Performance improvement of heat recovery systems has huge potential for energy conservation but puzzles researchers due to the nonlinear coupled properties. The traditional modelling approaches focus on individual components, which introduces numerous non-independent variables and further complicates the system optimization. In this contribution, through the thermo-electric analogy method, the equivalent power flow diagram is built based on the system layout, then the corresponding governing equations are derived according to the circuitous philosophy, which reveals the overall transfer and conversion laws of heat. Then, by analyzing the pressure variations of fluids in various components, the flow resistance balance equations are established, which describes the pressure distribution in circulation loop. Moreover, through combining with the coupling relations between the temperatures and pressures of fluids, the inherent physical constraints among operating parameters are revealed by introducing few intermediate variables, which provides convenience for model computation. On this basis, through reasonably matching the mass flow rates of working fluids, the net power generation is maximized under variable working conditions. The optimization results indicate the parameters variation of flue gas significantly impacts the optimal operating state of system, while the empirical constant backpressure operation strategy apparently deviates from the optimums, and the most deviation reaches 8.2%.

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