A simple and systematic procedure is developed to determine the effectiveness and exit fluid temperatures of complex assemblies of identical heat exchangers. Three complex assemblies have been chosen to illustrate the procedure. The excellent agreements between the results of the procedure developed and those in the literature validate the procedure. Parametric studies, including those of coupling method, flow arrangement, ratio of heat capacity rates of both fluids, number of transfer units, and pass number, have been performed to investigate their effects on the effectiveness of assemblies with identical crossflow shell-and-tube heat exchangers. Moreover, the assembly with non-identical heat exchangers is also studied to examine the general applicability of the present procedure.