Vapour pressures of some inorganic sulphates at high temperatures

The vapour pressures of some inorganic sulphates at high temperatures were determined by the combined use of the Knudsen effusion, transpiration, and matrix isolation methods. After a detailed comparison with the results of other investigators, it is concluded that the principal vapour species in the case of K₂SO₄, Rb₂SO₄, and Cs₂SO₄ are the undecomposed sulphate molecules themselves, and in the case of Li₂SO₄ the decomposition products, Li, SO₂, and O₂. The sodium salt also decomposes to some extent into Na, SO₂, and O₂, but it is deduced that the vapour concentration of the species Na₂O₄ is probably greater than was formerly supposed. The decomposition of alkaline earth sulphates is also discussed, especially in the light of the dependence of the Knudsen effusion results upon the size of the orifice used. On the basis of the vapour constitutions deduced, thermodynamic functions for the important species present are tabulated up to 1400 K or above. Reference is also made to the function of sodium sulphate in the glass-making industry and to the possible mechanism of its corrosive action on furnace walls

A renormalisation approach to excitable reaction-diffusion waves in fractal media

Of fundamental importance to wave propagation in a wide range of physical phenomena is the structural geometry of the supporting medium. Recently, there have been several investigations on wave propagation in fractal media. We present here a renormalization approach to the study of reaction-diffusion (RD) wave propagation on finitely ramified fractal structures. In particular we will study a Rinzel-Keller (RK) type model, supporting travelling waves on a Sierpinski gasket (SG), lattice

Fractal morphology of deposits in heat exchangers and their physical properties

Our fundamental hypothesis in this paper is that aggregated deposits grown on a substrate can be construed as media endowed with fractal properties over a finite range of temporal and spatial scales. We present image analysis of industrial deposits that confirm their fractal morphology and then derive an equation governing the thermal conductivity which displays an explicit dependence on the box-counting fractal dimension. We also study the percolation properties of shuffled Sierpinski carpets (SSC) by developing a real space renormalization group (RSRG) theory approach. The theoretical results are critically discussed with reference to the numerical solution of the steady-state heat equation in simulated fouling material