Abstract: Based on Tinkers flow model and the concepts of equivalent piping diagram suggested by HTRI (Heat Transfer Research Inc.), the authors, in this paper, proposed a "row by row" calculating method for solving flow ratesof WA and WE in streams A and E respectively. For practical uses, however, this "row by row" method is somewhat tedious. After some simplified treatment, and can be obtained. These results are quite satisfactory for most situations. Furthermore, a complete mathematical model for fluid flow and pressure drop calculation is given in this paper as follow: Since the K values are functions of the stream Reynolds numbers, experimental data from 14 models have been correlated to give resulting equations for resistance coefficient K of individual stream. For K&, however, the situation is much more complicated and a purely empirical correlation of K缺 has the following: form. By means of the mathematical model and experimental result, and flows rates of five streams can be solved simultaneously by trial and error.