A is 100 kW, and item B 200 kW, will the peak HRR of items A and B be 300 kW?
1
2.
Description of Experiments In December 2019 and February 20201, 40 "re experiments were conducted at the National Fire Research Laboratory at NIST, Gaithersburg, on behalf of the U.S. Nuclear Regulatory Commission. All of the experiments but two were conducted under a 6.1 m (20 ft) by 6.1 m hood with a nominal capacity of 3 MW. Two experiments were conducted under a larger hood of dimension 12.4 m (40 ft) by 8.4 m (28 ft) with a nominal capacity of 10 MW. The exhaust rate of the smaller hood ranged between approximately 13 m3/s (27500 ft3/min) to 17 m3/s (36000 ft3/min). The larger hood was set to approximately 42 m3/s (89000 ft3/min).
Details on the facility and measurements can be found in Ref. [3].
The items burned are described in Figs. 1 and 2. These consist of commercially avail-able materials constructed mainly of wood, paper, and plastics. Each item was weighed2 before and after the experiment on a load cell accurate to 10 g. A steel garbage can partially "lled with water was used to collect and weigh the burn residue after each experiment.
The "res were all ignited using one or more 7.5 cm (3 in) segments of approximately 1 cm (0.5 in) diameter cotton rope soaked in approximately 10 mL of acetone. For some items like the wood cribs and pallets, a small amount of crinkle paper was used to sustain the ignition until steady burning was achieved.
The "oor beneath the burning item was protected with a single layer of gypsum board covered by a single layer of concrete board. If plastics were involved, the test item was placed in a steel pan to contain the molten plastic.
136 of 40 experiments were conducted in December 2019; 4 experiments were conducted in February 2020.
2The mass measurements were made with a Mettler Toledo Jaguar series load cell with a range from 10 g to 150 kg.
2
Box #1:
Single-wall corrugated box with nominal dimensions 61 cm by 61 cm by 46 cm (24 in by 24 in by 18 in) "lled with crinkle paper, a common packing material made by shredding craft paper. The box alone had a mass of approximately 1.6 kg (3.5 lb), and the box and paper com-bined had a mass of 8.0 kg (18 lb). The box top "aps were closed, end over end, but not sealed with tape.
Box #2:
Single-wall corrugated box with nominal dimensions 41 cm by 30 cm by 30 cm (16 in by 12 in by 12 in) "lled with dry cotton rags. The box alone had a mass of approximately 0.8 kg (1.8 lb), and the box and rags combined had a mass of approximately 4.5 kg (10 lb). The box top was taped shut for the burns.
Box #3:
Single-wall corrugated box with nominal dimensions 53 cm by 53 cm by 53 cm (21 in by 21 in by 21 in) "lled with 100 rigid polystyrene cups. The corrugated box and inner lin-ers alone had a mass of approximately 3.5 kg (7.7 lb), and the total combined mass was approximately 7.0 kg (15 lb).
The top was taped shut. This item was originally developed by FM Global for use in rack storage commodity testing.
Tarp: Lightweight plastic tarp with di-mensions 3.0 m by 2.4 m (10 ft by 8 ft) draped across a steel rod. Its mass was approximately 0.8 kg (1.8 lb).
Figure 1: Description of test items.
3
Pallet: Pine wood pallet with dimen-sions 122 cm by 102 cm by 12 cm (48 in by 40 in by 4.75 in). Its mass was approximately 16.0 kg (35 lb). Its moisture content was less than 5 %.
Shown at right are two pallets, which were ignited with 1 kg (2.2 lb) of crin-kle paper distributed evenly throughout the lower pallet.
Crib: Pine wood crib with dimensions 56 cm by 56 cm by 46 cm (22 in by 22 in by 18 in) constructed of slats with a cross-section 3.8 cm (1.5 in) square.
Its mass was approximately 39 kg (86 lb).
Its moisture content was less than 5 %. It was ignited with 0.75 kg (1.7 lb) of crinkle paper stuffed in the space below the "rst row of slats.
Bin #1: Cylindrical, open-top plastic trash bin approximately 71 cm (28 in) tall with an opening diameter of 51 cm (20 in).
Its mass was approximately 2.7 kg (5.9 lb). The bin was half "lled with crinkle paper for a combined mass of 5.0 kg (11 lb).
Bin #2: The same as Bin #1, but with the rags and cardboard of Box #2 mixed in. The total mass was approximately 9.5 kg (21 lb).
Figure 2: Description of test items (cont.)
4
3.
Results The heat release rate (HRR) and photographs of each experiment are given in Figs. 3 through 42.
A summary of the 40 experiments is given in Table 2. The uncertainty of each mea-surement includes both aleatoric and epistemic sources and is expressed in terms of a 95 %
con"dence interval, sometimes referred to as 2 uncertainty because it is equivalent to two standard deviations. The uncertainty calculation for a particular heat release rate measure-ment is fairly complex, but, in general, the relative uncertainty is approximately 7 % for general combustibles for which the combustion kinetics are unknown; and 4.5 % for mate-rials with known chemical make-up. The difference in uncertainty values is largely due to the uncertainty of the heat of combustion based on oxygen consumption, HO2. For these experiments, items containing only wood and paper were taken as cellulose and assigned a value of 13.61 kJ/kg of oxygen consumed [4]; whereas an average value of 13.1 kJ/kg was assigned to the items that contained plastics or other materials. Further details of the calorimetry and uncertainty calculation can be found in Ref. [3].
Note that in Table 2 where no value is given, the measured quantity was found to be less than its uncertainty value.
Table 1 provides the average heats of combustion and product yields for the items de-scribed in Figs. 1 and 2, excluding the tarps for which reliable yields could not be de-termined. The gas species and soot yields and the heat of combustion are calculated by dividing the measured total heat or mass in the exhaust hood by the measured mass loss of the fuels. That is, these values represent heat or mass generated per unit mass of fuel con-sumed. The Residue Yield is calculated by dividing the "nal mass by the initial mass of the item. Note that in order to burn as much of the items as possible, it was necessary to mix up the residue with a pike hook until all of the combustible material had been consumed.
Table 1: Average heat and product yields of the various test items.
Item H (MJ/kg)
CO Yield CO2 Yield Soot Yield Residue Yield Box #1 14.8+/-0.5 0.039+/-0.001 1.48+/-0.05 0.0014+/-0.0003 0.031+/-0.016 Box #2 13.8+/-0.5 0.066+/-0.003 1.33+/-0.05 0.0042+/-0.0019 0.035+/-0.020 Box #3 25.4+/-1.5 0.055+/-0.002 2.13+/-0.08 0.0976+/-0.014 0.003+/-0.002 Pallet 17.2+/-0.5 0.031+/-0.001 1.66+/-0.06 0.0033+/-0.0006 0.059+/-0.024 Crib 16.7+/-0.5 0.023+/-0.001 1.63+/-0.06 0.0020+/-0.0003 0.053+/-0.034 Bin #1 27.6+/-1.7 0.021+/-0.004 2.18+/-0.08 0.0153+/-0.0027 0.090+/-0.040 Bin #2 20.8+/-1.2 0.031+/-0.001 1.80+/-0.07 0.0099+/-0.0029 0.040+/-0.020 5
Table 2: Summary of test results.
Test No.
Initial Mass Final Mass HO2 Peak HRR Total Energy Time to H
CO CO2 Soot No.
Item Items (kg)
(kg)
(MJ/kg)
(kW)
(MJ)
Peak (min)
(MJ/kg)
Yield Yield Yield 1
Box #1 1
8.00+/-0.02 0.25+/-0.02 13.6+/-0.4 328+/-15 116+/-4 4.7+/-0.2 15.0+/-0.5 0.035+/-0.001 1.50+/-0.05 0.0015+/-0.0003 2
Box #1 2
16.00+/-0.02 0.45+/-0.02 13.6+/-0.4 481+/-21 236+/-8 4.9+/-0.2 15.2+/-0.5 0.036+/-0.001 1.51+/-0.06 0.0010+/-0.0005 3
Box #1 4
32.00+/-0.02 0.66+/-0.02 13.6+/-0.4 944+/-40 479+/-15 3.3+/-0.2 15.3+/-0.5 0.034+/-0.001 1.51+/-0.05 0.0005+/-0.0003 4
Box #1 8
64.00+/-0.02 1.28+/-0.02 13.6+/-0.4 2581+/-101 979+/-31 4.1+/-0.2 15.6+/-0.5 0.030+/-0.001 1.56+/-0.06 0.0005+/-0.0001 5
Pallet 2
33.00+/-0.02 2.63+/-0.02 13.6+/-0.4 934+/-40 502+/-16 3.9+/-0.2 16.5+/-0.5 0.038+/-0.001 1.60+/-0.06 0.0035+/-0.0006 6
Pallet 4
65.40+/-0.02 3.50+/-0.02 13.6+/-0.4 1801+/-73 1073+/-34 4.5+/-0.2 17.3+/-0.6 0.026+/-0.001 1.68+/-0.06 0.0025+/-0.0004 7
Pallet 4
66.30+/-0.02 3.83+/-0.02 13.6+/-0.4 2049+/-82 1092+/-34 3.8+/-0.2 17.5+/-0.6 0.037+/-0.001 1.67+/-0.06 0.0052+/-0.0012 8
Pallet 8
136.25+/-0.02 6.55+/-0.02 13.6+/-0.4 4174+/-158 2229+/-70 3.7+/-0.2 17.2+/-0.5 0.032+/-0.001 1.66+/-0.06 0.0039+/-0.0006 9
Pallet 8
132.00+/-0.02 7.21+/-0.02 13.6+/-0.4 3141+/-122 2186+/-69 5.9+/-0.2 17.5+/-0.6 0.022+/-0.001 1.68+/-0.06 0.0015+/-0.0004 10 Box #2 1
4.50+/-0.02 0.13+/-0.02 13.6+/-0.4 114+/-6 62+/-2 3.2+/-0.2 14.2+/-0.5 0.078+/-0.003 1.33+/-0.05 0.0056+/-0.0019 11 Box #2 4
17.98+/-0.02 0.53+/-0.02 13.6+/-0.4 345+/-16 250+/-8 3.3+/-0.2 14.3+/-0.5 0.059+/-0.002 1.40+/-0.05 0.0035+/-0.0008 12 Box #2 4
18.10+/-0.02 0.59+/-0.02 13.6+/-0.4 342+/-16 246+/-8 5.2+/-0.2 14.0+/-0.4 0.055+/-0.002 1.39+/-0.05 0.0059+/-0.0024 13 Crib 1
39.39+/-0.02 2.85+/-0.02 13.6+/-0.4 396+/-18 597+/-19 23.1+/-0.2 16.3+/-0.5 0.023+/-0.001 1.59+/-0.06 0.0020+/-0.0003 14 Crib 2
79.90+/-0.02 4.74+/-0.02 13.6+/-0.4 907+/-38 1263+/-40 21.6+/-0.2 16.8+/-0.5 0.023+/-0.001 1.63+/-0.06 0.0021+/-0.0004 15 Crib 4
156.02+/-0.02 7.38+/-0.02 13.6+/-0.4 1402+/-58 2523+/-79 24.5+/-0.2 17.0+/-0.5 0.021+/-0.001 1.66+/-0.06 0.0016+/-0.0003 16 Crib 8
318.14+/-0.02 10.67+/-0.02 13.6+/-0.4 2301+/-91 5120+/-160 37.5+/-0.2 16.7+/-0.5 0.026+/-0.001 1.63+/-0.06 0.0024+/-0.0007 17 Bin #1 1
5.00+/-0.02 0.37+/-0.02 13.1+/-0.7 159+/-11 131+/-8 8.4+/-0.2 28.2+/-1.7 0.019+/-0.004 2.21+/-0.08 0.0094+/-0.0027 18 Bin #1 2
10.00+/-0.02 0.85+/-0.02 13.1+/-0.7 445+/-31 257+/-15 8.7+/-0.2 28.1+/-1.7 0.017+/-0.001 2.23+/-0.08 0.0174+/-0.0073 19 Bin #1 4
20.00+/-0.02 1.75+/-0.02 13.1+/-0.7 587+/-41 512+/-30 5.6+/-0.2 28.1+/-1.7 0.019+/-0.001 2.22+/-0.08 0.0185+/-0.0051 20 Bin #1a 4
52.84+/-0.02 3.64+/-0.02 13.1+/-0.7 2319+/-155 1028+/-61 2.6+/-0.2 20.9+/-1.2 0.019+/-0.001 1.82+/-0.07 0.0093+/-0.0015 21 Box #1a 8
96.24+/-0.02 3.35+/-0.02 13.6+/-0.4 3240+/-125 1506+/-48 2.5+/-0.2 16.2+/-0.5 0.018+/-0.001 1.58+/-0.06 0.0005+/-0.0002 22 Tarp 1
0.78+/-0.02
13.1+/-0.7 12+/-4
0.8+/-0.2
23 Tarp 1
0.78+/-0.02
13.1+/-0.7 11+/-4
1.3+/-0.2
24 Tarp 2
1.56+/-0.02
13.1+/-0.7 16+/-5 8.3+/-4.5 1.2+/-0.2
25 Box #3 1
6.89+/-0.02 0.03+/-0.02 13.1+/-0.7 619+/-43 174+/-11 4.5+/-0.2 25.4+/-1.5 0.051+/-0.002 2.13+/-0.08 0.109+/-0.014 26 Box #3 2
13.98+/-0.02 0.05+/-0.02 13.1+/-0.7 888+/-61 355+/-21 5.7+/-0.2 25.5+/-1.5 0.049+/-0.002 2.14+/-0.08 0.098+/-0.013 27 Box #3 4
28.00+/-0.02 0.06+/-0.02 13.1+/-0.7 1430+/-133 700+/-43 5.8+/-0.2 25.1+/-1.5 0.056+/-0.002 2.09+/-0.08 0.096+/-0.014 28 Box #3 8
56.00+/-0.02 0.11+/-0.02 13.1+/-0.7 2826+/-246 1438+/-88 5.3+/-0.2 25.7+/-1.6 0.057+/-0.002 2.17+/-0.08 0.085+/-0.011 29 Bin #2 1
9.45+/-0.02 0.33+/-0.02 13.1+/-0.7 225+/-16 190+/-11 9.6+/-0.2 20.9+/-1.2 0.029+/-0.001 1.82+/-0.07 0.0108+/-0.0029 30 Bin #2 2
19.11+/-0.02 0.95+/-0.02 13.1+/-0.7 462+/-32 370+/-22 8.1+/-0.2 20.4+/-1.2 0.032+/-0.001 1.75+/-0.06 0.0086+/-0.0018 31 Bin #2 4
37.84+/-0.02 1.37+/-0.02 13.1+/-0.7 972+/-66 772+/-46 6.9+/-0.2 21.2+/-1.3 0.032+/-0.001 1.84+/-0.07 0.0100+/-0.0016 32 Box #1 1
8.00+/-0.02 0.37+/-0.02 13.6+/-0.4 133+/-7 104+/-3 3.8+/-0.2 13.6+/-0.4 0.050+/-0.002 1.37+/-0.05
33 Box #1 2
16.00+/-0.02 0.55+/-0.02 13.6+/-0.4 267+/-12 223+/-7 9.1+/-0.2 14.4+/-0.5 0.042+/-0.002 1.43+/-0.05
34 Box #1 4
32.00+/-0.02 1.22+/-0.02 13.6+/-0.4 288+/-13 442+/-14 8.8+/-0.2 14.4+/-0.5 0.046+/-0.002 1.43+/-0.05 0.0019+/-0.0010 35 Box #2 8
36.00+/-0.02 1.81+/-0.02 13.6+/-0.4 290+/-13 433+/-14 4.5+/-0.2 12.7+/-0.4 0.073+/-0.003 1.18+/-0.04
36 Bin #1b 2
10.00+/-0.02 0.90+/-0.02 13.1+/-0.7 330+/-29 253+/-15 12.5+/-0.2 27.8+/-1.7 0.021+/-0.001 2.11+/-0.08 0.0214+/-0.0072 37 Box #1 4
32.00+/-0.02 0.87+/-0.02 13.6+/-0.4 930+/-39 459+/-15 8.0+/-0.2 14.7+/-0.5 0.043+/-0.002 1.50+/-0.05 0.0023+/-0.0006 38 Box #1 4
32.00+/-0.02 0.98+/-0.02 13.6+/-0.4 1964+/-79 471+/-15 2.9+/-0.2 15.2+/-0.5 0.039+/-0.001 1.51+/-0.05 0.0023+/-0.0005 39 Bin #1 4
20.00+/-0.02 2.54+/-0.02 13.1+/-0.7 705+/-49 453+/-27 8.9+/-0.2 25.9+/-1.5 0.028+/-0.001 2.13+/-0.08 0.0113+/-0.0019 40 Box #3 4
28.00+/-0.02 0.11+/-0.02 13.1+/-0.7 2071+/-139 710+/-43 4.0+/-0.2 25.5+/-1.5 0.064+/-0.002 2.14+/-0.08 0.099+/-0.013 a
The test items are set on two pallets.
b The two bins are set one inside the other.
6
3.1 Test 1, Single Box with Crinkle Paper Single box with crinkle paper, ignited at the base of each vertical face. The spike in HRR just after 15 min resulted from stirring the residual material.
0 5
10 15 20 25 Time (min) 0 50 100 150 200 250 300 350 Heat Release Rate (kW)
Test 1; Boxes with Crinkle Paper; 1x1x1 Figure 3: Heat release rate and photographs of Test 1.
7
3.2 Test 2, Two Boxes with Crinkle Paper Two boxes with crinkle paper, ignited at the base of each vertical face. The spike in HRR just after 25 min resulted from stirring the residual material.
0 5
10 15 20 25 30 35 Time (min) 0 100 200 300 400 500 Heat Release Rate (kW)
Test 2; Boxes with Crinkle Paper; 2x1x1 Figure 4: Heat release rate and photographs of Test 2.
8
3.3 Test 3, Four Boxes with Crinkle Paper Four boxes with crinkle paper, ignited at the base of each vertical face. The spike in HRR after 30 min resulted from stirring the residual material.
0 10 20 30 40 Time (min) 0 200 400 600 800 1000 Heat Release Rate (kW)
Test 3; Boxes with Crinkle Paper; 2x2x1 Figure 5: Heat release rate and photographs of Test 3.
9
3.4 Test 4, Eight Boxes with Crinkle Paper Eight boxes with crinkle paper, ignited at the base of each vertical face. The spikes in HRR after 30 min resulted from stirring the residual material.
0 10 20 30 40 50 Time (min) 0 500 1000 1500 2000 2500 3000 Heat Release Rate (kW)
Test 4; Boxes with Crinkle Paper; 2x2x2 Figure 6: Heat release rate and photographs of Test 4.
10
3.5 Test 5, Two Pallets, Stacked Two wood pallets with 1 kg crinkle pa-per distributed evenly along the bottom of the stack. The "re was ignited with four igniters, one in each quadrant of the bottom pallet.
0 10 20 30 40 Time (min) 0 200 400 600 800 1000 Heat Release Rate (kW)
Test 5; Wood Pallets; 1 stack of 2 Figure 7: Heat release rate and photographs of Test 5.
11
3.6 Test 6, Four Pallets, Stacked Four wood pallets, stacked, with 1 kg crinkle paper distributed evenly along the bottom of the stack. The "re was ignited with four igniters, one in each quadrant of the bottom pallet.
0 10 20 30 40 Time (min) 0 500 1000 1500 2000 Heat Release Rate (kW)
Test 6; Wood Pallets; 1 stack of 4 Figure 8: Heat release rate and photographs of Test 6.
12
3.7 Test 7, Four Pallets, Two Stacks of Two Four wood pallets, two stacks of two, with 1 kg crinkle paper distributed evenly along the bottom of each stack.
The "re was ignited with eight igniters, one in each quadrant of each stack.
0 10 20 30 40 50 Time (min) 0 500 1000 1500 2000 Heat Release Rate (kW)
Test 7; Wood Pallets; 2 stacks of 2 Figure 9: Heat release rate and photographs of Test 7.
13
3.8 Test 8, Eight Pallets, Four Stacks of Two Eight wood pallets, four stacks of two, with 1 kg crinkle paper distributed evenly along the bottom of each stack.
The "re was ignited with 16 igniters, one in each quadrant of each stack.
0 10 20 30 40 50 Time (min) 0 1000 2000 3000 4000 5000 Heat Release Rate (kW)
Test 8; Wood Pallets; 4 stacks of 2 Figure 10: Heat release rate and photographs of Test 8.
14
3.9 Test 9, Eight Pallets, One Stack Eight wood pallets, stacked, with 1 kg crinkle paper distributed evenly along the bottom of the stack. The "re was ignited with four igniters, one in each quadrant of the stack.
0 10 20 30 40 50 Time (min) 0 500 1000 1500 2000 2500 3000 3500 Heat Release Rate (kW)
Test 9; Wood Pallets; 1 stack of 8 Figure 11: Heat release rate and photographs of Test 9.
15
3.10 Test 10, Single Box of Rags One box "lled with cotton rags, ignited on four sides. The spikes in HRR after 20 min were caused by breaking up the pile of ash and debris.
0 10 20 30 40 50 Time (min) 0 20 40 60 80 100 120 Heat Release Rate (kW)
Test 10; Boxes of Rags; 1x1x1 Figure 12: Heat release rate and photographs of Test 10.
16
3.11 Test 11, Four Boxes of Rags Four boxes "lled with cotton rags, ig-nited at eight points.
The spikes in HRR after 30 min were caused by breaking up the pile of ash and debris.
0 10 20 30 40 50 60 Time (min) 0 100 200 300 400 Heat Release Rate (kW)
Test 11; Boxes of Rags; 2x2x1 Figure 13: Heat release rate and photographs of Test 11.
17
3.12 Test 12, Four Boxes of Rags, Separated Four boxes "lled with cotton rags, sep-arated by a half width, ignited at eight points. The spikes in HRR after 30 min were caused by breaking up the pile of ash and debris.
0 10 20 30 40 50 Time (min) 0 100 200 300 400 Heat Release Rate (kW)
Test 12; Boxes of Rags; 2x2x1; separated Figure 14: Heat release rate and photographs of Test 12.
18
3.13 Test 13, Single Wood Crib Single wood crib with 0.75 kg crinkle paper evenly distributed at the base and ignited at two points. At approximately 48 min, the hot coals were spread out and raked into a water bath.
0 10 20 30 40 50 Time (min) 0 100 200 300 400 Heat Release Rate (kW)
Test 13; Wood Cribs; 1x1x1 Figure 15: Heat release rate and photographs of Test 13.
19
3.14 Test 14, Two Wood Cribs, Side by Side Two wood cribs with 0.75 kg crinkle paper evenly distributed at the base of each and ignited at four points.
0 10 20 30 40 50 60 Time (min) 0 200 400 600 800 1000 Heat Release Rate (kW)
Test 14; Wood Cribs; 2x1x1 Figure 16: Heat release rate and photographs of Test 14.
20
3.15 Test 15, Four Wood Cribs, Two by Two Array Four wood cribs with 0.75 kg crinkle paper evenly distributed at the base of each and ignited at four points. At ap-proximately 60 min, the hot coals were spread out and at 80 min raked into a water bath.
0 20 40 60 80 Time (min) 0 500 1000 1500 Heat Release Rate (kW)
Test 15; Wood Cribs; 2x2x1 Figure 17: Heat release rate and photographs of Test 15.
21
3.16 Test 16, Eight Wood Cribs, Four Stacks of Two Eight wood cribs, four stacks of two, with 0.75 kg crinkle paper evenly dis-tributed at the base of each stack and ignited at four points.
0 20 40 60 80 100 Time (min) 0 500 1000 1500 2000 2500 Heat Release Rate (kW)
Test 16; Wood Cribs; 2x2x2 Figure 18: Heat release rate and photographs of Test 16.
22
3.17 Test 17, Single Plastic Trash Bin Filled with Crinkle Paper Single plastic trash bin, half "lled with crinkle paper. Single ignition point on top of paper. After 50 min, the residue in the pan was spread out to hasten burning.
0 10 20 30 40 50 60 Time (min) 0 50 100 150 Heat Release Rate (kW)
Test 17; Trash Bins; 1x1x1 Figure 19: Heat release rate and photographs of Test 17.
23
3.18 Test 18, Two Plastic Trash Bins Filled with Crinkle Paper Two plastic trash bins, half "lled with crinkle paper. Single ignition point on top of paper in each bin. After 20 min, the residue in the pan was spread out to hasten burning.
0 10 20 30 40 50 Time (min) 0 100 200 300 400 500 Heat Release Rate (kW)
Test 18; Trash Bins; 2x1x1 Figure 20: Heat release rate and photographs of Test 18.
24
3.19 Test 19, Four Plastic Trash Bins Filled with Crinkle Paper Four plastic trash bins, half "lled with crinkle paper. Single ignition point on top of paper in each bin. The bins are wired together to ensure that the melt remains in the catch pan. After 40 min, the residue in the pan was spread out to hasten burning.
0 10 20 30 40 50 60 70 Time (min) 0 100 200 300 400 500 600 700 Heat Release Rate (kW)
Test 19; Trash Bins; 2x2x1 Figure 21: Heat release rate and photographs of Test 19.
25
3.20 Test 20, Four Plastic Trash Bins Filled with Crinkle Paper Atop Two Pallets Four plastic trash bins, half "lled with crinkle paper, atop two pallets. Single ignition point on top of paper in each bin and four ignition points in each quadrant of the pallet stack. The bins were wired together to ensure that the melt remains in the catch pan.
0 10 20 30 40 Time (min) 0 500 1000 1500 2000 2500 Heat Release Rate (kW)
Test 20; 4 Trash Bins; 2 Pallets Figure 22: Heat release rate and photographs of Test 20.
26
3.21 Test 21, Eight Boxes Filled with Crinkle Paper Atop Two Pallets Eight boxes "lled with crinkle paper sit atop two pallets. The base of the pallet stack has 1 kg crinkle paper, evenly dis-tributed and ignited in each quadrant.
0 10 20 30 40 50 Time (min) 0 500 1000 1500 2000 2500 3000 3500 Heat Release Rate (kW)
Test 21; 8 Boxes; 2 Pallets Figure 23: Heat release rate and photographs of Test 21.
27
3.22 Test 22, Single Hanging Plastic Tarp A single plastic tarp, initially hanging 30 cm (1 ft) above the "oor, ignited in two locations. The "re spread slowly and erratically.
0 5
10 15 Time (min) 0 2
4 6
8 10 12 14 Heat Release Rate (kW)
Test 22; Tarps; Single; rev 1 Figure 24: Heat release rate and photographs of Test 22.
28
3.23 Test 23, Single Hanging Plastic Tarp, Replicate 2 A single plastic tarp, with 15 cm (6 in) dragging on "oor, ignited in two loca-tions. The "re spread slowly and errat-ically.
0 5
10 15 20 25 Time (min) 0 2
4 6
8 10 12 Heat Release Rate (kW)
Test 23; Tarps; Single; rev 2 Figure 25: Heat release rate and photographs of Test 23.
29
3.24 Test 24, Two Hanging, Overlapping Plastic Tarps Two overlapping plastic tarps, with 15 cm (6 in) dragging on "oor, ignited in two locations. The "re spread slowly and erratically.
0 5
10 15 20 Time (min) 0 5
10 15 Heat Release Rate (kW)
Test 24; Tarps; Double Figure 26: Heat release rate and photographs of Test 24.
30
3.25 Test 25, Single Box, Plastic Commodity Single box "lled with polystyrene cups, ignited at the base of each vertical face.
0 5
10 15 20 Time (min) 0 100 200 300 400 500 600 700 Heat Release Rate (kW)
Test 25; Plastic Commodity; 1x1x1 Figure 27: Heat release rate and photographs of Test 25.
31
3.26 Test 26, Two Boxes, Plastic Commodity Two boxes "lled with polystyrene cups, ignited at the base of each vertical face.
0 5
10 15 20 25 Time (min) 0 200 400 600 800 1000 Heat Release Rate (kW)
Test 26; Plastic Commodity; 2x2x1 Figure 28: Heat release rate and photographs of Test 26.
32
3.27 Test 27, Four Boxes, Plastic Commodity Four boxes "lled with polystyrene cups, ignited at the base of each vertical face.
0 5
10 15 20 25 30 35 Time (min) 0 500 1000 1500 Heat Release Rate (kW)
Test 27; Plastic Commodity; 2x2x1 Figure 29: Heat release rate and photographs of Test 27.
33
3.28 Test 28, Eight Boxes, Plastic Commodity Eight boxes "lled with polystyrene cups, ignited at the base of each vertical face.
0 5
10 15 20 25 30 35 Time (min) 0 500 1000 1500 2000 2500 3000 Heat Release Rate (kW)
Test 28; Plastic Commodity; 2x2x2 Figure 30: Heat release rate and photographs of Test 28.
34
3.29 Test 29, Single Plastic Bin Filled with Rags and Paper Single plastic bin with the same amount of crinkle paper as in Test 17, along with the entire box and rags of Test 10.
Single ignition point on top of paper and rags.
0 10 20 30 40 50 Time (min) 0 50 100 150 200 250 Heat Release Rate (kW)
Test 29; Trash Bins with Rags and Paper; 1x1x1 Figure 31: Heat release rate and photographs of Test 29.
35
3.30 Test 30, Two Plastic Bins Filled with Rags and Paper Two plastic bins with the same amount of crinkle paper as in Test 17, along with the entire box and rags of Test 10.
Single ignition points on top of paper and rags.
0 10 20 30 40 50 60 Time (min) 0 100 200 300 400 500 Heat Release Rate (kW)
Test 30; Trash Bins with Rags and Paper; 2x1x1 Figure 32: Heat release rate and photographs of Test 30.
36
3.31 Test 31, Four Plastic Bins Filled with Rags and Paper Four plastic bins with the same amount of crinkle paper as in Test 17, along with the entire box and rags of Test 10.
Single ignition points on top of paper and rags.
0 10 20 30 40 50 60 70 Time (min) 0 200 400 600 800 1000 Heat Release Rate (kW)
Test 31; Trash Bins with Rags and Paper; 2x2x1 Figure 33: Heat release rate and photographs of Test 31.
37
3.32 Test 32, Single Box with Crinkle Paper, Single Ignition Point Single box with crinkle paper, ignited at the base of one vertical face. The spike in HRR at 40 min resulted from stirring the residue.
0 10 20 30 40 50 Time (min) 0 50 100 150 Heat Release Rate (kW)
Test 32; Boxes with Crinkle Paper; 1x1x1 Figure 34: Heat release rate and photographs of Test 32.
38
3.33 Test 33, Two Boxes with Crinkle Paper, Single Ignition Point Two boxes with crinkle paper, ignited at the base of one vertical face. The spike in HRR at 40 min resulted from stirring the residue.
0 10 20 30 40 Time (min) 0 50 100 150 200 250 300 Heat Release Rate (kW)
Test 33; Boxes with Crinkle Paper; 2x1x1 Figure 35: Heat release rate and photographs of Test 33.
39
3.34 Test 34, Four Boxes with Crinkle Paper, Single Ignition Point Four boxes with crinkle paper, ignited at the base of one vertical face. The spike in HRR at 60 min resulted from stirring the residue.
0 10 20 30 40 50 60 70 Time (min) 0 50 100 150 200 250 300 Heat Release Rate (kW)
Test 34; Boxes with Crinkle Paper; 2x2x1 Figure 36: Heat release rate and photographs of Test 34.
40
3.35 Test 35, Eight Boxes of Rags Eight boxes "lled with cotton rags, ig-nited at eight points. The spike in HRR at 60 min resulted from stirring the residue.
0 20 40 60 80 Time (min) 0 50 100 150 200 250 300 Heat Release Rate (kW)
Test 35; Boxes of Rags; 2x2x2 Figure 37: Heat release rate and photographs of Test 35.
41
3.36 Test 36, Two Plastic Trash Bins Filled with Crinkle Paper, One Inside the Other Two plastic trash bins stacked together and "lled with crinkle paper. Single ig-nition point on top of paper in the bin.
The spike in HRR at 32 min and 46 min resulted from stirring the residue.
0 10 20 30 40 50 60 Time (min) 0 100 200 300 400 Heat Release Rate (kW)
Test 36; 2 Trash Bins and Crinkle Paper Figure 38: Heat release rate and photographs of Test 36.
42
3.37 Test 37, Four Boxes with Crinkle Paper, Separated Four boxes with crinkle paper, ignited at the base of each exterior vertical face (8 ignition points). The boxes are sep-arated by 0.6 m (2 ft). The residue was stirred up at approximately 20 min and 28 min.
0 5
10 15 20 25 30 35 Time (min) 0 200 400 600 800 1000 Heat Release Rate (kW)
Test 37; Boxes with Crinkle Paper; 2x2x1 Figure 39: Heat release rate and photographs of Test 37.
43
3.38 Test 38, Four Boxes with Crinkle Paper, Separated Four boxes with crinkle paper, ignited at the base of each vertical face (16 ig-nition points). The boxes were sepa-rated by 0.6 m (2 ft). The residue was stirred up at approximately 23 min.
0 10 20 30 40 Time (min) 0 500 1000 1500 2000 Heat Release Rate (kW)
Test 38; Boxes with Crinkle Paper; 2x2x1 Figure 40: Heat release rate and photographs of Test 38.
44
3.39 Test 39, Four Plastic Trash Bins Filled with Crinkle Paper, Separated Four plastic trash bins, half "lled with crinkle paper, separated by the top di-ameter, and set within individual steel pans. Single ignition point on top of pa-per in each bin. The residue was stirred up at approximately 30 min and 40 min.
0 10 20 30 40 50 60 Time (min) 0 200 400 600 800 Heat Release Rate (kW)
Test 39; Trash Bins; 2x2x1 Figure 41: Heat release rate and photographs of Test 39.
45
3.40 Test 40, Four Boxes, Plastic Commodity Four boxes "lled with polystyrene cups, ignited at the base of each verti-cal face (16 ignition points). Similar to Test 27, but the boxes were separated by 0.53 m (21 in).
0 5
10 15 20 25 30 Time (min) 0 500 1000 1500 2000 Heat Release Rate (kW)
Test 40; Plastic Commodity; 2x2x1 Figure 42: Heat release rate and photographs of Test 40.
46
4.
Discussion In general, the peak heat release rate (HRR) of the "res occurred at the same time or shortly after all of the exposed surface area of the burning item was engulfed in "ame. This sug-gests that the peak HRR is proportional to the exposed surface area. Figure 43 displays the relationship between the increased peak HRR of multiple items as a function of the relative increase in surface area. In theory, the relationship should be linear, i.e. double the sur-face area, double the HRR. In the case of the box "res, two boxes sitting side be side have 8/5 = 1.6 times the exposed surface area of a single box. A 2 by 2 array of four boxes has 12/5 = 2.4 times the area. A 2 by 2 by 2 array of eight boxes has 20/5 = 4 times the area.
For stacked pallets, four pallets have approximately 1.8 times the surface area of two; eight pallets have approximately 3.4 times the surface area of two. However, for multiple cribs and bins, the exposed surface area is nearly linearly proportional to the number of items.
There is a small amount of overlap in the exposed surfaces of the wood cribs, but not much.
Of course, there are exceptions to the simple rule, and in the sections to follow, the various items and test parameters are examined in more detail.
0 1
2 3
4 5
6 7
8 Surface Area Multiplier 0
1 2
3 4
5 6
7 8
Peak HRR Multiplier Figure 43: Increase in peak HRR as a function of increasing surface area.
47
4.1 Boxes Figure 45 displays the HRR of one, two, four, and eight boxes "lled with crinkle paper (top), polystyrene cups (middle), and cotton rags (bottom). The results for the crinkle paper and polystyrene cups are fairly typical for simply-shaped items whose burning rate is largely a function of surface area. The results for the boxes of rags, however, do not exhibit this simple trend, probably because the cotton rags are packed tightly in the boxes and do not burn readily. When the pile of residue was "rst stirred up, a considerable amount of the combustible mass remained buried under the pile of ash.
One complication of the simple assumption that peak HRR is proportional to exposed surface area is that in many instances, the "re does not or cannot engulf all of the exposed surface area at the same time. The location and power of the ignition source(s) is impor-tant. Consider the boxes of crinkle paper burned in Tests 32-34 (Fig. 44) versus Tests 1-3 (Fig. 45, top). In the former, only one igniter was used, whereas in the latter, an igniter was placed at the base of each exposed vertical surface. The peak HRR in Tests 1, 2, and 3 is 2.5, 1.8, and 3.3 times that of Tests 32, 33, and 34. Tests 32-34 do not exhibit the linear relationship between peak HRR and exposed surface area.
0 10 20 30 40 50 60 Time (min) 0 100 200 300 400 Heat Release Rate (kW)
Boxes with Paper, Single Ignition Test 32: One Box Test 33: Two Boxes Test 34: Four Bins Figure 44: HRR of boxes "lled with paper and ignited at a single point.
48
0 5
10 15 20 25 30 Time (min) 0 500 1000 1500 2000 2500 3000 Heat Release Rate (kW)
Boxes with Paper Test 1: One box Test 2: Two Boxes Test 3: Four Boxes Test 4: Eight Boxes 0
5 10 15 20 25 30 Time (min) 0 500 1000 1500 2000 2500 3000 Heat Release Rate (kW)
Boxes with Plastic Test 25: One Box Test 26: Two Boxes Test 27: Four Boxes Test 28: Eight Boxes 0
5 10 15 20 25 30 Time (min) 0 100 200 300 400 500 Heat Release Rate (kW)
Boxes with Rags Test 10: One Box Test 11: Two Boxes Test 12: Four Boxes Test 35: Eight Boxes Figure 45: Heat Release Rate of boxes "lled with crinkle paper (top), polystyrene cups (middle), and cotton rags (bottom).
49
4.2 Wood Pallets and Cribs Wood pallets and cribs are often used in "re testing because they exhibit reliable and re-peatable burning behavior. This can be seen in the results shown in Fig. 46. The top plot shows the HRR for single stacks of pallets consisting of two, four, and eight pallets (a sin-gle pallet is dif"cult to burn without a heat source to sustain the "re). The peak HRR is nearly linear with the number of pallets because the surface area is nearly linear with the number of pallets. This trend is noted by Babrauskas in the SFPE Handbook [5].
50
0 5
10 15 20 25 30 Time (min) 0 1000 2000 3000 4000 Heat Release Rate (kW)
Wood Pallets Test 5: Two Pallets Test 6: Four Pallets Test 9: Eight Pallets 0
5 10 15 20 25 30 Time (min) 0 1000 2000 3000 4000 5000 Heat Release Rate (kW)
Wood Pallets Test 8: 4 stacks of 2 Test 9: 1 stack of 8 0
20 40 60 80 100 120 Time (min) 0 500 1000 1500 2000 2500 3000 Heat Release Rate (kW)
Wood Cribs Test 13: One Crib Test 14: Two Cribs Test 15: Four Cribs Test 16: Eight Cribs Figure 46: Heat Release Rate of pallets and cribs.
51
4.3 Plastic Trash Bins The plastic trash bins were either partially "lled with crinkle paper or completely "lled with crinkle paper, cardboard, and rags. In the latter case (bottom graph of Fig. 47), the cellulosic fuels dominate the burning behavior and the simple trend in peak HRR emerges.
In the former case, the trend for the peak HRR is less clear because the burning behavior is dominated by the melting, dripping, and pooling of plastic, something that is less repeatable in multiple experiments.
0 10 20 30 40 50 60 Time (min) 0 200 400 600 800 1000 Heat Release Rate (kW)
Plastic Bins with Paper Test 17: One Bin Test 18: Two Bins Test 19: Four Bins 0
10 20 30 40 50 60 Time (min) 0 200 400 600 800 1000 Heat Release Rate (kW)
Plastic Bins with Paper and Rags Test 29: One Bin Test 30: Two Bins Test 31: Four Bins Figure 47: Heat Release Rate of plastic trash bins.
52
4.4 Combinations There are a few examples where multiple items have been burned together and separately.
For example, Test 20 is a combination of the items included in Tests 5 and 19, where four plastic bins "lled with crinkle paper (Test 19) stand atop two pallets (Test 5). The resulting peak HRR of the combined items is 50 % greater than the sum of the individual peak HRRs.
However, Test 21 is a combination of Tests 4 and 5 (eight boxes sitting atop two pallets),
but the peak HRR of the combined items is only 92 % of the sum of the individual peak HRRs. In the "rst instance, it appears that the increased radiative feedback from the larger "re enhances the rate of burning of the combined itesm, yet this does not appear to the be the case in the second instance. For Test 36, two plastic bins are nested one inside the other, and the peak HRR doubles, even though the surface area changes very little. There does not appear to be a simple explanation of these cases, which is why the trend shown in Fig. 43 is fairly rough.
53
4.5 Separations Most of the 40 experiments conducted involved multiple items placed closely together or stacked. However, in some experiments, the items were separated. By separating the items, the surface area is increased which ought to increase the peak HRR. However, this was not always the case. For example, Fig. 48 displays the HRR of four boxes "lled with crinkle paper that were con"gured and ignited in different ways. In Test 3, the four boxes were placed side by side and ignited in 8 locations. In Test 35, the four boxes were ignited only in one location. In Tests 37 and 38, the four boxes were separated by 0.6 m (2 ft) and ignited with 8 and 16 igniters, respectively. There is a signi"cant difference in the peak HRR in these cases, owing as much to the number of igniters as to the nominal exposed surface area. Notice in Tests 3 and 37, the number of igniters is the same, and the initial peak in the HRR involves roughly the same amount of surface area; however in Test 37, where the boxes were separated, there is a second peak in the HRR owing to the additional exposed surface area.
0 10 20 30 40 50 60 Time (min) 0 500 1000 1500 2000 Heat Release Rate (kW)
Four Boxes Test 3: 8 igniters; no separation Test 35: 1 igniter; no separation Test 37: 8 igniters; separation Test 38: 16 igniters; separation Figure 48: Heat Release Rate of four boxes "lled with crinkle paper.
54
5.
Conclusion Forty experiments were conducted in which multiple quantities of transient combustibles were burned and their heat release rates (HRR) measured, with the objective to determine the HRR of multiple items based on the HRR of a single item. The peak HRR is roughly proportional to the exposed surface area, but the con"guration of items and the number of ignition points also play a role. Given the in"nite number of potential combustibles, con"gurations, and ignition scenarios, it is not possible to develop a simple rule that would predict the increase in HRR given an increase in the number of combustibles. However, the assumption that the peak HRR is proportional to the exposed surface area will probably suf"ce for most practical applications.
Acknowledgments This work was partially funded by the U.S. Nuclear Regulatory Commission, Of"ce of Nuclear Regulatory Research. Matthew Bundy, Michael Selepak, Marco Fernandez and Laurean DeLauter of the National Fire Research Laboratory assisted in conducting these experiments and in processing the data.
References
[1] A. Lindeman, M. Randelovic, and M. Salley. Heat Release Rate and Fire Charac-teristics of Fuels Representative of Typical Transient Fire Events in Nuclear Power Plants. NUREG-2232, Nuclear Regulatory Commission, Washington, D.C., August 2019. This work is also published by the Electric Power Research Institute as EPRI 3002015997.
[2] M. Salley, A. Lindeman, and M. Randelovic. Methodology for Modeling Transient Fires in Nuclear Power Plant Fire Probabilistic Risk Assessment. NUREG-2233, Nu-clear Regulatory Commission, Washington, D.C., December 2019. This work is also published by the Electric Power Research Institute as EPRI 3002016054.
[3] R.A. Bryant and M.F. Bundy. The NIST 20 MW Calorimetry Measurement System for Large-Fire Research. NIST Technical Note 2077, National Institute of Standards and Technology, Gaithersburg, Maryland, December 2019.
[4] M.J. Hurley, editor. SFPE Handbook of Fire Protection Engineering. Springer, New York, 5th edition, 2016.
[5] V. Babrauskas. SFPE Handbook of Fire Protection Engineering, chapter Heat Release Rates. Springer, New York, 5th edition, 2016.
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