Optimal Design Of Heat-exchanger Networks Based On State Space

Since the current energy issue is the most important factor of distracting the development of China, energy saving and emission reduction has been defined as an essential considering index when a flowsheet is designed or reformed. The optimization of heat exchanger networks which has been acknowledged as the most mature technical improvement measure is a typical method of energy saving.Because the optimization of heat exchanger networks has important theoretical significance and practical application value, it is widely used among scholars and technicists. Until now it is still a popular research field. There are three main methods: thermodynamics-based heuristics, mathematical optimization, artificial intelligence algorithm. Mathematical optimization gets the optimal networks under some certain constraint by means of solving the specific mathematical model. As it is scientific and accurate, mathematical optimization is widely used.In this paper, mathematical optimization is being used to start of heat-exchanger networks research. It mainly focuses on the following aspects:At first, the mathematical model is based on state space superstructure. It ensures the structure and solution space are integrality, and being optimized under diffident conditions by adjusting the distribution network and operation network.Secondly, streams with phase change are included. By bring in a universal formula which calculate the enthalpy of the stream, phase change is easily added to normal optimization.Thirdly, the streams are allowed to mixing and splitting when these streams have the same physical property. This conception effectively solves the mismatching problem when it is not allowed by the heat capacity flowrate.Finally, the advantages and disadvantages of this model are illustrated by some cases.