ASHRAE ST-16-003-2016 Performance of Stairwell Pressurization System with Open Stairwell Doors.pdf

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1、 2016 ASHRAE 21This paper is based on findings resulting from ASHRAE Research Project RP-1447.ABSTRACTThe National Research Council of Canada (NRC)conducted full-scale fire experiments to investigate whetherpressurecompensatingsystemsareneededtomaintaintenableconditions within pressurized stairwells

2、. Ten tests wereconducted in the NRC 10-story test facility with the stairwellin the facility pressurized. The tests were conducted with thestairwell door on the fire floor closed and selected stairwelldoors on the other floors open. Two fire scenarios with ashieldedsprinkleredfireandanonsprinklered

3、fireweretestedwith varying number and location of open stairwell doors.Tenability analyses were conducted with experimentaltest results to investigate the performance of the pressurizedstairwell with and without pressure compensating systems.Withoutcompensatingforpressurelosses,thepressurediffer-enc

4、e across the stairwell door on the fire floor decreasedconsiderably with open stairwell doors. However, a non-compensated stairwell remained tenable for 30 minutes aslong as the door on the fire floor was closed both for theshieldedsprinkleredfireandthenonsprinkleredfirescenarios.It is concluded tha

5、t if the base pressurization system meets therequirement of the design pressure difference with a properarrangement of air injection points, the stairwell will remaintenable as long as the door on the fire floor is closed for bothsprinklered and nonsprinkled fire scenarios used in the tests.INTRODUC

6、TIONFor many years, the building codes in the United Statesand Canada have required pressurized stairwells in a numberof different types of occupancies. The intent of these pressur-izedstairwellsistomaintaintenableconditionsinthestairwellduring a building fire. The stairwell pressurization smokecont

7、rol system is designed to maintain pressure differences inan acceptable range. The minimum pressure difference is avalue intended to limit smoke migration into the stairwell andthe maximum pressure difference is a value intended toprevent excessive door opening forces.When a stairwell door is opened

8、, the pressure differencecan drop significantly, causing the pressure difference acrossthe stairwell door on the fire floor to be below the minimumdesign value. Many pressurized stairwells have been built thatcan maintain pressures in the acceptable range by compensat-ing for doors opening and closi

9、ng. A number of these pressurecompensating systems have been developed as discussed inASHRAEs Handbook of Smoke Control Engineering byKloteetal.(2012).Theextenttowhichpressurecompensatingsystems should be used is, however, a topic of debate withinthe engineering community.The International Building

10、Code (ICC 2015), which hasbeen adopted in all 50 states, does not explicitly require pres-sure compensating stairwell pressurization systems. On theother hand, NFPA 92 (NFPA 2015) requires that pressurizedstairwells be designed to maintain acceptable pressure differ-ences across each remaining close

11、d door with the number ofdoors used in the system design open. This indirectly requirespressure compensating systems as it states that no pressuredifference across the closed stairwell doors shall be less thanthe minimum design pressure difference.In the report “Tenability and Open Doors in Pressuri

12、zedStairwells,” Klote (2004) indicated that the discussion aboutthe need for pressure compensating systems in sprinkleredPerformance of Stairwell PressurizationSystem with Open Stairwell DoorsYoon J. Ko, PhD Gary D. Lougheed, PhDYoonJ.KoisaresearchofficerandGaryD.Lougheedisaprincipalresearchofficerw

13、ithNationalResearchCouncilCanada,Ottawa,Ontario,Canada.ST-16-003 (RP-1447)Published in ASHRAE Transactions, Volume 122, Part 2 22 ASHRAE Transactionsbuildings has intensified in recent years. The study usedcomputer methods of analysis to study the effect of stairwelldoors being improperly propped op

14、en on tenability conditionsin the stairwell and in the building. The study found that tena-ble conditions were maintained in the stairwell with multiplestairwell doors open under certain conditions. These findingsare very encouraging. However, the study did not address thecommonlyoccurringconditionw

15、herethedooronthefireflooris closed, but some other doors in the stairwell are open.Objectives and ScopeAsafollow-uptoASHRAEResearchProject1203(Klote2004), Research Project 1447 was initiated by ASHRAE toinvestigate whether pressure compensating systems areneeded to maintain tenable conditions within

16、 pressurizedstairwells. For RP-1447, the National Research Council ofCanada (NRC) conducted full-scale fire experiments in a 10-story facility (Ko and Lougheed 2015). A tenability analysiswas conducted using the experimental results to investigatethe performance of pressurized stairwell smoke contro

17、lsystems with and without pressure compensation. The testsetup was designed such that a quantifiable comparison oftenability versus time for the two approaches can be exploredin the case that a pressure compensating system is found to beneeded.The stairwell in the NRC 10-story test facility was pres

18、-surized. The tests were conducted with the stairwell door onthefirefloorclosedandselectedstairwelldoorsonotherfloorsopen.Testswereconductedcoveringthefollowingtestparam-eters:Sprinklered and nonsprinklered firesCompensating and noncompensating stairwell pressur-ization systemsNumber and location of

19、 open stairwell doorsThis paper provides 1) a detailed description of the full-scale fire tests conducted in the NRC 10-story facility, 2) adescription of the reasoning underlying the test plan, and3) test data recorded during the tests that was used to deter-mine tenability in the stairwell and on

20、the fire floor.Tenability AnalysisTenabilitywasdeterminedforeachexperiment,takingintoaccount temperature exposure, toxicity, and visibility for occu-pantsinthestairwell.Kloteetal.(2012),ISO13571(ISO2012),andtheSFPEHandbookofFireProtectionEngineering(Purser2008) provide guidance and methodologies for

21、 evaluating theeffects of smoke on occupants as well as the time available foroccupantstoescapefromafire.Thetenabilityanalysisprovidedinthethreereferencesisbasedonthefractionaleffectivedosage(FED) approach. These methods were previously used toconduct a tenability analysis for RP-1203 (Klote 2004).C

22、onditions in the space are considered tenable if thefollowing conditions are true:The temperatures in the stairwell remain below the ther-mal tolerance of humans for the duration of the test.The FED, when calculated as described by RP-1203 (Klote2004), is less than a value of 0.50 at all locations i

23、n thestairwell. The results were also analyzed using theapproach provided in ISO 13571 (ISO 2012), which pro-vides the following equations dealing with the effects of theoxygen vitiation as well as the effects of carbon dioxide(CO2)-induced hyperventilation, which can increase theeffects of narcotic

24、 gases such as carbon monoxide (CO).(1)(2)(3)(4)where= hyperventilation factor induced by CO2t = time, min=CO2concentration, vol%=O2concentration, vol%CCO= CO concentration, vol%The visibility in the stairwell is greater than 7.6 m (25 ft)assuming light-reflecting signs.(5)whereS = visibility, m (ft

25、)C = a nondimensional constant characteristic of thetypeofobjectbeingviewedthroughthesmoke(3was used, assuming a light-reflecting sign)OD = optical density measured by a smoke densitymeter, 1/m (1/ft)Previous StudiesStairwell pressurization smoke control systems arefrequently used to maintain positi

26、ve pressure in a stairwellrelative to the remainder of the building to limit smoke migra-tion from the fire floor to the stairwell. Without a pressuriza-tionsmokecontrolsystem,smokecanmigrateintoastairwell.In winter, for a fire below the neutral plane, smoke tends toenter and flow up the shaft due t

27、o the stack effect. Therefore,the performance of the noncompensating pressurizationsystem depends on the following aspects:FED HVCO2FEDCOFEDO2+=HVCO2EXP0.1903 CCO2t 2.0004+7.1-=FEDCOt 2.7640t105CCOt1.036dt=FEDO2ttdEXP 8.13 0.54 20.9 CO2-0t=HVCO2CCO2CO2SC2.303 OD-=Published in ASHRAE Transactions, Vo

28、lume 122, Part 2 ASHRAE Transactions 23The pressure difference due to the buoyancy of hotsmoke and stack effectThe decrease in the pressure difference provided by thestairwell pressurization system with stairwell doorsbeing improperly propped open or open during buildingevacuationBuoyant Pressure an

29、d Smoke Temperature. When afire grows in a compartment, hot smoke moves upward andexpands and fills the upper part of the compartment. If acompartment door is open, hot smoke moves out of thecompartment primarily by buoyancy force.The buoyant pressure caused by the hot smoke can beexpressed by Equat

30、ion 6 (Tamura 1994):(6)wherePf= pressure difference caused by fire, Pa (lb/ft2)g = gravitational constant, m/s2(ft/s2)h = height of interest, m (ft)hnpl= height of neutral pressure level, m (ft) = air density, kg/m3(lb/ft3)T = temperature, K (R)a = adjacent to the fire compartmentf = fire compartmen

31、tTamura (1994) measured pressure differences across thestair shaft and elevator shaft walls in the NRC 10-story exper-imental tower for temperatures ranging from 300C to 840C(572F to 1544F) at steady state. The results are comparedwiththebuoyantpressurecalculatedbyEquation6. Tempera-turesweremeasure

32、dattheceilingabovegasburnersplacedonthe second floor of the experimental tower. The buoyant pres-surefromsmokewithatemperatureof300C(572F)isabout10 Pa (0.04 in. w.g.). The buoyant pressure from smoke witha temperature between 300C and 800C (572F and 1472F)is between 10 and 15 Pa (0.04 and 0.06 in. w

33、.g.).Minimum and Maximum Allowable Pressure Differ-ences Required for Stairwell Pressurization Systems.Tamura (1994) discussed the minimum allowable pressuredifferences required for stairwell pressurization systems. Theminimum pressure difference is the sum of the buoyant pres-sure difference caused

34、 by hot smoke, by stack action, and bypossible wind action. For sprinklered buildings, the minimumpressure difference suggested by NFPA 92 is 12.5 Pa (0.05 in.w.g.), which is based on the expected buoyant pressure of 7.5Pa (0.03 in. w.g.) from a sprinklered fire with smoke tempera-ture being about 2

35、00C (392F). For nonsprinklered build-ings,theminimumpressuredifferencesuggestedbyNFPA92(NFPA 2015) is 25 Pa (0.10 in. w.g.) when the ceiling heightis 2.7 m (9 ft). This value is based on the expected buoyantpressure of 14.9 Pa (0.06 in. w.g.) from a nonsprinklered firewith the smoke temperature grea

36、ter than 800C (1472F) andan allowance for pressure differences caused by stack andwind action. The maximum allowable pressure difference is87 Pa (0.35 in. w.g.), which does not exceed door-openingforces. The design pressure difference used for the stairwellpressurization system, therefore, is in the

37、 range of 2587 Pa(0.100.35 in. w.g.).Tenability and Open Doors in Pressurized Stairwells.Klote (2004) conducted simulations using CONTAM (Dols etal. 2000) to study the effect of stairwell doors being improp-erly propped open on tenability conditions in the stairwell.Eighty scenarios were analyzed, c

38、onsidering many factorsincluding weather, stair geometry, building leakage, fire type,fire location, and number and location of open doors. Thebuildings used for the simulations were 7 stories and 21stories. Only non-pressure-compensating stairwell pressur-ization systems were investigated.Fire scen

39、arios used in the simulations were 1) a 633 kW(600 Btu/s) sprinklered fire, 2) a 633 kW (600 Btu/s) shieldedfire,and3)a4326kW(4100Btu/s)nonsprinkleredfire. Anal-ysis of tenability considered visibility and exposure to heatand toxic gases.Klote(2004)foundthatwithanoncompensatingstairwellpressurizatio

40、n system, an open door on the fire floor oftenresulted in untenable conditions in portions of the stairwell.For instance, in all the simulations with one or three doorsopen near the top floor, the stairwell became untenablebecause of the open stairwell door on the fire floor.The exceptions were simu

41、lation Nos. 70 and 80, wheretenable conditions were found even with the door on the firefloor open along with the doors near the top floor. In thesesimulations, tenable conditions were maintained by openingthe exterior stairwell door between the stairwell and the exte-rior of the building. In these

42、simulations, the nonsprinkleredfire was simulated with constant temperatures of 120C and520C (248F and 936F) specified in the corridor on the firefloor and in the fire room, respectively.Nodataweregeneratedforapressurecompensatingstair-well pressurization system with an open door on the fire floor.T

43、hus, comparisons for the performance of pressurized stair-well smoke control systems with and without pressurecompensating systems were not discussed. Also, RP-1203 didnotaddressthecommonlyoccurringconditionwherethedooron the fire floor is closed but some other door in the stairwellis open.Details o

44、f the pressurization system including the airsupply rate and the arrangement of air injections in the stair-well were not provided in RP-1203. No pressure data wereprovided,andthedecreaseinthepressuredifferencesbetweenthe stairwell and the fire floor caused by different open doorscenarios were not d

45、iscussed.The method of analysis used for RP-1203 was a combi-nationofzonefiremodelingandnetworkmodeling.Whiletheresults of this analysis resulted in valuable insight, the reportfor RP-1203 indicated that the method had significant limita-tions (Klote 2004).Pfgh hnplaf=gh hnplaTfTa/Tf=Published in AS

46、HRAE Transactions, Volume 122, Part 2 24 ASHRAE TransactionsTEST DESCRIPTIONTest FacilityThefireexperimentswereconductedintheNRC10-storytower facility that is part of the NRC full-scale fire test facil-itieslocatedinMississippiMills,Ontario(Figure1).TheNRC10-story facility was designed to represent

47、conditions in thecentercoreofahigh-risebuilding.Ithasbeenusedextensivelyfor studies on smoke control systems and smoke movement(Tamura 1994; Hokugo et al. 1995; Said and MacDonald1991).The typical floor height of the tower is 2.4 m (7.9 ft),exceptforthefirstandsecondfloors,whichare3.4m(11.2ft).The t

48、ower is constructed of 200 mm (7.9 in.) thick monolithicreinforced concrete. A plan view of a typical floor is shown inFigure 2.The experimental tower contains all the shafts and otherfeatures necessary to simulate air and smoke movementpatterns in the center core of a typical multistory building,includingthestairshaft.Thestairshaftisequippedwithastan-dard staircase and there is an exterior door that directly opensto the outside