An approximate method for oxygen diffusion in a sphere with simultaneous absorption

The oxygen diffusion problem is usually formulated in two stages: first, the steady state and second, the moving boundary stage. In this paper, we will consider the solution of the second stage in which a new semi‐analytical method for solving such a problem was developed. The present method starts by assuming a polynomial representing the profile of oxygen concentration, and then by some mathematical manipulation a system of linear equations is obtained. Numerical solution for the system with a simple scheme relating the moving boundary and its velocity leads to the unknown functions in the assumed polynomial.