A Rather General Variational Principle for Purely Dissipative Non‐Stationary Processes

A general variational principle concerning non‐stationary purely dissipative phenomena, obeying O NSAGER 's reciprocal relations, is presented. The principle expresses that the variation of the sum of the total entropy production and the time derivative of the M ASSIEU function is equal to zero. It is shown that the E ULER ‐L AGRANGE equations corresponding to arbitrary variations of the state variables yield the conservation laws. Other general criteria for non‐stationary processes have been given by G LANSDORFF ‐P RIGOGINE and G YARMATI . They are compared with our principle. Two illustrative examples are considered: coupled heat and electrical conduction in an isotropic medium and chemical reactions coupled with diffusion of matter and heat conduction in a multi‐component fluid.