This book introduces new physical quantities and optimization methods for heat transfer, marking a departure from traditional heat transfer enhancement approaches that emerged in the 1970s in response to the global energy crisis. By drawing an analogy between heat conduction and electrical conduction, and through derivations from the energy conservation equation, this book presents the concept of entransy, demonstrates that it invariably decreases during spontaneous heat transfer in isolated systems, and entransy dissipation can serve as a measure of heat transfer irreversibility. On this basis, this book reveals fundamental principles for heat transfer optimization, such as the least action for heat transfer, the entransy extremum and the minimum entransy dissipation resistance. In addition, this book presents the utilization of the entransy balance equation as a global constraint for the optimization of heat transfer and thermodynamic systems, and introduces heat current models as key tools for such system analyses. This book is intended for senior undergraduate and graduate students with an interest in thermal engineering, as well as researchers working on thermal systems in fields such as architecture, electronics, aerospace, and chemical engineering.
