Burning Rate of Wood: A Physics Lab Experiment Analysis

This physics assignment examines the burning rate of wood, a crucial factor in fire growth modeling and the structural endurance of wooden materials. The report delves into the experimental investigation of wood's burning rate, focusing on mass loss, heat release, and charring rates. The introduction highlights the importance of understanding wood's combustion properties due to its widespread use and fire risk. The assignment then explores the pyrolysis theory, discussing the production of charcoal, gases, and vapors under varying temperature conditions. The theory presents equations to calculate the mass burning rate per unit area and the relationship between heat flux and mass loss, providing a framework for analyzing experimental data. The assignment refers to the effective gasification heat and the impact of external flux on the burning process. The report includes references to relevant sources, supporting the theoretical concepts and experimental approaches discussed.

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Burning rate of wood
Introduction
The rate of burning is an important factor in fire growth modelling and endurance of structures of
woods. Investigations in the rate of burning on some selected wood is done as determined by
mass loss, release of heat and rates of charring. (Brenden, 2016, p. 234)
Wood being one of the most ecological, visually pleasing and environmental friendly material, it
plays an important role in building and furnishing of various structures. The unavoidable danger
of fire makes wood‘s burning rate to be investigated. Igniting resistance and a reduced rate of
releasing heat, products of timber have been needed for a wrong time to resist burn once it is
exposed to heat or fire.
Constant burning of solid wood that is combustible happens when the thermal energy reacting to
the surface provides volatile evolution so that there is a continuity in combustion. This kind of
burning will create a mean mass reduction loss in line with the combustible material time that
depends upon external flux in case it is present, the flame’s heat flux and loss of heat at the
surface. Therefore, by assuming parameter i.e. the effective gasification of heat for every
material that defines the thermal energy needed for generating 1kg of at a gasification
temperature over non-transient burning period using the approach of energy balance, a simple
mass rate expression will be developed. (Chen & Putranto, 2017, p. 432)
While predicting wood’s fire resistance, analysis is carried out, based on reducing the cross
section of the wood.

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Pyrolysis Theory
Charcoal, gases and vapor’s relative proportion production rate on wood widely range depending
on temperature conditions, pressure, geometry, time, and environment under which the process
takes place.
Slow pyrolysis rate of wood produces more charcoal, oxygenated gas and low flammable vapor,
and releases energy. Fast pyrolysis rate produces little carbon or no carbon at all, forms gases
and that are hydrogenated and consumes a lot of energy. (Forest Products Laboratory (U.S.),
2015, p. 313)
Under a single heating condition dimensions, assumedly, the rate of mass burning per unit area
can be presented as:
In the environment of a cone heater, the heat flux originating from the cone can be constantly
held over the area of the surface of a small sample that is set on an orientation that is horizontal.
Since the cell of the load is attached, the loss of mass can be directly measured in the figure
below for samples of wood that is typical.

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The constant loss of mass can be approximated based on balance of energy on the bare surface
as:
When the numerator is the net remaining surface’s heat flux, and the denominator Lv is
gasification’s effective heat. The second equation can also be written as:
The temperature of the surface that would be fixed is referred to as pyrolysis temperature for
those materials that are non-charming, and the char temperature for the materials that are
charming. Based on constant temperature and net heat, rearrangement of equation 3 can be
written as: (Kyōto Daigaku ; Mokuzai Kenkyūjo, 2016, p. 219)
Therefore, when M can be approximated for various fluxes of heat, will provide a straight line
with a 1/Lv slope and intercept

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References
Brenden, J. J., 2016. Rate of Heat Release from Wood-base Building Materials Exposed to Fire.
3rd ed. London: U. S. Department of Agriculture, Forest Service, Forest Products Laboratory.
Chen, X. D. & Putranto, A., 2017. Modelling Drying Processes. 4th ed. Texas: Cambridge
University Press.
Forest Products Laboratory (U.S.), 2015. Review of Information Related to the Charring Rate of
Wood. 3rd ed. Chicago : Forest Products Laboratory.
Kyōto Daigaku ; Mokuzai Kenkyūjo, 2016. Wood Research. 2nd ed. Texas: Wood Research
Institute, Kyoto University.