Comments to the Paper Uncertainty of Heat Release Rate Calculation of the ISO5660-1 Cone Calorimeter Standard Test Method

Abstract

In a paper in this Journal by Enright and Fleischmann [1] some years ago, the authors gave an interesting presentation of the uncertainty associated with the measurement of heat release rate (HRR) for the Cone Calorimeter. This paper which is a major contribution on the subject was a first attempt at analytical quantification of uncertainty due to instrument and calculation assumptions. In order to illustrate the uncertainty calculation, data from the cone calorimeter were used. The sample tested was an upholstered furniture composite. It has been shown that the greatest component uncertainties can be attributed to the assumed effective heat of combustion E, the assumed stoichiometric expansion factor b and the measured oxygen concentration. They concluded among others that the heat release rate uncertainty is very strongly coupled with any assumed stoichiometric expansion factor b at lower heat release rate values. They showed that b contributes significantly to the relative uncertainty of the HRR calculation at low HRR levels; see Fig. 3 of the paper [1], p. 165: component uncertainty history for the stoichiometric expansion factor. However, a mistake seems to have been made in the calculation of this component uncertainty. At low HRR levels, the contribution of the stoichiometric expansion factor b on the HRR uncertainty should be negligible and not ‘‘significant’’. In order to illustrate this statement let us recall that the HRR is proportional to the mass flow rate of the incoming air which can be related to the mass flow rate of the exhaust gases according to the following equation: _ me Me ¼ð 1 � /Þ _ ma Ma þ a/