In this paper, we analyze some kinds of potential energies, such as the geopotential energy, the electrostatic potential energy, the chemical potential energy, the mass entransy and so on. It is found that they all can be expressed as the product of a conservative extensive quantity and an intensity quantity. This kind of potential energy is named potential entransy. Based on the concept of potential entransy, the potential entransy decrease principle is developed. It is found that the potential entransy of an isolated system always decreases when the extensive quantity is transferred in the system. Furthermore, the criteria of equilibrium state for an isolated system and a common closed system are derived on the basis of the concept of potential entransy. It is found that when an isolated system reaches its equilibrium state, its potential entransy is a minimum value. When a common closed system reaches its equilibrium state, its quasi-free potential entransy is also a minimum value. In addition, when a closed system with prescribed potential is in its equilibrium state, its free potential entransy is also a minimum value. When the principles above are used in heat transfer, the entransy decrease principle for heat transfer and the thermal equilibrium criteria can be developed. We think that the new physical quantity, entransy in heat transfer, is the core concept of the subject, because it can be used to describe the irreversibility of heat transfer, optimize heat transfer processes, measure the disorder degree of one system, and set up the thermal equilibrium criteria.