The application of thermomechanical dynamics (TMD) to the analysis of nonequilibrium irreversible motion and a low temperature Stirling heat engine

Thermomechanical dynamics (TMD) is a theoretical model to study nonequilibrium irreversible states (NISs) proposed by authors, and the method of TMD developed from the analysis of nonequilibrium irreversible motion of a drinking bird system [1]. The TMD model solved, for the first time, the nonequilibrium irreversible motion of a drinking bird. The time-dependent progresses of physical quantities, such as work W(t), internal energy E(t), energy dissipation or entropy S(t), and temperature T(t) of a drinking bird motion, are consistently obtained [2].

We apply the TMD method to the analysis of NISs of a low temperature Stirling engine [3]. We proposed the dissipative equation of motion for heat engines in the TMD method, which consists of the external driving force composed of thermal work and frictional variations. The low temperature Stirling engine is the second example solved consistently by the TMD method, and time-dependent thermodynamic work W(t), internal energy E(t), energy dissipation or entropy S(t) and temperature T(t), are self-consistently studied.

The TMD model suggests that the trajectory, velocity and acceleration of particles are well described by Newtonian mechanics, when the dissipations of energy caused by frictional variations and thermal fluctuations do not affect motions of particles so much. The physical implications are fundamental for the concept of the macroscopic phenomena in NISs [3].