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Development of a Model for the Heat Release Rate of Wood: A Status Report.


pdf icon Development of a Model for the Heat Release Rate of Wood: A Status Report. (63848 K)
Parker, W. J.

NBSIR 85-3163; 108 p. May 1985.

Sponsor:

Federal Emergency Management Agency, Washington, DC

Available from:

National Technical Information Service
Order number: AD/A-160275

Keywords:

heat release rate; wood; pyrolysis; heat of combustion; thermal conductivity; computer models

Abstract:

This report describes the status of the development of a method for predicting the heat release rate of wood for different thicknesses, moisture contents, and exposure conditions. A computer model has been set up on a microcomputer. Experimental techniques have been devised to obtain the imput data required by the model. These include (1) the thermal conductivity as a function of temperature and percent loss, (2) the kinetic constants needed to describe the mass loss rate, (3) the heat of combustion of the volatile pyrolysis products, and (4) the contraction factors due to charring. Sufficient data on these parameters were taken to exercise the model. Heat release rates and effective heats of combustion were measured as a function of external radiant flux on 12.5 mm thick dry vertical specimens of Douglas fir particle board. The calculated and measured peak heat release rate curves are similar in shape and amplitude but differ significantly in time scale. This may be due to the lack of thermal conductivity data on the char in the high temperature range. There is very good agreement between the calculated and measured effective heats of combustion. The initial results with the model are promising.