THE CONCENTRATION SHUNT ADMITTANCE OF SPHERICAL SHELLS

抄録

The process involved in the transference of heat or matter between phases may embrace convective, diffusive, or conductive transport. The experimental determination of values of such transfer and diffusion coefficients, or of thermal conductivity, is often conveniently done by means of frequency response. This involves a knowledge of the relation between the flux between phases and the concentration (of heat or matter) in one of them. This relation between complex vectors has been called the shunt admittance by analogy with other systems. Specification of this admittance requires that the geometry and structure of the system be defined.
One important system comprises a fluid phase flowing adjacent to a stationary system. The latter may be continuous, or a collection of discrete solids. The estimation of parameters requires two things: the experimental measurement of the cyclic perturbation in the flowing phase and the above mentioned shunt admittance of the stationary phase.
Equations are presented giving the shunt admittance of a homogeneous spherical shell with radial symmetry. This is of interest because it occurs in a number of processes; e.g., in a "shrinking core" chemical or metallurgical reaction, or a faulty sintered sphere.
Numerical values of the admittance are plotted with dimensionless coordinates and parameters.
A discussion is presented of the extension of the method to microscopically inhomogeneous shells of porous solids.