In this paper

an improved mixed-integer nonlinear programming（MINLP）model is presented which can synthesize heat exchanger networks where utility cost

exchanger areas and selection of matches are optimized simultaneously.By the use of the stagewise superstructured transshipment model and concepts of endothermic and exothermic potentialities of the process streams

the proposed model eliminates the unreasonable assump tion on isothermal mixing for stream splits under the condition where all the constraints are linear.The optimal network can be obtained by solving only one MINLP problem.Examples are presented to illustrate that the proposed simultaneous synthesis model has more advantages than others.