ABSTRACT
This chapter provides mathematical preliminaries for the two-point Hermite expansion and explains the averaging technique to various mass transfer problems. When the governing equation(s) for mass transfer appears as a partial differential equation, the solution usually requires tedious and complex analytical and/or numerical techniques. In most experimental studies related to mass transfer, the measured quantity is not the local concentration but either the average or bulk concentration. Instead of solving for the local concentration, an alternative approach is to obtain the average concentration by integrating the governing equation over either the area or the volume of the system. Since integration eliminates position dependence, the averaging procedure paves the way to an equation simpler to solve by reducing the number of independent variables by one.
