The thermal dynamics of gas compression and expansion processes have been studied and experimented from some decades ago. Predicting the performance of oleopneumatic suspensions requieres some knowledge about them, not being enough assuming a polytrophic exponent for both processes because it represents to ignore the destruction of available energy due to irreversibilities and to model the gas like an ideal exponential spring. Likewise, for those suspensions getting warm for strong dry-friction or any present irreversibility source, it results useful to add to the analysis the generated heat in order to set the mean growing temperature ratio. In this paper a method to appraise the origin and amount of the existing entrophy sources and their influence over the instantaneous poly-trophic index is presented. A discussion is made to fit the polytrophic index limits and its interrelation with the thermal time constant for the heat transfer phenomena. Real equation of state is taked into account but not stratification, vortex formation or other local effects that may occur inside the pneumatic chamber. Experiments were done with a kind of suspension varying frequencies, strokes and velocities. The results along our observations are resumed.
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