Finite-time Thermodynamics Approach to the Phase Transition of the Second Order

A new formula for the specific heat jump ΔC｜Tc to the phase transition of the second order and generalized Ehrenfest equation are derived by means of the method of endoreversible Carnot cycle, which can mirror the irreversible features in a phase transition of the second order. The results are universal for reversible phase transition and irreversible phase transition of various substances. Then, the irreversible phase transition of the second order for simple system (P,V,T), the superconducting transition and paraelectricity-ferroelectrics transition are discussed by means of the new formula for the specific heat jump.