Abstract
As a theoretical checks on the conclusion for the possibilities in the spontaneous ignition of wood pillar as a cause of fire in Happokan-hotel case which had been refered to in Part I of the report, computer simulations have been pursued with respect to the critical conditions for the spontaneous ignition of wood spheres of various size. Above checks have been primarily concerned with the anisotropies in the thermal conductivity and diffusion constant or permeability of water vapor in the real wood-system and with the circumference-temperature of the heat-bath and radii of the wood spheres. Secondly, the checks have been concerned with the problems on the transfer the ignition-point for the spontaneous ignition in wood-spheres induced by the change in the surface-temperature of the sphere or heat-flux and in the activation energy of the thermal decomposition. Thirdly, checks have been pursued with the change in the critical condition for the ignition as induced by the presence of neighboring materials such as insulating materials and mortars, which wrapped the sphere.
The effect of nominal moisture-contents of wood as a function of relative humidity of the environment to retard the ignition has been discussed with respect to the quasi-stationary state problems as revealed in the solutions of non-linear differential equations. Finally, the numerical computations for the ignition of wood materials has been pursued with the case of arbitrary shape and size and with different activation energies in the respective part of the material as an example of the real cases.
Very good coincidences have been observed between calculated values and observed ones in the respective cases, which support our conclusion in Part I of the report. The numerical computations have been conducted by I.B.M. 1620-type computer.
