Approximate Solutions: The Integral Method

There are various situations where it is desirable to obtain approximate analytic solutions. An obvious case is when an exact solution is not available or cannot be easily obtained. Approximate solutions are also obtained when the form of the exact solution is not convenient to use. Examples include solutions that are too complex, implicit, or require numerical integration. The integral method is used extensively in fluid flow, heat transfer, and mass transfer. Because of the mathematical simplifications associated with this method, it can deal with such complicating factors as phase change, temperature-dependent properties, and nonlinearity.