ASHRAE CH-06-3-3-2006 Experiments for the Characterization of Design Fires for Commercial Buildings《商业大厦火灾设计特点实验》.pdf

1、CH-06-3-3 Experiments for the Characterization of Design Fires fox Commercial Buildings George Hadjisophocleous;PhD, PEng Member ASHRAE ABSTRACT This paperpresents a study to characterize designjres for commercial buildings. The study.includes a survey of different stores, which was conducted to det

2、erminejre load and type of combustibles and to design representative fuel packages, medium- and full-scale testing using the fuel packages, and computer modeling. The experiments were conducted in collaboration with the Fire Research Program of the National Research Council of Canada (NRC) using NRC

3、S full-scale facilities. In total, 168 different stores were surveyed and the data collected were analyzed to determine the totaljre load in each of the stores, thejre load density, and the contribution of different combustible materials to the total jre load. The survey was conducted in 2003 in the

4、 Canadian cities of Ottawa and Gatineau. The data from the conducted sumey show that clothing stores occupy 30% of the totaljoor area ofall suweyedstores, restaurants 13%. storage areas 9%, arts and crafts supplies 5%, and fast jood outlets 4%. The data also show that the jre load in stores consists

5、 of a vast variation of combustibles with different contributions depending on the type ofstore. Analysis of the data found a clear correlation between thefloor area of stores andjre load densities. The jre load density decreases as thefloor area increases. Based on the survey data, a number offuel

6、packages were designed representing$re load densities and types of combustibles of diferent stores. The developed fuel packages were used tope form exper- iments to characterize design $res for commercial buildings. The results from the medium-scale experiments show that the fuel package representin

7、g shoe storage areas produced the highest heat release rate, followed by the fuelpackage repre- senting fast-food outlets. The experimental data were analyzed Ehab Zalok to determine the relative tenability levels based on the CO and CO2 concentrations of the products of combustion. INTRODUCTION The

8、 use of engineered fire protection designs for build- ings is becoming more acceptable in many countries. These designs are done using engineering calculations and tools that include both computer models and experiments to demon- strate acceptable performance. In many of these calculations or tests,

9、 fires that are representative ofthose expected in build- ings are used to evaluate building performance. These fires are known as design$res. The increasing use of engineered solu- tions results in the need to identiSl and characterize design fires for various buildings so that their use is accepta

10、ble by all involved in the design and approval process, including design- ers, stakeholders, and the authority having jurisdiction. The burning characteristics of design fires depend on the type, amount, and arrangement of combustible materials, available ventilation in the room of fire origin, and

11、the ignition source. The type and arrangement of combustibles affect the growth characteristics, while the total amount of fuel and ventilation characteristics in the compartment of fire origin govern the intensity and duration of the fire. The key param- eters that define a design fire include heat

12、 release rate (HRR), flame temperature, and production rates of toxic gases. The complete specification of design fires requires knowledge of all stages ofthe fire: growth, steady burning (fully developed), and decay. The growth characteristics of the design fire influ- ence the time of detection as

13、 well as the time when conditions in the compartment of fire origin become untenable. The faster the fire is detected, the earlier occupants will be notified of the fire and begin to evacuate the building; however, the time George Hadjisophocleous is a professor and Ehab Zalok is a doctoral candidat

14、e at Carleton University, Ottawa, Ontario, Canada. 394 02006 ASHRAE. available to the occupants to evacuate safely depends on the time when untenable conditions are reached in their compart- ments or the exit routes. The ability of compartment barriers to withstand the fire attack and contain the fi

15、re, preventing it from spreading to other compartments in the building, depends on the intensity and duration of the fire. A fire in a compartment with limited fuel is more likely to be contained than a fire in a compartment with large amounts of fuel. The work presented in this paper is aimed at ch

16、aracteriz- ing design fires for commercial premises. To this end, efforts were made to characterize the combustibles in stores by conducting a survey to collect relevant data. The fire load survey was conducted on 168 commercial premises. Premises surveyed were the typical stores in shopping centers

17、, such as clothing stores, fast food shops, restaurants, shoe stores, and bookstores. The survey was conducted in 2003 in the Cana- dian cities of Ottawa and Gatineau. The data collected were total fire load, fire load density, type of combustibles (wood, plastics, cloth, food, etc.), compartment fl

18、oor area, and venti- lation characteristics (area and availability). The results of the survey of different stores and their analysis produced nine different fuel packages representing fire load densities and types of combustibles in stores. The identified fuel packages were used to perform medium-s

19、cale experiments in a room test facility. The data obtained from these tests are presented and discussed in this paper. The next steps toward the charac- terization of design fires for commercial premises include large-scale tests of the representative fuel packages and computer modeling using compu

20、tational fluid dynamics (CFD) models such as the Fire Dynamics Simulator (FDS) (McGrattan et al. 2002). SURVEY AND FUEL PACKAGES The quantity of movable combustibles in a compartment is commonly expressed as the total heat energy (MJ) that can be released through complete combustion and is known as

21、the fire load. The fire load is often expressed as an energy density (fire load per unit floor area in MJ/m2) to enable extrapolation to compartments of different sizes. At times, the contribution of the combustible parts of the building structure (the fixed fire load) are included in the total fire

22、 load. However, it is often the quantity of the buildings combustible contents (the movable fire load) that is needed for most fire safety evaluations. The survey for this paper was conducted by visiting the buildings and listing the contents and their pertinent characteristics. Weights were determi

23、ned by a combination of the direct weighing and inventory techniques. As shown in Figure 1, the area contribution of the differ- ent establishments to the total area of the buildings surveyed is mainly from clothing stores, followed by restaurants, stor- age areas, and fast food outlets. Bennetts et

24、 al. (1997) also found that clothing stores are the major occupancy in shopping centers. The area of clothing stores is 34.7% of the total area; restaurants arc 13.9%, storage areas are 5.8%, and fast-food outlets are 4.5%. Natches Sales 0.59% Travel Agencies Clothing Retail qa TW Shoes Retail /Conf

25、erence Room /$ 0.15% Tailors /- 0.56% I*. _I,- / Fabric Shops 0.51% st Food Shop 3.90% t Food Shops I rocers Retail 2.95% 0.94% Mail Room 0.29% 0.87% 2.69% 0.37% 2.78% Figure I Percentage offloor area of different premises to the total floor area of surveyed premises ASHRAE Transactions: Symposia 39

26、5 Figure 2 shows the frequencies of fire load densities of the 168 surveyed stores. It can be seen that the distribution frequency follows a lognormal distribution and is positively skewed, indicating that, on the whole, high values of fire load have low occurrence. The fire load densities have a lo

27、gnormal distribution with a mean of 750 MJ/m2, a maximum of 5305 MJ/m2, a minimum of 56 MJ/m2, and a standard deviation of 832 MJ/m2. The four fire load densities at the extreme right of the figure are for a bookstore, a storage area for the bookstore, a shoe store, and a greeting card shop. The res

28、ults of the survey are summarized in Table 1. Detailed results of the fire load survey have been published elsewhere (Hadj isophocleous 2003, 2004). FUEL PACKAGES Based on the analysis of the survey data, a number of fuel packages have been designed to represent fire load densities and types of comb

29、ustibles of the different stores. Details of these packages are shown in Table 2. Three fuel packages are used to represent clothing stores due to the large variation of 7A Fast-food Outlet 88 1 30 L 1 0.30 19.28 38.92 0.00 41.5 31.81 I Fire Load Density (MJ/m*) Figure2 Frequencies of Jre load densi

30、 of the 168 surveyed stores. the types of fuels found in these stores. The first package, 3A, represents the combination of combustibles in small stores, those less than 100 m2 in floor area. The second, 3B, repre- sents stores that have high wood content and less clothing content. These stores are

31、typically high-end clothing stores that use wood as decorative material for shelving and flooring and as lining material on walls and ceilings. The third, 3C, represents stores with low wood content and high clothing content. In this kind of store, shelving is mainly made of steel with some wooden t

32、ables, and the internal store lining consists mainly of noncombustible materials, such as cement floor tiles, bricks for walls, and reinforced concrete ceilings. FIRE TESTS SETUP Fire experiments were conducted in an IS0-9705- compatible room (IS0 1993), which was instrumented to measure the heat re

33、lease rate (HRR), mass loss, gas tempera- tures, and heat flux. The dimensions of the room are 2.4 by 3.6 by 2.4 m, with a 0.8 by 2.0 m doorway in one of the 2.4 by 2.4 m walls (Figure 3). The door opening is directly under a fume hood, which is connected to an exhaust duct having a diameter of 406

34、111111. To facilitate calculation of the heat release rate by using the oxygen consumption method (Jans- sen 199 i), measurements of mass flow rate and concentrations Total Fire Load for All 168 Stores in the Survey Table 1. Floor Area, Fire Load Density, and Standard 95th Deviation Percentile Mean

35、Range 183 333 Floor Area 3.25- m21 O2 1,707 M J/m2 747 5,305 833 2,050 Fire Load Density 5 6- 1126- 77,166 167,383 Total Fire Load IMJ1 527339 511,413 Table 2. Fire Load Densities and Data for Combustible Materials Used in Design Fires for Medium-Scale Tests Fire Load Test Title Density (MJ/mZ) Test

36、 ID 1 A Computer Showroom 8 12 2A Storage Area 2320 3A Clothing Store 66 1 3B Clothing Store 66 1 3C Clothing Store 66 1 4A Toy Store 1223 SA Shoe Storage 4900 6A Bookstore 5305 Contribution of Combustible Materials (%) Woodl Rubber1 Food Total Paper Leather Products Mass (kg) Textiles Plastics 3.08

37、 50.59 46.33 0.00 0.00 31.69 5.60 31.10 49.10 8.50 5.70 102.1 55.0 6.00 37.00 2.00 0.00 34.65 23.0 1 .o0 76.00 0.00 0.00 36.28 86.0 2.00 12.00 0.00 0.00 35.44 6.59 18.65 74.76 0.00 0.00 60.42 1 .o0 0.00 34.00 65.0 0.00 214.8 0.40 0.00 99.60 0.00 0.00 302.9 , * Total masses of combustible materials o

38、nly; noncombustible materials are not included. 396 ASHRAE Transactions: Symposia Heat Flux Meter -% TC Tree -, Load Cells 7 Figure 3 Test setup in the ISO-9705-compatible room. Figure 5 Heat release rate of all tests, excluding clothing stores, .from O to 2,l O0 seconds. of oxygen, carbon dioxide,

39、and carbon monoxide were taken in the hood exhaust duct. The smoke density was measured in the duct using a pulsed white light meter. The instrumentation of the test room consisted of a tree of thermocouples located in the middle of the room and a tree of thermocouples attached to the inner wall clo

40、se to the doorway, as well as a thermocou- ple at the top of the door frame to measure the temperature of gases leaving the room. In addition, one thermocouple was placed on the floor close to a heat flux meter in the middle of the room and five thermocouples were placed at the ceiling. For measurin

41、g mass loss rate, a 1.8 by 1.8 m suspended steel platform was constructed in the test room at a height of 200 mm above the floor. The platform was connected to four load cells using four cables attached to the comers with a total capacity of up to 18 14 kg. Medium-scale 1 by 1 m fuel packages repres

42、enting combustibles found in the above-mentioned stores were tested. The fuel packages were placed on top of the platform inside the test room. The combustible materials used were chosen carefully to represent combustibles that usually exist in these premises (Table 2). All packages were ignited usi

43、ng a 75 kW propane T-burner running for four minutes to simulate an ignition source from a large-size wastepaper basket. (a) (b) Figure 4 Photographs show a test progress (test 3B)- ignition and fully developed. o Figure 6 Heat release rate of all clothing stores from O to 2,l O0 seconds. TEST RESUL

44、TS AND OBSERVATIONS This section presents the results of the tests performed using the different fuel packages. A summary of the test results, including heat release rate, heat flux values, peak temperatures, gas concentrations, and smoke and visibility, is presented in Tables 3 through 6. Figure 4

45、shows the test in progress for one of the clothing fuel packages at ignition time (a) and later in the test (b). Figures 5 and 6 show the HRR of all tests from ignition to 2,l O0 seconds. For comparison, three curves have been added that show fast, medium, and slow t-squared fires. Results from the

46、tests (Table 3) show high HRR values for the shoe storage test (1,881 kW) even though the test had to be extinguished five minutes from test start, fast-food outlets (1,562 kW), and clothing stores (mostly clothing) (1,528 kW), followed by storage areas (1,386 kW), bookstores (1,182 kW), toy stores

47、(1,080 kW), clothing stores (mostly wood) (733 kW), and small clothing stores (720 kW). The lowest HRR was for the computer showroom test (409 kW). As shown in Table 3, heat flux at floor level for the shoe storage area test reached a value of 2 1.2 1 kW/m2 due to the high gas temperatures. Flashove

48、r, however, did not take place because the test was extinguished five minutes after ignition. ASHRAE Transactions: Symposia 397 Table 3. Heat Release Rate and Heat Flux Values of Test Results Peak HRR Time3 (kW) 240 341 4092 1800 1386 480 720 240 733 210 1528 300 1080 360 9542 840 1881 300 1087 1182

49、 2100 Test Title Test ID Peak Heat Flux (kW/mz) 1.14 11.6 3.74 4.22 11.4 18,4 21.2 17.6 IA 2A 3A 3B 3c 4A 5A 6A 7A Computer Showroom Storage Area Clothing Store4 Clothing Store Clothing Store6 Toy Store Shoe Storage7 Bookstore Fast-food Outlet 1562 390 I 14 Reuresents the first peak. Mostly wood. * Represents the second peak. Mostly cloth. Incomplete test Time of the corresponding HRR. Small stores. Time (I, Figure 7 Peak gas temperature with time. Flashover occurred in the bookstore test, in which a high heat flux value of 17.64 kW/m2 was sustained for abo