Performance optimization of irreversible heat devices in the nonlinear response regime: Insights from the ecological criterion

Minimally nonlinear irreversible (MNI) models provide a valuable prototype for understanding the thermodynamic performance of heat devices working in the nonlinear response regime. In this paper, we study the thermodynamic optimization of MNI heat devices under the ecological criterion. The general formulas of efficiency and coefficient of performance (COP) for nonlinear heat engines and refrigerators are derived, and some bounds available for efficiency and COP are explicitly presented. Furthermore, the optimal characteristics of nonlinear heat devices are detailedly elucidated. Besides, the relationship between the ecological criterion and the trade-off optimization is definitely clarified, which illustrates the universality of our results. Our work provides instructions for designing and optimizing real heat devices operating in the external environment.