Research On Method Of Heat Exchanger Network Synthesis Based On ΔT-Contribution Of Streams

With the deepening of the world energy crisis, the energy saving of process system is by more and more people's attention. As an important energy recovery system of process industrial, heat exchanger networks design directly determines the level of energy recovery and economy of the process system. Therefore, heat exchanger networks synthesis gradually becomes a hotspot. Meanwhile, the existed methods of heat exchanger networks synthesis exist some problems and defects, need further research urgently.In the existing methods of heat exchanger networks synthesis, pinch design method is a mature one, and its theoretical basis is based on the similar heat transfer coefficient of the streams in the process system, but this assumption is not practical in the actual process industry. Therefore, this paper aimed at the process system with different heat transfer coefficient of streams, researched heat exchanger networks synthesis based on the theory ofΔT-contribution. Based on this topic, the main research work are as follows:1. This paper deducted the relational theory formula ofΔT-contribution values in the view of the heat transfer driving force, becauseΔT-contribution of streams is the foundation of the method proposed in this paper. On the basis ofΔT-contribution, this paper proposed the method of heat exchanger networks synthesis systemically. This paper displayed the detailed steps of this method, discussed and studied this method through a case study, the results show that: this method is reasonable to the transfer temperature's distribution, thus can reduce the area and the total annual cost of heat exchanger networks.2. Through the deep research of heat exchanger networks synthesis method based onΔT-contribution values, this paper put forward the three-level optimization strategy and introduced the detailed procedure. This paper studied the three-level optimization strategy in deep, studied and discussed the range of parametersκand z, and used a two-dimensional optimization method in this range. This process includes the optimization of superstructure, that is we need further optimize the superstructure of networks, thus in the fixed energy cost, we can get lower investment cost. The last step is networks optimization and energy relaxation, further simplify the structure of heat exchanger networks, improve the flexibility and regulatory.3. On the basis of theories upwards, this paper developed the software of heat exchanger networks synthesis based on MATLAB GUI. This software can use the conventional pinch design method to synthesize heat exchanger networks. At the same time, the method proposed in this paper can also be used in the software to synthesize heat exchanger networks. The software provides a quick test and comparing platform for this paper's theory research. Subsequently, the effectiveness and practicability of the software system is tested by some case studies.4. Finally, several cases were analyzed and studied using the software of heat exchanger networks synthesis. The first one focused on the detailed steps of the three-level optimization strategy, and another two cases lay stress on networks design to the actual process system. The results show that compared with the traditional pinch design method, the transfer temperature's distribution is more reasonable using the method this paper proposed, the area and the total annual cost are lower, the structure of networks can be simpler. The method this paper proposed can be used to solve actual heat exchanger networks synthesis problems with the streams having different heat transfer coefficient.