Heat transfer optimization is ubiquitous because improving heat transfer performance could increase the energy utilization or reduce the weight or size of heat transfer equipments. This article discusses the optimization in heat transfer using the new physical quantity, entransy, in recent years. Entransy describes the heat transfer ability. When heat is transferred from a high temperature to a low temperature and entransy dissipation is produced. Heat transfer is irreversible from the viewpoint of entransy. The entransy transfer efficiency can be defined using the concept of entransy. Definition of entransy, entransy flux, and entransy dissipation are given and the entransy balance equations are derived for conduction, convection and thermal radiation based on the energy equation. The minimum entransy dissipation principle for prescribed heat flux boundary conditions and a maximum entransy dissipation principle for prescribed temperature boundary conditions are investigated. These two principles are called entransy dissipation extreme (EDE) principle. An equivalent or average thermal resistance of a system can be defined based on the entransy dissipation and the EDE principle becomes the minimum thermal resistance principle. These principles can be used to optimize heat transport with constraints and some examples are presented. The relation of entransy with thermomass is discussed and comparison between EDE and entropy generation optimization is made. The essence of the entansy is the energy of thermomass.

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