AFT xStream's primary steady solver uses a modified Newton-Raphson matrix method to obtain a system level balance of mass and energy. When the Solver is finished, the continuity and energy equations are satisfied at all branching sections. Once solved, it is a simple matter to go back and sum up all mass flows and energy at each branch to verify that these equations are satisfied. In fact, AFT xStream does just that.

After the primary steady solver converges, AFT xStream loops over each junction and adds up the inflow and outflow of mass and energy and compares the sum to the solution tolerances. If it appears that any junction is out of tolerance, a warning is given in the output.

In the Solution Balance Summary table AFT xStream provides additional information on the balance at each junction. This table can be displayed by selecting the option in the Output Control window General Output folder. Figure 1 shows an example of the Solution Balance Summary table.