Nonlinearity is the source of difficulties in moving boundary problems. As a result, analytical solutions for phase
change problems are only known for a couple of physical situations that have a simple geometry and simple boundary conditions. The most well known analytical solution for a one-dimensional moving boundary problem, called the Stefan problem, was discovered by Neumann. Some analytical approximations for one-dimensional moving boundary problems with different boundary conditions have been produced. These include the
quasistationary approximation, perturbation methods, the Megerlin method, and the heat balance integral method <1>. In all these methods, it is assumed that the melting or solidification temperature is constant. The quasistationary approximation technique can be applied to one phase Stefan problems to obtain closed form solutions for a semi-infinite domain with imposed temperature at one end, imposed flux and also for a convective boundary condition at one end of the slab. However, this approximation is valid only for the case of low Stefan Number.