  A discrete Boltzmann model (DBM) is developed to investigate the hydrodynamic
and thermodynamic non-equilibrium (TNE) effects in phase separation processes.
The interparticle force drives changes and the gradient force, induced by
gradients of macroscopic quantities, opposes them. In this paper, we
investigate the interplay between them by providing detailed inspection of
various non-equilibrium observables. Based on the TNE features, we define a TNE
strength which roughly estimates the deviation amplitude from the thermodynamic
equilibrium. The time evolution of the TNE intensity provides a convenient and
efficient physical criterion to discriminate the stages of the spinodal
decomposition and domain growth. Via the DBM simulation and this criterion, we
quantitatively study the effects of latent heat and surface tension on phase
separation. It is found that, the TNE strength attains its maximum at the end
of the spinodal decomposition stage, and it decreases when the latent heat
increases from zero. The surface tension effects are threefold, to prolong the
duration of the spinodal decomposition stage, decrease the maximum TNE
intensity, and accelerate the speed of the domain growth stage.
