Electrical circuit analogy for heat transfer analysis and optimization in heat exchanger networks

Electrical circuit analogy is an effective method for the performance analysis of various heat transfer processes, whereas there is no equivalent thermal circuit for heat exchanger networks (HENs). In view of this limitation, and based on the concept of entransy-dissipation-based thermal resistance (EDTR), we introduce an equivalent thermal circuit to represent the heat transfer process in a heat exchanger, and then analyze the temperature variations of all the working fluids in each heat exchanger to establish the equivalent thermal circuits for such three basic layouts of HENs as multiple-loop, series, and parallel. The combination of these equivalent thermal circuits gives the overall equivalent thermal circuit for any HEN consisting of the three basic layouts. Accordingly, the inherent relationships, i.e., the constraint equations, of all the parameters in a HEN are built by circuitous philosophy. Based on these constraint equations together with the Lagrange multiplier method, we propose a mathematical method for the optimization of heat transfer performance in HENs. Finally, as an example, the heat transfer processes in a district heating system is analyzed and optimized by the newly proposed equivalent thermal circuit and the corresponding optimization method to show the applications.