CEN/TR 16988:2016
(Main)Estimation of uncertainty in the single burning item test
Estimation of uncertainty in the single burning item test
The measuring technique of the SBI (single burning item) test instrument is based on the observation that, in general, the heats of combustion per unit mass of oxygen consumed are approximately the same for most fuels commonly encountered in fires (Huggett [12]). The mass flow, together with the oxygen concentration in the extraction system, suffices to continuously calculate the amount of heat released. Some corrections can be introduced if CO2, CO and/or H2O are additionally measured.
Messunsicherheit - Thermische Beanspruchung durch einen einzelnen brennenden Gegenstand (SBI)
Ocena negotovosti s preskusom enega samega gorečega predmeta
Merilna tehnika instrumenta za preskušanje gorljivosti posameznega predmeta (SBI) temelji na ugotovitvi, da je toplota zgorevanja na enoto mase porabljenega kisika na splošno približno enaka za večino goriv, ki so običajna pri požarih (Huggett [12]). Masni pretok skupaj s koncentracijo kisika v sistemu za odvajanje zadostuje za neprekinjeno izračunavanje količine sproščene toplote. Nekateri popravki se lahko uporabijo, če se dodatno izmerijo vrednosti CO2, CO in/ali H2O.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-november-2016
2FHQDQHJRWRYRVWLVSUHVNXVRPHQHJDVDPHJDJRUHþHJDSUHGPHWD
Estimation of uncertainty in the single burning item test
Messunsicherheit - Thermische Beanspruchung durch einen einzelnen brennenden
Gegenstand (SBI)
Ta slovenski standard je istoveten z: CEN/TR 16988:2016
ICS:
13.220.40 Sposobnost vžiga in Ignitability and burning
obnašanje materialov in behaviour of materials and
proizvodov pri gorenju products
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
CEN/TR 16988
TECHNICAL REPORT
RAPPORT TECHNIQUE
July 2016
TECHNISCHER BERICHT
ICS 17.200.01
English Version
Estimation of uncertainty in the single burning item test
Messunsicherheit - Thermische Beanspruchung durch
einen einzelnen brennenden Gegenstand (SBI)
This Technical Report was approved by CEN on 4 July 2016. It has been drawn up by the Technical Committee CEN/TC 127.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16988:2016 E
worldwide for CEN national Members.
Contents Page
European foreword . 4
1 Scope . 5
1.1 General . 5
1.2 Calculation procedure . 5
1.2.1 Introduction . 5
1.2.2 Synchronization of data . 5
1.2.3 Heat output . 5
2 Uncertainty . 9
2.1 Introduction . 9
2.2 Elaboration of terms and concepts . 11
2.2.1 Mean and variance . 11
2.2.2 Estimation of the confidence interval for the population mean . 12
2.2.3 Sources of uncertainty . 12
2.2.4 Standard uncertainties for different distributions . 12
2.2.5 Combined uncertainty . 15
2.2.6 Expanded uncertainty . 16
2.2.7 Uncorrected bias . 16
2.3 Combined standard uncertainties . 17
2.3.1 Combined standard uncertainty on sums . 17
2.3.2 Combined standard uncertainty on averages . 18
2.3.3 Combined standard uncertainty of a product and a division . 19
2.3.4 Combined standard uncertainty on the heat release rate (Q) . 20
2.3.5 Combined standard uncertainty on the depletion factor (ϕ) . 22
D°
2.3.6 Combined standard uncertainty on the initial O -concentration (X ) . 22
2 O2
2.3.7 Combined standard uncertainty on the volume flow rate (V ) . 23
D298
2.3.8 Combined standard uncertainty on the air density (ρ ) . 24
air
2.3.9 Combined standard uncertainty on specimen heat release rate (Qspecimen) . 24
2.3.10 Combined standard uncertainty on the average heat release rate (Q ) . 24
av
2.3.11 Combined standard uncertainty on FIGRA . 25
2.3.12 Combined standard uncertainty on THR600s . 25
2.3.13 Combined standard uncertainty on the volume flow (V(t)) . 25
2.3.14 Combined standard uncertainty on the smoke production rate (SPR) . 25
2.3.15 Combined standard uncertainty on specimen smoke production rate (SPR) . 26
2.3.16 Combined standard uncertainty on the average smoke production rate (SPR ) . 26
av
2.3.17 Combined standard uncertainty on SMOGRA . 26
2.3.18 Combined standard uncertainty on TSP600s . 27
2.4 Confidence interval classification parameters . 27
2.5 Standard uncertainty on the different components . 28
2.5.1 Uncertainty on the data acquisition (DAQ). 28
2.5.2 Transient error . 28
2.5.3 Aliasing error . 28
2.5.4 Uncertainty on data synchronicity . 29
2.5.5 Uncertainty on the component E and E’ . 30
2.5.6 Uncertainty on the component φ . 36
2.5.7 Uncertainty on the component p . 36
atm
2.5.8 Uncertainty on the component T . 36
room
2.5.9 Uncertainty on the component α . 38
2.5.10 Uncertainty on the component c . 38
2.5.11 Uncertainty on the component A and L . 39
2.5.12 Uncertainty on the component q . 40
gas
2.5.13 Uncertainty on the component k . 40
t
2.5.14 Uncertainty on the component k . 43
p
2.5.15 Uncertainty on the component Δp . 44
2.5.16 Uncertainty on the component T . 44
ms
2.5.17 Uncertainty on the component I . 46
Annex A (informative) List of symbols and abbreviations . 48
European foreword
This document (CEN/TR 16988:2016) has been prepared by Technical Committee CEN/TC 127 “Fire
Safety in Buildings”, the secretariat of which is held by BSI.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
1 Scope
1.1 General
The measuring technique of the SBI (single burning item) test instrument is based on the observation
that, in general, the heats of combustion per unit mass of oxygen consumed are approximately the same
for most fuels commonly encountered in fires (Huggett [12]). The mass flow, together with the oxygen
concentration in the extraction system, suffices to continuously calculate the amount of heat released.
Some corrections can be introduced if CO , CO and/or H O are additionally measured.
2 2
1.2 Calculation procedure
1.2.1 Introduction
The main calculation procedures for obtaining the HRR and its derived parameters are summarized
here for convenience. The formulas will be used in the following clauses and especially in the clause on
uncertainty.
The calculations and procedures can be found in full detail in the SBI standard [1].
1.2.2 Synchronization of data
The measured data are synchronized making use of the dips and peaks that occur in the data due to the
switch from ‘primary’ to ‘main’ burner around t = 300 s, i.e. at the start of the thermal attack to the test
specimen. Synchronization is necessary due to the delayed response of the oxygen and carbon dioxide
analysers. The filters, long transport lines, the cooler, etc. in between the gas sample probe and the
analyser unit, cause this shift in time.
After synchronization, all data are shifted so that the ‘main’ burner ignites – by definition – at time
t = 300 s.
1.2.3 Heat output
1.2.3.1 Average heat release rate of the specimen (HRR )
30s
A first step in the calculation of the HRR contribution of the specimen is the calculation of the global
HRR. The global HRR is constituted of the HRR contribution of both the specimen and the burner and is
defined as
φ(t)
′
HRR (t)= EV (t)x (1)
total D298 a_O2
1+ 0,105φ(t)
where
is the total heat release rate of the specimen and burner (kW);
HRR (t)
total
′ is the heat release per unit volume of oxygen consumed at 298 K, = 17 200 (kJ/m3);
E
is the volume flow rate of the exhaust system, normalized at 298 K (m3/s);
Vt()
D298
is the mole fraction of oxygen in the ambient air including water vapour;
x
a_O2
is the oxygen depletion factor.
ϕ()t
φ(t)
The last two terms x and express the amount of moles of oxygen, per unit volume,
a_O2
1+ 0,105φ(t)
that have chemically reacted into some combustion gases. Multiplication with the volume flow gives the
amount of moles of oxygen that have reacted away. Finally this value is multiplied with the ‘Huggett’
factor. Huggett stated that regardless of the fuel burnt roughly a same amount of heat is released.
The volume flow of the exhaust system, normalized at 298 K, V (t) is given by
D298
k Dp(t)
t
V (t)=cA (2)
D298
k T (t)
ρ ms
where
c
0,5 1,5 −0,5
(2T /ρ ) 22, 4 [K⋅ m ⋅ kg ]
A is the area of the exhaust duct at the general measurement section (m2);
is the flow profile correction factor; converts the velocity at the height of the bi-directional
k
t
probe in the axis of the duct to the mean velocity over the cross section of the duct;
is the Reynolds number correction for the bidirectional probe, taken as 1,08;
k
ρ
Dpt() is the pressure difference over the bi-directional probe (Pa);
is the temperature in the measurement section (K).
Tt()
ms
The oxygen depletion factor ϕ()t is defined as
xO (30s.90s){1−xCO (t)}−xO (t){1−xCO (30s.90s)}
2 2 2 2
φ(t)= (3)
xO (30s.90s){1−xCO (t)−xO (t)}
2 2 2
where
is the oxygen concentration in mole fraction;
xtO ()
is the carbon dioxide concentration in mole fraction;
xtCO ( )
Ys.Zs mean taken over interval Y s to Z s.
The mole fraction of oxygen in ambient air, taking into account the moisture content, is given by
H 3816
x = xO (30s.90s) 1− exp 23,2− (4)
a_O2 2
100p T (30s.90
...
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