An organic and porous insulation material has the following properties: thermal conductivity (k = 0.05 w. m- density (p = 40 kg. m3). specific heat capacity (cp = 2000 j. kg 1. • heat of combustion of the material (ah. = 15 mj. kg-1). • in-depth radiation can be neglected and emissivity can be assumed to be ε = 0.9. • the reaction rate for the material is m'' = 0.2.exp(-2000/t) kg. m3.5-1. the raw insulation material is normally placed for storage purposes in cubes of dimensions 0.8 m x 0.8 m x 0.8 m. under these conditions, the heat transfer coefficient for losses is hr=38 w. m2.k-1. i. ii. iii. iv. describe the conditions under which a solid fuel can experience spontaneous ignition. [5 points] assuming that the spontaneous ignition phenomenon for solids can be formulated as the semenov model, justify whether this material will experience spontaneous ignition at an ambient temperature of 25°c. [5 points] determine the ambient temperature that will lead to spontaneous ignition of cubes of dimensions 0.8 m x 0.8 m x 0.8 m. [5 points] assuming that the material is always stored in cubes at an ambient temperature of 25°c, determine the critical length of the cube (l), below which spontaneous ignition will not occur. [5 points] using the energy balance formulation, describe the effect of the cube size, the ambient temperature and the heat transfer in the spontaneous ignition phenomenon. [5 points] describe the assumptions and limitations of the semenov model to represent the spontaneous ignition phenomenon of solids. [5 points) what are the main improvements included in the frank-kamenetski model compared to semenov's model? [5 points] describe the relationship between the frank-kamenetski and the thomas model to describe the spontaneous ignition of solids