Heat and Mass Transport From Thermally Degrading Thin Cellulosic Materials in a Microgravity Environment.
Heat and Mass Transport From Thermally Degrading Thin
Cellulosic Materials in a Microgravity Environment.
Kushida, G.; Baum, H. R.; Kashiwagi, T.; diBlasi, C.
Journal of Heat Transfer, Vol. 114, No. 2, 494-502, May
Sponsor:National Aeronautics and Space Administration, Lewis
Research Center, Cleveland, OH
cellulosic materials; reduced gravity; thermal
A theoretical model describing the behavior of a
thermally thin cellulosic sheet which is heated by
external thermal radiation in a quiescent microgravity
environment is developed. This model describes thermal
and oxidative degradation of the sheet and the heat and
mass transfer of evolved degradation products form the
heated cellulosic surface into the gas phase. At
present, gas phase oxidation reactions are not included.
Without buoyancy, the dominant vorticity creation
mechanism in the bulk of the gas is absent except at the
material surfacy by the requirement of the no-slip
condition. The no-slip condition is relaxed, permitting
the flow to be represented by a velocity potential.
This approximation is permissible due to the combination
of a microgravity environment and low Reynolds number
associated with slow small-area heating by external
radiation. Two calculations are carried out; heating
without thermal degradation and heating with thermalo
degradation of the sheet with endothermic pyrolysis,
exothermic thermal oxidative degradation and highly
exothermic char oxidation. The results show that
pyrolysis is the main degradation reaction. Moreover,
self-sustained propagation of smoldering for cellulosic
materials is very difficult due to the lack of
sufficient oxygen supply in a quiescent environment.